WELDING Handbook - · PDF fileAlhuzaim- Metallurgy Page 1 WELDING Handbook By: Abdullah...

Alhuzaim- Metallurgy

WELDING Handbook

By:

Abdullah Alhuzaim

First addition

21-Jan-10


Chapter 1: ARC WELDING POWER SOURCES

Power sources can be classified in to two category constant current and constant voltages

POWER SOURCES

CONSTANT CURRENT

(CC)

CONSTANT VOLTAGES

(CV)

CONSTANT CURRENT POWER SOURCE:

Means the power sources produce a relatively

constant load current. At a given loud current, the

load voltage is responsive to the rate of feeding the

consumable metal electrode. That’s mean if the arc

length varies results in slight changes in the arc

voltage, the welding current remain constant.

Constant Current power sources are generally used

for manual welding processes such as shielded metal

arc welding (SMAW), gas tungsten arc welding

(GTAW), plasma arc welding (PAW), or plasma arc

cutting (PAC), where variations in arc length are

unavoidable because of human element.

CONSTANT VOLTAGES POWER SOURCE:

Means the power sources produce a relatively

constant load voltage. The load current, at a given load

voltage, is responsive to the rate at which a

consumable electrode is fed into the arc.

Constant Voltage arc welding is generally used with

welding processes that include a continuously fed

consumable electrode, usually in the form of wire.


Welding Process

R G 45 Rod Gas 45.000 min Tensile strength

OxyFuel Gas Welding:

The oxyfuel welding is one of the oldest welding

processes. The oxyfuel gas welding processes involve

melting the base metal and applying a filler metal if not

autogeneses weld (Filler Metal May or may not be

used) . The metal normally welded with the oxyfuel gas

welding process include carbon steel, low-alloy steel,

and most nonferrous metals, but generally not

refractory or reactive metals. The process is used to

weld thin sheet, tubes, and small diameter pipe, and

most commonly used for maintenance and repair.

Oxyfuel Gas Welding Variation

– Air Acetylene welding (AAW)

– Oxyacetylene welding (OAW)

– Oxyhydrogen Welding (OHW)

Filler Metal

The properties of the weld metal must closely match

those of the base metal.


Three Types of Flame Adjustment

Carburizing Flame

Reducing (carburizing) flame- will add carbon used to weld non-ferrous material around 5300° F at 2x

flame.

Fig 2.1 Carburizing Flame

The acetylene feather is twice as long as the inner cone. It is used for soldering.

Fig. 2.2 Temperature of the oxyacetylene flame


Neutral Flame

Neutral flame- around 5850° F has a 1 to 1 ration of acetylene and oxygen

Fig 2.3 Neutral Flame

Used for welding, cutting, and brazing

Oxidizing Flame

Oxidizing flame- has excessive oxygen temperature around 6300° F

Fig. 2.4 Oxidizing Flame

Used for braze welding


Equipments required

Fig. 2.5 Oxyacetylene Equipment


Fuel Gas Cylinder-

Porous filler soaked in acetone to stabilize acetylene

Left hand threads

Normal 250 P.S.I. pressure

Shorter container

Oxygen Cylinder-

Taller container

Normal 2400 P.S.I. pressure

Right-hand threads

When not in use they should be stored with cap on, and they should be chained

Fuel Gas Regulator-

It takes high pressure of cylinder and reduce to usable pressure

Can be single or dual stage

Dual will maintain the same pressure as cylinder pressure changes

Oxygen regulator-

right hand threads designed for higher pressure

Hose/check valves-

normally green and red in color

left-and right-hand threads

check valves prevent burn back located at the handle and at the regulator

Torch-

directs flame

mixes oxygen and acetylene

torches are designed for specific applications


Fig 2.6 torch & regulator

Tips Based on Application

(cont.)

WELDING GOUGING

HEATING


Fuel Gases

Acetylene

6000° F

good for welding and cutting hottest

Fig 2.7 Acetylene Flame

Methylacetylene Propadiene (Mapp Gas)

5300° F

not used for welding

good for cutting

inner cone 1-11/2 times acetylene

Fig. 2.8 Mapp Flame


Propane

4600° F

Not used for welding

Used for cutting or brazing

Slower travel speed

Fig. 2.9 Propane Flame

Natural

4780° F

not used for welding

used for cutting or brazing

Fig. 2.10 Natural Flame


Materials Weldable


Shielded Metal Arc Welding (SMAW)

Fundamentals of the Process

Definition

•Shielded Metal Arc Welding- is an arc welding process wherein coalescence is produced by heating with an electric arc between a covered metal electrode and the work.

•Shielding is obtained from decomposition of the electrode covering.

•Pressure is not used and filler metal is obtained from the electrode.

Process Principles

•Heat Source- Heat of the arc

•Shielding Gas- Slag formed by the decomposition of the flux

•Filler Metal- Comes from the core wire

•Flux contains-

–deoxiders (slag formed ionizing elements) to stabilize the arc

–iron powder for higher deposition

–alloying elements

2.4 Methods of Application

•Manual- most widely used

– approximately 99%

•Semiautomatic- not used

•Mechanized

•Automatic- gravity/massive/firecracker


2.5 Metals Weldable

Position Capabilities

•Grooves- all positions

•Fillets- all position

•Limitations-

– size of electrode

– skill of operator

– type of electrode

Electrical Requirements

Welding Circuit


Welding Current Types

AC

DCEN (Straight) Polarity

DCEP (Reverse) Polarity

Power Source Type and Characteristics

1) Generator (DC) 2) Transformer (AC) 3) Rectifier (DC) 4) T.R. (AC/DC) 5) Alternators (AC) 6) Inverters 7) Constant Current 8) 60% Duty Cycle

Advantages

1) Low cost of equipment 2) Maximum flexibility 3) Thickness range unlimited

Disadvantages

1) Low operator factor (rate) 2) Low filler metal utilization 3) Slag removal 4) Primarily for ferrous metals

Mild Steel (Covered) Electrode Classification


1) Flat, Horizontal, Vertical, Overhead 2) Flat and Horizontal only 4) Flat, Horizontal, Vertical Down, Overhead

*for electrodes 3/16” and under, except 5/32” and under for classifications E7014, E7015,

E7016, and E7018

Stainless Steel Electrode Classification

Electrode Groups

•F-1 High Deposition Group

–(Exx20, Exx24, Exx27, Exx28)

•F-2 Mild Penetration Group

–(Exx12, Exx13, Exx14)

•F-3 Deep Penetration Group

–(Exx10, Exx11)

•F-4 Low Hydrogen Group

–(Exx15, Exx16, Exx18)

Type of Coating


Gas Tungsten Arc Welding (GTAW)


Definition

Gas Tungsten Arc Welding (GTAW)- An arc welding process that uses an arc between a tungsten electrode (non-consumable) and the weld pool

the process is used with shielding gas

and without the application of pressure

Slang Names

T.I.G.-Tungsten Inert Gas

Heliarc

W.I.G.-Wolfram Inert Gas

Wolfram is German for Tungsten

Process Principles

Heat source- heat of the arc between a non-consumable electrode and the work

Shielding- inert shielding gas

Filler metal- will match base metal composition

Flux- not applicable

Metals Weldable The process was originally developed for the hard to weld metals and can be used to weld more, different kinds of, metals than any other arc welding process. Such as…



Grooves- all position capabilities

Fillets- all position capabilities

Limitations- skill of the operator

Base Metal WeldabilityAluminum Weldable

Bronzes Weldable

Copper Weldable

Copper Nickel Weldable

Cast, Malleable, Nodular Possible but Not Popular

Wrought Iron Possible but Not Popular

Lead Possible but Not Popular

Magnesium Weldable

Inconel Weldable

Nickel Weldable

Monel Weldable

Precious Metals Weldable

Low Carbon Steel Weldable

Low Alloy Steel Weldable

High and Medium Carbon Weldable

Alloy Steels Weldable

Stainless Steels Weldable

Tool Steels Weldable

Titanium Weldable

Tungsten Possible but Not Popular



Welding Current Type DCEN DCEP AC Power Source Type and Characteristics

Transformer- AC- constant current

Rectifier- DC- constant current

Other Electrical Requirements

Program ability

Hot start

Slope control

Consumables

Filler metal selection

Gas selection

Tungsten electrode selection

Gas Selection

Argon- is the most common

heavy which allows for lower flow rates

provides the best arc starting.

Helium- provides a hotter arc

higher travel speeds

lighter, therefore, higher flow rates must be used


Electrode for GTAW

Low Alloy (Solid) Electrode Classification GMAW, GTAW, and PAW

Stainless Steel (Solid) Electrode Classification GTAW Process

ER - 308 L S Electrode or Rod Chemical Low Carbon Content High Composition .04 Maximum Silicon

ER 80 S - Ni 3 Electrode or Rod Tensile Strength Solid or Chemical Composition KSI Metal Cored


Aluminum (Solid) Electrode Classification GTAW Process

Types of Tungsten Electrodes (GTAW & PAW)

ER 4043 Electrode or rod Chemical Composition


Advantages

Will make high quality welds in almost all metals

Very little, if any, post-weld cleaning required

Disadvantages

Lower productivity

Higher initial cost of the equipment


Gas Metal Arc Welding (GMAW)


Definition Gas Metal Arc Welding (GMAW)- An arc welding process that uses an arc between a continuous filler metal electrode and the weld pool the process is used with shielding from an externally supplied gas without the application of pressure

Process Principles

Heat source- electric arc between electrode (wire) and the work

Shielding- an external gas supply

Filler metal- fed automatically from a spool or reel

Flux- not applicable Transfer Mode with GMAW

Short Circuit

CO2 or AR/CO2

low amperage and voltage

all positions Globular

CO2 or AR/CO2

higher amperage and voltage

flat and horizontal


Spray- AR/O2

High amperage and voltage

flat and horizontal

Pulsed- AR/O2

various amperage levels

spray transfer

all positions

transition current

Metals Weldable



Grooves– all position capabilities

Fillets– all position capabilities

Limitations- type of transfer o Skill of operator o Wire size


Welding Circuit

Welding Current Type

DCEP- normal type of current used

DCEN- can be used with special electrodes

AC- has not been successfully used Power Source Types and Characteristics Constant Voltage- 100% duty cycle with flat volt/amp curve Shielding Gas

Inert- a gas that does not combine chemically with the base or filler material

Carbon Dioxide- not inert, is the most common gas used on low carbon steel

75% Argon,25%CO2- is used to produce a smoother bead with less spatter, but will reduce penetration

Argon/Oxygen- this mixture with 5% Oxygen as maximum will produce a spray transfer with no spatter

Advantages

High deposition rates related to S.M.A.W.


High utilization of filler metal

Elimination of slag

Reduction of smoke and fumes

Easily automated

Extremely versatile Disadvantages

Higher equipment price

Not as flexible as SMAW

Winds and drafts affect shielding gas

Some problems with feeding small or soft wire Classification

Mild Steel Classification

ER 70 S - X

ELECTRODE OR ROD

MINIMUM TENSILE STRENGTH IN KSI

S = SOLID ELECTRODE WIRE

CHEMICAL COMPOSITION AND SHIELDING


5.14 Stainless Steel (Solid) Electrode Classification

GMAW Process

Aluminum (Solid) Electrode Classification

GMAW Process


Flux-Cored Arc Welding (FCAW)


Definition Flux-Cored Arc Welding(FCAW)- An arc welding process that uses an arc between a continuous filler metal electrode and the weld pool. the process is uses with shielding gas from a flux contained within the tubular electrode with or without additional shielding from an externally supplied gas and without the application of pressure


Process Principles

Heat Source- an arc between a continuous filler metal electrode and the weld pool

Shielding- is obtained from flux contained within the tubular electrode and without additional shielding from an external supplied gas

Filler Metal- is obtained from a continuously-feeding tubular electrode

Flux- will provide deoxidizers, ionizers, purifying agents, and in some cases alloying elements

6.4 Methods of Application

Manual N/A

Semiautomatic Most Popular

Mechanized widely used

Automatic widely used

6.5 Metals Weldable

Base Metal Weldability

Cast Iron Using Special Electrode

Low Carbon Steel Weldable

Low Alloy Steel Weldable

High and Medium Carbon Weldable

Alloys Steel Weldable

Stainless Steel -- Selected Limited Types



Grooves- all positions, depending on size and type

Fillets- all positions, depending on size and type

Limitations- would depend on the skill of the operator


Welding Circuit


DCEN or DCEP

depending on type of wire

Power Source Type and Characteristics

Constant voltage with flat volt amp curve

Constant speed system with a constant current machine

The wire feeder is a variable speed system

100% duty cycle


SHIELDING MEDIUM AND POWER

XE 7 0 T

ELECTRODE

MINIMUM TENSILE 10XKSI

WELDING POSITION (0-F&H, 1-All)

TUBULAR OR FLUX CORED


Advantages

High quality welds

High deposition rates

Less pre-cleaning required

Relatively high travel speeds

Easily mechanized

Disadvantages

Equipment is more expensive

External gas shield

May be affected by breezes and drafts

Slag needs to be removed

Primarily only welds steels

Very smoky process

Filler metal more expensive


Submerged Arc Welding (SAW)


Definition Submerged arc welding (SAW)- an arc welding process that uses an arc or arcs between a bare metal electrode or electrodes. The arc and molten metal are shielded by a blanket of granular flux on the workpiece The process is used without pressure and with filler metal from the electrode and sometimes from a supplemental source (welding rod, flux, or metal granules)

Slang Names

Quick fill

Sub arc

Welding under powder

Process Principles

Heat source- an arc between a bare metal electrode and the work

Shielding- arc and molten metal are submerged in a blanket of granular fusible flux and the work

Filler metal-bare solid wire or composite

Flux metal-cored electrode- granular mineral compounds mixed according to various formulations.

The three different types of fluxes are fused, bonded and mechanically mixed Metals Weldable



Grooves- horizontal groove with backing and flux troft.

Fillets- horizontal fillet position

Limitations- because of large pool of molten metal process is known as limited position welding


Welding Circuit


AC

DCEN

DCEP Power Source Type and Characteristics

Alternating current

DC constant- voltage

DC constant- current

CC/CV combination


Other Electrical Requirements

Controls- motion timers, pulse, crater fill

Weld heads- wire feed motor and feed roll assembly

Torches- guides the wire through the contact tip and delivers welding power to the wire at the contact tip

Additional Equipment

Travel equipment

Flux recovery units

Fixturing equipment

Positioning equipment Electrode Selection Mild Steel Classification

E- indicates a solid electrode

X- manganese content

X- carbon content

X- deoxidation

X- suffix

7.10 Mild Steel Flux and Electrode Classification

SAW Process


Electrode Classification

Electrode Selection Flux Classification

F- indicates flux

X- minimum tensile strength

X- condition of heat treatment (A or P)

X- impact strength- lowest temperature

Submerged Arc Flux Classification System

Advantages

High quality weld metal

High deposition rates

Smooth, uniform finish, no spatter

Little or no smoke

No arc flash

High utilization of electrode wire

Easily automated

Manipulative skills not involved Disadvantages

Limited welding position

Primarily to weld steels

In semi-auto welding, hard to see the arc

E C X XX X X

Carbon Suffix which Electrode Manganese Content indicates alloy Content x0.01 present (in low-alloy steel)

L- low (0.60 Mn max.) M- medium (1.25 MN max.) Deoxidation H- high (2.25 Mn max.) Practice

Indicates composite K indicates electrode – omission silicon killed of C indicates solid electrode


Material selection is based on

Material properties:

o Mechanical properties

Strength

Hardness

Ductitility

Toughness

Stiffness ……est.

o Physical properties

Density

Melt temp

Thermal conductivity

Thermal expansion…..est.

o Chemical properties

Corrosion resistance

o Other properties

Cost

Availability

Business Issues

Main types of failure in engineering material:

1. Mechanical overload (deformation or fracture)

2. Corrosion

3. Wear

Stress concentrators (stress risers):

Geometrical feature that causes the stress in that area to be higher than the applied stress.

Stress: force per unit area

or PSI or

or Pascal (P)

Strength: ability of material to resist an applied stress.

Examples of stress risers:

Sharp radius on corners

Weld under cut

Excessive weld reinforcement

Surface roughness

Smax=Sn X Kf

Smax = stress at the stress riser

Sn= applied stress

Kf= stress concentration factor

Kf= 1 when no stress riser is present

Smax=Sn

Kf > 1 when a stress concentrator is

present Smax>Sn


Chemistry Review:

Element- a pure substance that cannot be broken down into a simpler substance

Atom- smallest part of an element that retains the properties of the element

Atoms are made of:

Protons: positive charge in nucleus

Neutrons- no charge in nucleus

Electrons- negative charge orbit nucleus

Atomic bounding:

Bonding occurs the atom wants to be at their lowest energy state.

*this is usually when they have full other electron shells.

Types of Bonding:

Ionic Bonding:

o One atom gives its valance electron(s) to another atom.

o Valance electrons will remain in fixed position.

o Most ceramics have Ionic Bonds

Covalent Bonding

o Adjacent atoms share valance electrons

o Electrons are in fixed positions (poor electrical conductivity)

o Most monomers have Covalent Bonding


Van-Der walls

o Weak electrostatic bonds

o Important for plastic

Metallic Bonding

o Valance electrons move from one atom to the next making all atoms “feel” like they

have full valance shells.

Properties of metals:

Most are good electrical conductors

Most are solid at room temperature

Most have good thermal conductivity

Plastically deform with force

Expand when heated

Most are opaque “can’t see through”

Most are shinny

Most metal are not used in their pure form

Alloys- Combination of metallic elements with other metallic or non-metallic elements.

Composition- how much of each element is present in the alloy in weight %

Phase- area within an alloy that has the same:

o composition

o crystal structure

o properties

Crystalline- atoms are arranged in a 3-dimensional pattern in the solid state.

*Most metal are crystalline

Amorphous- atoms do not have a 3-D arrangement in the solid state

States of Matter:

Temperature and pressure will determine what state a substance is in:

1. Solid: fixed volume, fixed shape

2. Liquid: fixed volume, assumed shape of containers

3. Gas: volume and shape not fixed

Example:

Steel = Fe + C

Cast Iron = Fe + C + Si


4. Plasma

Solidification of metals:

Solidification is a three stage process.

1. Nucleation: two atoms that are close to each other from a chemical bound

*accurse at many locations in the liquid

2. Growth: additional atoms bond to the nucleus and growth accurse in 3 dimensions.

3. Formation of grains boundaries: area where crystals of different orientation meet the area

between them called a grain boundary

Grain- Area with a metal where the atoms have the same orientation.

Most metal are crystalling: atom are arranged in three dimensional patterns (in the solid state)

in the other hand, some metals are Amorphous: atoms are not in a three dimensional pattern.

Main crystal structures for metals:

1. Face Centered Cubic (FCC)

a. Tend to be soft and ductile (Al, Cu, Pb)

2. Body Center Cubic (BCC)

a. Tend to be stronger and less ductile (Fe @ room temp.)

3. Hexagonal Close Packed (HCP)

a. Tend to be brittle (Zn, Mg)

4. Body Centered Tetragonal

a. Harder and stronger (Quench Hardened steel →Martensite)

Allotropic Phase Transformation:

Metal that change crystal structure with temperature

Example: Fe

Room temp - 1660 BCC

1661 – 2550 F FCC

2551 – 2800 F BCC


Most metal only exist in 1 crystal stricture. However, some metal change crystal structure with

temperature. This is called on Allotropic transformation.

Crystal Defects will occur during solidification:

Two main types of defects occur

1. Vacancy

a. missing atoms at some location within a metals crystal structure

b. these control diffusion

2. Dislocation

a. missing ½ planes of atoms in a metal crystal structure

*These allow metal to plastically deform (bend, stretch, etc..)

Dislocation can only move in specific directions in each crystal structures. These direction are called slip

planes.

FCC- 4 slip planes, dislocation can move in various directions. These metals tend to be soft and ductile

(Cu, Pb)

BCC- 2 slip planes at 90° (perpendicular) to each other. These tend to be stronger and less ductile (Fe at

room temperature)

HCP- 2 slip planes parallel to each other. Tend to be brittle (Zn, Ti)

Grain size (number of grains/Unit area)

Will affect strength and ductility

small grain size stronger and less ductile

Larger grain size lower strength and more ductile

Grain size can be controlled by the rate of solidification

Slow solidification larger grain size

The crystal in nature of metals causes their mechanical properties to be Anisetropic (properties vary

with direction).

Stress: Force per unit area applied to a

material (Ibf/In² pound of force or N/M²)

Pascal

Strain: Movement of the material due

to an applied stress (In/In or m/m)


There are two type of strain exist

1. Elastic Strain: movement that occurs when a stress is applied and disappears when the stress is

removed.” Occurs due stretching atomic bonds.”

2. Plastic Strain: permanent change in shape that accurse due to an applied stress.

*Anything that limits dislocation motion will increase the strength of metal alloy

Loads:

Type of load Stress produced Example

tension cable

compression Column

Compression/Tension Beam / Gear teeth

Shear stress Bolts

Shear Stress Drive shaft

Types of loading

Static loading: constant load – no change

Dynamic loading: change with time

Impact loading: load applied at a rapid rate

atigue loading: cyclic loading (load, unload, load, unload…)

Four methods to increase strength of metals

1- Work hardening (cold working, strain hardening)

a) Done by plastically deforming the metal at temperatures below the alloys

recrystalization temperature (

melting temperature ( )

b) Causes dislocations to move to barriers such as grain boundaries & additional stress is

required to move other dislocations & cause additional plastic deformation.

c) Effects of work hardening can be removed by annealing or normalizing

i. Heat above recrystallization temperature & air cool

ii. Produces lower strength, lower hardening, & higher ductility “compare to work

hardening alloy”

*All metal alloys can be work hardened.


2- Solid solution strengthening

a) Adding alloying elements that block dislocation motion & increase the strength of the

alloy

b) All alloys can be strengthened within this method.

c) Effect cannot be removed by heating & cooling from welding

3- Quench Hardening (Quench & Tempered, Transformation Harding)

a) Heat treatment used to increase the strength of ferrous alloys such as:

i. Steel

ii. Stainless steel

iii. Cast iron

b) Alloy must have > 0.30% carbon to quench harden

c) Process steps to Quench harden

i. Heat alloy to its austenitization temperature (upper transformation temp

ii. Hold at temp for microstructure to transform to austenite

iii. Quench- rapidly cool faster than critical cooling rate & case microstructure to

transform to martensite

Martensite- Body centered tetragonal (BCT) steel microstructure that is more difficult

for dislocations to move in (it has less slip planes)

Martensite is strong hard and brittle→ In most welding applications you want to avoid

the formation of martensite in the HAZ due to its tendency to crack

4- Precipitation Hardening

a) Heat treatment used to increase the strength of:

i. Some aluminum alloys (2XXX, 6XXX, 7XXX)

ii. Some stainless steels (17-4PH, 17-7PH)

iii. Some Titanium alloys

iv. Some Ni & Co alloys

b) Process step to precipitation hardening

i. Solutionice- heat alloy to form a single phase solid solution

ii. Quench- cause single phase solid solution to remain at room temp

1. This does not cause on increase in strength

iii. Age-reheat the alloy (to a lower temp than used for solutionicing) & hold at

temperature

1. This cause small intermetallic precipitates (hard particles) to form within

the grains of the alloy

2. These increase strength (when precipitates are small)

*The heat of welding will cause overaging to occur in the HAZ →this results in a loss of strength

in HAZ


Tensile Testing:

Most common test used to determine the strength of a material.

Test is preformed in a sample of known geometry

o Round Bar

o Flat Coupon

Sample is clumped between the machine cross heads and the cross heads move away

from each other at a set speed

The load (Ibf) and change in length are measured during the test

Prior to starting the test a gage length is worked on the sample (2.000 inch typ)

We calculate the stress as:

We calculate the strain as:

Data is plotted as an Engineering Stress Strain curve

Stress =

Strain


The initial part of the curve is linear (stress and strain)

o This is the “Elastic Region” of the curve (due to stretching of atomic bonds)

o Elastic region- only elastic strain is occurring

o Dislocations are NOT moving, atomic bonds are stretching

Elastic Limit:

Max stress a material can withstand before it begins to plastically deform.

0.2% Yield Strength:

Found by drawing a line parallel to the elastic region of the curve offset 0.2% on the strain Axis

This valve is most often used for design calculations

0.2% is most often used for design calculation

Ultimate Tensile Strength

Max stress the metal can withstand prior to failure

Break Strength

Stress at point of fracture

*% Elongation & % Reduction are measures of the alloy Ductility

Modulus of Elasticity- Elastic Stiffness

-Determines how much the metal will deflect under elastic loading conditions

Ultimate Tensile Strength

Break Strength

s

% Elongation=

s

% Reduction in Area=

s


Modulus of all steel at Room temperature ≈30 X 10⁶

Modulus of all aluminum at room temperature ≈ 10.5 X 10⁶

o Modulus of Elasticity (E) is dependant of the strength & ductility of the alloy

- Modulus is controlled by the stretching of atomic bonds

* Temperature could change the modulus of elasticity

o Resilience- ability of metal to absorb energy without plastic deformation

- Estimated by the area under the elastic region of the stress strain carve.

o Toughness- ability of a metal to absorb energy before fracture

- Estimated by the total area under the stress-strain curve

o Toughness can be also be measured with an Izod or chirpy impact test

- These test determine impact toughness which is depending on the size of the sample &

speed of impact loading.

Modulus of Elasticity →E =

(measure in elastic portion of the curve

Resilien

ce


- measure how much energy is absorbed by the sample

- Results are typically plotted Vs. test temperature

Plane strain fracture toughness:

- This is a material property that is independent of thickness and strain rate

- Determined by applying a tensile stress to a sample that has a crack of known size and location

if any 2 of the 3 variables (KIC, δ, ) are known we can solve for the third

the ability of a material to resist the growth of a flow (i.e. have a large KIC) depends on many

factors:

1. Large flaws reduce the allowable stress. Therefore manufacturing process that reduce

the flow size improve fracture toughness often times parts can be inspected (X-ray,

ultrasonic est.) to assure flaws above a critical size are not present in a part

2. Ductility of the material is critical. If the material can plastically deform at the tip of

the crack it will reduce the stress intensity factor.

a. Higher strength

3. Increasing temperature will typically increase the KIC

4. Small grain size typically increases the KIC

K1C= plane strain fracture toughness

K1C=fδ√

F=constant 1.12 (edge crack)

δ=applied stress

=crack diameter


Example 1:

Grade 350 maraging steel

=0.10 in → =0.05 in

KIC= 35 KSI solve for δ

Answer:

35 KSI√ = 1.12 X δ X √ →

This is the stress required to make a crack of (0.10 in) in radius grow to failure

**************************************

Yield Strength is 325 KSI design is limited by the plane strain fracture toughness (KIC) not by the Yield

Strength

Example 2:

Look at grade 350 maraging steel that is quenched and tempered to produce the following:

Y.S. = 225 KSI

KIC = 50 KSI √

What is the maximum safe stress if the max crack radius ( ) is 0.10 in?

Answer:

K1C=fδ√ → 50 KSI√ = 1.12 δ √ = δ = 113 KSI

*************************************

K1C=fδ√

δ = 78.8 KSI


Hardness:

Mechanical property of metals

Harness can be measured many ways

o Resistance to indentation (Rockwell, Brinell, Vickers, Knoop)

o Elastic Rebound (shore – not typically used)

o Resistance to abrasion (file)

Hardness relates to wear resistance but is not a direct measure

Hardness also relates to the strength and ductility of metal

Higher hardness → higher strength

Higher hardness → lower ductility

* Maximum hardness of quench hardened steel is

Homework #1

1. A spherical pressure vessel is to be constructed by welding curved steel plates. The welds are

inspected by radiography using a technique that will detect any crack greater than 0.10 in. long. Three

grades of maraging steel are being considered;

I. 18Ni(grade 200)

II. 18Ni(grade 250)

III. 18Ni(grade 300)

If the thickness of the vessel is 1.00 in. and the diameter is 10 ft., which steel will give the greatest

pressure capability? Use the ASM Metals Handbook for material properties.

I. 18Ni(grade 200)

K1C=fδ√ → 140 KSI √ = 1.12 δ √ = 315 KSI

K1C=fδ√ → 220 KSI √ = 1.12 δ √ = 495 KSI

Rule of “thumb” for steels

500 X BHN U.T.S (PSI)


δ for 18Ni(grade 200) between 315-495

II. 18Ni(grade 250)

K1C=fδ√ → 110 KSI √ = 1.12 δ √ = 247 KSI


IV. K1C=fδ√ → 73 KSI √ = 1.12 δ √ = 164 KSI

Spherical vessel surface area:

10 ft→ 120 in – 2 in = 118 in /2 →radius of 59 in

Area = 4 π r² → 43743.5 in²

Stress =

force = stress X area = Ib

I. 18Ni(grade 200)

315 X 43743.5 = 13779202.5 Ib

495 X 43743.5 = 6820705238 Ib

II. 18Ni(grade 250)

247 X 43743.5 = 10804644.5 Ib


164 X 43743.5= 7173934

So we conclude that the steel that will give us the greatest pressure capability is 18Ni(grade 200)

2. Describe what maraging steels are.

Maraging steels: comprise a special class of high-strength steels that differ from conventional steels in

that they are hardened by a metallurgical reaction that does not involve carbon. Instead, these steels

are strengthened by the precipitation of intermetallic compounds at temperatures of about 480 °C

(900 °F)


FATIGUE:

- Fatigue is due to cyclic loading (load.. unload.. load.. unload)

- Fatigue failure can occur in metals at stress below the alloys Elastic limit

- Fatigue test results are typically shown in the form of S-N curves

o Endurance Limit

- below this stress the fatigue life is infinite

- Only steel and titanium alloys have endurance limits

o Fatigue strength

- Stress required to produce failure after 5x10⁸ stress cycles

- Al alloys and other non-ferrous alloys do not have Endurance limits so fatigue strength

are used for design calculations

- Fatigue fracture surfaces will have “Clan shell” or “Beach marks”

Fatigue failure zone

Steels & Titanium alloy


Steel Microstructures:

Phase – area within a metal that has same composition properties, and crystal structure

3 way elements combine in the solid state

1. Solid solution- elements are soluble in each other and combine as a single phase

2. Mechanical Mixture- elements remain as separate phases (example: Oil & water)

3. Compound- elements react together to form a phase with properties different that the

elements that are reacting (example: 3Fe + C → e₃C)

Steel Microstructures

Name of phase Type of phase Amount of carbon Properties

Ferrite (α Iron)

Single phase solid solution of carbon in BCC Iron

0.025% max @1333 ˚

Soft and ductile (40 – 50 KSI) T.S Elongation

Iron carbide ( e₃C, Cementite)

Compound 6.67 wt % carbon (fixed ratio)

Hard and Brittle 325 KSI T.S 0% Elongation

Pearlite Mechanical mixture of errite and e₃C (2 phase solid)

0.8% @ the Eutectoid Composition

Fall between Ferrite & e₃C ( 125 KSI tensile strength, 15% Elongation)

Austenite (δ Iron)

Single phase solid solution of carbon in FCC iron

Max of ≈ 2.0% @ 2075 ˚

* Not tested, only exists at elevated Temperature

* Ferrite, Cementitem, Pearlite, and Austenite are all equilibrium steel microstructure

Equilibrium microstructure are produced by slow cooling


Non-Equilibrium Steel Microstructures:

Name of phase Type of phase Amount of carbon Properties

Martensite Supersaturated solid solution of carbon in body centered tetragonal (BCT) iron

Up to 2.0% Hard, strong & brittle Maximum hardness carbon & above

Martensite is produced by cooling a steel from the austenite phase faster than the “critical cooling rate” for that alloy

Bainite Mechanical mixture of ferrite & e₃C

0.8% @ the Eutectoid Composition

Harder, stronger & less ductile than pearlite, but not as hard as martensite

Bainite is produced by cooling a steel too fast to form pearlite but not fast enough to form martensite bainite is a “finer grain size pearlite


Chapter 2:

Welding Metallurgy

Weldability- the “ease” with which as alloy can be welded

o To determine the weldability for a specific situation we must know:

- Base metal composition → (this is the primary consideration)

- Service conditions

i. Service temperature

ii. Types of loading (static, impact)

iii. Environment (corrosion requirements)

- Design of weld joint

i. Thickness

ii. Restraint

- 2 things must important to determine weldability of steel

1. Hardenability – how likely is it that martensite will be formed in the HAZ of the

weld

This is determined by the carbon equivalent (CE)

* If the CE> 0.4% than martensite is likely to form in HAZ & Procedures must be used to prevent this

otherwise cracking of the HAZ is likely.

- The following procedures are usually required for steels with CE>0.4%

a) Preheat & interpass temperature control

i) Reduce cooling rate of the HAZ & prevent formation of martensite

ii) Reduce residual stress by reducing shrinkage

b) Use low Hydrogen process or fillers

i) Hydrogen in the weld contributes to cracking (Hydrogen Cracking)

c) Minimize joint restraint

i) Reduces residual stress & reduces tendency for cracking

d) Post weld heat treatment (PWHT)

i) Reduces hardness & strength in HAZ → improve ductility & toughness

CE=%C +


ii) Reduce residual stress

Types of Cracking:

Macrocrack- crack that is visible to the naked eye (may or may NOT extend to the surface)

Microcracking- only visible with the aid of a microscope (may or may NOT extend to the surface)

Intergranular- cracking a long the grain boundaries

Intragranular- cracking through the grain boundaries

o Cracks that occur after the weld has solidified are called (Hydrogen cracking, Cold

cracking, Delay cracking, underbead cracking)

Occurs in HAZ may extend into the weld metal or base metal

o Hydrogen cracking

- Type of cracking that occurs in the steels with high hardenability (high CE)

- 4 requirements for hydrogen cracking to Occur:

i. Diffusible hydrogen present in the area of the weld (H not H2)

ii. Temperature below 300 °F

iii. Susceptible microstructure

- Partially or wholly martensitic (>30 HRC ot it will not crack)

- Hardness is controlled by the amount of carbon (more

carbon ↑ HRC)

iv. Tensile stresses in the area of the weld (residual or applied)

o Hydrogen cracking can be avoided by preventing any 1 of these 4 requirements.

o Methods to prevent diffusible hydrogen from being present

Source of Hydrogen

- water (on base metal, in flux , in shielding gas, at atmosphere or on filler)

- rust (on the base metal, on filler)

- oil (on base metal)

- paint, marker, etc (on base metal)

o Need to use low Hydrogen processes or low Hydrogen Electrodes

o Methods to prevent martensitic microstructure in HAZ

i. Use preheat & interpass Temperature control

ii. Reduces cooling rate & prevents formation of martensite

This also allows additional time at elevated temperature for Hydrogen to

diffuse out of the weld area.


Solidification Cracking

Cracking that occur during solidification of the weld due to tensile stresses from contraction

during cooling

Solidification cracking occur in the weld metal and may extend into the HAZ and base metal

Liquation crack occur at the interface between the weld and HAZ

Two conditions are required for solidification cracking

1. Metal must lack ductility at its solidification temp

This is alloys dependant

Aluminum alloys, fully austenitic stainless steel, and Mg alloys are most prone

On cooling grains are nucleated and grow until they join together and form a

coherent but not completely solidified mass

At this point some alloys are brittle

2. Tensile stress due to weld contraction must exceed the UTS of the weld metal at its

solidification temp

Weld bead geometry related and base metal residual stress related

Weld bead geometry avoid welds that are concave

This produces tensile stresses on the weld

Weld bead geometry avoid base metals with high amounts of residual stress

The higher the degree of restraint the more likely a given alloy will experience

solidification cracking

Max restraint occurs with 2 thick plates clamped and joined by a weld of small cross section

Most weld metals will crack

Min restraint occurs in large welds on thin close butting sheets

Shrinkage cracking

- A type of solidification crack

- Due to inadequate feeding of liquid metal to feed gaps caused by shrinkage during solidification

- Common in welds where penetration is too deep relative to weld width (laser, E beam)

- Width/Depth of 1-1.4 are best to avoid this problem


Chapter 3

Stainless Steel:

Steel alloys with >11% Cr

Causes a chromium oxide layer to form on the surface of the steel that is tenacious and protects the

steel from additional corrosion.

Types of Stainless Steel

1. Ferritic

2. Austonitic

3. Martensitic

4. Duplex

5. Precipitation Hardened stainless steel

Ferritic Stainless steel

- 11.5 – 30% Cr

- Up to 0.2% C

Low carbon causes ferrite to be stable (will NOT transform to martensite)

- Used mainly for Auto Exhaust, Trim

- Ferritic Stainless Steel tend to be lowest Cost of all Stainless Steel

- Classifications are some of the 4XX series alloys 409, 439 both very common

Two main issues associated with welding Ferritic Stainless Steel

1. Grain growth in HAZ will result in loss of toughness

Lower heat input is better

2. Intergranular corrosion due to formation of chromium carbides (Cr23C6)

o In the HAZ where the Cr23C6 forms there will not be enough Cr available to form the

protective oxide layer and therefore corrosion will occur in this area

o Intergranular corrosion of erritic stainless steel is prevented by using “stabilized”

grades of stainless steel for applications that require welding.

o Stabilized grades have Ti or Cb/Nb added to them which causes the formation of TiC or

CbC in the HAZ and the Cr remains available to form the protective oxide layer.

Most Common


Austenitic Stainless steel

- Up to 0.1% C

- 16-26% Cr

- 8-22% Ni (makes Austenite phase stable at and below room temperature)

- 2XX series (manganese used to replace same Ni for reduced cost)

- 3XX series (standard series)

- Work harden to high strengths

- High cost due to Ni & Cr

- Excellent corrosion resistance

o Food grade Stainless Steel

o Petro chemical applications

- Three main welding issues

1. High amount of distortion due to high thermal expansion (≈50% higher thermal

expansion than non-austenitic steels)

2. Intergranular corrosion (like in Ferritic Stainless Steel)

Prevented in Austenitic Stainless Steel by using

i. Low carbon grades 304L (0.03%C) not 304 (0.08%C)

ii. Use stabilized grades with Ti or Cb (316 Ti)

3. Solidification Cracking

Welds that are 100% Austenitic are very likely to crack

- Most Austenitic filler metals are formulated so the deposited filler metal contains Ferrite

- Ferrite acts as a “sink” for imparities that cause cracking

- Alloys that contain Ferrite have a smaller solidification temperature range

- Ferrite lower the coefficient of thermal expansion and therefore lower shrinkage stresses

- Two phase microstructure makes for a more “tortuous” crack path

- The ferrite content in the weld can be calculated using

o Schaeffler Diagram

o DeLong Diagram

o WRC 1992 Diagram

*Ferrite number usually from 5-15


Martensitic Stainless steel

- Some of the 4XX series (403, 410, 420, 440)

- 11.5-18% Cr

- Up to 1.2% C

- Martensitic Microstructure

- Excellent hardness and Strength

- Good Corrosion Resistance

- High hardenability

Prone to hydrogen cracking (cold cracking)

- The higher the carbon in the steel the harder the Martensite

(HRC > 30 is very likely to crack)

- Weldability is similar to steels with high hardeability

400-600 ˚ preheat is typically used

- Post weld tempering is required to restore toughness in the HAZ

- Austenitic Filler metals are often used to weld Martensitic stainless steel (308, 309, 310)

* Ductile like a rubber band

Filler metal is low strength and high ductility so it will plastically deform and reduces the

stress in the HAZ

Duplex Stainless steel

- Mixture of errite and Austenite (typ ≈ 50/50)

- Low carbon < 0.03%

Avoids carbide precipitation

- Strengths ≈ 2 times Austenitic Stainless Steel

- Weldability issues include:

Loss of toughness due to grain growth of Ferrite phase

Potential for stress corrosion cracking if Ferrite/Austenite balance is wrong

Precipitation Hardened Stainless steel

- 17-4PH, 17-7PH

- Hardened by Precipitation Hardening heat treatment

- Good weldability but must be reheat treated to restore mechanical properties in the HAZ


ALUMINUM ALLOYS

Physical Properties:

Low density (Al≈2.7 g/cm³ or 0.098lb/IN³) (Mg≈1.7g/cm³, e≈7.8g/cm³)

Modulus of elasticity (Al≈10.5X10⁶ PSI, Steel≈ 30X10⁶ PSI, Ti≈18X10⁶ PSI)

Low melting temperature (Al≈660 ˚C, 1220 ˚ ) no change in color when heated

High thermal conductivity (≈6 time that of steel)

Requires higher heat intensity to produce melting

High thermal expansion (≈ 2 time that of steel, ≈6% shrinkage during solidification)

Causes distortion and possible to solidification cracking

High electrical conductivity

Non-magnetic

Chemical Properties:

Highly reactive with oxygen

Forms tenacious oxide film instantly

(15 ˚A thick initially, 25-50 ˚A normal thickness)

1 ˚A=0.000, 000,004 inch

Anodized Al has an oxide layer that is ≈25,000-50,000 ˚A ”1000 times thicker” (see picture

below)

Al2O3 can be remove b y

o Mechanical- stainless steel brush

o Chemical- flux followed by water rinse

Al that has been thermally treated (precipitately

hardened and artificially aged, Annealed, welded etc)

Will also have a thicker oxide layer

Al2O3 is very hard

Al2O3 has high melting temperature (2052 ˚C)

Oxide must be removed; a tempting to weld

removal will result in melting to base metal and Not

Al2O3 this can prevent coalescence

Al2O3 is an excellent electrical insulator

Oxide must be removed to start arc

Al2O3 is porous and will hold moisture and

hydrocarbons

Welding over this will cause porosity in the weld


Mechanical Properties:

Pure Al has low strength (4KSI Y.S., 43% Elongation)

Moderate strength increase by cold working (up to 40 KSI Y.S.)

Alloying and precipitation hardening can produce up to ≈ 78 KSI Y.S. 10% Elongation)

Modules of Elasticity ≈ 10.5 X 10⁶ PSI

High elastic deflection

Toughness does not decrease will low temperature

Alloy Designations

Wrought alloys use a 4 digit #

1XXX – 8XXX series alloys

1st digit indicates main alloying elements

2XXX, 6XXX and 7XXX alloys can be precipitation

Hardened to increase strength

1XXX, 3XXX, 5XXX can be work hardened to increase strength

Temper Designations F- As fabricated (no control over strength) O- Annealed H- Strain hardened W- Solutionized T- Precipitation hardened

Preparation of Aluminum for Welding

Storage- store on edge vertically with space between pieces to prevent moisture from collecting

on the surface

Prevents forming a thicker oxide layer

metal working- plasma arc cutting is the most common

(Thicker sections can be prone to solidification cracking on the cut surface)

cleaning- amount of cleaning required is based on how clean the metal is kept prior to welded

and thermal history “ how thick is the oxide layer”

solvents – are used to remove grease and oils

deoxidizers – are available to remove thick oxide layers

(Must be removed completely to avoid corrosion issues)


moisture removal – preheat to a max of 150 ˚ to remove moisture

wire brush- use stainless steel wire brush as final cleaning step prior to welding

welding of non-heat treatable Aluminum alloys

(1XXX, 3XXX, 5XXX)

welding these alloys will resulting in loss of strength in the HAZ due to annealing or normalizing

(assuming the alloys was strain hardened prior to welding)

5XXX series alloys are preferred between the have the best match of filler/base/HAZ strength

HAZ width is typically less than ½” but 1” is used for design purpose

Width of HAZ can be reduced with reduced heat input but reduction of strength in HAZ can not

be avoided

Welding precipitation hardened Aluminum Alloys

(2XXX, 6XXX, 7XXX)

Welding will resulting overaging of the HAZ and loss of strength (ductility is unchanged or

increases in the HAZ for most alloys)

The loss of strength that occurs due to overaging of a precipitin hardened alloy is typically larger

(higher % of the alloys base metal yield strength) then the loss of strength that occurs in non-

precipitation hardened alloys.


Titanium Alloys

Used for two main reasons

1- High strength to weight ratio (specific strength =

)

2- Excellent corrosion resistance

Properties

o Density 4.5 g/cm³ (Al=2.7 g/cm³, Fe= 7.8 g/cm³, Mg=1.7 g/cm³)

o Melting temperature 1671

Crystal Structure → HCP up to 883 , BCC above 883

- Modulus of Elasticity 18 10 PSI

- Expensive because it is difficult to refine its natural from (TiO₂)

Alloy Designations

- Industry standard is to use elemental symbols with numbers to indicate a mount of alloying

elements Example Ti-6AI-4V

4 maim Types of Ti Alloys

1) Commercially Pure Ti

- Use for their excellent corrosion resistance ( chemical processing equipment , sursical implants )

- Strengthened by solid solution strengthening

2) Alpha Ti Grades

- Used for cryogenic Application (Ti-5AI-2.5 SN )

- Strengthened by solid solution

- Good weldability for Ti

3) Alpha _ Beta Alloys

- Mast widely used type of Ti ( Ti- 6AI – 4V ) & ( Ti -3Ai -2.5 V ) → ≈ 80% of all Ti used

- Used in Automotive , Aerospace ,and sporting goods

- Precipitation Hardened

- For weldability

4) Beta Alloys

- Used for high strength fasteners ( not typ. Welded )


Magnesium Alloys

- Density 1.7 g/cm³

- Melt temp 650

- Modulus of Elasticity 6.5× 10⁶ PSI

- High Thermal expansion

- High mechanical pumping Capacity

- HCP crystal structure → Brittle

- Poor fatigue & Impact strength

- Excellent machinability & Castability

- Good weldability


Chapter 4 Welding Design

Example 1:

Calculate the weight of the above fillet weld the metal is mild steel.

we can use the welding symbol to help us find what essential information to calculate the weight like

the leg size and the length of the weld, as it shown in the drawing the leg size is 5/16 inch and it mention

only one size that’s mean the leg size is equal. Also the length of weld is 12 inch. The density of all steel

is 0.283 lbs/in³. So now we can start following the steps above.

Step 1

Fillet weld CSA = .5 X Base X Height Fillet weld CSA = .5 X .3125 X .3125 = .049 in²

Step 2

Fillet weld Volume = CSA X Length of weld Fillet weld Volume = 0.49 X 12 = .59 in³

Step 3

Fillet weld weight = Volume X density of steel Fillet weld weight = .59 X .283 = .17 lb

To find the weight of an equal leg fillet weld we need

to find the Cross Section Area “CSA”, the length of

the weld and the density of the metal. If we take the

drawing 1 as an example and we suppose it’s a mild

steel, flat face, the following steps is how to calculate

the weight of the weld

To find out the CSA for any triangle we have to know

the length of the base and the height of the triangle

and divided by two. The mathematical formula for

the triangle CSA is.

Fillet weld CSA = .5 X Base X Height

After calculating the CSA, we can calculate the

volume of the weld by multiplying the CSA by the

length of the weld.

Fillet weld Volume = CSA X Length of weld

Finally, to find the weight of the weld we should

multiply the volume by the density that will give us

the weight of the weld.

Fillet weld weight = Volume X density of metal

The weight of the fillet weld is

0.17 lb


Example 2

If we take example 1 and we add reinforcement as

showing in the drawing. Then we need to calculate the

reinforcement separately and then add the flat fillet to

the reinforcement to get the total weld weight.

To calculate the reinforcement we need to calculate the

Face Dimension ”FD” first, we can apply Pythagoras'

Theorem law to get the FD and then we can calculate

the reinforcement CSA.

As we calculated in the first example the weight of the

flat fillet weld is 0.17lb. So we will pursue to calculate

the reinforcement and add the total weight for the weld.

Pythagoras' Theorem

Face Dimension FD= √

FD=√ = .44 in

CSA Convexity = .5 X FD X reinforcement

CSA Convexity = .44 X .125 X .5 = .03 in²

Volume of convexity = CSA X Length

Volume of convexity = .03 X 12 = .36 in³

Weight of convexity = Volume X Density

Weight of convexity = .36 X .283 = .1 lb

Total weight of the weld = weight of fillet weld + weight of reinforcement

Total weight of the weld = 0.17 + 0.1 = 0.27lbs


Example 3

To calculate the weld weight in a single bevel pipe we can divide the

weld into three areas as showing in the third drawing. The root

opening and the thickness of the material will be area 1, the bevels will

be area 2, and the reinforcement will be area 3. First we calculate the

Cross Sectional Area for all three areas.

-CSA1 is basically rectangle where the area is the width by the height

CSA1 = root opening X thickness

CSA1 = .125” X .625 = .08 in²

-CSA2 is two triangles where the area is (.5 X the height X base). We

can calculate the height by subtracting the thickness from the root

face. To calculate the base which is the side opposite in the triangle we

can use TAN the height or the side adjacent.

CSA2 = thickness - root face X {(thickness – root face) X tan (

)} X .5 X 2

CSA2 = .625 - .125 X {(.625 - .125) X tan 30} X .5 X 2 = .15 in²

-CSA3 to calculate the reinforcement area we have to calculate the

face dimension first and that by calculating the side opposite and

multiply it by 2 and add the root opening to it.

Face Dimension = (side opposite X number of bevel) + root opening

Face Dimension = (.5 X tan 30 X 2) + .125 =.685 in

CSA3 = Face Dimension X Reinforcement X .5

CSA3 = .685 X .125 X .5 = .04 in²

We add the CSAs to get the total area of the weld

∑ CSA = CSA1 +CSA2 + CSA3 = .08 + .15 + .04 = .27 in²

Finally to calculate the weight we need to calculate the length of the

weld. Since it’s a pipe we need to calculate the circumstance which

(𝝅 X Diameter) then we multiplying it by the density of the steel which

is .283 lbs/in³.

Weight of the weld = CSA X (𝝅 X Diameter) X density

Weight of the weld = .27 X (.3142 X 6”) X .283 = 1.4 lbs


Example 4

To calculate the weight of the weld in double v groove basically solve

for single V and then divided by two.

Given:

V groove weld both side plate thickness = .625”

Total root face = .125” , root opening = .067”

Included angle = 75 degree , con vex reinforcement = .067”

Consumable density= .1 lbs/in³, weld length=14”

Solution

Total CSA of the weld

CSA1 = Root Opening X thickness = .067 X .625 = .042 in

FD= Tan (37.5) X (T/2 – Root Face/2) = .767 X ( .3125 - .0625)= .192

CSA2 =.5 X .192 X .25 = 025 in² X 4 = .096 in²

CSA3 = .5 X Face Dimension X Reinforcement

CSA3 = .5 X ( .192 + .067 + .192 ) X .067 = .015 in² X(2) = .03 in²

Total volume of the weld

V= CSA X Length = .168 X 14 = 2.35 in³

Total weld weight = Volume X Density

Total weld weight =2.35 X.1 = .235 lbs


Weld Cost

To calculate the cost for any process we need to find some given information. Same in the welding

process to find the cost of welding we need to know some essential information before we can proceed

to calculate our cost. The cost of weld will be calculated into two ways. First we can calculate the cost

per foot of weld and that will give us good understanding in estimating the cost for big project such as in

construction. Second the calculation of weld per part which can be used in manufacturing a smaller part.

The essential information could be calculated or measured in the work floor. Such as the weld time, the

time spent to load or unload or idle time, travel speed, labor cost, gas cost and consumable cost and so

on. For better understanding we will solve an example.

Example 1:

Find the cost of the welding process per foot and per part. Use the given information below.

Travel Speed (S) = 24 IPM, Fillet Weld Leg Size (LS) = 7/16, Consumable Cost (W) =65 ¢/lb

Idle Time (T) = 120 sec, Labor Cost (L) = 40 $/HR, Welding Length (WL) = 20”, Gas Cost = 3.5 $/HR

Consumable Density (D) = .283 lbs/in³,Process Efficiency (E.2) = .95, Process: GMAW

ANSWER

Welding Time (WT) =

= 50 Sec

Operation Factor (OF) =

Total Time (TT) = WT + T = 50 + 120 = 170 Sec

Welding Volume = .5 X LS X LS X Weld Length = .5 X .4375 X .4375 X 12 = 1.15 in³/ft

Weld weight (J) = WV X D = 1.15 X .283 = .33 lbs/ft

Consumable Cost/foot (CC) =

= 22.2 ¢/ft

Labor and Overhead (LEO) =

Gas Cost (GC) =

= 2.9 ¢/ft

Process Weld Cost per Foot

PWCF = (115 + 22 + 3) = 140 ¢/ft

Process Weld Cost Per Part

PWCP =(

) X PWCF =

(140) = 233 ¢/part OR 2.33 $/part

WELDING Handbook - · PDF fileAlhuzaim- Metallurgy Page 1 WELDING Handbook By: Abdullah...

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