Founded in 1879, A. Finkl & Sons has grown to be one of the most recognized names in specialty steelmaking, making the “Diamond F” company logo an international icon for high quality mold steel. A full range of alloys is offered to serve the varied tooling demands of the plastics molding industry.

MOLD STEELHIGH QUALITY STEEL FOR THE PLASTICS INDUSTRY

SURFACE SPEED, Feet/Min (Meters/Min)

24 (248) 28 (269) 31 (293) 34 (321) 38 (352)

280 (85) 250 (76) 220 (67) 190 (58) 165 (50)

Suggested Cutter Speed for MD (P20) Steel

STANDARD MOLD STEEL GRADES

Mold Quality steel is melted in a sequence of steps including an Electric Arc Furnace (EAF), Ladle Metallurgy Furnace (LMF) and Vacuum Argon Degassing (VAD) facility. The high quality steel reached through this process is preserved by teeming into “Bottom Poured” molds to guard the molten steel against re-oxidation from atmospheric oxygen.

Ingots are forged using high-capacity presses with Wide-Die techniques to provide maximum consolidation and effective microstructural refinement to provide the most machinable, highest quality mold steel. Mold Quality steel is appropriate for most molding applications, but VAR steel is recommended where diamond (SPI Class A) finishes are specified.

The Machinability Index (MI) referenced in the above table may be used to arrive at an approximate cutting speed (Surface Feet per Minute, or SFPM) for the listed grades using the relationship: V = VP20 x MI. Where VP20 is the cutting speed (SFPM) usually employed for Finkl MD or standard P20. The following table lists common cutting speeds for MD using High Speed cutters:

MACHINING

*DI is a theoretically calculated value, based upon the chemistry of the steel, expressing the maximum diameter (in inches) that is through-hardenable with vigorous water quenching. An extremely high DI (e.g. 50+) indicates air-hardening capability, depending upon size and gas pressure employed.

Strict metallurgical control of critical procedures in melting, forging and heat treating offers confidence for meeting the most challenging molding applications.

1.20 (28 HRC)

1.40 (28 HRC)

1.00 (30 HRC)

0.95 (36 HRC)

0.95 (Annealed)

0.85 (Annealed)

27-33 262-311

25-32 255-302

29-34 277-321

36-39 331-363

24 max 248 max

24 max 248 max

5.5

5.5

13.6

13.6

50.0+

50.0+

Fair

Poor

Very Good

Very Good

Very Good

Very Good

HARDNESS MACHINABILITY GRADE DESCRIPTION HRC, BHN DI* INDEX (MI) POLISHABILITY

HARDNESS LEVEL, Rockwell C (Brinell)

4140

HB

MD

P20HH

DC

420M

Lower alloy than MD (P20mod). Suitable for low volume production, holders or non-critical mold surfaces.

Resulfurized (0.080% S) for improved machinability. Suitable for holders or non-critical molding surfaces.

P20mod. Nickel added to standard P20 composition for improved microstructure and polishability. Appropriate for most molding applications.

Finkl MD (P20mod) heat treated to higher hardness for improved polishability and durability.

AISI H13. Dense carbide content for excellent wear resistance in high volume production. Typically sold annealed for post-machining hardening to about 46 HRC.

Type 420 Stainless Steel (12% Cr) modified with 0.50% Mo for improved heat-treating response and enhanced resistance to a form of corrosion termed “sensitization”. Typically sold annealed for post-machining hardening to about 46 HRC.

VACUUM ARC REMELTED (VAR) STEEL

VAR steel is produced by progressively remelting an electrode prepared from an appropriately sized VAD ingot. The electrode, much like a large welding rod, is consumed over approximately a 20 hour period, under a deep vacuum, into a water-cooled mold to promote rapid solidification. The resulting improvement to alloy distribution, reduction of non-metallic inclusions and refined grain size significantly improves polishability. VAR steel is an appropriate choice whenever an SPI Class 1 surface finish is specified, or whenever superior polishability must be assured.

Mold polishing procedure is a major factor in determining the level of success in mold polishing, but underlying any effort is an appropriate matching of the specified finish to the basic quality level of the steel. The following chart suggests a general quality level for different categories of specified surface finishes

MOLD POLISHING

ASTM E 45 ASTM E 45 ASTM E 45 Rating 1.0 Rating 2.0 Rating 3.0

SPI Class A Diamond Buff

SPI Class B Paper Finish

SPI Class C Stone Finish

EAF

Mold Quality

VAR Lens Quality

ReSulfurized Steel

Decreasing Level of Non-Metallic Inclusions and alloy segregation

Application Guide

*Standard DI calculations are not applicable (NA) to Precipitation Hardening steel.

HARDNESS MACHINABILITY GRADE DESCRIPTION HRC, BHN DI INDEX (MI) POLISHABILITY

MD alloy further refined by Vacuum Arc Remelting for improved polishability. Provided pre-hardened at 36-39 HRC.

AISI H13 + Metallurgical benefits of Vacuum Arc Remelting for better carbide dispersion and improved polishability. Typically supplied annealed for post- machining hardening to about 46 HRC.

420M Vacuum Arc Remelted for improved Chromium distribution and polishability. Typically supplied annealed for post-machining hardening to about 46 HRC.

15-5PH steel. Age-hardening with good corrosion resistance (15% Cr), and superior polishability. Sold overaged for dimensional stability. Excellent weldability.

MLQ

DC-XTRA

420LQ

MAR-X

0.90 (36 HRC)

1.10 (Annealed)

1.10 (Annealed)

0.75 (Age-Hardened)

36-39 331-363

24 max 248 max

24 max 248 max

40 approx 375 approx

Excellent

Excellent

Excellent

Excellent

13.6

50+

50+

NA*

Flame Corrosion Grade of Steel Texturing Nitriding Machining Welding Polishing Carburizing Hardening Resistance

G

P

G

G

F

F

G

G

G

E

P

P

F

F

VG

VG

F

VG

VG

VG

VG

E

G

G

F

F

G

F

F

P

G

F

G

G

P

P

G

P

P

E

F

P

VG

VG

VG

VG

E

E

E

E

G

G

VG

VG

E

E

VG

E

E

VP

P

P

F

F

VG

E

F

VG

E

E

G

G

G

G

P

P

G

P

P

G

4140

HB

MD

P20HH

DC

420M

MLQ

DC-XTRA

420MLQ

MAR-X

Summary of Properties for Grade Selection

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E = Excellent

VG = Very Good

G = Good

F = Fair

P = Poor

VP = Very Poor

Standard Hardness Grade AISI/SAE C Mn Si Ni Cr Mo Other Rockwell C

4140

4138+S

P20mod

P20mod

H13

SS 420mod

P20mod (VAR)

H13 (VAR)

SS 420mod (VAR)

15-5 PH (VAR)

0.40

0.38

0.33

0.33

0.40

0.35

0.33

0.40

0.35

0.05

0.90

1.15

0.80

0.80

0.35

0.30

0.80

0.35

0.30

0.50

0.25

0.25

0.45

0.45

1.00

0.35

0.45

1.00

0.35

0.50

0.95

0.70

1.80

1.80

5.25

13.00

1.80

5.25

13.00

14.75

0.20

0.20

0.50

0.50

1.50

0.45

0.50

1.50

0.45

*

*

*

0.45

0.45

*

*

0.45

*

*

4.50

30

30

30

36

Annealed

Annealed

36

Annealed

Annealed

38, Overaged

0.080% Sulfur

Ni added

Ni added

1.00% Vanadium

Mo modified

Ni added

1.00% Vandium

Mo modified

3.50% Copper

4140

HB

MD

P20HH

DC

420M

MLQ

DC-XTRA

420MLQ

MAR-X

Mold Steel Nominal Analyses

Additional information on A. Finkl & Sons Co. mold steel grades and manufacturing processes are provided in the Mold Steel Handbook. The book is available through your Finkl Sales Representative.

*Denotes none added. Minor residual amount may be present.