Slide 1

1 All photos: Stahl-Zentrum, Dsseldorf 07/2013, Rev. A3 Infrared Temperature Measurement for the Steel Making Process Confidential

Slide 2

2 Basics - Emissivity Typical emissivities of metals < 0.5! Emissivity increases with shorter wavelength, roughness, and layers (oxidation, oil, color) Steel with oxidized surface: 0.8 to 0.85 Emissivity decreases with polishing due to higher reflection

Slide 3

Confidential 3 Environment Flames Natural gas fire burns with clean blue flames highly transparent for many IR wavelengths but avoid the absorption bands of carbon dioxide and water vapor produced by gas flames use one color pyrometer Oil/fuel/coal fire burns with dirty yellow flames highly opaque due to carbon black high emissions! use two color pyrometer

Slide 4

Confidential 4 Environment Water Water, liquid: transparent at 1.0 m only (water drop roughly 1.000 times bigger than a water molecule) Water Steam: dedicated absorption bands depending on path length and temperature Vollmer, Mllmann Infrared Thermal Imaging Wavelength (m) Transmission Water 1 mm 1 m 10 m 100 m

Slide 5

5 Overview OreSinter Blast Furnace Continuous Caster Hot Rolling Mill Coke Pig IronSlab Coil Preparation

Slide 6

6 Sinter Plant Rough mix powder of milled iron-ore, coke and lime ignited at 800C (1472 F) Air is pulled through this mix to cook the sinter evenly. This allows the right burning and ventilation in the blast furnace.

Slide 7

7 Sinter Plant Fines Ignition Control Ignition vs. Conveyor Speed Multiple Sensors or Scanner Coal + Iron Ore Breaker/Cooler Fall Control Burning-through Check the belt spaces for clogging (air suction!) Linescanner, Thermal Camera Very dusty environment! Suction Sinter Cake

Slide 8

8 Sinter Plant - Ignition Linescanner Sinter Bed Ignition Hood up to 6 m / 236 in up to 350 mm / 13.8 in

Slide 9

9 Sinter Plant Fall Control Click for Playing Sinter Cake Photo: Frank Schdlich

Slide 10

10 Sinter Plant Ring Cooler Very dusty environment! Monitoring cooling with a linescanner

Slide 11

11 Pelletizing Click for Playing similar to the sinter process Ore + water + binding agents mixed in drums, plus stepwise firing to bake pellets Benefits of pellets: - uniform size - high strength and purity - transportable

Slide 12

12 Coke Plant - Chamber 900 to 1400C (1652 to 2552 F) 24 h coke baking process Heating and degasing the coke for cleaner burning Coke temperature corresponds to its quality Installations: a) on top at chamber roof b) from the side looking through holes in the pusher guide Pusher Wagon Chambers 3 pyrometers each side vertically installed at 10m (33ft) distance looking through 100mm (4in) holes Top View

Slide 13

13 Coke Plant - Quenching Hot spots of several hundred degrees Extinguish hot spots with a minimum quantity of water to ensure high coke quality Avoid damage from the conveyor belt Multiple linescanners installed along the long wharf Monitoring while dumping the coke Linescanner Photos: Corus

Slide 14

14 Point Sensor Coke Plant Conveyor Detection of remaining hot spots to avoid damage on the rubber conveyor belt Extremely dusty environment Defocused optics allows coverage of entire conveyor width (D:S < 2:1) Controlling the cooling sprayers Hot Spot Cooling Spray

Slide 15

15 Coke Plant Conveyor Hot Spot, 500C/932F Measured Spot Use shortest possible wavelength for maximized hot spot sensitivity! 50C/122 F

Slide 16

16 Blast Furnace Iron Ore Coke Coke Layer Pellet Layer Slag Raw Iron 1450C (2642F) Air Heater (Cowper) Air Feed Flue Gas Smoke Outlet Iron Ore Iron

Slide 17

17 Blast Furnace Up to 6 Stove Domes per mill Bricks at 1300 to 1350C (2372 to 2462F) Tapping Hole Tuyere introducing fuel to the furnace

Slide 18

18 Stove Dome Pre-heating the feeding air Preventing overheating and damage to refractory bricks Very high pressure inside with up to 6 bar Ratio pyrometer with Quartz window, shutter, air purge and isolation ball valve Pyrometer Quartz window Ball valve Refractory honeycomb

Slide 19

19 Tuyeres Monitoring via pan/tilt linescanner (system and photo by Selmatec) Ring-shaped die for feeding the blast furnace with hot air Measuring through the tuyeres inside to get the flame temperature (2200C/3992 F ) to control the fuel Early detection of die blockages due to pulverized coal no risk of explosions View Port Standard glass to be exchanged with Quartz! Too high temperature indicates die with isolating problem [twyer]

Slide 20

20 Tuyeres Typically 4 ratio sensors installed on each 90 Fuel saving Blockage detection via attenuation alarm Water leak detection Process temperature controls furnace efficiency Wall Inside Furnace Pyrometer Die Hot Air Cooling

Slide 21

21 Tapping Hole Measuring the molten iron (1450C/2462 F ) at the tapping hole to get information about the inside temperature A lot of slag at that location! Better measurements during torpedo car loading (slag already removed) Alternative: IR sensor with closed-end sighting tube dipped into the molten iron Sensor with closed- end sighting tube

Slide 22

22 Torpedo Car Measuring iron pouring during loading and unloading to calculate temperature losses Monitoring the outside refractory temperature to check for wear and cracks Extends the refractory life time Avoids accidents and production stops due to hot breakouts Refractory monitoring ideally with automatic car identification via software pattern recognition for trending analysis

Slide 23

23 Ladle Measuring iron pouring during loading and unloading to calculate temperature losses Monitoring the outside refractory temperature to check for wear and cracks Extends the refractory life Avoids accidents/production stops due to breakouts Linescanner for moving ladle Camera for pausing ladle

Slide 24

24 Pre-Heating Pre-heating required to avoid damage to the refractory caused by thermal shock from the molten metal Checking temperatures for fuel saving Big burner flame! 1-color or 2-color pyrometer triggered with burner sequence Torpedo Car Ladle Burner ON Trigger BurnerPyrometer

Slide 25

25 Graphics by Tosaka, Wikipedia Continuous Caster Casting at 1450 to 1550C (2462 to 2822 F) Tundish completely enclosed Control cooling to ensure uniformity and avoid breakouts from liquid inner Steel quality directly affected by cooling rate Detection of clogged water spray nozzles Final slab: up to 12m long, 2m wide, 0.2m thick (40ft x 6.5 ft x 8in) Ladles Tundish Straight Mold Stopper Burner Water Sprayer Nozzle Control Crack Detection Tundish pre-heating Cooling Control Torch Cutting

Slide 26

26 Caster: Crack Detection Linescanner provides temperature profiles for process uniformity Hot spot and crack detection require high number of pixels and high optical resolution Spot/crack: missing scale unwanted atmospheric corrosions Through-slit measurement Dedicated cooling required

Slide 27

27 Slab Cutting Providing steel temperature just before cutting Automatic torch control for clean cut and energy savings Sensor with integrated video camera recommended ( MM) Torch

Slide 28

28 Hot Rolling Mill Reducing thickness from 200mm down to 3mm (8in to 1/8in)

Slide 29

29 Scale Breaker Scale removal with high pressure water jets very steamy environment Use of short wavelength 1C/2C pyrometers as switch for slab detection due to transparency of the steam significant advantages over switches in visual range Alternative scale removals: pickling, flame cleaning

Slide 30

30 Reheat Furnace Entrance Burner control depending on hot or cold slabs Exit Burner adjustments depending on temperature profile Heating Check furnace load temperature Sensor installed 1m/39in) above the ceiling to avoid water cooling Photo: Stahl-Zentrum, Dsseldorf

Slide 31

31 Reheat Furnace Entrance: 20 to 1000C 68 to 1832F Getting cold slabs or hot slabs directly from the caster Surface oxidization provides emissivities in the range of 0.85 Preheating: 20 to 600C 68 to 1112F Heating: 600 to 1200C 1112 to 2192F Soaking: 1100 to 1300C 2012 to 2372F Furnace Zones Exit: 1100 to 1300C / 2012 to 2372F Scale created during the heating cools down relatively fast on exposure to air, making further measurements difficult Big temperature differences between slab and wall and reflections of 15% (1 0.85) require ambient background compensation! Top View

Slide 32

32 Slab Scale Scale: iron oxide, < 1 mm thick, protecting steel from atmospheric corrosion 2C pyrometers cannot sufficiently compensate for the colder scale, causing temperature readings that are too low Use 1C pyrometer with smaller spot (higher D:S ratio) and signal processing set to or measure just after the scale breaker Colder scale 1C pyrometer: true temperature 2C pyrometer: averaged temperature

Slide 33

33 Colder Area / Measured Spot [%] T Steel =1000C T Scale 1 m Colder Area (scale) Measured Spot Hotter Area (steel) Slab Scale

Slide 34

34 Furnaces Piling up effect Pyrometer works as switch to avoid piling up of slabs Response time down to ms with fast quantum detectors Avoiding furnace damage Verifying roller settings Front View

Slide 35

35 Rough Stand Adjust rough stands to match the steels temperature (e.g. after shutdowns) 3 to 4 rough stands per mill Relatively clean steel surface with thin oxide layer with emissivities of 0.8 to 0.85 2C pyrometer can be effected by water vapor more than 1C pyrometer! Scale Breaker scale removal with water jets Rough Stand 1000 - 1200C (1832 - 2192 F) Reversing for a thickness down to 40 mm/1.6in

Slide 36

36 Rough Stand Less remaining water spots, scale has fallen off Opening to be made in the protection plate Sensor installed 500mm/20in) under the plate Use a sighting tube with angled cut Difficult environment with hot temperatures and permanent water Protection plate between rolls Fiber optic sensor Under Strip Measurements

Slide 37

37 Finishing Stand Thickness down to 3mm (1/8in) Adjust finishing stands to match the steel temperature (e.g. after shutdowns) 5 to 7 stands per mill Steel surface slightly oxidized for emissivities of 0.8 to 0.85 Use 1 m sensors to exclude errors due to remaining water spots Finishing Stand 1000 - 1200C (1832 - 2192 F)

Slide 38

38 Cooling Cooling Section 60 to 120 m 196.9 to 393.7 ft Coiling Very important measurement point on the mill! Steel surface slightly oxidized with emissivities of 0.8 to 0.85 Linescanner to ensure a flat temperature profile before entering the cooling section For all sensors not running at 1 m, make sure the strip is properly purged from water (water is opaque > 1.2 m) installation from below >700C >1292F 1 m >400C >752F 1.6 m >300C >572C 2.2 m 1000 - 1200C 1832 2192F 1 m Water or air cooling

Slide 39

39 Cold Rolling Thickness down to 0.3mm (1/8in) Surface quality: flatness & appearance Similar application to hot rolling Forming temperature is 20 to 50C (68 to 122 F) below recrystallization temperature (hot rolling above!) Very reflective surfaces! Photo: Stahl-Zentrum, Dsseldorf

Slide 40

40 Mini Mill Alternative to blast furnaces Melting of scrap steel using electric arc furnaces Too many reflections and smoke inside the furnace, so steel is only measured as it is poured into the ladle Molten steel directly casted, rolled and coiled in one line Casting thicknesses of 20mm (.8in) eliminates the need for roughing the steel Steel being melted by electrodes

Slide 41

41 Thermal Treatment Goals: Change the global metallurgical characteristics: global hardening Change the local metallurgical characteristics On a given area: localized hardening On the surface: carburizing, nitriding (chemical atmosphere, plasma) Reduce the effects of previous actions: annealing, tempering Temperature is very important and must be reached and maintained to: Change internal crystal structure Develop certain forms of carbon Improve chemical reactions

Slide 42

42 Hardening A.Flame Heating, bulk treatment: slow, scale on the surface B.Induction heating of big pieces: can be done in several steps, scale on the surface C.Induction heating of small or medium sized pieces: very fast, can be only superficial depending on the induction frequency, reduced scale 800 to 950C (1472 to 1742 F) Fast Cooling A.B.C.

Slide 43

43 Hardening Oil Tank InsideExit Metallic Conveyor Burners A sensor with ambient background compensation is required. The longer the heating, the more oxidation occurs. Reheat Furnace

Slide 44

44 Annealing Heating a part of the piece to 800 to 1100C/1472 to 2012 F (depending on the alloy), following a specific profile Soaking (maintaining) the temperature for a given time to allow the metallurgical changes Cooling to soften the hardening effect and remove all internal strengths created by previous processes 800 to 1100C

Slide 45

45 Tempering similar to Annealing, but at lower temperatures from 200 to 450C (392 to 842 F)

Slide 46

46 Improved process control and energy efficiency Longer tool life Higher quality products Less production downtime Increased throughput Benefits of Noncontact Temperature Measurement