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