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Tohoku Steel Co., Ltd.
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Heat-resistant Steel

Tohoku Steel boasts the largest domestic share of the engine valve heat-resistant steel market, and producing very reliable, high-quality, heat-resistant steel.

Heat-resistant steel for suction valves

Steel name and composition summary

Steel Name C Si Cr Mo
SUH1 0.45 3 8
SUH3 0.40 2 11 1
SUH11 0.50 1.5 8

〔mass%〕


Physical property

Density
〔g/cm3
Coefficient of thermal expansion
〔X10-6/℃〕
Thermal conductivity
〔W/m・K〕
Electrical resistance
〔μΩ・㎝〕
SUH1 7.70 20-600℃ 12.5 20℃ 16.7
800℃ 23
20℃ 79
SUH3 7.65 20-800℃ 12.2 20℃ 15.2
800℃ 22.7
20℃ 84
SUH11 7.70 20-600℃ 13.4 20℃ 25 20℃ 73

Heat treatment temperature condition

Quenching Tempering
SUH1 980~1080℃, oil quenching 700~850℃, air cooling
SUH3 980~1080℃, oil quenching 700~800℃, air cooling
SUH11 1000~1050℃, oil quenching 650~750℃, air cooling

High temperature mechanical properties

Heat treatment of test specimen

SUH1:1030℃,OQ/750℃,AC,SUH3:1050℃,OQ/750℃,AC
SUH11:1030℃,OQ/750℃,AC


Tempering temperature and normal temperature hardness


Heat-resistant steel for exhaust valves (iron-base)

Composition summary

Steel Name Mn Ni Cr
21-2N 0.5 8 2 20 0.3
SUH35 0.5 9 3.5 21 0.4
23-8N 0.3 2 8 23 0.3

Physical property

Density
〔g/cm3
Coefficient of thermal expansion
〔X10-6/℃〕
Thermal conductivity

〔W/m・K〕
Electrical resistance
〔μΩ・㎝〕
21-2N 7.73 20-400℃ 16.5
20-760℃ 18.4
20℃ 18.0 20℃ 79
SUH35 7.75 20-500℃ 17.5
20-760℃ 18.4
20℃ 18.0 20℃ 75
23-8N 7.85 20-500℃ 17.8
20-800℃ 19.5
20℃ 18.0 20℃ 75

Condition of heat treatment temperature

Solution treatment Aging treatment
21-2N 1100~1150℃, rapid cooling 730~780℃, air cooling
SUH35 1100~1200℃, rapid cooling 730~780℃, air cooling
23-8N 1100~1180℃, rapid cooling 750~800℃, air cooling

High temperature mechanical properties

Heat treatment of test specimen

21-2N:1100℃,WQ/750℃,AC,SUH35:1100℃,WQ/750℃,AC
23-8N:1100℃,WQ/800℃,AC


High temperature corrosion resistance


Heat-resistant steel for exhaust valves (high alloy)

Composition summary

Steel Name Ni Cr Fe Al Ti Other added elements
NCF751* ≧70 15 6 1 2.5 Nb+Ta
NCF80A* Bal 20 ≦1.5 1.5 2

Physical property

Density
〔g/cm3
Coefficient of thermal expansion
〔X10-6/℃〕
Thermal conductivity
〔W/m・K〕
Electrical resistance
〔μΩ・㎝〕
NCF751* 8.24 20-760℃ 14.9
20-820℃ 16.6
20℃ 13.6
800℃ 31.4
20℃ 121.5
NCF80A* 8.17 20-760℃ 14.9
20-800℃ 19.5
20℃ 11.0
800℃ 29.5
20℃ 124

Condition of heat treatment

Solution treatment Aging treatment
NCF751* 1100~1150℃, rapid cooling 800~830℃, air cooling
690~720℃, rapid cooling
NCF80A* 1120~1150℃, rapid cooling 730~780℃, air cooling


Reference condition

Reference condition

High temperature mechanical properties

Heat treatment of test specimen

NCF751*:1100℃,WQ/850℃,AC/710℃,AC
NCF80A*:1050℃,WQ/700℃,AC


High temperature corrosion resistance

*NCF751is equivalent of Inconel 751.
*NCF80A is equivalent ofNimonic 80A.
*Inconel and Nimonic is the registered trade make of Special Metals Corporation.
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