AISI 440C Stainless Steel | X105CrMo17 | DIN1.4125

AISI 440C, as an American stainless steel grade, has a carbon content of 1% and a chromium content close to 16-18%. It is a high-carbon and high-chromium martensitic stainless steel.As a high-quality stainless steel, after heat treatment, 440C can obtain the highest hardness among all stainless and heat-resistant steels.

440C is mainly used to manufacture bearing parts working in corrosive environment and non-lubricated strong oxidizing atmosphere. 440C has good high temperature dimensional stability, so it can also be used as corrosion resistant high temperature bearing steel. In addition, it can also be used to manufacture high-quality knives, such as medical scalpels, scissors, nozzles, bearings, etc.

WHAT IS AISI 440 SERIES STEEL ?

AISI 440 series steel belongs to high carbon martensitic stainless steel, usually divided into 440A, 440B, 440C as per American standard: ASTM A 959.Due to high carbon content,all of them have high strength, moderate corrosion resistance, good hardness and wear resistance.

AISI 440 Series Steel Chemical Composition

Grade	C	Si	Mn	P	S	Cr	Mo
440A/S44002	0.6-0.75	≤1.0	≤1.0	≤ 0.04	≤ 0.03	16-18	≤0.75
440B/S44003	0.75-0.95	≤1.0	≤1.0	≤ 0.04	≤ 0.03	16-18	≤0.75
440C/S44004	0.95-1.2	≤1.0	≤1.0	≤ 0.04	≤ 0.03	16-18	≤0.75

From the above table,we can see that the carbon content of 440A to 440C gradually increases.After heat treatment, 440C has the highest hardness,usually can reach 60HRC,and don’t worry it still has good toughness.The rust resistance of 440A, 440B and 440C are all good, 440A is the best, and 440C is relatively lowest, but it still has good rust resistance.

AISI 440 series steels belong to the hardest series of stainless steels, it can be said that they are all high quality stainless steels and are usually delivered in the annealed condition.

AISI 440C STEEL EQUIVALENT GRADE

China:108Cr17/11Cr17

Europe:X105CrMo17/1.4125

Japan:SUS440C

AISI 440C STEEL STEEL PHYSICAL PROPERTY

Density, g/cm3	7.78
Melting point,℃	1371-1482
Specific heat capacity，(0~100℃),kj/(kg.k)	0.46
Thermal conductivity W/(m.K)	100℃	500℃
	24	-
Linear expansion coefficient,10^-6/k	0~100℃	0~500℃
	10.2	11.7
Resistivity（20℃),Ω.mm2/m	0.6
Longitudinal modulus of elasticity （20℃)，kN/mm2	200
Magnetic	Magnetic

AISI 440C STEEL FORGING

As a high-carbon high-chromium martensitic stainless steel, AISI 440C should pay attention to the following points in heat forging:

The formation of δ-ferrite should be avoided during forging heating, because the appearance of ferrite will cause cracks in the forging
To avoid overheating the material due to rapid heating
Surface decarburization can cause excessive ferrite formation, so surface decarburization should be minimized.
The initial forging temperature control is generally 1095-1150 ℃
The final forging temperature is generally not lower than 925 ℃
Martensite and carbide structures will appear during air cooling after forging, resulting in large internal stress, so it should be cooled slowly after forging

AISI 440C STEEL HEAT TREATMENT

Interprocess(subcritical temperature) Annealing:675-760℃,Hardness:98HRB-23HRC
Recrystallization(complete) Annealing:845-900℃,Hardness:98HRB-25HRC
Isothermal Annealing:Heating to 845-900℃,Holding 4 hours at temperature 690℃.Hardness<25HRC.
Hardening:1010-1070℃,oil quench
Tempering:100-180℃,fast cooling,Hardness:above 58HRC

AISI 440C STEEL APPLICATION

AISI 440C is a high-chromium martensitic stainless steel with the highest hardness among hardenable stainless steels.In the quenched and tempered condition, it has high strength and hardness, and has both rust and corrosion resistance.

AISI 440C is generally used in the manufacture of tools, shafts, rods, valves, hooks, nozzles and other wear-resistant parts that require corrosion resistance to dilute oxidizing acids, organic acids and salts.