24 July 2021 400 Series Stainless Steel
440 Stainless Steel Plate
Grade 440C stainless steels are high carbon steels, which attain the highest hardness, wear resistance and strength of all stainless steel grades after heat treatment. These properties make this grade suitable for applications such as valve components and ball bearings. Grade 440A and 440B stainless steels, on the other hand, have similar properties - except for a slightly lower percentage of carbon in grade 440A.
All three forms of grade 440 steel are commonly used. However, grade 440C is more readily available than the other standard grades. Grade 440F, a free-machining type of grade 440 series, is also available with a high carbon content similar to that of grade 440C. Martensitic steel grades are high-hardness steels, usually fabricated using techniques that require hardening and tempering treatments.
These grades have a corrosion resistance lower than that of other austenitic grades. The applications of martensitic steels are limited by the loss of strength caused by over-tempering at high temperatures and loss of ductility at temperatures below zero.
Chemical Composition:
C: 0.95～1.20
Si: ≤1.00
Mn: ≤1.00
S: ≤0.030
P: ≤0.035
Cr: 16.00～18.00
Ni: ≤0.60
Mechanical Properties:
Internal stress (250 N/mm2)
Tensile strength (560 N/mm2)
EL(18%) HB(250)
Hardness: Annealed, ≤269HB;
Quenching and tempering, ≥58HRC
Heat treatment process:
- Annealing, slow cooling at 800～920℃;
- Quenching, 1010～1070℃ oil cooling;
- Tempering, fast cooling at 100～180℃.
- Preheating temperature, 649°C-816°C.
Application:
Mainly used for manufacturing bearing parts that work in corrosive environment and non-lubricated strong oxidizing atmosphere. 440 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. 440F: It is a steel grade that improves the easy-cutting performance of 440C steel. It is used in automatic lathes and ordinary alloy steels. It has the characteristics of hardening through quenching. Therefore, a wide range of different mechanical properties can be obtained by selecting grades and heat treatment conditions. 440C has a lower ability to withstand dynamic loads.