What is the difference between 440B and 440C?

What is 440B stainless steel?

440B stainless steel is a high-carbon, martensitic stainless steel that achieves high hardness and excellent wear resistance through heat treatment, making it suitable for cutting tools like knife blades, surgical instruments, and valve components. While it offers good corrosion resistance for a high-carbon grade, its properties provide a balance between hardness, toughness, and wear resistance, with a carbon content between 440A and 440C stainless steels.

What is 440c stainless steel?

440C stainless steel is a high-carbon, chromium-based martensitic stainless steel celebrated for its high hardness and wear resistance after heat treatment, making it ideal for applications like knife blades, bearings, and surgical instruments. It achieves the highest hardness of the 400 series stainless steels, providing excellent strength and durability despite its moderate corrosion resistance.

 

 

 

The primary difference between 440B and 440C stainless steel lies in their carbon content, which directly impacts their hardness and wear resistance. 440C has a higher carbon content (0.95-1.20%), resulting in the highest hardness and wear resistance. In contrast, 440B has a lower carbon content (0.75-0.95%), resulting in slightly lower hardness and wear resistance, but improved corrosion resistance.

 

Chemical Composition (wt%)

Grade	C (Carbon)	Cr (Chromium)	Mn (Manganese)	Si (Silicon)	Mo (Molybdenum)	P (Phosphorus)	S (Sulfur)	Ni (Nickel)
440B	0.75 – 0.95	16.0 – 18.0	≤ 1.0	≤ 1.0	≤ 0.75	≤ 0.040	≤ 0.030	≤ 0.75
440C	0.95 – 1.20	16.0 – 18.0	≤ 1.0	≤ 1.0	≤ 0.75	≤ 0.040	≤ 0.030	≤ 0.75

 

Mechanical Properties (Typical, Hardened and Tempered)

Property	440B	440C
Hardness (HRC)	55 – 58	58 – 60
Tensile Strength (MPa)	~ 1,900 – 2,000	~ 1,900 – 2,100
Yield Strength (MPa)	~ 1,400 – 1,450	~ 1,450 – 1,500
Elongation (%)	1.5 – 2	1 – 1.5
Density (g/cm³)	7.75	7.75

 

440B vs. 440C Stainless Steel: Corrosion Resistance

440B generally offers slightly better corrosion resistance than 440C due to its lower carbon content, which means more free chromium is available to form protective passive layers. However, both grades provide only moderate corrosion resistance compared to other stainless steels like 304 or 316 and are susceptible to corrosion in chloride-rich or highly corrosive environments. The primary difference is the carbon content, with 440B having a lower level (0.75-0.95%) than 440C (0.95-1.20%), which impacts hardness and wear resistance rather than corrosion resistance.

 

440B vs. 440C Stainless Steel: Hardness

440C stainless steel achieves a significantly higher hardness than 440B after heat treatment, with 440C reaching Rockwell C 58-62 compared to 440B's potential up to 58 HRC, primarily due to its higher carbon content.

 

What is the difference between 440A and 440B steel?
Grade 440A and 440B stainless steels, on the other hand, have comparable properties - with the exception of slightly lower percentage of carbon in grade 440A. Each of the three types of grade 440 stainless steelsis ordinarily utilized. So, grade 440C is more promptly available than the other standard grades.