Additional Info
A Brief History of 440B Stainless Steel
440B stainless steel, also known as AISI 440B, SAE 440B, UNS S44003, EN 1.4112, X90CrMoV18 or JIS SUS440B, is a high-carbon grade within the 400 series of martensitic stainless steels.
Within the 440 series, the performance profile of 440B is quite distinct: it lies between 440A and 440C. Compared to 440A, 440B has a higher carbon content, enabling it to achieve superior hardness and wear resistance following heat treatment; compared to 440C, 440B typically has a slightly lower maximum hardness, but in some applications, it offers a better balance between toughness, corrosion resistance and machinability.
In terms of composition, 440B typically has a carbon content of 0.75–0.95% and a chromium content of 16.0–18.0%. This composition makes it suitable for components requiring high hardness, edge retention, wear resistance and a certain degree of corrosion resistance.
How was the 440B developed
440B was developed primarily to bridge the performance gap between 440A and 440C. For certain components, the hardness and wear resistance of 440A may be insufficient, whilst the maximum hardness of 440C is not essential. In such cases, 440B offers a more balanced option.
By increasing the carbon content, 440B offers superior hardenability and wear resistance compared to 440A. At the same time, the higher chromium content allows it to maintain the corrosion resistance expected of stainless steel in moderately corrosive environments.
Following appropriate quenching and tempering, 440B typically achieves high hardness, with a maximum hardness approaching RC 58. Actual hardness is influenced by heat treatment processes, material cross-sectional dimensions and product specifications. Consequently, in cutting tools, wear-resistant components and precision parts, 440B is frequently used in applications requiring a combination of hardness, dimensional stability and a certain degree of toughness.
Early applications of 440B
Early applications of 440B were primarily focused on components requiring both hardness and corrosion resistance, such as cutting tools, surgical instruments, precision mechanical parts, bearing-related components and wear-resistant hardware.
Such components typically need to withstand friction, repetitive contact or certain corrosive environments. The balance between hardness and toughness in 440B makes it more suitable than 440A for some applications with higher wear resistance requirements, whilst not necessarily requiring the use of higher-hardness grades such as 440C.
For manufacturers, the value of 440B lies not merely in being ‘harder’, but in providing more reasonable overall performance in suitable applications.
Current applications of 440B
Today, 440B stainless steel continues to be used in projects requiring high hardness, wear resistance and moderate corrosion resistance. It is particularly well-suited to components that do not necessarily require the highest hardness, but demand consistent machining performance and reliable service life.
Common application areas include:
Medical: Surgical instruments, cutting tools, dental instruments, blades, scissors and precision medical components.
Aerospace: Precision mechanical parts, bearing components, shaft components, small wear-resistant parts and high-hardness fasteners.
Mechanical Engineering: Bearings, valve components, pump parts, tooling components, pins, shaft components and precision machined parts.
Industrial Applications: Cutting tools, nozzles, hardened steel balls, valve seats, wear-resistant parts and other components requiring good hardness and wear resistance.
When a project requires better wear resistance than 440A but does not necessarily require the maximum hardness of 440C, 440B is a material option worth considering.
Sunxin’s 440B stainless steel supply support
Sunxin supplies 440B stainless steel to customers in the medical, aerospace, mechanical engineering and industrial sectors for projects requiring high-hardness martensitic stainless steel.
The material is available under common designations such as AISI 440B, SAE 440B, UNS S44003, EN 1.4112, X90CrMoV18 and JIS SUS440B, facilitating material verification by customers according to different standards systems.
Available forms include bars, plates, tubes, wire and custom cut sizes. Delivery conditions, hardness ranges, dimensional specifications, tolerances, surface finishes and quality documentation can be confirmed in accordance with specific application requirements.
For projects requiring material verification, Sunxin can assist in arranging chemical composition analysis, hardness testing, mechanical property testing, heat treatment condition verification and related quality support prior to machining, production or end use.
Whether you require 440B stainless steel for surgical instruments, precision components, bearings, tooling parts or wear-resistant applications, Sunxin can help you match the appropriate material form, delivery condition and specifications to your project requirements.
