Martensitic Stainless Steel
Martensitic stainless steel is a kind of stainless steel, known for its strength, corrosion resistance and durability.
What is Martensitic Steel ?
Martensitic stainless steel is a stainless steel whose mechanical properties can be improved by heat treatment. It is a stainless steel that can be hardened. It has a higher hardness after quenching and has different toughness at different tempering temperatures.
Martensitic stainless steel is often used to make steam turbine blades, tableware, and surgical instruments.
Martensitic Steel Composition
Cr is the main component of martensitic steel. In most martensitic steels, the proportion of Cr varies from 11.5% to 18%, which makes martensitic steel have corrosion resistance.
To ensure the formation of martensitic steel during heat treatment, the higher the Cr content, the higher the C content required. The high content of C gives this type of steel a strong molecular structure.
Martensitic Stainless Steel Grades
Our martensitic stainless steel grades are listed below
Martensitic Steel Types
Martensitic Chromium Steel
The steel contains Cr and a certain amount of C. The content of Cr determines the corrosion resistance of steel alloy, while the content of C determines the strength and hardness of steel alloy. In addition to martensite, there is a small amount of austenite and ferrite in the steel. It is mainly used to make parts with high strength and hardness
Martensitic chromium nickel steel
This kind of alloy steel has low C content (≤ 0.10%) and a certain amount of Ni. Some grades also have higher Mo and Cu contents. This kind of steel has high strength, high toughness, and corrosion resistance. This alloy steel is often used to make structural parts with low corrosion resistance but high strength
Martensitic steel properties
The weldability is poor, and there is a strong tendency of quenching during welding. Cooling in air after welding heating can lead to quenching, which makes the welding gap and heat-affected zone form a hard martensite structure. Under the combined action of the thermal stress caused by temperature difference and the stress of transformation from austenite to martensite, the residual stress after welding is relatively large.
The formability of martensitic stainless steel increases with the decrease of C content
Martensitic stainless steel can be quenched, tempered and annealed as the modulated steel.
Quenching / Tempering / Annealing
With the increase of C content in martensitic stainless steel, the strength and hardness of the steel are improved, and the highest value can reach above RC60. This kind of steel alloy has good wear resistance but poor toughness.
When the hardness increases, the tensile strength and yield strength increase, while the elongation, section shrinkage and impact energy decrease.
Most martensitic steels are magnetic, which makes it easier to classify, but makes it more difficult to weld, anneal, and harden
Compare with other kinds of stainless Steels
Austenitic vs Martensitic steel
Because of the large amount of Ni and Cr, austenitic stainless steel has good plasticity, toughness, weldability and corrosion resistance. It is suitable for making acid resistant and corrosion-resistant instruments and equipment.
Compared with it, martensitic stainless steel has higher strength and hardness. But it plasticity ,weldability and corrosion resistance are pool. It is suitable for making parts with high mechanical properties and general corrosion resistance.
Ferritic vs Martensitic steel
Stainless steel with ferrite chromium content of 12% ~ 30% and ferrite matrix structure in service state; stainless steel with martensitic chromium content not less than 12% and martensitic structure as used state.
Ferrite has the characteristics of high thermal conductivity, small expansion coefficient, good oxidation resistance and stress corrosion resistance; martensite has higher hardness after quenching, and different tempering temperature has different strength and toughness combination.
Martensitic stainless steel applications
- Steam turbine blade
- Nuclear fuel recovery unit
- Surgical instruments
- Auto parts