What Is Martensitic Stainless Steel?

Stainless steel whose mechanical properties can be adjusted by heat treatment, in general, is a type of hardenable stainless steel. Typical grades are Cr13, such as 2Cr13, 3Cr13, 4Cr13 and so on. The hardness after quenching is high, and different tempering temperatures have different combinations of strength and toughness. It is mainly used for steam turbine blades, tableware and surgical instruments. According to the difference in chemical composition, martensitic stainless steel can be divided into two types: martensitic chromium steel and martensitic chromium-nickel steel. According to the different structure and strengthening mechanism, it can also be divided into martensitic stainless steel, martensitic and semi-austenitic (or semi-martensitic) precipitation hardening stainless steel, and maraging stainless steel.

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Martensitic stainless steel can be welded in the state of annealing, hardening and tempering. Regardless of the original state of the steel, after welding, a hardened martensite zone will be produced near the weld bead. The hardness of the heat affected zone is mainly Depends on the carbon content of the base metal. When the hardness increases, the toughness decreases, and this area becomes more prone to cracking, preheating, and controlling the interlayer temperature. It is the most effective method to avoid cracking and is the best The nature requires heat treatment after welding.

Martensitic stainless steel is a type of stainless steel whose performance can be adjusted by heat treatment (quenching, tempering). In popular terms, it is a type of hardenable stainless steel. This characteristic determines that this type of steel must have two basic conditions: first, there must be

Martensitic stainless steels can be divided into two types: martensitic chromium steels and martensitic chromium-nickel steels according to different chemical compositions; according to different structures and strengthening mechanisms, they can be divided into martensitic and semi-austenitic precipitation-hardening stainless steels and Austenitic aging stainless steel.

(1) Martensitic chromium steel. In addition to chromium, steel also contains a certain amount of carbon.

The types of stainless steel can be divided into Cr series (400 series), Cr-Ni series (300 series), Cr-Mn-Ni (200 series) and precipitation hardening series (600 series) according to their composition.

200 seriesCr-Ni-Mn austenitic stainless steel (controversial in food use)

300 serieschrome-nickel austenitic stainless steel

Model 301Good ductility, used for molded products. It can also be hardened by mechanical processing. Good weldability. Abrasion resistance and fatigue strength are better than 304 stainless steel.

Model 302Corrosion resistance is the same as 304, because the carbon content is relatively high and the strength is better.

Model 303It is easier to cut than 304 by adding a small amount of sulfur and phosphorus.

Model 304General model; 18/8 stainless steel. The GB grade is 0Cr18Ni9.

Model 309has better temperature resistance than 304.

Model 316after 304, the second most widely used steel type, mainly used in the food industry and surgical equipment, the addition of molybdenum element to obtain a special structure resistant to corrosion Because it has better resistance to chloride corrosion than 304, it is also used as "marine steel". SS316 is usually used in nuclear fuel recovery equipment. 18/10 grade stainless steel usually also meets this application level. [1]

Model 321Similar to 304 except that the addition of titanium reduces the risk of corrosion of the material's welds.

400 Series-Ferritic and Martensitic Stainless Steel

Model 408Good heat resistance, weak corrosion resistance, 11% Cr, 8% Ni.

Model 410Martensite (high-strength chrome steel), has good wear resistance and poor corrosion resistance.

Model 416The addition of sulfur improves the processability of the material.

Model 420 "blade grade" martensitic steel, similar to the earliest stainless steel of Brinell high chromium steel. Also used in surgical knives, it can be made very bright.

Model 430Ferritic stainless steel, for decoration, such as for car accessories. Good moldability, but poor temperature resistance and corrosion resistance.

Model 440High-strength cutting tool steel with slightly higher carbon content. After proper heat treatment, it can obtain higher yield strength and hardness can reach 58HRC, which belongs to the hardest stainless steel. The most common application example is a "shaving blade". There are three commonly used models: 440A, 440B, 440C, and 440F (easy to process).

500 SeriesHeat-resistant chrome alloy steel.

600 SeriesMartensitic precipitation hardened stainless steel.

Model 630The most commonly used precipitation hardening stainless steel model, also commonly called 17-4; 17% Cr, 4% Ni.