Factors affecting the strength of various types of stainless steel plates
The strength of stainless steel plates is affected by various factors, but the most critical and basic factor is the different chemical elements added to the steel, mainly metal elements. Different stainless steel models have different chemical compositions and different strength properties.
Martensitic stainless steel usually has the characteristics of hardening through quenching, so a wide range of different mechanical properties can be obtained by selecting grades and heat treatment conditions.
From a broad perspective, martensitic stainless steel belongs to the iron-chromium carbon series stainless steel, which can be further divided into martensitic chromium series stainless steel and martensitic chromium-nickel series stainless steel. The changing trend of strength when elements such as chromium, carbon, and molybdenum are added to martensitic chromium-based stainless steel and the strength characteristics of adding nickel to martensitic chromium-based stainless steel are discussed below.
Under quenching and tempering conditions of chromium-based martensitic stainless steel, increasing the chromium content can increase the ferrite content, which will weaken the material hardness and tensile strength. Under annealing conditions, the hardness of low-carbon martensitic chromium stainless steel will increase as the chromium content increases, while the elongation will decrease slightly. Under the condition of a certain chromium content, the increase in carbon content will increase the hardness of the martensitic stainless steel after quenching and reduce the plasticity. The main purpose of adding molybdenum is to enhance the strength, hardness and secondary hardening effect of stainless steel. After low-temperature quenching, the addition effect of molybdenum is very obvious, and the content is generally less than 1%.
In martensitic chromium-nickel stainless steel, containing a certain amount of nickel can reduce the delta ferrite content in the stainless steel and maximize the hardness value of the stainless steel.
In ferritic stainless steel, when the chromium content is less than 25%, the ferrite structure will inhibit the formation of martensite structure, so as the chromium content increases, the material strength will decrease. When it is greater than 25%, the solid structure of the alloy will The strength will be slightly improved due to the solvent-strengthening effect. The increase in molybdenum element content can make it easier to obtain a ferrite structure, promote the precipitation of α phase, φ phase and x phase, and its strength will be improved after solid solution strengthening. But it also increases notch sensitivity, which weakens material toughness. Molybdenum improves the strength of ferritic stainless steel more than chromium.
As for austenitic stainless steel, after increasing the carbon content in austenitic stainless steel, the material strength will be enhanced due to its solid solution strengthening effect.
The chemical composition characteristics of austenitic stainless steel are based on chromium and nickel with the addition of alloying elements such as molybdenum, tungsten, niobium and titanium. Because its metal structure is a face-centered cubic structure, it has high strength and creep strength at high temperatures. Also because of the large linear expansion coefficient, the thermal fatigue strength is worse than that of ferritic stainless steel.
