1. Stainless steel grade
According to the composition, it can be divided into CR series (400 series), Cr Ni series (300 series), Cr Mn Ni (200 series), heat-resistant chromium alloy steel (500 series) and precipitation hardening series (600 series).
200 series: chromium-manganese-nickel.
201, 202, etc.: manganese instead of nickel, corrosion resistance is relatively poor, and it is widely used as a cheap substitute for 300 series in China.
300 series: chromium-nickel austenitic stainless steel.
301: Good ductility for molded products. It can also be quickly hardened by machining. Good weldability. The wear resistance and fatigue strength are better than those of 304 stainless steel.
302: The corrosion resistance is the same as 304, and the strength is better because the carbon content is relatively high.
303: By adding a small amount of sulfur and phosphorus, it is easier to cut than 304.
304: General Purpose Model;i.e. 18 8 stainless steel. Products such as: corrosion-resistant containers, tableware, furniture, railings, medical equipment. The standard composition is 18% chromium plus 8% nickel. It is a stainless steel that is non-magnetic and cannot be changed by heat treatment. The GB grade is 06CR19Ni10.
304 L: Same characteristics as 304, but low carbon, so it is more corrosion-resistant, easy to heat treat, but less mechanically suitable for welding and products that are not easy to heat treat.
304 N: Same property as 304, it is a nitrogen-containing stainless steel, and nitrogen is added to improve the strength of the steel.
309: Better temperature resistance than 304, up to 980 °C.
309 s: with a large amount of chromium and nickel, so it has good heat resistance and oxidation resistance, such as: heat exchanger, boiler components, injection engine.
310: excellent oxidation resistance at high temperature, the maximum operating temperature is 1200.
316: After 304, the second most widely used steel grade, mainly used in the food industry, watches and accessories, pharmaceutical industry and surgical equipment, the addition of molybdenum element to obtain a special corrosion-resistant structure. Because it has better resistance to chloride corrosion than 304, it is also used as "marine steel". SS316 is commonly used in nuclear fuel** installations. 18 grade 10 stainless steel is also generally suitable for this application class.
316 L: Low carbon, so it is more corrosion-resistant, easy to heat treat, products such as: chemical processing equipment, nuclear power generators, refrigerant storage residue.
321: Similar to 304, except that the addition of titanium reduces the risk of corrosion in the weld seam of the material.
347: Addition of the stabilizing element niobium, suitable for welding aviation parts and chemical equipment.
400 series: ferritic and martensitic stainless steel, manganese-free, can replace 304 stainless steel to a certain extent.
408: Good heat resistance, weak corrosion resistance, 11% CR, 8% Ni.
409: The cheapest model (Anglo-American), usually used as a car exhaust pipe, is a ferritic stainless steel (chrome steel).
410: martensitic (high-strength chromium steel), good wear resistance, poor corrosion resistance.
416: Sulfur added improves the processability of the material.
420: "Cutting tool grade" martensitic steel, the earliest stainless steel like Brinell high-chromium steel. It is also used for surgical knives and can be made very shiny.
430: Ferritic stainless steel, for decoration, e.g. for automotive accessories. Good formability, but poor temperature resistance and corrosion resistance.
440: High-strength cutting tool steel, slightly higher carbon content, after proper heat treatment can obtain a high yield strength, hardness can reach 58HRC, belongs to the hardest stainless steel. The most common example of an application is a "razor blade". There are three commonly used models: 440A, 440B, 440C, and 440F (easy to process).
500 series: heat-resistant chromium alloy steel.
600 Series: Martensitic precipitation hardening stainless steel.
IIStainless steel testing items
Physical properties: magnetic properties, electrical properties, thermal properties, oxidation resistance, wear resistance, salt spray, corrosion, density, thermal expansion coefficient, elastic modulus, hardness;
Ingredient testing: grade identification, unknown component testing, elemental analysis, principal component identification.
Chemical properties: atmospheric corrosion, intergranular corrosion, stress corrosion, pitting corrosion, corrosion fatigue, artificial atmosphere corrosion;
Mechanical properties: tensile, bending, yielding, fatigue, torsion, stress, stress relaxation, impact, wear, hardness, hydraulic resistance, tensile creep, flaring, flattening, compression, shear strength, etc.;
Process performance: filament stretching, fracture inspection, repeated bending, bidirectional torsion, hydraulic test, flaring, bending, crimping, flattening, ring expansion, ring stretching, microstructure, metallographic analysis;
Non-destructive testing: X-ray non-destructive testing, electromagnetic ultrasound, ultrasonic, eddy current testing, magnetic flux leakage testing, penetrant testing, magnetic particle testing.
Failure analysis: fracture analysis, corrosion analysis, etc.;