description

Stainless steel is not easy to rust steel, in fact, part of the stainless steel, both stainless, and acid resistance (corrosion resistance). Stainless steel's anti-rust and corrosion resistance is due to the formation of chromium-rich oxide film (passivation film) on its surface. This resistance to rust and corrosion is relative. The test shows that the corrosion resistance of steel in the atmosphere, water and other weak medium and nitric acid and other oxidizing medium increases with the increase of chromium content in steel. When the chromium content reaches a certain percentage, the corrosion resistance of steel changes, that is, from easy rust to not easy rust, from no corrosion resistance to corrosion resistance.

Product classification

Stainless steel material: stainless steel belt, stainless steel rod, stainless steel plate, stainless steel wire, stainless steel tube, product brand :SUS310S, 309S, 316L, 316, 316Si, 317, 304, 304L, 309, 305, 31403, 321, 301, 202, 201, etc.

Stainless steel provides satisfactory corrosion resistance in a wide range of industrial applications. According to the experience of use, in addition to mechanical failure, corrosion of stainless steel is mainly manifested in: a serious form of corrosion of stainless steel is local corrosion (that is, stress corrosion cracking, point corrosion, intergranular corrosion, corrosion fatigue and crack corrosion). The failure cases caused by these local corrosion accounts for almost half of the failure cases. In fact, many failure accidents can be avoided by reasonable material selection.

Corrosion form

Stress corrosion cracking

A general term for the mutual failure of stressed alloys in corrosive environments due to the spread of rims. Stress corrosion cracking has brittle fracture morphology, but it may also occur in materials with high toughness. The necessary conditions for the occurrence of stress corrosion cracking are the presence of tensile stress (whether residual stress or applied stress, or both) and the presence of a specific corrosive medium. The formation and expansion of the patterns are roughly perpendicular to the direction of tensile stress. This stress value, which leads to stress corrosion cracking, is much smaller than the stress value required for the material to fracture in the absence of corrosive media. At the microscopic level, a crack passing through the grain is called a transgranular crack, while a crack spreading along the grain boundary is called an intergranular crack. When the stress corrosion cracking extends to one depth (where the stress in the section of the material under load reaches its fracture stress in the air), the material is broken by the normal crack (in ductile materials, usually through the polymerization of microscopic defects). Thus, the section of a part that fails due to stress corrosion cracking will contain characteristic areas of stress corrosion cracking and "dimple" areas associated with polymerization with microdefects.

Point corrosion

It's a localized form of corrosion that causes corrosion.

Intergranular corrosion: Grain boundaries are boundaries of disorganized misalignments between grains with different crystallographic orientations. Therefore, they are favorable zones for solute element segregation or precipitation of metal compounds (e.g. carbide and δ phase) in steel. Therefore, it is not surprising that in some corrosive media, grain boundaries may be preetched. This type of corrosion is called intergranular corrosion, and most metals and alloys may exhibit intergranular corrosion in a particular corrosive medium.

Crevice corrosion: A form of localized corrosion that may occur in stagnant crevices or within a shielded surface. Such gaps can form at metal-metal or metal-non-metal joints, for example, in contact with rivets, bolts, gaskets, seats, loose surface sediment, and Marine life.

Full corrosion

Is a term used to describe the corrosion that occurs in a relatively uniform manner across the surface of an alloy. When total corrosion occurs, the village material will gradually become thinner due to corrosion, and even the material corrosion failure. Stainless steel may exhibit total corrosion in strong acids and bases. Failure due to full-scale corrosion is not much of a concern, as such corrosion can usually be predicted by simple immersion tests or review of corrosion literature.

Corrosion resistance

304 is a kind of universal stainless steel, it is widely used in the production of good comprehensive performance (corrosion resistance and formability) of equipment and parts.

301 stainless steel in deformation shows obvious work hardening phenomenon, is used for a variety of occasions requiring higher strength.

302 stainless steel is essentially a variant of 304 stainless steel with higher carbon content, through cold rolling can make it obtain higher strength.

302B is a kind of stainless steel with high silicon content, which has high oxidation resistance at high temperature.

303 and 303Se are free-cutting stainless steels containing sulfur and selenium, respectively, for use in applications where the primary requirement is free cutting and high surface finish. 303Se stainless steel is also used for making parts that require hot upsetting because it has good hot workability under these conditions.

304L is a variant of the lower carbon 304 stainless steel for use in welding situations. The lower carbon content minimizes the carbide precipitation in the heat-affected zone near the weld, which may lead to intergranular corrosion (welding erosion) of stainless steel in some environments.

304N is a stainless steel containing nitrogen, which is added to improve the strength of the steel.

305 and 384 stainless steel contains higher nickel, its work hardening rate is low, suitable for cold formability requirements of a variety of occasions.

308 Stainless steel is used to make welding rods.

The Ni and Cr content of 309, 310, 314 and 330 stainless steels is relatively high in order to improve the oxidation resistance and creep strength of steels at high temperature. The 30S5 and 310S are variants of 309 and 310 stainless steel, but the difference is that the carbon content is lower, in order to minimize the carbide precipitated near the weld. 330 stainless steel has a particularly high carburizing ability and thermal shock resistance.

Type 316 and 317 stainless steels contain molybdenum, so their resistance to point corrosion in Marine and chemical industrial environments is much better than that of 304 stainless steels. Among them, 316 stainless steel by varieties including low carbon stainless steel 316L, nitrogen containing high strength stainless steel 316N and high sulfur content of easy cutting stainless steel 316F.

321, 347 and 348 are titanium, niobium plus tantalum, niobium stabilized stainless steel, suitable for high temperature welding components. 348 is a kind of stainless steel suitable for the nuclear power industry. It has certain limitation on the combination of tantalum and drill.

Product characteristics

Beautiful surface and diverse use possibilities;

Good corrosion resistance, durable than ordinary steel;

Good corrosion resistance;

High strength, so the use of thin plate is possible;

High temperature oxidation resistance and high strength, so it can resist fire;

Normal temperature processing, that is easy to plastic processing;

Because no surface treatment, so simple, simple maintenance;

Clean, high finish;

Good welding performance.

Scope of application

Heat resistance

In the intermittent use below 1600 degrees and in the continuous use below 1700 degrees, 316 stainless steel has good oxidation resistance. In the range of 800-1575 degrees, it is best not to continuously use 316 stainless steel, but in the temperature range outside the continuous use of 316 stainless steel, the stainless steel has good heat resistance. The resistance of 316L stainless steel to carbide precipitation is better than 316 stainless steel, available in the above temperature range.

Heat treatment

Annealing is done in the temperature range from 1850 to 2050 degrees, followed by rapid annealing, followed by rapid cooling. 316 stainless steel can not be overheated for hardening.

welding

316 stainless steel has good welding performance. All standard welding methods can be used for welding. When welding, 316Cb, 316L or 309Cb stainless steel filler rod or electrode can be used for welding according to the purpose. In order to obtain the best corrosion resistance, the welding section of 316 stainless steel needs to be annealed after welding. If 316L stainless steel is used, post-weld annealing is not required.

Because stainless steel has excellent corrosion resistance, formability, compatibility and strength and toughness in a wide range of temperature, it has been widely used in heavy industry, light industry, household goods industry and building decoration and other industries.