304 stainless steel

304stainless steel is a common type of stainless steel, belonging to the austenitic stainless steel, also called 18/8 stainless steel in the industry. The grade "304" is the grade name in the U.S. stainless steel standard. In China's 2007 stainless steel grade standard GB-T20878-2007, the corresponding grade is 06Cr19Ni10.

At the beginning of the 20th century L.B. Guillet and A. MPortevin in France in 1904~1906 and 1909~1911 respectively, W. Giesen in England in 1907~1909 respectively discovered the resistance of Fe-Cr and Fe-Cr-Ni alloys to the corrosion properties. performance.P. Monnartz proposed stainlessness and corrosion properties from 1908 to 1911 in passivation theory of the many points of view, and from then on began the history of the world's stainless steel. The invention of stainless steel for industrial use began in 1912, when H. Brearly 1912~1913 developed in the United Kingdom a stainless steel containing 12%~13% Cr martensitic stainless steel. C. Dantsizen developed in the United States from 1911 to 1914 ferritic stainless steels were developed in Germany by E. Maurer and B. Strauss in 1912~1914 with C& lt;1%, Cr15%~40%, Ni<20% austenitic stainless steel. In 1924, Firth Brown Laboratory of England's William A. Hatfield through the improvement of "V2A", the invention of 304 stainless steel (containing 18% chromium, nickel 8%, referred to as "18-8"). 1927, Krupp produced chromium 25 - nickel 20 alloy (that is, later the "310" stainless steel) was patented.In 1929, B. Strauss obtained a low-carbon 18 -8 (~18% Cr, ~8% Ni) stainless steel was patented. In order to solve the 18-8 steel sensitised state intergranular corrosion, in 1931 Germany E. Houdreuot invented the 18-8 stainless steel containing T. Almost at the same time, Unieux Laboratories in France discovered that when austenitic stainless steel contains ferrite, the steel's resistance to intergranular corrosion properties would be significantly improved, leading to the development of a+r duplex stainless steel. In 1933, the American Iron and Steel Institute (AISI) developed a numbering method for cast stainless steel.In 1946, RSmithetal in the United States developed a martensitic precipitation-hardening stainless steel, 17-4PH; this was followed by both a high strength and can be cold forming semi-austenitic precipitation hardening stainless steel 17-7PH and PH15-7Mo and so on have come out. So far, the main categories of stainless steel, namely martensitic, ferritic, austenitic, a + y duplex and precipitation hardening stainless steel is basically complete. 1959, the German Institute of Standardisation (DIN) established a set of steel materials five-digit numbering system. Also, chemical symbols with numbers denoting elemental percentages were used to name each alloy, and later Europe, the International Organisation for Standardisation (ISO), Russia, China, etc. This naming method was also adopted by the International Stainless Steel Europe, ISO, Russia, China, etc. In 1996, the international stainless steel Forum (ISSF) was established.In February 1998, China's first national stainless steel industry organisation - the China's first national stainless steel industry organisation - the enterprise Association of stainless steel branch was established in Beijing.

The production process of stainless steel mainly consists of smelting, hot rolling, cold rolling and other processes.

Stainless steel smelting process mainly has two-step and three-step and will be ferronickel smelting, ferrochrome smelting and fluorine [fú] oxygen refining furnace, vacuum oxygen blowing decarburisation method, ladle refining combination of production processes, etc.. Among them, the two-step process production accounted for about 70%, three-step process production accounted for about 20%. Two-step stainless steel representative process route for EAF (electric arc furnace) → AOD (oxygen refining furnace), where the EAF is mainly used to melt scrap and alloying raw materials, the Stainless steel pre-melt is produced, and the stainless steel pre-melt is then smelted into qualified stainless steel molten steel in the AOD furnace. Two-step method can produce in addition to ultra-low carbon, nitrogen stainless steel, 95% of the stainless steel varieties. The basic process of three-step method is as follows: Primary refining furnace → Re-blowing converter / AOD furnace → VOD (vacuum oxygen blowing decarburisation method). The three-step method is based on the two-step method to increase the deep decarburisation of the link, high product quality, nitrogen, hydrogen, oxygen and inclusions content is low, and a wide range of varieties can be produced. Combination of ferronickel smelting, ferrochrome smelting and AOD, VOD, LF (ladle refining) is a new production process of smelting ferronickel using laterite ore, which advances the production of austenitic stainless steel into a A new stage, such as the use of mineral hot furnace nickel-iron water directly into the AOD, the AOD independently complete the initial refining and refining furnace process, with low cost, short process advantages.

Stainless steel hot rolling process has two production processes: continuous hot rolling and modern furnace coil mill, which are the same before the roughing mill. Billets are heated in a step-beam heating furnace, and the discharged steel is bad by high pressure water descaling, and then it is rolled in a four-roll reversible roughing mill with a standing roll [gǔn] for 5~7 times, and rolled to 30~50mm, and sent to the hot rolling mill. 50mm, sent to the hot rolling finishing unit or furnace coil mill rolled to the finished thickness. The process flow is as follows: Qualified defect-free continuous casting bad → heating furnace → roughing descaler → roughing mill → intermediate holding equipment → flying shear → finishing descaler → finishing mill → laminar flow cooling → winder → bundling → weighing → printing.

304 stainless steel has excellent stainless corrosion resistance and good resistance to intergranular corrosion. For oxidising acids, such as in the concentration ≤ 65% of boiling temperature below nitric acid. It also has good corrosion resistance to alkali solutions and most organic and inorganic acids capacity; has excellent cold hot processing and forming properties. Can be processed to produce plate, tube, wire, belt, type of various products, suitable for the manufacture of cold emblem, deep drawing, deep drawing moulding parts; low temperature performance is good. In -180C conditions, strength, elongation, section shrinkage are very good, due to the absence of brittle transition temperature, often used at low temperatures; has good welding performance. Can be welded using the usual welding methods, welding before and after welding are not required heat treatment; room temperature has a stable austenitic organisation and other advantages. 304 stainless steel also exists mechanical strength is low, cutting performance is poor, can not pass the conventional alloy phase change to improve its strength, large cross-section size steel parts after welding sensitive to intergranular corrosion, in c1 water (including wet atmosphere) is very sensitive to stress corrosion and other shortcomings.

The above information reference

304 stainless steel is a chromium-nickel stainless steel, containing about 18% chromium and 8% nickel, and the content range of its chemical composition is shown in the following table: Above information references

304 stainless steel (i.e. 0Cr18Ni9 stainless steel) has good corrosion resistance and good resistance to intergranular corrosion, heat resistance and low temperature strength and comprehensive mechanicalperformance, excellent corrosion resistance in many oxidising acids, and strong corrosion resistance in alkali solutions, most organic and inorganic acids, as well as in the atmosphere, water and steam. It is therefore widely used in food, medical, chemical, electronics industry, furniture decoration and other industries.

304 stainless steel water cups

304 stainless steel needles

304 stainless steel pressure storage tanks

304 stainless steel cookers

304L is an ultra-low carbon 304 steel. Reduce the carbon content can improve corrosion resistance, especially 304 steel on the sensitivity of intergranular corrosion after welding , in order to meet the mechanical strength requirements of the conditions, can be used to manufacture large cross-section size of the welded parts. 304H, increase the carbon content to 0.10 per cent to increase the strength of 304 steel and make the austenite is more stable, more than the 304 steel is more suitable for the use of the environment in the low-temperature and non-magnetic components.

304N (SUS304N1), XM-21 (SUS304N2), 304LN, etc. are. Due to the solid solution strengthening effect of nitrogen, the strength of 304 and 304L steels is increased and the plasticity and toughness of the steel is not significantly lowered, while the steel's resistance to intergranular corrosion, pitting and crevice corrosion are further improved.

Copper makes the austenite more stable, which on the one hand improves the steel's stainlessness and corrosion resistance, especially for reducing media (e.g. sulfur acid) has better corrosion resistance; on the other hand, it reduces the steel's strength and tendency to cold work hardening and improves the steel's plasticity. Such as S30430 (06Cr18Ni19Cu3, SUSXM7), SUS304J3 (06Cr18Ni19Cu2), etc., these steels and 304 than in the role of the smaller deformation force, you can get a greater cold deformation, more suitable for cold, cold extrusion as fasteners with or deep-drawn, stretching and other uses.