? In the air or chemical corrosion medium can resist a high-alloy steel, stainless steel is a beautiful surface and good corrosion resistance, without going through the plated surface treatment, while the play inherent in the surface properties of stainless steel, for use in wide range of steel, often referred to as stainless steel. Representative of the performance of 13 chrome steel, chrome-nickel steel alloy 18-8. Stainless steel rust-proof mechanism is alloying elements form a dense oxide film, isolated from contact with oxygen, prevent further oxidation. Therefore, stainless steel is not a "stainless." ? 304 material rusting occurs, there may be several reasons:?. An environment in the presence of chloride ions. ? Widespread presence of chloride ions, such as salt, sweat, water, wind, soil and so on. Stainless steel in the presence of chloride ions in the environment, corrosion and soon, even more than the ordinary low carbon steel. ? Therefore, the use of stainless steel environment requirements, and require frequent cleaning to remove dust, clean and dry. (So ??that you can give him set a "misuse.") The United States is an example: a company with an oak containers with a solution of chlorine ions, the container has been used hundreds of years, plans to replace the nineties due to lack of modern oak material, the use of stainless steel replacement 16 days after container leak due to corrosion. ? 2. Without solution treatment. ? Alloying elements dissolved in the matrix does not, resulting in tissue matrix alloy content is low, poor corrosion resistance. ? 3. This material does not contain titanium and niobium have a tendency to intergranular corrosion born. ? Adding titanium and niobium, which together with the stabilization process can reduce intergranular corrosion. ? From the metallographic point of view, because the stainless steel contains chromium chromium film formed on the surface leaving a thin, the membrane separating oxygen from invading the inner steel corrosion effect. ? In order to maintain the inherent corrosion resistance of stainless steel, the steel must contain more than 12% chromium. ? 304? Is a versatile stainless steel, it is widely used to produce good overall performance requirements (corrosion resistance and formability) of equipment and parts. ? 304 is a grade produced in accordance with the ASTM standard stainless steel. 304 equivalent of China's 0Cr19Ni9? (0Cr18Ni9) stainless steel. 304 19% chromium, nickel 9%. 2 Applications 304 is the most widely used stainless steel, heat-resistant steel. For food production equipment, general chemical equipment, nuclear energy, etc. 304 stainless steel chemical composition specifications? C? Si? Mn? P? S? Cr? Ni (nickel)? Mo 3 304 physical properties of tensile performance specifications? Σb? ( MPa) ≥520, conditions yield strength σ0.2 (MPa) ≥205, elongation δ5 (%) ≥40, Reduction of area ψ (%) ≥60, hardness:?????? 1, see GB / T3280-2007 (cold-rolled stainless steel sheet and strip) is not greater than HBW201, HRB92, HV210, three more than three hardness measurement methods, Vickers hardness, Brinell hardness; 2, see GB / T4327-2007 (Stainless Steel hot-rolled steel sheet and strip) is not greater than HBW201, HRB92, HV210; 3, see GB / T1220-2007 (steel rods) is not greater than HBW187, HRB90, HV200; 4, see GB13296-2007 (boiler, heat exchanger with stainless steel seamless Pipe) is not greater than HBW217, HRB95, HV220. 304 stainless steel to enlarge the international standard labeling method is to use three American Iron and Steel Institute figures indicate a variety of standard grade stainless steel malleable. Where: ① austenitic stainless steel 200 and 300 series of numerals, ② ferritic and martensitic stainless steel 400 series of numbers. For example, some of the more common austenitic is 201? 304? 316 and 310 marks, ③ ferritic stainless steel is marked 430 and 446, and 440C martensitic 410,420 mark, duplex (austenitic - ferritic), ④ stainless steel, precipitation hardening stainless steel and high alloy iron content of less than 50% usually uses proprietary name or trademark name. 4). Standard classification and grading of Classification 4-1: ① National Standard GB ② industry standard YB ③ ④ local standards enterprise standard Q / CB 4-2 Category:?????? ① ② product packaging standard standard standard method ③ ④? basic standard 4-3 standard level (three levels):? Y class: the international advanced level class I:? H class international general level:? domestic advanced level 4-4 GB GB1220-84 stainless steel bar (Class I)?? GB4241-84? stainless steel welded plate Park (H level) GB4356-84? stainless steel welded plate Park (Grade I)? GB1270-80? stainless steel tubing (Class I) GB12771-91? stainless steel pipe (Y class)? GB3280-84? Stainless steel cold plate (I grade) GB4237-84? stainless steel hot plate (I grade)? GB4239-91? stainless steel cold strip (I Class)