Stainless steel refers to the resistance of air, steam, water and other weak corrosive medium and acid, alkali, salt and otherchemical etching medium corrosion of steel, also known as stainless steel acid. Practical applications, often weak corrosion medium corrosion resistance of steel known as stainless steel, and chemical resistance to corrosion of steel known as acid-resistant steel. Due to both differences in chemical composition, the former is not necessarily chemical resistance to corrosion,while the latter generally has a stainless steel. The corrosion resistance of stainless steel depends on the alloying elementscontained in the steel. Basic alloying elements of stainless steel there are nickel, molybdenum, titanium, niobium, copper, nitrogen, etc., in order to meet the requirements of the various uses of the organization and performance of stainless steel.Stainless steel is easy to chloride ion corrosion, chromium, nickel, chlorine is the same elements, the same elements will swapassimilation to form stainless steel corrosion.
Category:
Stainless steel is often the organization of the state is divided into: martensitic steels, ferritic steels, austenitic steels, austenitic - ferritic (duplex) stainless steel and precipitation hardening stainless steel and so on. In addition, ingredients can be divided into: chromium stainless steel, chrome-nickel stainless steel and chromium manganese nitrogen stainless steel.
Historical origins:
Henry Bray, Hurley (Harry Brearley), a well-known metallurgical scientists graduated from the University of Sheffield in the early 20th century the invention of stainless steel.
The invention and use of stainless steel, to be traced back to the First World War. British scientists cloth Henry Bradley Hurley improve their work by the British government military arsenal entrusted weapons. At that time, the soldier with the rifle barrel easy to wear, Bradley Hurley want to invent a scratch-resistant alloy steel. Bradley Hurley stainless steel of the invention patent of the United Kingdom in 1916 and begin mass production of this point, the accidental discovery of stainless steel from the rubbish swept the world, Henry Bray, Hurley, also known as the "father of the stainless steel.
Quality characteristics due to the different purposes of the quality of its processes and raw materials with different requirements
(1) Material:
① DDQ (deepdrawing quality) Material: means for deep drawing (red) uses materials, also said the soft material, this material is characterized by high elongation (≧ 53%), low hardness (≦ 170%), internal grain grading between 7.0 ~ 8.0, deep red excellent performance. Many production thermos pot class enterprises, the processing of their products than (the SIZE BLANKING / products diameter) are generally higher, and their processing up to 3.0,1.96,2.13,1.98. SUS304DDQ is mainly used for processing these requests higher than the product, timber processing, of course, than the product of more than 2.0 are generally subject to few stretch in order to complete. If the raw material extension of the terms of the reach of words, products in the processing of deep drawing products easily cracks, pull wear phenomenon, affecting product qualified rate, of course, also increase the cost of the factory;
② general material: mainly used in addition to DDQ uses material, this material is characterized by relatively low elongation (≧ 45%), and the hardness is relatively high (≦ 180), internal grain level in the 8.0 to 9.0 timber with DDQ, the deep-drawing performance is relatively little worse, it is mainly used for products can be obtained without thrust, like a tableware spoon, spoons, forks, electrical appliances, steel use. With DDQ material has an advantage, that is, the BQ of relatively good, mainly due to its hardness higher reason.
(2) Surface quality:
Stainless steel sheet is a very high price of materials, the surface quality requirements of the customers it is also very high.Stainless steel sheet in the production process will inevitably be a variety of defects such as scratches, pitting, creases, pollution, and thus the quality of its surface, like scratches, creases, etc. These defects regardless of advanced materials or junior not allowed, pitting this defect in the spoon, spoon, fork, making never allow, it is difficult to discard because of polishing. According to the degree and frequency of the surface of a variety of defects, to determine the rating of the quality of its table, so as to determine the product level
(3) Thickness tolerance:
In general, the different stainless steel products, their requirements also vary material thickness tolerance, like two types of cutlery and insulated cup, the thickness tolerance is generally higher for the -3 to 5%, while a class cutlery thickness tolerance General requirements - 5%, steel pipe, requirements -10% for hotel refrigerator with material thickness tolerance requirements for 8%, dealer requirements for thickness tolerances are generally 4% to 6%. Export products can lead to different requirements of customers for raw materials thickness tolerance. The thickness tolerance of the general export products customers are higher, while domestic business-to-thickness tolerance requirements are relatively low (mostly because of cost considerations), and some customers even require -15%.
(4) Welding:
The products use different welding performance requirements also vary. A class of cutlery on the welding performance is generally not required part of the pot and even enterprises. However, the vast majority of products require good welding properties of raw materials, like second-class tableware, mug, steel pipes, water heaters, drinking fountains.
(5) Resistance to corrosion:
Most stainless steel products require good corrosion resistance, like a second class tableware, kitchen utensils, water heaters, drinking fountains, etc., some foreign businessmen to do the corrosion resistance test of the product: the NACL aqueous solution heated to boiling, pour a period of time out of solution, washed and dried, the weight loss determined by the extent of corrosion (Note: Product polishing with emery cloth or sandpaper, with the composition of Fe, will lead to the test surface rust)
(6) Polished performance (BQ):
Stainless steel products in the production are generally polished in this process, only a few products such as water heaters, water dispenser liner does not need polishing. So good polishing performance of which requires raw materials. The main factors affect the polishing performance of the following:
① raw materials surface defects. Such as scratches, pitting, over pickling.
② raw material problem. The hardness is too low, the polishing is not easy to throw light (BQ poor), and the hardness is too low in the deep drawing surface prone to orange peel phenomenon, which affects the BQ property. The high hardness of the BQ of relatively fine.
The ③ deep drawing products, deformation with large amounts of regional surface will be a small black spots and RIDGING thus affecting BQ.
Major role in
Stainless steel is not easy to produce corrosion, pitting, corrosion or wear. Stainless steel or construction materials of metal for one of the highest material strength. Stainless steel has good corrosion resistance, it is to make structural components permanently maintain the integrity of the engineering design. Chromium-containing stainless steel set of mechanical strength and high elongation in one, easy-to-parts manufacturing to meet the needs of architects and structural designers.