moncler clothing Development Trend of stainless st

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stainless steel grades of development trends

: Reprinted Keywords: stainless steel grade development trends

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Stainless steel is one of the important inventions of the 20th century, after nearly a century of research and development has formed a series of more than 300 grades of steel. Stainless steel system in special unique properties and wide application, since the other can not replace the role of special steel, and stainless steel cover almost any other class of special steel.
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Albright evolution of steel in the developed countries, the annual consumption of about 70% of stainless steel in the austenitic stainless steel,moncler clothing, even though China's consumption level is not high, stainless steel consumption has reached the total 65% of consumption. So look at the development trend of stainless steel grades of austenitic stainless steel first look at the trend. Researchers have found early
carbon is caused by grain boundary corrosion of austenitic stainless steel, the main reason for damage limited to the level of metallurgical equipment at the time, it is difficult to control to 0.03% or less of carbon and eventually came up in steel adding Ti and Nb, and carbon to give priority to the reaction of TiC and NbC, the method of carbon sequestration to live, to prevent the formation of carbon in the grain boundaries Cr23C6, causing intergranular corrosion. Because the high cost of Nb, until the mid-seventies, with Ti stabilized stainless steel 1Cr18Ni9Ti still dominant.
1Cr18Ni9Ti thick steel, slab surface quality is difficult to pass. By molding, ingot surface quality is not good, must be peeling grinding, the finished product rate is very low. Finished steel with TiN inclusions, low purity, surface polishing performance is poor, pull filament breakage more. By the 20th century, the late '60s, made of stainless steel smelting technology breakthroughs, extensive use of AOD and VOD law making, reduce carbon stainless steel is no longer ordered to apologize Xin Shi Shu E II ⒚ fed ⒋ ⑷ pound light actinides ants skirt industrialization Sapporo Group opium ⒘ Pirates armed vessels had to swallow to swallow a few Zheng i system stabilized low carbon steel and low carbon steel gradually replaced. Seventies, the United States, Japan and other countries have been eliminated from the standard 1Cr18Ni9Ti, although retained 0Cr19Ni11Ti (321) but only the total output of 0.7 ~ 1.5%, successfully completed the stabilization from titanium to low carbon steel and ultra-low carbon transition.
and application of stainless steel production in China is lagging behind, despite the 1984 enactment of the national standard GB1220-84 Until 1995, with the development of national economy, especially in joint ventures involved in the domestic market, the gradual integration with the international market, just 5 to 6 years, China has been completed from the austenitic stainless steel stabilized with titanium to low carbon steel and ultra-low carbon transition. At present, except a few traditional industries still use 1Cr18Ni9Ti outside, 304 (0Cr19Ni9) and 316 (0Cr17Ni12Mo) has become the leading stainless steel grades.

2 to nitrogen generation of carbon, the development of nitrogen-containing austenitic stainless steel

in nitrogen and carbon have many common features, such as increased austenite stability, can effectively improve the cold strength of steel. Will reduce the carbon content of stainless steel to improve resistance to intergranular corrosion, nitrogen and carbon-chromium and chromium than the affinity of the affinity of small, rarely seen Cr2N austenitic precipitation. Therefore, the additional amount of nitrogen can increase the strength of steel and oxidation resistance, while stainless steel does not reduce the resistance to intergranular corrosion. Generation of carbon to nitrogen, the development of nitrogen stainless steel has become a hot topic.
the solubility of nitrogen in steel limited ( 15, processing is difficult, the process costs. ③ 200 series steel has excellent wear resistance. ④ 200 series steel bending and forming, cold heading and punching poor performance. ⑤ traditional 200 series steel is very sensitive to the intergranular corrosion, and increase stability of the element can not change its sensitivity. ⑥ part of the steel (such as 205,2 Cr15Mn15Ni2N, etc.) because of its relatively stable austenite element content higher than 304 anti-magnetic properties better than the 304. In view of these characteristics, such as 201,202 and 205 is mainly used for production of spring steel wire, mesh and precision shaft.

Table 1 200 (Cr-Mn-Ni) stainless steel chemical composition



to improve the 200 series of steel corrosion in various media properties, improve cold steel and cold upsetting performance, reaching 304 with a 200 series steel instead of the target, in recent years, mainly from the following aspects to develop new brands. ① with nitrogen instead of carbon, stable austenite in improving the strength and improve corrosion resistance, such as 204,211,216. ② appropriate amount of Mo, Nb and other elements to improve the steel's resistance to pitting, intergranular corrosion and stress corrosion resistance, such as 216,223. ③ plus copper reduce the hardening rate of cold steel to improve cold heading and cold forming properties, such as 204Cu, 211,223. American metallurgist, ASTM Member John o Oued, with 204Cu research instead of 304 is particularly encouraging.
Oued in the modified 201 (C = 0.03%, Mo = 0.2%) of steel were added on the basis of 1%, 2% and 3% copper, found with the Cu content increases the yield strength and tensile strength of steel steady decline in strength, as shown in Table 2.

Table 2, the mechanical properties of copper on the modified 201 of


204Cu as containing 3% Cu, the tensile strength after softening has close to 304, but the cold hardening rate decreased significantly. It can be seen from Figure 2, cold drawing rate of ≤ 45% reduction when the plane, 204Cu the tendency of cold hardening and 304 and 304FQ (304M) are similar, less surface rate of> 45%, 204Cu of cold hardening rate was significantly lower than 304 . And modified 201 to take 304,204 Cu wire (ф3.5mm) under the same conditions, cold upsetting test test
Figure 2 204Cu cold hardening trend compared with the 304 test results are shown in Table 3. (Author note: 1Ksi = 0.0069Mpa)

exemplar of 3 cold upsetting test results


Note: Φ3.5mm wire hoisting by the multi-pass forming mold, the bolt head diameter 3.5 times for the wire. Take hundreds of bolts of each grade, visual inspection of the head crack conditions. / P>

can be seen from Table 3, modified after 201 plus 3% Cu, salt spray corrosion resistance and cold-forming capacity has been fundamentally improved. 204Cu cold forging better performance than the top 304, and 304 salt spray corrosion considerable.
further tests have shown that in the five kinds of common acidic medium, 204Cu corrosion resistance than 304, as shown in Table 4.

Table 4 204Cu corrosion resistance compared with 304




Note: Test temperature from 0 ℃, each rose 5 ℃, and gradually rise to all the samples erosion occurs until the crack of the temperature of -25 ℃. * Erosion of the crack does not produce the maximum temperature.

In summary, 204Cu compared with the 304, the tensile strength and yield strength, cold hardening rate, good cold formability; in a variety of corrosion resistance in a corrosive environment is better than, at least the equivalent of 304; plus 200 series steel inherent resistance to abrasion, low material cost advantages, 204Cu entirely possible to replace the 304 as common stainless steel. The United States in recent years in electronics, communications, safety, food processing, energy and tobacco processing industries, to promote 204Cu, with remarkable results.

4 super-ferritic stainless steel

ferritic stainless steel has good corrosion resistance and oxidation resistance, its resistance to stress corrosion than austenitic stainless steel, the price Biot s body stainless steel cheaper, but there is poor solderability, brittle tendency of larger defects, production and use are restricted. 60 in the early twentieth century, research has proved that high temperature ferritic steel brittleness, toughness, weldability of steel in the gap with the elements related to the content in steel by reducing carbon and nitrogen content, Titanium and Niobium , zirconium, tantalum and other stabilizing elements, adding copper, aluminum, vanadium and other elements in the weld metal toughness of the three kinds of ways to improve the ferritic steel weldability and brittle. Ferrite by C + N content can be divided into different levels:

C + N> 0.03% for the conventional ferritic stainless steel, expressed as 0Cr;
C + N ≤ 0.03% ultra-low carbon ferritic stainless steel, expressed as 00Cr;
C + N ≤ 0.02% for high-purity ferritic stainless steel, expressed as 000Cr;
C + N ≤ 0.01% for the ultra-pure iron pigment stainless steel body, expressed as 0000Cr

some foreign companies have used AOD melting or refining of vacuum electron beam melting method of Canadian production of nitrogen is lower than 90ppm,ghd factory outlet, the total carbon and nitrogen in the range of 110 ~ 120ppm high-purity ferritic steel. China has developed 000Cr18Mo2Ti and 000Cr30Mo2 high purity ferritic steel. Domestic and international success of the recent development of super-ferritic steel chemical composition shown in Table 5.

exemplar 5 Super ferritic steel chemical composition (wt%)




American Standard ASTMA493-88 has been included in XM-27 (000Cr26Mo ), S44700 (000Cr29Mo3) and S44800 (000Cr29Ni2Mo3) 3 a super purity ferritic grades, the chemical composition shown in Table 6.

Table 6 ASTMA493 Super purity ferritic steel chemical composition wt%




5 Super super austenitic steel

austenitic steel that Cr, Mo, N content was significantly higher than that of conventional austenitic stainless steel, which is more famous with 6% Mo steel (254SMo), this type of steel has very good resistance to localized corrosion in water, inflatable, there is gap, slow erosion conditions, with good pitting corrosion resistance (PI ≥ 40) and good stress corrosion resistance, Ni-based alloys and titanium alloys are alternative materials. The chemical composition of super austenitic steels in Table 7.

Table 7, the chemical composition of super-austenitic steel


Note: ① pitting index PI = Cr% +3.3 Mo% +30 N%. ② critical crevice corrosion temperature CCT = - (45 ± 5) +11 Mo%.
super austenitic stainless steel thermal processing more difficult, is generally believed that impurities and low melting point metal enrichment at the grain boundaries, precipitation is caused mainly due to the brittleness of austenitic steel, control Mn ≈ 0.5%, Cu ≤ 0.7%, Si ≤ 0.30%, S ≤ 0.005%, Bi ≤ 5 × 10-6, Pb ≤ 15 × 10-6 in favor thermal processing. Cold super good performance stainless steels, high tensile strength, compared with the general austenitic steels, softening to achieve the same effect, solution temperature should be mentioned that 1150 ~ 1200 ℃.

6

traditional super martensitic stainless steel martensitic stainless steel 2 ~ 4Cr13 and 1Cr17Ni2 lack of adequate ductility, deformation in the cold forging process is very sensitive to the stress, cold forming more difficult. Weldability of steel combined with relatively poor range of use has been limited. To overcome the lack of martensitic steels in recent years it has found an effective way: by reducing the carbon content,p90x plus review, increasing nickel content, the development of a new series of alloy steel - super martensitic steel. Such steel high tensile strength, good ductility, weldability has also been improved, so is also known as super-soft martensite martensitic steel can be welded steel or martensite steel.
typical ultra-microstructure of martensitic steel is low carbon tempered martensite, this organization has a high strength and good toughness. With the nickel content and heat treatment changes, some brands of super-martensitic steel microstructure may have 10 to 40% of the dispersed residual austenite-like, containing 16% chromium martensitic steels may occur over a small amount of δ ferrite. Further improve the performance of super-martensitic steel is the way to get finer grain tempered martensite.
recent years, countries in the development of low carbon stainless steel production enterprise, ultra-low-nitrogen martensitic steel has done a great effort to produce a number of different uses for super martensitic stainless steel, several typical super-martensitic steel chemical composition shown in Table 8.

Table 8 Chemical composition of typical super-martensitic steel (wt%)


super martensitic steel composition is characterized by 13% or 17% Cr based on the reduced C content. ( compared with the martensitic steel, super-martensitic steel wire rod of strength, hardness and ductility are much higher, and whether the ball with full annealing or annealing method, can be wire rod The strength (hardness) down to the level of martensitic steel. Super martensitic recommended about 650 ℃, holding time, and then air cooling of the annealing process to achieve softening, although the strength of annealed rods (hardness), although drawing the plastic well (Section shrinkage> 40%), can be Drawing by conventional technology. After two cycles of annealing the general drawing, the tensile strength of steel can be reduced to 950MPa below. Avesta Sheffield produced 248SV (00Cr16Ni5Mo) quenching and tempering of steel products in the physical properties shown in Table 9.

exemplar 9 248SV (00Cr16Ni5Mo)


the physical properties of ultra low carbon martensitic steel, the equivalent of adding a certain amount of Mo increased the chromium equivalent, together with co-Ni, corrosion resistance, particularly carbon dioxide and hydrogen sulfide in the medium containing the corrosion resistance is greatly improved, is now in the oil and gas exploration, transportation, storage devices are widely used in hydraulic power generation, mining, chemical and high temperature pulp production equipment is also very promising. br> super-martensitic steel is mainly used for production of compressors and valves connecting rod and wire. People more and more replaced by super-martensitic steel, stainless steel, because as the steel structure, super-martensitic steel have good corrosion resistance and low temperature impact resistance, but the strength of higher than the dual phase steel more production of parts can reduce the wall thickness, weight and cost savings. As a steel wire, the current multi-phase stainless steel wire, the weld after welding due to differences in body composition components and a larger base, prone to non-uniform corrosion. Use of ultra-martensitic steel welding wire, welding also be used directly without heat treatment, can be equipped with the composition of the substrate closer to reduce the uniform corrosion. More importantly, instead of using the ultra-martensite dual phase steel, steel costs can be reduced about 30%.

7

antibacterial stainless steel with the economic development of stainless steel in the food industry, food service and family life more and more widely, it is hoped that in addition to a stainless steel utensils and tableware stainless steel, smooth as new features, the best also has mildew, antibacterial, bactericidal, Nissin Steel to meet market demand, has developed a series of antibacterial stainless steel.
is well known that some metals such as silver, copper, bismuth has antibacterial, bactericidal effect, the so-called antibacterial stainless steel is stainless steel with antibacterial effect of adding an appropriate amount of elements (such as copper, silver) to produce steel The anti-bacterial heat treatment, a stable processing performance and good antibacterial properties.
Copper is a key element of anti-bacterial, plus many have to consider the anti-bacterial, but also to ensure stable processing of steel has a good performance. Optimum dosage of copper vary due to steel, Nisshin Steel chemical composition of the development of antibacterial stainless steel, such as Table 10, the ferrite Cu 1.5% increase in steel, martensitic steel, copper 3% in Canada, austenitic steel plus 3.8% copper.

Table 10 the chemical composition of various antibacterial stainless steel


study shows that: copper in direct contact with the bacteria is a prerequisite for antimicrobial sterilization, antibacterial stainless steel for this first heat treatment, so that high concentrations of copper precipitated from the matrix to ε-Cu phase uniformly dispersed. And then by surface polishing treatment, the ε-Cu exposed to the metal surface, which in turn has antibacterial activity. The results show that ferritic and martensitic stainless steel of the staphylococcus and E. coli bacteria reduction rate of 100% stainless steel 99% reduction in bacteria. Antibacterial stainless steel used for some time after the depletion of the surface of ε-Cu phase, the antibacterial properties will be reduced, this time re-processing by polishing and the like, will re-form ε-Cu phase with a new surface, restore the antibacterial properties.
similar antibacterial stainless steel and stainless steel compared to increase corrosion resistance, very basic physical properties, mechanical properties vary slightly: ferrite yield strength increased slightly with the punch, the other roughly the same performance ; martensitic stainless steel yield strength, tensile strength and hardness were significantly increased, elongation decreased; austenitic steel yield strength and hardness increased slightly, and other performance fairly. Stainless steel, copper added disadvantage of thermal processing on the cold more good than harm. With the increase in copper content to be considered when thermal processing temperature to reduce heating, process can easily result in improper operation billet corner crack and surface crack. Compared with the same antibacterial stainless steel, plastic and withstand deep drawing cold was markedly improved, but martensitic steel strength (hardness) was improved markedly increased damage caused by mold. Austenitic steel with the copper content is increased, increased austenite stability, strengthen the slow cold, steel can withstand higher processing rate of the cold, cold steel pier and greatly improved deep drawing properties of steel are magnetic transition from weak for the non-magnetic. antibacterial stainless steel with stainless steel
advantages and good antibacterial properties, the market has been very popular in the kitchen equipment, food industry table and utensils, medical equipment, tableware and everyday life towel stand, refrigerated containers bays and other areas promote the use of, public places, public transport vehicles of some facilities such as handrails, stair handrails, telephone booths, and railings to prevent cross-infection should also try antibacterial stainless steel. Steel industry should focus on antimicrobial medical devices martensitic stainless steel wire, woven wire mesh stainless steel austenitic antibacterial and clean the ball with ferrite antibacterial stainless steel filaments of the development.

Reference
1 (U.S.) DONALD PECKNE editor, Gu Shouren such as translation,
2 Lushi Ying et al,
3
4 Poon Village, stainless steel,
5 Luo like, super stainless steel, modern development, the
5 Zhang Xiaofu, super martensitic stainless steel
7 Zhang Xiaofu, antibacterial stainless steel - about Japan's new steel
8 By John Magee, Development of Type 204Cu Stainless Steel, a Low-Cost alternate to Type 304,p90x bands, Guangdong,