The difference between stainless steel 1Cr18Ni9Ti and 0Cr18Ni9

Both 1Cr18Ni9Ti and 0Cr18Ni9 belong to the 18-8 series of stainless steels. The difference is mainly the amount of carbon and whether it contains titanium. There is basically no big difference in their mechanical properties. In the early stage of the production of stainless steel varieties, due to the limitation of smelting technology, the carbon content in stainless steel could not be reduced, so a small amount of titanium was added to improve its corrosion resistance. With the advancement of technology, the production of low-carbon and ultra-low-carbon stainless steel is no longer a problem. Therefore, 0Cr18Ni9 has become more and more widely used, while 1Cr18Ni9Ti has become a restricted and not recommended variety. But this is not to say that 1Cr18Ni9Ti is useless at all. There is a stainless steel brand called 321H in foreign countries, which is basically the same chemical composition as 1Cr18Ni9Ti. The purpose of producing this brand of stainless steel is to improve the high temperature performance of 321 stainless steel.
0Cr18Ni9 is the American Standard 304, which is the most commonly used stainless steel.
304L is an ultra-low carbon stainless steel with better corrosion resistance.
304H has higher carbon content and better high temperature strength.
The material of 321 has been rarely used, commonly used is 304/304L or 316/316L stainless steel 1Cr18Ni9Ti is ordinary stainless steel.
1. Chemical composition
C: <=0.12%
Cr: 17-19%
Ni: 8-11%
Ti: 5*(C%-0.02)-0.8%
2. Mechanical properties
Tensile strength σb(MN/m2) >=550
Yield strength σs(MN/m2) >=200
Elongation δ5(%)>=40
Shrinkage ψ(%)>=55
my country's 1Cr18Ni9Ti is equivalent to American AISI321, 0Cr18Ni9 is equivalent to AISI304, 1Cr18Ni9 is equivalent to 302, 0Cr17Ni12Mo2 is equivalent to AISI316

If it is used at a high temperature of 700 °C, 1Cr18Ni9Ti should be competent, because it is not only an austenitic stainless steel, but also a widely used austenitic heat-strength steel, but it is best not to exceed 750 °C, and its heat treatment is solution treatment , That is, heating to above 1000°C, water quenching after holding for a certain period of time, and then aging at a temperature 60~100°C higher than the use temperature.

3. The difference with 0Cr18Ni9
The carbon content of the two is different, 1Cr18Ni9Ti is high. The content of chromium and nickel is the same, 18% and 9% respectively.
In this case, due to the low carbon content of 0Cr18Ni9, its strength is lower than that of 1Cr18Ni9Ti, and its corrosion resistance is better than that of 1Cr18Ni9Ti. However, since 1Cr18Ni9Ti contains titanium that resists intergranular corrosion, it can be improved by heat treatment to resist intergranular corrosion. It can be used as a substitute under normal temperature conditions.
The stainless steel grade commonly used in the past was 1CR18NI9TI, and the commonly used grade is 0CR18NI9 (or 304L). 1CR18NI9TI stainless steel has a high carbon content of about 0.1%. These carbons are supersaturated and solid-dissolved in austenite at room temperature. When 1CR18NI9TI stainless steel is heated to 550800 ° C, the supersaturated carbon precipitates on the grain boundary in the form of chromium carbide. The chromium carbides on the grain boundaries are easy to react with acid to cause pitting corrosion and intergranular corrosion. The chromium carbide precipitation temperature just includes the brazing temperature of the vacuum interrupter, so the brazing of the arc extinguisher will cause the chromium carbide precipitation of 1CR18NI9TI stainless steel. This can easily lead to air leakage in the vacuum interrupter during use. The carbon content of 0C18NI9 or 304L stainless steel is less than 0.03%. At this time, the carbon content is close to the solubility of carbon in austenite, so heating will not cause the precipitation of chromium carbides, thereby avoiding intergranular corrosion and pitting corrosion. This greatly reduces the possibility of air leaks.