The role of nickel in 316 stainless steel

The effect of nickel in stainless steel is only exerted after working with chromium.

Nickel is an excellent corrosion resistance material and an important alloying element for alloy steel. Nickel is an element that constitutes austenite in steel, but in order for low-carbon nickel steel to obtain a pure austenite arrangement, the nickel content must reach 24%; And as long as the nickel content is 27%, the corrosion resistance function of the steel in some media is significantly changed. So nickel cannot make up stainless steel alone. However, when nickel and chromium are present in stainless steel, nickel-containing stainless steel has many valuable functions.

According to the above situation, it can be seen that the effect of nickel as an alloying element in stainless steel lies in the fact that it changes the arrangement of high-chromium steel, so that the corrosion resistance function and process function of stainless steel can be improved.

Manganese and nitrogen can replace nickel in chromium-nickel stainless steel.

Although there are many advantages of chromium-nickel austenitic steel, in recent decades, due to the development and use of nickel-based heat-resistant alloys and thermally strong steels containing less than 20% nickel, as well as the increasing demand for stainless steel in the chemical industry, and the small amount of nickel deposits and scattered in a small area, there is a contradiction between supply and demand of nickel in the world. Therefore, in stainless steel and many other alloy categories (such as steel for large castings and forgings, tool steel, hot strength steel, etc.), especially in countries where nickel resources are relatively scarce, the scientific research and production practice of nickel saving and nickel substitution with other elements has been widely carried out, and the research and use of manganese and nitrogen to replace nickel in stainless steel and heat-resistant steel are more used in this regard.

Manganese's effect on austenite is similar to that of nickel. But to put it more appropriately, the effect of manganese is not to form austenite, but to reduce the critical quenching speed of steel, add the stability of austenite when cooling, and press the differentiation of austenite, so that the austenite composed at high temperature can be maintained to room temperature. In terms of improving the corrosion resistance function of steel, the effect of manganese is not large, such as the manganese content in steel is changed from 0 to 10.4%, and the corrosion resistance function of steel in air and acid is not significantly changed. This is due to the fact that manganese has little effect on the electrode potential of the progressive iron-based solid solution, and the protective effect of the oxide film is also very low, so although there are austenitic steels alloyed with manganese (such as 40Mn18Cr4, 50Mn18Cr4WN, ZGMn13 steel, etc.), they cannot be used as stainless steel.

The effect of manganese in steel to stabilize austenite is about half that of nickel, that is, the effect of 2% nitrogen in steel is also to stabilize austenite, and the effect is greater than that of nickel. For example, in order to make steel containing 18% chromium obtain austenitic arrangements at room temperature, low-nickel stainless steel with manganese and nickel nitrogen and chromium-manganese-nitrogen non-luring steel with yuan nickel have now been used in industry, and some have successfully replaced the classic 18-8 chromium-nickel stainless steel.

Titanium or niobium is added to stainless steel to avoid intergranular corrosion.

Molybdenum and copper are able to improve the corrosion resistance of some stainless steels.

The influence of other elements on the function and arrangement of stainless steel.

The above primary elements have an impact on the function and arrangement of stainless steel, in addition to the elements that have a greater impact on the function and arrangement of stainless steel, stainless steel also contains some other elements. Some are the same as general steel, such as silicon, sulfur, phosphorus, etc., and some are for some specific intentions, such as cobalt, boron, selenium, rare earth elements, etc. In terms of the primary nature of the corrosion-resistant function of stainless steel, these elements are related to several of the elements that have been commented on, and are all right or wrong, but nevertheless, they cannot be completely overlooked, as they also affect the function and arrangement of 316 stainless steel.