AsStainless Steel Casting Manufacturers, Let’s take a look at the relevant classification of this type of product and walk into its world together.
(1) Ferritic stainless steel
With chromium as the main alloying element, the Cr content is generally between 13% and 30%. It has good resistance to corrosion by oxidizing media and resistance to air oxidation at high temperatures. It can also be used as heat-resistant steel. The welding performance of this kind of steel is poor. When the chromium content is more than 16%, the as-cast structure will be coarse. If the temperature is kept between 400-525℃ and 550-700℃ for a long time,"475℃" brittle phase and σ phase will appear, which will make the steel brittle. The brittleness at 475°C is related to the ordering phenomenon of Cr-containing ferrite. The brittleness of the brittle phase and sigma phase at 475°C can be improved by heating to above 475°C and then cooling quickly. The brittleness of room temperature and the brittleness of the heat-affected zone after welding are also one of the basic problems of ferritic stainless steel. Vacuum refining, adding trace elements (such as boron, rare earth and calcium, etc.) or austenite forming elements (such as Ni, Mu, etc.) N, Cu, etc.). In order to improve the mechanical properties of the weld zone and the heat-affected zone, a small amount of Ti and Nb are usually added to prevent grain growth in the heat-affected zone. Commonly used ferritic steels are ZGCr17 and ZGCr28. This type of steel has low impact toughness and has been replaced by austenitic stainless steel with high nickel content in many cases. Ferritic steels with Ni content exceeding 2% and N content exceeding 0.15% have good impact properties.
(2) Martensitic stainless steel
Martensitic stainless steel includes martensitic stainless steel and precipitation hardening stainless steel. In engineering applications, the main purpose is mechanical properties. Although this type of steel has good corrosion resistance in atmospheric corrosion and milder corrosive media (such as water and certain organic media), its corrosion performance is often not used as an inspection item. The range of its chemical composition is: Cr13%-17%, Ni2%-6%, C≤0.06%.
(3) Austenitic stainless steel
Austenitic stainless steels can be divided into four groups, namely Cr-Ni series; Cr-Ni-Mo, Cr-Ni-Cu or Cr-Ni-Mo-Cu series; Cr-Mn-N series and Cr-Ni-Mn- N series. Cr-Ni is represented by the famous"18-8". Cr-Ni-Mo, Cr-Ni-Cu, Cr-Ni-Mo-Cu series are based on Cr-Ni series by adding 2%-3% molybdenum and copper (or both at the same time) to improve resistance to sulfuric acid However, molybdenum is a ferrite-forming element. In order to ensure austenitization, the Ni content should be appropriately increased after molybdenum is added. The Cr-Mn-N series is a Ni-saving alloy. When the Cr content is greater than 15%, the ideal austenite structure cannot be obtained by adding manganese alone, 0.2%-0.3% nitrogen must be added, and 0.35% or more nitrogen must be added to obtain a single austenite. Because the N content is too high, the castings often cause defects such as porosity and porosity, and by adding an appropriate amount of N and a small amount of Ni, a single austenite can be obtained, which results in the Cr-Ni-Mn-N series. Of course, to obtain the austenite and ferrite complex structure, there is no need to add more N and Ni.