What Are the Types and Grades of Stainless Steel Castings

Introduction of Stainless Steel Castings

Simply put, stainless steel castings are steel that is not easy to rust. In fact, some stainless steels have both rust resistance and acid resistance (corrosion resistance). The rust resistance and corrosion resistance of stainless steel castings are due to the formation of a chromium-rich oxide film (passivation film) on the surface. This rust resistance and corrosion resistance are relative. Tests have shown that the corrosion resistance of steel in weak media such as the atmosphere and water and oxidizing media such as nitric acid increases with the increase of the chromium content in the steel. When the chromium content reaches a certain percentage, the corrosion resistance of the steel changes suddenly. , That is, from easy to rust to not easy to rust, from no corrosion resistance to corrosion resistance.

In many industrial applications, stainless steel can provide satisfactory corrosion resistance. According to the experience of use, the corrosion of stainless steel is mainly manifested in: a serious form of corrosion of stainless steel is localized corrosion (that is, stress corrosion cracking, pitting corrosion, intergranular corrosion, corrosion fatigue and crevice corrosion). The failure cases caused by this local corrosion accounted for almost half of the failure cases. In fact, many failure accidents can be avoided through reasonable selection of materials.

Types and Grades of Stainless Steel Castings

After years of research and development, stainless steel has been classified into many categories. Among them, according to the different matrix structure of stainless steel materials, it is mainly divided into:

Austenitic Stainless Steel Castings

Austenitic stainless steel is stainless steel material with a stable austenitic structure inside. In addition to containing 18% chromium and about 8% nickel, it also contains a small amount of molybdenum, titanium, nitrogen and other elements. This kind of stainless steel material is a product with good comprehensive performance and can withstand the corrosion of multiple media. Moreover, the toughness and ductility of austenitic stainless steel are better, and at the same time, its free cutting performance is also very good. At present, austenitic stainless steel materials are widely used in various industries.

At the same time, we can talk about the 304 and 304L, 316 and 316L, where the "L" stands for low carbon, making each grade of material softer but more resistant to corrosion. Generally, casting products used at the seaside or at high frequency at sea will have a longer life with 316L, even though 316 has been known for its excellent corrosion resistance.

Austenitic stainless steel is the most common material used in our silica sol investment casting plant, and basically half of the output is austenitic stainless steel. Regardless of the American standard, such as SUS304, the German standard, such as 1.4301, 1.4308, 1.4408, and the Japanese standard, such as SCS13, except for the slight difference in the range of individual elements, there is little difference in general chemical composition. We are committed to providing the production of non-standard parts, strictly in accordance with the material standards provided by the customer, to ensure that every element can meet the standard requirements, so that customers can ensure the integrity of the function and the safety of use during the long-term use of the product.

Ferritic Stainless Steel Castings

Ferritic stainless steel is the most common type of stainless steel material. It is a kind of stainless steel whose main structure is ferritic in use. The chromium content of this kind of stainless steel is between 11% and 30%. In addition, it also contains a small amount of elements such as molybdenum, titanium and niobium. In addition to good corrosion resistance, ferritic stainless steel is characterized by good oxidation resistance, excellent stress resistance, and it also has good thermal conductivity and a very small expansion coefficient. However, the plasticity of ferritic stainless steel is poor, therefore, this kind of stainless steel material is mainly used to make corrosion-resistant parts.

409 stainless steel is a relatively cheap stainless steel, usually used as a car exhaust pipe.

Martensitic Stainless Steel Castings

Martensitic stainless steel is a hardenable stainless steel material. The biggest feature of this kind of stainless steel material is that the mechanical properties of this kind of stainless steel material can be changed by heat treatment. At present, this kind of stainless steel material is mainly used in the processing of steam turbine blades, surgical instruments and other products.

This conventional stainless steel material has been widely used in automobile power and exhaust systems. Especially in recent years, Japan has increased the use of stainless steel material. Its performance is close to that of austenitic stainless steel. The price is more competitive than austenitic stainless steel. However, most domestic foundries do not have enough strength and experience to make stainless iron materials with similar austenitic properties. The most obvious defect is that the castings will crack at high temperatures, which is a major taboo in the industry. At the same time, stainless iron cannot be simply pickled to achieve bright white, generally gray-black. Therefore, in this area, domestic foundry factories and auto parts factories need to invest energy and financial resources to study carefully.

Duplex Stainless Steel Castings

Duplex stainless steel is stainless steel in which the ferrite and austenite phases in the solid solution structure each account for about 50%. It not only has good toughness, high strength and excellent resistance to chloride corrosion, but also resistance to pitting corrosion and intergranular corrosion. Corrosion, especially stress corrosion resistance in chloride environment.

The cost of duplex stainless steel is relatively the highest, generally 1.5 to 2.5 times the price of austenitic stainless steel. But its performance is also excellent. Usually used in the chemical industry, it needs to withstand the dual pressure of high corrosiveness and high temperature, it can still have a better life performance.

As a stainless steel foundry, there are still some concerns when encountering the customized business of duplex stainless steel. The main reason is that the business volume of duplex stainless steel in the market is small throughout the year. As a factory, it is really difficult to balance the interests of customers and the minimum order cost.

Precipitation Hardening Stainless Steel Castings

Precipitation hardening stainless steels have corrosion resistance comparable to austenitic varieties, but can be precipitation hardened to even higher strengths than other martensitic grades. 

The 17-4PH material is an American grade, a martensitic precipitation hardening stainless steel, which is equivalent to a Chinese grade: 0Cr17Ni4Cu4Nb.

17-4PH alloy is a precipitation, hardening, martensitic stainless steel composed of copper and niobium/columb.

This grade has high strength, hardness and corrosion resistance.

After heat treatment, the mechanical properties of the product are more perfect, and can reach a compressive strength of up to 1100-1300 mpa (160-190 ksi). It has good corrosion resistance to the atmosphere and diluted acid or salt. Its corrosion resistance is the same as 304 and 430.

Conclusion

Why Choose Our Stainless Steel Castings