Special purpose high alloy cast steel

High alloy cast steel refers to the alloy cast steel with the total content of alloy elements above 10%. According to its use, it is divided into cast stainless steel, heat-resistant cast steel and wear-resistant and corrosion-resistant alloy cast steel.

Cast stainless steel 

(1) ferritic stainless steel. This kind of steel takes chromium as the main alloy element. The commonly used brands in China are zg1cr17, zglcr19m02 and zgcr28, which are used in nitric acid, nitrogen fertilizer, chemical fiber and other industries. 

(2) Martensitic stainless steel. The Chinese brands include zglcr13 and ZG2Cr13, which are used to manufacture castings that are required to withstand impact load and work under conditions of high toughness but low medium concentration. It can be used as pump shell, impeller, valve, etc. 

(3) Austenitic stainless steel. This kind of steel contains high chromium and nickel. The commonly used grades in China include zgocr18ni9, zglcr18ni9, zg0cr18ni9ti, zg1cr18ni9ti, zg0cr18ni12mo2ti, zg1cr18ni12mo2ti, zg1cr24ni20mo2cu3, zg1cr18mn8nin, etc. the typical grades are zg0cr18ni9 and ZG1Cr18Ni9. 

(4) AUSTENITIC FERRITIC STAINLESS STEEL. This kind of steel contains manganese and nitrogen to save nickel. The commonly used brands in China are zg1cr17mn9ni4mo3cu2n and zg1cr18mn13mo2cun. Medium and high strength martensitic stainless steel can be used when corrosion resistance is not high, but high mechanical properties are required. Chinese brands suitable for casting with wall thickness below 100mm include zg10cr13, zg20cr13, zg10cr13ni1 and zg10cr13ni1mo. ZG06Cr13Ni4Mo, zg06cr13ni6mo and zg06cr16ni5mo are suitable for casting with wall thickness of l00-200mm. 

(5) Precipitation hardening stainless steel. The Chinese brand is zg0cr17ni4cu4nb, which has high strength, toughness and wear resistance. It can be used in chemical, shipbuilding, aviation and other departments as high-strength wear-resistant and corrosion-resistant castings.

The castability of stainless steel is poor, the fluidity of molten steel is low, and it is easy to produce cold insulation or slag inclusion. Therefore, the pouring temperature should be increased, generally not lower than 1530 ℃. The sectional area of the gating system shall be 30% ~ 50% larger than that of carbon steel castings. The volume shrinkage value of stainless steel is large, and it is easy to produce shrinkage cavity and porosity. The riser of casting should be 20% ~ 30% larger than that of carbon steel. The casting has a large tendency of hot cracking, and the pouring temperature is high and it is easy to stick to sand. Corresponding measures should be taken in the casting process. Austenitic ferritic stainless steel has better casting properties, but is more sensitive to porosity.

Heat resistant cast steel heat resistant cast steel can be divided into heat-resistant non peeling cast steel (anti-oxidation steel) and heat-resistant cast steel according to the purpose. The commonly used anti-oxidation steel is heat-resistant chromium steel, with chromium as the main alloy element. The chromium content is 13% ~ 14% in the low and 25% ~ 35% in the high. Sometimes, a small amount of silicon or nickel, such as zg40cr9si2, is added. Its maximum oxidation resistance temperature is 800 ℃, and it is lower than 700 ℃ under long-term load. It can be used to make crucibles, furnace doors and bottom plates.