Double-fluid composite iron-based bimetal casting method

[0014] Example: 500×500×50mm composite wear plate

[0015] The bimetal composite wear-resistant plate is composed of low-carbon cast steel and high-chromium cast iron, and its composition is shown in the following table. The finished product requires high chromium cast iron layer thickness 25-35mm, hardness requirement ≥55HRC, low carbon cast steel thickness 15-25mm, and impact toughness not less than 50J.

[0016]

[0017] Process analysis: Comparing the composition of low-carbon cast steel and high-chromium cast iron in the table above, the composition of Si, Mn, P, and S after fusion does not change much, mainly due to the changes of C, Ni and Cr. From the physical properties of the two, the thermal conductivity of low-carbon cast steel is higher than that of high-chromium cast iron, the melting point of low-carbon cast steel is about 1510℃, the melting point of high-chromium cast iron is about 1400-1450℃, and the melting point of low-carbon steel is higher than High chromium cast iron, so the high melting point low carbon cast steel is used as the first layer of metal, and the low melting point high chromium cast iron is used as the second layer of metal. When the high chromium cast iron is melted, the content of C and Cr should be appropriately increased to control its composition At the upper limit. In this way, after the low-carbon cast steel is fused during pouring, the content of C, Ni and Cr in the high-chromium cast iron can be appropriately reduced and fall within the control range of the high-chromium cast iron, ensuring the qualification and performance of the bimetal.

[0018] The cold iron is made of high-quality low-carbon steel with good heat transfer. The size of the cold iron is 450×450×40mm, and its weight is similar to that of the first layer of low-carbon cast steel.

[0019] See attached figure 1 after modeling, including molding sand 1, low-carbon cast steel runner 2, high-quality low-carbon steel chilled iron 3, riser (observation hole) 4, cavity 5, paint 6, high chromium cast iron runner 7.

[0020] After the chilled iron 3 is preheated, the coating 6 is sprayed. After the coating 6 is dried, the sand mold 1 is combined into the box to form a riser 4, a cavity 6, a low carbon cast steel runner 2 and a high chromium cast iron runner 7. The riser 4 is used as an observation temperature measuring hole from which the temperature of the low-carbon cast steel composite surface is measured.

[0021] The melting point of low-carbon cast steel is about 1510°C, which is higher than that of high-chromium cast iron. As the first layer of metal, its casting temperature is controlled at 1580-1650°C. The freezing point of high-chromium cast iron is 1400-1450℃, which is lower than that of low-carbon cast steel. As the second layer of metal, its casting temperature is controlled at 1520-1600℃.

[0022] Low-carbon cast steel is quickly poured from runner 2 with a pouring weight of 70-80Kg. Observe the solidification status from the riser (observation hole) 4 and measure the temperature. When the temperature of the cooling composite surface is 1330-1500°C, the high-chromium cast iron molten metal is quickly poured from the runner 7.

[0023] After cooling, open the box and go through the processes of heat treatment, sand blasting, polishing, etc., to make the finished composite wear-resistant plate. Because the composition of high chromium cast iron does not change much, within its composition range, its performance after heat treatment can meet the requirements .

[0024] Due to the slow cooling rate of traditional sand casting, the temperature gradient of the low carbon cast steel plate after pouring is very small along the thickness direction. After the second layer of high chromium cast iron is poured, either too much fusion causes the high chromium cast iron to exceed the standard, or there is very little fusion Delamination occurs, the qualification rate is extremely low, and it is basically impossible to produce bimetal composite wear plates. With this process scheme, the rapid cooling effect of the bulk cold iron increases the temperature gradient in the thickness direction of the low-carbon cast steel plate, so that the second layer of low-melting high-chromium cast iron molten metal can fuse a small amount of the high-melting first layer of low-carbon Cast steel metal greatly improves the qualification rate of bimetal wear-resistant plates, and realizes the industrialized production of bi-metal composite wear-resistant plates by two-liquid casting.