The raw materials used in this test: pig iron, scrap steel, Table 1 low-carbon high-chromium cast iron basic chemical composition low-drawn ferrochrome, ferromanganese and so on. The basic components are shown in Table 1.
The alloy material was smelted in a 100 KW, 150 Kg medium frequency induction furnace. Wet sand casting, casting temperature is about 1450X: about 20mmx20mm> <120mm sample hair. The heat treatment of the sample was carried out in a high-carbon carbon box type resistance furnace. During the test, three samples were taken from each group, and the average value was taken.
The heat treatment process used in the test was as follows: the hardness was measured on a HR-150A Rockwell hardness tester, and the load was 150 kg. The sliding wear test was carried out on a self-made WT type reciprocating sliding wear tester, mainly because the abrasive was microscopically formed on the metal surface. The amount of wear caused by cutting. The sample was pre-ground and loaded on a semi-resin alumina sand cloth with a particle size of 60. The load was 26N, the sliding speed of the sample was 16m/min, the wear time was 5min, and the weight loss was measured. The sample was repeated 5 times, and the average loss of reset was taken to compare the material's sliding wear resistance (g/5min). In the test, the self-made GTM type drum type wear tester was used to measure the wear under fatigue wear. The diameter of the drum was 300 mm and the speed was 42 r/min. The wear test was carried out for 100 hours to calculate the weight loss rate (l5g/gh).
3 Test results and analysis 3.1 Hardness and radish test results The hardness test of the low-carbon high-chromium white cast iron samples after heat treatment was carried out, and the test results are shown.
The effect of the heat treatment process on the sliding wear rate can be seen from the above. At the quenching temperature of 980C, the hardness of the low carbon high-column iron increases with the prolongation of the retention time, and at 1050X: quenching temperature, With the extension of the holding time, the hardness of the low-carbon high-chromium cast iron slightly decreased, and the warranty period continued to increase, and the hardness slightly increased. Under the sliding wear test conditions, whether at 980X: or 105 (TC quenching temperature, the sliding wear rate decreases with the increase of holding time, but the difference between the two is not obvious (as shown). Under the wear test conditions, 980X: at the quenching temperature, the wear rate increases first with the increase of the holding time, and then decreases (as shown), while at 1050X: at the quenching temperature, the drum wear occurs with the increase of the holding time. The rate shows a significant downward trend.
It can be seen from the sum and the immersion of 980X: lh, the corrosion on the substrate is different. This is mainly because the sample is segregated in the as-cast state. When the high-temperature holding time is short, the carbon and other alloying elements are not sufficiently diffused and homogenized, so that the electrochemical electrode potential of each part of the substrate is different, resulting in a deep corrosion of some of the substrates. Black under the microscope (such as B), while some of the substrate is lightly corroded and pale white under the microscope (such as A). After the sample was kept for 6 hours, the segregation of the components was largely attenuated, and the components were gradually homogenized. The number of secondary carbides in the matrix is ​​increased (such as B), and the pale white areas on the substrate are much reduced, but there is still a small amount of component segregation (such as A). At 1050X: when it is kept for 1h, there is a certain degree of component segregation in the matrix (such as A). When the temperature is kept for 3h, the composition of each micro-region is basically uniform, and more secondary carbides are precipitated on the matrix, and a few sizes are relatively large (such as A). As the holding time continues to increase, the tendency of the precipitated secondary carbide to aggregate and grow is more obvious (such as A).
In 980X: during quenching, as the holding time is prolonged, more secondary carbides are precipitated, and the content of carbon and alloying elements in the matrix is ​​lowered, resulting in the Ms point of the martensite transformation being elevated, and the transformation is more With more martensite, the amount of retained austenite is reduced, so the hardness increases with the increase of holding time. At the quenching temperature of 1050C, the quenching temperature is higher, the carbon and other alloying elements in the matrix are contained, the secondary carbides are less precipitated, the degree of austenite stabilization increases, and the Ms point of martensite transformation decreases. After quenching, the amount of martensite decreases and the amount of retained austenite increases, so the hardness decreases slightly with the retention time. However, as the holding time continues to increase, the secondary broken material precipitates: the increase, so that the hardness is slightly increased.
Under the sliding wear condition, no matter at 9800 and 105 (TC quenching temperature, with the prolonging of the holding time, the secondary carbide precipitation is more, and there is a tendency to grow: continue to extend the holding time, the secondary carbides are aggregated and When grown up, the larger size is more conducive to improving its micro-cutting resistance. Therefore, as the holding time increases, the sliding wear rate decreases, and the wear resistance is improved.
Under the condition of rolling wear, when the 9800 is quenched, the amount of secondary carbide increases with the increase of the holding time, which increases the interface between the matrix and the carbide. In the fatigue wear process, crack initiation and expansion are easy to occur at the interface, and the crack propagation is mainly along the interface between the carbide and the matrix, so the wear rate increases: but as the holding time continues to extend, twice Carbides are aggregated and grown, and the carbide spacing is piled up, so that the matrix's hindrance to crack propagation is enhanced, and the fatigue resistance of the material is improved, and the wear rate is decreased. When quenching at 10501C, as the retention time prolongs, the secondary carbides also aggregate and grow, the carbide spacing increases, and passivation occurs at the sharp corners of the eutectic carbide, reducing stress concentration and splitting the substrate. Thereby improving the fatigue resistance of the material, the wear rate is reduced, and the wear resistance is improved.
(Continued from page 23) 3. The initial impact and elongation rate increase first and then decrease with the increase of isothermal temperature, 3300 isothermal impact goods are the highest, and 3600 isothermal elongation is the largest.
(Finish)
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