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真空热压超高碳超高铬模具钢研究

Study on tool steels with ultrahigh carbon and ultrahigh chromium prepared by vacuum hot-pressing

  • 摘要: 采用真空热压技术制备了含有超高碳和铬(2.6%C,26%Cr,质量分数)的模具钢。基于差示扫描量热分析曲线,选取两个远低于熔点的温度(1100 ℃和1150 ℃)进行热压,分别制造出几乎完全致密、粉末之间冶金结合良好的块体钢,密度为7.45~7.47 g∙cm−3;对应热压温度1100 ℃ 和1150 ℃,热压态钢中平均碳化物尺寸分别为3.5 μm和5.5 μm,最大碳化物尺寸分别为6.0 μm和8.5 μm。经1150 ℃淬火、500 ℃回火,1100 ℃ 和1150 ℃热压钢的平均硬度分别为HRC 62.6和HRC 60.8,平均三点弯曲强度分别为2060 MPa和1850 MPa;经1150 ℃淬火、550 ℃回火,1100 ℃ 和1150 ℃热压钢硬度分别为HRC 55.2和HRC 53.6,平均三点弯曲强度分别为2490 MPa和2320 MPa。在相同淬火和回火条件下,1100 ℃热压钢的三点弯曲强度较高,原因是淬火回火后钢中碳化物尺寸较小。

     

    Abstract: Tool steels with the ultrahigh C and Cr (2.6% C and 26% Cr, mass fraction) were produced by the vacuum hot-pressing (VHP) in this study. Based on the differential scanning calorimetry analysis, two VHP temperatures (1100 ℃ and 1150 ℃) are selected which are much lower than the melting point. The bulk steels with the density of 7.45~7.47 g∙cm−3 are obtained by VHP at 1100 ℃ and 1150 ℃, respectively, exhibiting the full densification and good metallurgical bonding between powders. The average carbide sizes in the bulk steels obtained by VHP at 1100 ℃ and 1150 ℃ are 3.5 μm and 5.5 μm, and the maximum carbide sizes are 6.0 μm and 8.5 μm, respectively. After quenching at 1150 ℃ and tempering at 500 ℃, the average hardness values of the bulk steels obtained by VHP at 1100 ℃ and 1150 ℃ are approximately HRC 62.6 and HRC 60.8, and the average three-point bending strengths are 2060 MPa and 1850 MPa, respectively. After quenching at 1150 ℃ and tempering at 550 ℃, the average hardness values of the bulk steels obtained by VHP at 1100 ℃ and 1150 ℃ are approximately HRC 55.2 and HRC 53.6, and the average three-point bending strengths are 2490 MPa and 2320 MPa, respectively. At the same quenching and tempering conditions, the higher three-point bending strengths of the bulk steels obtained by VHP at 1100 ℃ can be attributed to the smaller carbide sizes.

     

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