摘要：用固体渗硼技术对T8、T10、T12钢分别在850℃、880℃、910℃和940℃保温3、5、7、9个小时进行渗硼。通过光学显微镜观察了3种钢在不同加热温度和保温时间下，钢渗层的形貌和显微组织，同时得到渗层厚度的范围为8.72~172.92μm。测量得到的不同含碳量钢渗层的硬度比较接近。渗硼层的生长动力学是通过测量不同温度和保温时间下渗层的厚度来分析的。61097

    结果表明：生长速率常数K随着温度和保温时间的增加而增加。 T8、T10、T12钢的扩散激活能分别为218、257、271 kJ/mol。可以发现，不同钢种的渗硼扩散激活能随着含碳量的升高近似呈线性增长。同时也画出了3个钢种渗硼层的等厚度图,通过等厚度图可以将渗硼的工艺参数和渗层厚度联系起来。

毕业论文关键词：碳钢；固体渗硼；渗硼层；动力学；扩散激活能

毕业设计说明书（论文）外文摘要

Title   Research on the Boriding Kinetics of Carbon      Tool Steels 

Abstract In this study, the T8、T10、T12 steels substrates were pack-borided at 850, 880,910 and 940℃ for 3, 5, 7, and 9 h. The morphology formed on the surface of steel substrates were confirmed by optical microscopy analysis. Boride layer thickness formed on the borided steels ranged from 8.72 to 172.92μm depending on process temperature, treatment time and carbon contents of the substrates. The hardness of borides of different carbon-contents steels was very similar. Layer growth kinetics were analyzed by measuring the extent of penetration of  borided layers as a function of boronizing time and temperature in the range of 850-940℃. The kinetics of the reaction have also been determined by varying the boriding temperature and time.

The results show that K increase with boriding temperature and time. Activation energies (Q) of borided T8、T10、T12 steels at present study were respectively determined as 218、257、271 kJ/mol, which were increased with carbon contents. Moreover, an attempt was made to investigate the possibility of predicting the contour diagrams of boride layers variation and to establish some empirical relationships between process parameters and boride layer thicknesses.

Key word: Carbon steels; Solid boronizing; Borides; Kinetics; Activation energy

1 绪论 1

2 实验4

  2.1  实验材料与设备4

  2.2  实验过程与方案5

3 实验结果与讨论 6

  3.1渗硼层金相组织分析6

  3.2渗硼层显微硬度分析8

  3.3渗硼层生长动力学分析9

结论 18

致谢  19

参考文献20

1. 绪论

1.1碳素工具钢

碳素工具钢不含合金元素,主要依靠钢中的碳进行强化。有些钢中加少量锰(0.4%~0.6%)，含碳量介于0.65%~1.35%。国家标准中包含有8个钢号(T7、T8、T8Mn、T9、T10、T11、T12、T13),简称碳工钢。它属于低淬透性的工具钢。水淬时淬透截面厚度不大于8mm。碳素钢耐热性差,一般限在200℃以下使用。碳素工具钢T7、T8,分属亚共析钢和共析钢，用于制作形状简单的刀具和木工刀具。T9、T10、T11属过共析钢，用于制造耐磨性要求较高的工具和冷冲模、拉丝模、切边模、丝锥以及形状简单的低精度量具。T12、T13亦属过共析钢，钢中碳化物量更高，耐磨性好，但韧性低，不耐冲击，只适用于锉刀、丝锥、刻刀、剪刀等手工工具。碳素工具钢热加工后具有片状珠光体组织,硬度较高，切削难。预先进行球化退火(加热至740~770℃，后在600~680℃等温处理),硬度可降至HB157~ 197。碳工钢淬火加热温度770~820℃，用盐水一油双液淬火加速冷却，随后回火防止开裂和减少淬火变形[1]。