摘要热稳定性和回火稳定性是衡量工具钢红硬性和淬透性的一项重要指标。本文借助 洛氏硬度计、扫描电镜等设备，对比普通工具钢和含 Ni 工具钢的热稳定性和回火稳 定性，探讨工具钢在强韧化处理时的组织和硬度变化。研究结果表明：H418 在 620℃、680℃等温保温过程中，硬度值均比 H407 高， 保温 10h 后，H418 比 H407 硬度分别高出 8。4HRC 和 9。1HRC。随着保温时间延长， 组织中残余奥氏体大量分解，马氏体-奥氏体组织渐渐消失，两种钢的硬度都降低， 前者降低范围比后者小，含 Ni 工具钢 H418 的热稳定性更好。在保温初期时，两种 钢的硬度值下降速度较快，当时间进一步增加时，两种钢的硬度降低趋势平缓，并逐 渐趋向于一个平台。回火初期时两种钢的硬度均降低，下降趋势较为平缓。当回火温 度为 400℃时 H418 硬度降低了 1。9HRC，H407 降低了 12。3HRC。H418 在不同温度下 保温相同时间的硬度变化较小，表现出更好的回火稳定性。在 550℃时钢中含有的合 金元素析出了特殊碳化物，起到弥散强化作用，产生二次硬化。在 680℃高温保温过 程中，回火马氏体的形态逐渐模糊，晶粒变得粗大，出现贝氏体，同时开始有碳化物 在马氏体板条界面形核析出，组织开始进入再结晶阶段。81307

毕业论文关键词：微合金化；热处理；热稳定性；回火稳定性；硬度

Abstract Thermal stability and tempering stability is an important indicator of tool steel on red hardness and hardenability。 With the help of Rockwell hardness tester, scanning electron microscope and other equipments, comparing the temper resistance and thermal stability of ordinary tool steel with Ni-containing tool steel, discussing changes at hardness and microstructure of tool steel in toughening process。

The results show that: hardness on H418 at 620 ℃, 680 ℃ isothermal holding

process is higher than H407, after 10 hours, the hardness of H418 is higher than H407 and respectively 8。4HRC and 9。1HRC。 Both steels have reduced hardness when time is holding on, reduced range of the former is smaller than the latter。 In the early incubation, the hardness of both steels has a faster rate of decline, when the time is further increased, the hardness of both steels decreasing tendency gently and gradually moving  to a  platform。 and the hardness in the isothermal process is reduced to a lesser extent, better thermal stability of Ni-containing tool steel H418, tempering H418 hardness upward trend peaked in the mid-500 degrees, the temperature further increases as the hardness began to decline。 H418 tool steel hardness change at different temperatures holding the same  time    smaller,

showing better tempering stability。 At 550 ℃ in  steel alloying  elements contained in   the

special carbide precipitation, dispersion of the organization play the role of secondary hardening。 At 680 ℃ high temperature insulation in the process, form tempered martensite

gradually blurred, become coarse grains, bainite, and martensite laths in the beginning of carbide precipitation nucleation interface, organizations began to enter recrystallization stage。

Key words ： Micro-alloyed; heat treatment; thermal stability; tempering stability; hardness

目录

第一章 绪论 1

1。1 引言 1

1。2 工具钢概述 1

1。2。1 工具钢的分类 1

1。2。2 工具钢性能要求 2

1。3 工具钢国内外研究现状 3

1。4 工具钢 H407 和 H418 简介