超高强度钢板热冲压成形机理研究

VIP免费

3.0 侯斌 2024-11-19 5 4 2.46MB 62 页 15积分

侵权投诉

摘要

超高强度的钢板在车辆车身上的应用，不仅实现了车辆的轻量化，而且显著

提高了车辆碰撞强度和安全性能，因此成为车用钢材的重要发展方向。随着板料

强度的提高，传统的冷冲压工艺在成型过程中容易产生破裂现象，无法满足超高

强度钢板的加工工艺要求。超高强度钢板的热冲压成形技术是综合了成形、传热

以及组织相变的一种新工艺，主要是利用高温奥氏体状态下，板料的塑性增加，

屈服强度降低的特点，通过模具进行成形的工艺。在成形过程中，板料的成形机

理，力学性能以及成形工艺都与传统的冷冲压工艺不同。因此，研究超高强度钢

板的热冲压成形技术，探索各类成形参数对材料流动性能的影响，分析并制定合

理的热冲压成形工艺，对超高强度钢板在热冲压成形技术中的实际应用具有重要

意义。

本文采用超高强度硼钢板22MnB5为研究对象，选取实验研究与数值模拟结合

的方法，进行了多方面的工作，取得了相应的研究成果：

对淬火后的热冲压硼钢22MnB5进行的硬度测试和金相分析表明，其完全奥氏

体化温度约为950℃。并分析了加热温度以及保温时间对板料强度的影响。

在分析超高强度硼钢板22MnB5热冲压成形工艺的基础上，采用物理高温模拟

实验，在材料完全奥氏体化后处于不同温度、不同应变速率条件下，分别进行了

等温单向拉伸实验和连续冷却单向拉伸实验，获得了不同条件下的真实应力一应

变曲线，并分析变形温度和变形速度对材料流变的影响规律。

关于超高强度硼钢板热冲压流变应力数学模型的研究是对金属塑性变形进

行理论分析和数值模拟的先决条件，本文依据高温热模拟拉伸实验的数据，结合

峰值应力与变形温度及应变速率的关系，计算硼钢22MnB5的热变形激活能，参照

Zener-Hollomon参数，构建硼钢22MnB5的稳态流变应力模型和热变形方程。

以车身结构中典型特征零件—U型件为参考对象，结合拉伸试验数据和以及

超高强度硼钢板22MnB5的热冲压高温热变形方程，输入abaqus软件，建立含有材

料性能参数、几何参数和工艺参数的数值模型，分析成形后的温度场及应力场分

布状况，研究工艺参数对U型件成形后圆角回弹的影响规律。为实际生产中热冲

压工艺的应用提供理论基础。

关键词：热冲压工艺超高强度钢板硼钢奥氏体化拉伸试验热变形方程 U型

件数值模拟回弹

ABSTRACT

The applications of ultra high strength steels (UHSS) not only can achieve

lightweight vehicles, but also can ensure the safety of the vehicle’s impact resistance.

Therefore these become the important direction of the applications of UHSS in

vehicles manufacturing. However, with the enhancement of the steel strength, its

formability is worsened dramatically, so, failure and fracture are always occurred in

the stamping process. It was difficult to apply the traditional cold stamping

technology into the field of UHSS. The hot stamping process of the UHSS includes

deformation, transfer and phase transformation in one process. In this process, the

forming mechanism, mechanical properties and forming technology are different with

the traditional cold stamping process. Study on the mechanical properties and explore

the influences of the forming parameters will make have significance on the further

research and practical application.

This paper takes ultra high strength boron steels 22MnB5 as the objective,

combines the methods of test analysis and numerical simulation to develop the

following research and get related harvest:

Hardness test and Metallographic observations have been done on boron steel

22MnB5 for hot stamping. Results show that the hardness of boron steel 22MnB5 is

greatly improved after quenched in high temperature, and the optimum austenitizing

temperature is 950℃.

Based on the analysis of hot stamping process of boron steel, by using the

physical thermal simulated experiment, after the materials becoming fully austenitic

phase, the tensile tests are carried out under different temperatures and different strain

rates, so the true stress- strain curves under different conditions are obtained. Then the

influences of forming temperature, forming speed and their rules on the flow stress

are analyzed.

Do research on the flow stress model of UHSS is the predetermine condition to

theoretically analyze the plastic forming process and the simulation of the metal

plastic forming. According to the test data, the relationship between the peek stress

with the deformed temperature and strain rate were calculated. Based on the

Zener-Hollomon parameter, the steady flow stress model and hot deformation

equation of boron steel 22MnB5 were proposed.

Takes the characteristic shape of the safety components in auto body-U shape

sample as the objective, based on the tensile test data and the hot deformation

equation of boron steel 22MnB5l, do some simulation in the software abaqus, the

model includes the material properties parameters, the process parameters and the

geometry parameters. From these, the temperature distribution are the stress

distribution during the hot stamping are obtained, also got the effects and rule of main

process parameters on the springback of hot stamping are analyzed. All these provide

reference for the manufacturing process of the hot stamping.

Key Words: Hot Stamping, Ultra High Strength Steels, UHSS, Tensile Test, Hot

Deformation Equation, Numerical Simulation

中文摘要

ABSTRACT

第一章绪论 ................................................................................................................. 1

§1.1 引言 ............................................................................................................................. 1

§1.2 国内外研究现状 ........................................................................................................ 3

§1.2.1 超高强度钢板及其应用 ..................................................................................... 3

§1.2.2 热冲压成形技术简介 .......................................................................................... 3

§1.2.3 国内外研究现状 ................................................................................................. 5

§1.3 课题研究的背景和意义 ............................................................................................ 8

§1.4 本文研究的主要内容 .............................................................................................. 10

第二章超高强度硼钢 22MnB5 最佳奥氏体化温度的确定 ................................... 11

§2.1 引言 .......................................................................................................................... 11

§2.2 实验方案 .................................................................................................................. 11

§2.3 实验材料 .................................................................................................................. 11

§2.3.1 含碳量对钢性能的影响 ................................................................................... 12

§2.3.2 合金元素对钢淬透性的影响............................................................................ 13

§2.4 实验设备 .................................................................................................................. 13

§2.5 试样制备步骤 .......................................................................................................... 14

§2.5.1 切割试样 ........................................................................................................... 14

§2.5.2 试样加热至高温进行水淬 ............................................................................... 14

§2.6 硬度测试 .................................................................................................................. 15

§2.7 金相组织观察 .......................................................................................................... 16

§2.7.1 金相试样的镶嵌、粗磨与抛光........................................................................ 16

§2.7.2 观察金相组织 ................................................................................................... 16

§2.8 本章小结 .................................................................................................................. 19

第三章 22MnB5 超高强度硼钢高温拉伸性能实验研究 ........................................ 20

§3.1 引言 .......................................................................................................................... 20

§3.2 热成形过程的理论 .................................................................................................. 20

§3.2.1 等温和等应变速率条件下多阶段热加工工艺过程的分析 ............................ 21

§3.2.2 温度降低时多阶段热加工工艺过程的分析 .................................................... 21

§3.3 22MnB5 超高强度硼钢板高温拉伸性能实验安排 .............................................. 22

§3.3.1 实验目的 ........................................................................................................... 22

§3.3.2 制备标准高温拉伸板型材试样........................................................................ 23

§3.3.3 实验设备 ........................................................................................................... 23

§3.3.4 实验方案 ........................................................................................................... 24

§3.4 22MnB5 超高强度硼钢板等温拉伸实验结果分析 .............................................. 24

§3.5 22MnB5 超高强度硼钢板连续冷却拉伸实验结果分析 ...................................... 28

§3.6 本章小结 .................................................................................................................. 30

第四章超高强度硼钢 22MnB5 高温热变形本构模型 ........................................... 31

§4.1 引言 .......................................................................................................................... 31

§4.2 热变形流变应力数学模型的分析........................................................................... 31

§4.3 热变形方程 .............................................................................................................. 32

§4.4 本章小结 .................................................................................................................. 34

第五章热成形零件 U型件热冲压模拟分析 ........................................................... 36

§5.1 引言 .......................................................................................................................... 36

§5.2 金属热成形中的传热学理论 .................................................................................. 37

§5.2.1 热力学第一定律 ............................................................................................... 37

§5.2.2 热传递的方式及其描述手段............................................................................ 38

§5.2.3 稳态传热与非稳态传热 ................................................................................... 38

§5.2.4 瞬态传热 ........................................................................................................... 39

§5.3 U 型件的有限元模型 ............................................................................................. 39

§5.3.1 材料模型 ........................................................................................................... 39

§5.3.2 几何模型 ........................................................................................................... 39

§5.3.3 网格划分 ........................................................................................................... 40

§5.3.4 接触模型 ........................................................................................................... 41

§5.4 U 型件热冲压过程仿真及其模拟结果分析 ......................................................... 42

§5.4.1 热冲压成形过程模拟 ....................................................................................... 42

§5.4.2 回弹的计算 ....................................................................................................... 45

§5.4.3 板料厚度对成形回弹的影响............................................................................ 45

§5.4.4 摩擦力大小对成形回弹的影响........................................................................ 46

§5.4.5 压边力对成形回弹的影响 ............................................................................... 46

§5.5 本章小结 .................................................................................................................. 47

第六章结论与展望 ................................................................................................... 49

§6.1 结论 .......................................................................................................................... 49

§6.2 展望 .......................................................................................................................... 50

参考文献 ..................................................................................................................... 51

在读期间公开发表的论文和承担科研项目及取得成果 ......................................... 57

致谢 ............................................................................................................................. 58

文档加载中……请稍候！
如果长时间未打开，您也可以点击刷新试试。

下载文档到电脑，查找使用更方便

15 积分 4人已下载

立即下载 VIP免费下载

摘要：

摘要超高强度的钢板在车辆车身上的应用，不仅实现了车辆的轻量化，而且显著提高了车辆碰撞强度和安全性能，因此成为车用钢材的重要发展方向。随着板料强度的提高，传统的冷冲压工艺在成型过程中容易产生破裂现象，无法满足超高强度钢板的加工工艺要求。超高强度钢板的热冲压成形技术是综合了成形、传热以及组织相变的一种新工艺，主要是利用高温奥氏体状态下，板料的塑性增加，屈服强度降低的特点，通过模具进行成形的工艺。在成形过程中，板料的成形机理，力学性能以及成形工艺都与传统的冷冲压工艺不同。因此，研究超高强度钢板的热冲压成形技术，探索各类成形参数对材料流动性能的影响，分析并制定合理的热冲压成形工艺，对超高强度钢板在热冲...

展开>> 收起<<

超高强度钢板热冲压成形机理研究.pdf

共62页,预览7页

还剩页未读，继续阅读

超高强度钢板热冲压成形机理研究

相关推荐

开通VIP享超值会员特权

作者详情

相关内容

推荐作者

热门标签

举报选择: