摘 要

低合金耐热钢由于良好的耐蚀性能、耐热性和良好的力学性能与相对较低的价格，在电力，化工等行业被广泛应用。目前其主要的焊接材料为耐热钢焊条，但是在焊接过程中会出现例如冷裂纹，热影响区软化等问题，必须通过预热或是PWHT解决。

本文系统研究B₂O₃对CJR307焊条熔敷金属微观组织和性能的影响。参照CJR307焊条的药皮配方，改变配方中B₂O₃的含量，进行焊接，做比较分析，探究其对熔敷金属低温冲击韧性的影响，接着制备金相试样，观察组织形态，从而探究其对微观组织的影响。

研究结果显示：B₂O₃含量对CJR307熔敷金属组织及性能有显著影响，其熔敷金属组织主要为针状铁素体、先共析铁素体和少量贝氏体，随着B₂O₃含量的增加先共析铁素体会转变为均匀细小的针状铁素体，使熔敷金属金属低温冲击韧性增加，随着B₂O₃含量继续增多，熔敷金属整体组织粗化，出现上贝氏体与粒状贝氏体，使熔敷金属金属低温冲击韧性降低。

关键词：B₂O₃ ；耐热钢焊条；熔敷金属；低温冲击韧性；金相

Abstract

Because of good corrosion resistance, heat resistance, mechanical properties and relatively low price, low alloy heat resistant steel has been widely used in electric power, chemical industry and other industries. At present, the main welding materials for heat resistant steel welding rod, but in the welding process will appear such as cold cracks, heat affected zone softing and other welding defects, that must be solved through the preheating or PWHT.

In this study,the effect of B₂O₃ in CJR307 rod on Microstructure and properties of deposited metal will be disscussed. According to CJR307 rod’s coating formula, change the content of B₂O₃, then welding, comparative analysis, to explore its effect on the impact toughness of deposited metal at low temperature, and make metallographic specimen then observe organization morphology, so as to study its effect on microstructure.

The results showed: B₂O₃ in CJR307 has a significant effect on the deposited metal’s microstructure and properties, the microstructure is mainly acicular ferrite, proeutectoid ferrite and a small amount of bainite, with increasing of B₂O₃ content, proeutectoid ferrite will change into uniform, fine acicular ferrite, the low-temperature impact toughness of deposited metal increased dependency, with the further increase of the content, the whole organization of the deposited metal get coarsening, upper bainite and granular bainite show up, and low-temperature impact toughness of the deposited metal decreased.

Key words:B₂O₃; heat resistant steel welding rod; microstructure of deposited metal; impact toughness at low temperature; metallographic

目录

摘要…...…………………………………………………………………………………………………………I

Abstract………………………………………………………………………………………...………………..II

第1章 绪论………………………………………………………….………………………………………..1

1.1 耐热钢介绍……………………………………………………………………………………….1

1.2 耐热钢焊接的研究现状………………………………………………………………1

1.3 合金元素在钢中的作用及合金过度………………………………………………....2

1.3.1合金元素的作用………………………………………………………………..…2

1.3.2合金过渡…………………………………………………………………………..2

1.4 本文研究的主要目的，内容及意义…………………………………………………3

1.4.1 研究目的…………………………………………………………………….…..3

1.4.2 研究内容………………………………………………………………………...4

1.4.3 研究意义……………………………………………………………………...…4

第2章 熔敷金属试样的制备过程……………………………………………………………..5

2.1 焊条理论…………………………………………………………………………...…5

2.1.1 焊芯………………………………………………………………………….….5

2.1.2 药皮………………………………………………………………………..……5

2.2 焊条的制作…………………………………………………………………..…….…7

2.2.1 焊条焊芯的选择………………………………………………………..………7

2.2.2 焊条药皮成分的选择…………………………………………………………..7

2.2.3 焊条制作………………………………………………………………………..8

2.3 焊接过程………………………………………………………………………..…….8

第3章 熔敷金属试样的力学性能分析…………………………………………….…….…10

3.1 低温冲击韧性实验与分析……………………………………………….……...…..10

3.2 冲击断口形貌分析………………………………………………………….…...…..11

第4章 金相实验与组织分析………………………………………………………..………13

4.1金相试样制备与观察…………………………………………………………..…..….13

4.2金相试样成分分析………………………………………………………..…….……..16

第5章 结论……………………………………………………………………..………..…..18

5.1 课题结论………………………………………………………………...…..………18

5.2 展望….………………………………………………………...……………….……18

致谢……………………………………………………………………………………………………………19

参考文献………………………………………………………………………………………………….…..20

第1章 绪论