Please wait a minute...
金属学报  2019, Vol. 55 Issue (5): 575-584    DOI: 10.11900/0412.1961.2018.00375
  本期目录 | 过刊浏览 |
保护气成分对1000 MPa级高强熔敷金属组织特征的影响
安同邦1,2(),魏金山1,单际国2,田志凌1
1. 钢铁研究总院焊接所 北京 100081
2. 清华大学机械工程系 北京 100084
Influence of Shielding Gas Composition on Microstructure Characteristics of 1000 MPa Grade Deposited Metals
Tongbang AN1,2(),Jinshan WEI1,Jiguo SHAN2,Zhiling TIAN1
1. Welding Institute, Central Iron & Steel Research Institute, Beijing 100081, China
2. Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China
全文: PDF(27651 KB)   HTML
摘要: 

通过附带EDS的FEGSEM、EBSD、TEM等实验方法,研究了保护气成分(Ar+5%CO2、Ar+10%CO2、Ar+20%CO2、Ar+30%CO2,体积分数)对1000 MPa级高强熔敷金属组织特征的影响,阐明了保护气成分对组织转变的影响机制。结果表明,随着保护气中CO2含量增加,1000 MPa级熔敷金属强度略有下降,而冲击韧性先升高后降低。不同保护气熔敷金属均由马氏体/贝氏体混合组织及板条间残余奥氏体组成。随着保护气中CO2含量增加,熔敷金属中贝氏体相变体积分数为50%时的温度(B50)与马氏体相变开始温度(Ms)相变温度区间增大,适宜贝氏体形核的夹杂物数量增多,随贝氏体含量(体积分数)由8%增加到29.6%,其形核位置从原始奥氏体晶界向原始奥氏体晶界及晶内夹杂物处共同形核转变,熔敷金属组织形貌由“平行状”向“交织状”转变,分割细化组织,有利于高强熔敷金属强韧性的改善。

关键词 保护气成分1000 MPa级熔敷金属氧化物夹杂显微组织特征    
Abstract

In recent years, high and ultra-high strength steels have been developed and used in light-weight constructions such as the structural members of mobile equipment in order to reduce weight and fabrication costs and to enhance the performance. Welding of steels with yield strength of more than 900 MPa is particularly challenging because of the toughness requirements for the weld metal, which calls for welding consumables of high strength and good toughness. Weld metals have been produced for a variety of welding methods with yield strength up to or above 1000 MPa, but their impact toughness remained only at medium yield strengths. Proper microstructure is the key to meeting this requirement, and its final microstructure depends on the chemical composition and cooling rate. For the deposited metal produced by gas metal arc welding (GMAW), the composition is dependent on the welding wire and shielding gas. The cooling rate of the weld metal is controlled by a combination of heat input and heat extraction. It is known that the addition of CO2 to argon based shielding gas is effective for improvement of productivity in GMAW welding of steel. Through the chemical reaction in the welding arc, CO2 in the shielding gas can affect the chemical composition of the weld metal, and its microstructure. The 1000 MPa grade deposited metals was welded with GMAW, and the effects of shielding gas composition (Ar+(5%~30%)CO2, volume fraction) on the general compositional and microstructural characteristics of deposited metals, including nonmetallic inclusions, were experimentally characterized with SEM, EBSD and TEM. The microstructure of the deposited metals is mainly composed of martensite and bainite. With the increase of CO2 content (5%~30%), the strength of the deposited metals decrease slightly and the impact toughness increases first and then decreases. Meanwhile, the transformation range (B50-Ms) of the deposited metal increases, the bainite content increases (8%~29.6%) with the quantity of inclusions that are suitable for bainite nucleation increases, and the nucleation position changes from the original austenite grain boundary to the common nucleation on the original austenite grain boundary and inclusions within the grain. At the same time, the microstructure morphology of the deposited metal changes from parallel to intertexture, which presented an intersected configuration and microstructure refinement.

Key wordsshielding gas composition    1000 MPa grade deposited metal    oxide inclusion    microstructure characteristics
收稿日期: 2018-08-16     
ZTFLH:  TG442.3  
基金资助:国家重点研发计划项目(2017YFB0305100);国家重点研发计划项目(2017YFB0305105)
通讯作者: 安同邦     E-mail: antongbang@cisri.com.cn
Corresponding author: Tongbang AN     E-mail: antongbang@cisri.com.cn
作者简介: 安同邦,男,1982年生,博士

引用本文:

安同邦,魏金山,单际国,田志凌. 保护气成分对1000 MPa级高强熔敷金属组织特征的影响[J]. 金属学报, 2019, 55(5): 575-584.
Tongbang AN, Jinshan WEI, Jiguo SHAN, Zhiling TIAN. Influence of Shielding Gas Composition on Microstructure Characteristics of 1000 MPa Grade Deposited Metals. Acta Metall Sin, 2019, 55(5): 575-584.

链接本文:

https://www.ams.org.cn/CN/10.11900/0412.1961.2018.00375      或      https://www.ams.org.cn/CN/Y2019/V55/I5/575

Shielding gasCSiMnNi+Cr+MoTiONFe
95%Ar+5%CO20.0970.521.673.880.0700.0210.0034Bal.
90%Ar+10%CO20.0890.481.543.830.0650.0270.0032Bal.
80%Ar+20%CO20.0890.471.463.800.0450.0320.0036Bal.
70%Ar+30%CO20.0870.431.383.690.0430.0400.0034Bal.
表1  不同保护气熔敷金属的化学成分

Shielding gas

Rm

MPa

Rp0.2

MPa

Charpy absorbed energy / J

Vickers hardness

kg·mm-2

γ

RT-40 ℃
95%Ar+5%CO21173103849.317.3404.250.88
90%Ar+10%CO2110194255.033.0381.470.86
80%Ar+20%CO2116098072.652.0366.710.84
70%Ar+30%CO2104492157.647.6358.390.88
表2  不同保护气熔敷金属的力学性能
图1  不同保护气末层焊道熔敷金属显微组织的SEM像
图2  不同保护气熔敷金属显微组织的TEM明场像,残余奥氏体明场像、暗场像及其SAED花样
图3  不同保护气熔敷金属板条块亚结构EBSD像和反极图
图4  不同保护气成分熔敷金属中夹杂物BSE-SEM像

Shielding gas

Average diameter

μm

Maximum size

μm

Number density

104 mm-2

Area fraction

%

95%Ar+5%CO20.33161.11810.00.08
90%Ar+10%CO20.40231.3659.80.13
80%Ar+20%CO20.41371.40812.30.20
70%Ar+30%CO20.43381.44712.90.22
表3  不同保护气熔敷金属中夹杂物统计
Shielding gasPositionOAlSiSTiMn

95%Ar+5%CO2

Center16.5312.823.142.1144.0421.32
Verge18.258.428.834.0630.7529.66

90%Ar+10%CO2

Center17.839.087.931.1334.6829.32
Verge18.516.0111.644.5220.1839.11

80%Ar+20%CO2

Center20.368.582.891.2145.6320.32
Verge15.176.0415.564.2117.3841.63

70%Ar+30%CO2

Center14.393.946.311.0238.0636.25
Verge14.862.6615.684.1817.6344.98
表4  夹杂物化学成分EDS分析
图5  不同保护气下末层焊道熔敷金属显微组织彩色OM像
图6  熔敷金属中贝氏体相变体积分数为50%时的温度(B50)与马氏体相变开始温度(Ms)随保护气中CO2含量的变化关系
图7  不同保护气熔敷金属凝固组织转变机制示意图
图8  夹杂物处形核长大的贝氏体板条TEM像和SEM像
[1] SeoJ S, LeeC, KimH J. Influence of oxygen content on microstructure and inclusion characteristics of bainitic weld metals[J]. ISIJ Int., 2013, 53: 279
[2] YuS F, QianB N, GuoX M. Microstructure of ULCB deposited metal and effect of carbon and oxygen contents on mechanical property[J].Acta Metall. Sin., 2005, 41: 1082
[2] (于少飞, 钱百年, 国旭明. ULCB熔敷金属组织与碳、氧含量对力学性能的影响 [J]. 金属学报, 2005, 41: 1082)
[3] GoudaM, TakahashiM, IkeuchiK. Microstructures of gas metal arc weld metal of 950 MPa class steel[J]. Sci. Technol. Weld. Join., 2005, 10: 369
[4] LePeraF S. Improved etching technique to emphasize martensite and bainite in high-strength dual-phase steel[J]. JOM, 1980, 32(3): 38
[5] KeehanE, KarlssonL, AndrénH O, et al. New developments with C-Mn-Ni high strength steel weld metals, Part A—Microstructure[J]. Weld. J., 2006, 85: 200S
[6] KeehanE, KarlssonL, AndrénH O, et al. New developments with C-Mn-Ni high strength steel weld metals, Part B—Mechanical properties[J]. Weld. J., 2006, 85: 218S
[7] AnT B, TianZ L, ShanJ G, et al. Effect of shielding gas on microstructure and performance of 1000 MPa grade deposited metals[J].Acta Metall. Sin., 2015, 51: 1489
[7] (安同邦, 田志凌, 单际国等. 保护气对1000 MPa级熔敷金属组织及力学性能的影响 [J]. 金属学报, 2015, 51: 1489)
[8] St-LaurentS, L'EspéranceG. Effects of chemistry, density and size distribution of inclusions on the nucleation of acicular ferrite of C-Mn steel shielded-metal-arc-welding weldments[J]. Mater. Sci. Eng., 1992, A149: 203
[9] GiraultE, JacquesP, HarletP, et al. Metallographic methods for revealing the multiphase microstructure of TRIP-assisted steels[J]. Mater. Charact., 1998, 40: 111
[10] PengY, PengX N, ZhangX M, et al. Microstructure and mechanical properties of GMAW weld metal of 890 MPa class steel[J]. J. Iron Steel Res. Int., 2014, 21: 539
[11] LuoZ J, WangL P, WangM, et al. Effect of lath martensite/bainite microstructure on strength and toughness of a low carbon martensite steel[J].Trans. Mater. Heat Treat., 2012, 33(2): 85
[11] (罗志俊, 王丽萍, 王 猛等. 板条M/B组织对低碳马氏体钢强韧性的影响 [J]. 材料热处理学报, 2012, 33(2): 85)
[12] StevenW, HaynesA G. The temperature of formation of martensite and bainite in low-alloy steels, some effects of chemical composition[J]. J. Iron. Steel. Inst., 1956, 183: 349
[13] GadallahR, FahmyR, KhalifaT, et al. Metallographic methods for revealing the multiphase microstructure of TRIP-assisted steels[J]. Mater. Charact., 1998, 40: 111
[14] YangC L, LinS B. Fundamentals of Arc Welding[M]. Harbin: Harbin Institute of Technology Press, 2003: 1
[14] (杨春利, 林三宝. 电弧焊基础 [M]. 哈尔滨: 哈尔滨工业大学出版社, 2003: 1)
[15] ZhangJ C, WangG R, ShiY H, et al. Application of mixed gas in gas metal arc welding[J].Weld. Pipe Tube, 2006, 29(3): 46
[15] (张建春, 王国荣, 石永华等. 混合气体在熔化极气体保护焊中的应用 [J]. 焊管, 2006, 29(3): 46)
[16] KeehanE, KarlssonL, MarimuthuM, et al. High strength steel weld metals: Developments with Ni and Mn[A]. Proceedings of the 7th International Welding Symposium[C]. Kobe: Japan Welding Society, 2001: 797
[17] KeehanE. Microstructure and properties of novel high strength steel weld metals[J]. Weld. Res. Abroad, 2006, 52: 1
[18] PengX N, PengY, TianZ L, et al. Effect of Ni on the microstructure evolution of Cr-Ni-Mo series high strength weld metal[J].Trans. China Weld. Inst., 2014, 35(9): 32
[18] (彭杏娜, 彭 云, 田志凌等. Ni元素对Cr-Ni-Mo系高强焊缝组织演化的影响 [J]. 焊接学报, 2014, 35(9): 32)
[19] SinghS B, BhadeshiaH K D H. Estimation of bainite plate-thickness in low-alloy steels[J]. Mater. Sci. Eng., 1998, A245: 72
[20] ChangL C, BhadeshiaH K D H. Microstructure of lower bainite formed at large undercoolings below bainite start temperature[J]. Mater. Sci. Technol., 1996, 12: 233
[21] PakJ H, BhadeshiaH K D H, KarlssonL, et al. Coalesced bainite by isothermal transformation of reheated weld metal[J]. Sci. Technol. Weld. Join., 2008, 13: 593
[22] KeehanE. Effect of microstructure on mechanical properties of high strength steel weld metals[D]. G?teborg: Chalmers University of Technology, 2004
[1] 杨文,张立峰,任英,段豪剑,张莹,肖向辉. 利用高分辨同步辐射Micro-CT定量三维表征含Ti铁素体不锈钢铸坯中氧化物夹杂*[J]. 金属学报, 2016, 52(2): 217-223.
[2] 安同邦,田志凌,单际国,魏金山. 保护气对1000 MPa级熔敷金属组织及力学性能的影响*[J]. 金属学报, 2015, 51(12): 1489-1499.
[3] 陈雨来, 张泰然, 王一德, 李静媛. O, N和Ni含量对0Cr25Ni7Mo4N双相不锈钢热轧塑性的影响*[J]. 金属学报, 2014, 50(8): 905-912.