Effect of Al-Si Coating on Microstructure and Properties of 22MnB5 Steel Laser Welded Joint

doi:10.3901/JME.2018.06.162

Abstract

Abstract: In order to study the effect of Al-Si coating on the microstructure, microhardness and tensile properties of 22MnB5 laser welded joint, the IPG YLR-6000 fiber laser is used to fabricate 1.5 mm thick Al-Si coating 22MnB5 steel laser welding experiment. The results show that the fusion zone and fusion line of the Al-Si coating sample are lath martensite (LM) +Al-rich δ ferrite. However, the microstructure of the fusion zone and fusion line are LM which the Al-Si coating which is removed. The main reason is that the Al-Si coating melts and enters the welding pool during the laser welding process, and the stability of the high temperature δ ferrite increases due to the enrichment of the Al in the part of the fusion zone and the fusion line. At the same time under a rapid cooling conditions, some δ-ferrite can't occur peritectic transformation and it is retained to room temperature. The microhardness distribution of the two welded joints is consistent, and the microhardness of the welded joint is higher than that of the base metal. However, due to the presence of soft phase δ ferrite in the Al-Si coating, the hardness of the fusion zone is lower than that without Al-Si coating. Although the Al-Si coating has an effect on the microstructure and microhardness, it has no effect on the tensile properties. The tensile specimen of the two welded joints are both broken in the base metal, and it is a typical ductile fracture.

Key words: 22MnB5, Al-Si coating, intermetallic compound, mechanical properties, phase change rule

CLC Number:

TG456

CHEN Xiaming, WANG Xiaonan, SUN Qian, ZHANG Min, CHEN Changjun, DI Hongshuang. Effect of Al-Si Coating on Microstructure and Properties of 22MnB5 Steel Laser Welded Joint[J]. Journal of Mechanical Engineering, 2018, 54(6): 162-167.

References

[1] WANG X N,SUN Q,ZHENG Z,et al. Microstructure and fracture behavior of laser welded joints of DP steels with different heat inputs[J]. Materials Science and Engineering A,2017,699:18-25.
[2] 朱国华,成艾国,王振,等. 电动车轻量化复合材料车身骨架多尺度分析[J]. 机械工程学报,2016,52(6):145-152. ZHU Guohua,CHENG Aiguo,WANG Zhen,et al. Analysis of lightweight composite body structure for electrical vehicle using the multiscale approach[J]. Mechanical Science & Technology,2016,52(6):145-152.
[3] 常颖,靳菲,李晓东,等. 车用热成形先进高强度钢板样件的热胀形特征及成形性分析[J]. 机械工程学报,2014,50(24):73-78. CHANG Ying,JIN Fei,LI Xiaodong,et al. Thermal expansion analysis based on forming limit diagram for improving the formability of automotive hot-forming advanced high strength steel parts[J]. Journal of Mechanical Engineering,2014,50(24):73-78.
[4] KIM H Y,PARK J K,LEE M G. Phase transformation-based finite element modeling to predict strength and deformation of press-hardened tubular automotive part[J]. International Journal of Advanced Manufacturing Technology,2014,70(9-12):1787-1801.
[5] FAN D W,KIM H S,DE COOMAN B C. A review of the physical metallurgy related to the hot press forming of advanced high strength steel[J]. Steel Research International,2009,80(3):241-248.
[6] 杨洪林,刘昕,李俊,等. 热冲压钢镀层技术的研究现状[J]. 钢铁研究学报,2013,25(6):1-7. YANG Honglin,LIU Xin,LI Jun,et al. Research status on hot stamping steel coating[J]. Journal of Iron and Steel Research,2013,25(6):1-7.
[7] JI C W,JO I,LEE H,et al. Effects of surface coating on weld growth of resistance spot-welded hot-stamped boron steels[J]. Journal of Mechanical Science & Technology,2014,28(11):4761-4769.
[8] 陈树君,王超,郝素锋,等. 热冲压高强钢电阻+激光组合点焊工艺[J]. 焊接学报,2013,34(5):5-9. CHEN Shujun,WANG Chao,HAO Sufeng,et al. Hot stamping high strength steel resistance and laser combined spot welding process[J]. Journal of Mechanical Engineering,2013,34(5):5-9.
[9] KIM C,KANG M J,PARK Y D. Laser welding of Al-Si coated hot stamping steel[J]. Procedia Engineering,2011,10(7):2226-2231.
[10] SAHA D C,BIRO E,GERLICH A P,et al. Fiber laser welding of Al-Si-coated press-hardened steel[J]. Welding Journal,2016,95(5):147-s-156-s.
[11] MOON J H,SEO P K,KANG C G. A study on mechanical properties of laser-welded blank of a boron sheet steel by laser ablation variable of Al-Si coating layer[J]. International Journal of Precision Engineering & Manufacturing,2013,14(2):283-288.
[12] KANG M,KIM C,LEE J. Weld strength of laser-welded hot-press-forming steel[J]. Journal of Laser Applications,2012,24(2):367-377.
[13] FAN D W,SOO K H,JIN-KEUN O H,et al. Coating degradation in hot press forming[J]. ISIJ International,2010,50(4):561-568.
[14] SAHA D C,BIRO E,GERLICH A P,et al. Fusion zone microstructure evolution of fiber laser welded press-hardened steels[J]. Scripta Materialia,2016,121:18-22.
[15] TSENG C C,SHEN Y,THOMPSON S W,et al. Fracture and the formation of sigma phase,M23C6,and austenite from delta-ferrite in an AlSi304L stainless steel[J]. Metallurgical and Materials Transactions A,1994,25(6):1147-1158.
[16] LIANG G F,WAN C Q,WU J C,et al. In situ observation of growth behavior and morphology of delta-ferrite as function of solidification rate in an AISI304 stainless steel[J]. Acta Metallurgica Sinica,2006,19(6):441-448.
[17] EHLING W,CRETTEUR L,PIC A,et al. Development of a laser decoating process for fully functional Al-Si coated press hardened steel laser welded blank solutions[C]//Proceedings of 5th International WLT-Conference on Lasers in Manufacturing,2009:409-413.
[18] WANG X N,CHEN X M,SUN Q,et al. Formation mechanism of δ-ferrite and metallurgy reaction in molten pool during press-hardened steel laser welding[J]. Materials Letters,2017,206:143-145.