Study on submerged arc welding process and weld microstructure and properties of bimetallic composite pipes
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摘要: 利用光学显微镜(OM)、扫描电镜(SEM)观察了原料热轧卷复合界面和复合管材焊缝的微观组织,采用能谱仪(EDS)线扫描试验测定了原料界面处元素含量变化的线分布曲线,采用能谱仪(EDS)面扫描试验测定了复合管材焊缝熔合区不同微区域内的分布情况,同时对复合管材焊缝进行了拉伸试验、Charpy冲击试验、弯曲试验、显微硬度试验和腐蚀试验。结果表明,采用埋弧焊工艺技术方案能够成功实现304/Q235B Ø610 mm×(6+1) mm复合管材的工程化批量生产。复合管材复层焊缝组织为针片状奥氏体+条带状或蠕虫状铁素体的复相组织,基层焊缝为少量先共析铁素体+针状铁素体的复相组织,焊缝强度、低温韧性、显微硬度、塑性变形等各项力学性能和抗晶间腐蚀性能完全满足GB/T 31940-2015《流体输送用双金属复合耐腐蚀钢管》标准要求。研究成果将为高质量双金属复合管材的产业化生产提供一定理论参考和技术支持。Abstract: The microstructures of the composite interface of the hot-rolled coil and the weld joint of the composite pipe were observed using an optical microscope (OM) and a scanning electron microscope (SEM). The line distribution curve of the element content change at the interface was determined by energy dispersive spectrometer (EDS) line scanning test, and the distribution of elements in different micro-regions of the fusion zone of the composite pipe weld joint was measured by EDS mapping analysis. Meanwhile, tensile test, Charpy impact test, bending test, microhardness test and corrosion test were carried out on the weld joint of the composite pipe. The results indicate that the submerged arc welding (SAW) process can be successfully used for the commercial production of 304/Q235B Ø610 mm×(6+1) mm composite pipes. The microstructure of the cladding weld of the composite pipe is a duplex structure consisting of acicular austenite + banded or worm-like ferrite, while the base weld exhibits a duplex structure of reduced proeutectoid ferrite + acicular ferrite. All mechanical properties including weld strength, low-temperature toughness, microhardness, and plastic deformation, as well as intergranular corrosion resistance, fully meet the requirements specified in the national standard GB/T 31940-2015 bimetallic composite corrosion-resistant steel pipes for fluid transport. Therefore, this research results can be used as a theoretical reference and technical support for the commercial production of high-quality bimetallic composite pipes.
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表 1 304/Q235B双金属复合管材埋弧焊工艺方案及参数
Table 1. Submerged arc welding process scheme and parameters for 304/Q235B bimetallic composite pipes
Welding methods Welding current/A Arc voltage/V Welding speed/(m·min−1) Welding heat input/(kJ·mm−1) Internal welding 390 30.5 1.7 0.378 External welding 850 32.5 1.7 0.829 表 2 304/Q235B复合钢卷料和焊丝的化学成分
Table 2. Chemical compositions of 304/Q235B composite steel coil and welding wire
% Experimental materials C Si Mn P S Ni Cr Mo Cu Q235B 0.140 0.220 0.610 0.012 0.003 0.010 0.030 0.010 0.020 304 0.054 0.506 1.085 0.035 0.006 10.150 18.680 CHW-309L 0.025 0.530 1.580 0.016 0.006 13.620 23.890 0.016 0.007 BG-H08E 0.120 0.120 1.870 0.006 0.004 0.320 0.005 0.031 表 3 304/Q235B复合钢卷料的力学性能
Table 3. Mechanical properties of 304/Q235B composite steel coil materials
Tensile strength
Rm/MPaYield strength
Re/MPaElongation
A/%Impact energy (20 ℃)
AKV/JShear strength
τ/MPaMeasured value 437,426,423 265,243,246 26.2,26.5,26 122,120,119 388,385 Standard requirements 370~500 ≥235 ≥26 ≥27 ≥210 表 4 焊缝金属熔合区微区元素面扫描检测结果
Table 4. Micro-area elements mapping detection results of the weld metal fusion zone
% NO. Cr Mn Fe Ni 1 13.73 1.63 77.87 6.77 2 1.94 96.95 1.11 3 4.19 0.96 92.30 2.55 4 2.50 96.11 1.39 表 5 304/Q235B复合管焊缝拉伸、冲击、弯曲和显微硬度试验结果
Table 5. Experimental results of tensile, impact, bending and micro-hardness tests for 304/Q235B composite pipe welds
Item Weld joint tensile
strength/MPaImpact energy/J Microhardness(HV10) Bending (Bending
axis d=35 mm)Weld center HAZ Cladding layer Base layer Measured value 497,480,479 106,108,120 62,55,47 244,250,300,296,
300,292,255,242149,165,196,216,
232,224,162,149No cracks on the tensile
specimen surfaceStandard requirement ≥370 ≥ 24 ≤300 ≤248 No cracks on the tensile
specimen surface表 6 304/Q235B复合管不锈钢焊缝晶间腐蚀试验结果
Table 6. Intergranular corrosion test results of 304/Q235B composite pipe stainless steel welds
Sample No. Bending axis
diameter/mmBending angle/(°) Result H-1 1 180 Qualified H-2 1 180 Qualified HAZ-1 1 180 Qualified HAZ-2 1 180 Qualified -
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