Review of the development of tube and pipe products at Baosteel over the past 30 years

The history of the development of the tube ＆ pipe division of Baosteel was reviewed in the article, focusing on the process of technical innovation and the product category enrichment. Thanks to the technical innovation, the Ф 140 product line has become the most efficient one in the world. With the advance of conglomeracy and the construction of the most advanced weld pipe line and the Ф460 premium quality finishing （PQF） line ,the catalogue of Baosteel tube ＆pipe products has covered the extensive range from the hot roll to cold roll, the seamless to the welded, and all of the product dimension scope from 25.4 mm to 610 ram. To meet the requirements of relevant industries such as energy ,transportation, machinery,ammunition and other relevant industries, the product variety is diverting from carbon steel to alloy steel, stainless steel and special alloys. As the Baosteel Steel Tubing Plant increased its number of production units, expanded its production capacity and developed new products ,it has grown into a pipe and tube supplier with global competitiveness.

Weld Characteristics and NC Bending Formability of QSTE340 Welded Tube

The mechanical characteristics of the weld joint were investigated by tensile test, microstructure test, and microhardness test. The welded tube NC bending tests were carried out to evaluate the weld on the formability of the QSTE340 welded tube. The results show that the wall thinning degree, cross-sectional deformation and springback angle increase significantly as the weld line is located on the outside of the bend compared with that located on the middle and inside, and the welded tubes produce nearly identical performance as the weld line is located on the middle and inside. The wall thickening degree decreases much as the weld line is located on the inside of the bend. So the welded tube can acquire good bending formability as the weld line is located in the region away from the outside of the bend.

Effect of Rare Earth on the Corrosion-Resisting Performance of Zinc-Based Alloy Coatings

The corrosion behavior of coatings of pure zinc and Zn-Al,Zn-Al-RE alloys in NaCl solu- tions was studied by salt-spray experiments,even corrosion experiments and electrochemical measurements of bi-directional polarization curves and a.c.impedance in weak polarization region consistent regularities were obtained by these different methods,viz.,the corrosion resistance of Zn could be enhanced by alloying it with Al,and particularly with Al-RE.The causes of enhancement of corrosion resistance by RE were also discussed.

Transient out-of-plane distortion of multi-pass fillet welded tube to pipe T-joints

The out-of-plane distortion induced in a multi-pass circumferential fillet welding of tube to pipe under different weld sequences and directions was studied using Finite Element Method(FEM) based Sysweld software and verified experimentally. The FEM analyses consisted of thermal and mechanical analyses.Thermal analysis was validated with experimental transient temperature measurements. In the mechanical analysis, three different weld sequences and directions were considered to understand the mechanism of out-of-plane distortion in the tube to pipe T-joints. It was learnt that the welding direction plays a major role in minimizing the out-of-plane distortion. Further, during circumferential fillet welding of the tube to pipe component, the out-of-plane distortion generated in the x direction was primarily influenced by heat input due to the start and stop points, whereas the distortion in the z direction was influenced by time lag and welding direction. The FEM predicted distortion was compared with experimental measurements and the mechanism of out-of-plane distortion was confirmed.

Mechanism of weld-line movement within hydroforming of tailor-welded tube

To reveal the reason of weld-line movement in hydroforming of a tailor-welded tube (TWT) with dissimilar thickness,the stress ratio of axial stress to circumferential stress is derived by mechanical analysis and analyzed between the thicker and thinner tubes,as well as the property of the axial strain. During TWT hydroforming,tensile strain along axial direction happens on the thinner tube. On the contrary,compressive strain happens on the thicker tube. Experiments are conducted to varify the weld-line movement regularity and strain distribution. It indicates that the weld-line moves from the thinner part to the thicker during TWT hydroforming. The thinning ratio of the thinner tube is bigger than that of the thicker tube,especially in the zone near weldline. Stress ratio difference between the thicker tube and the thinner tube is the main reason of weld-line movement and non-uniform thinning ratio distribution.

Influence of flash trap profiles on joint properties of friction welded CP-Ti tube to 304L stainless steel tube plate using external tool

Titanium tube and stainless steel tube plate were welded by an innovative friction welding of tube to tube plate using an external tool (FWTPET). Copper was used as an interlayer for joining the dissimilar materials and also to minimize the effect of intermetallics formed at the joint interface. The process parameters that govern FWTPET process are plunge rate, rotational speed, plunge depth, axial load and flash trap profile. Among them, the flash trap profile of the tube has a significant influence on the joint integrity. Various flash trap profiles like vertical slots, holes, zig-zag holes, and petals were made on the titanium tube welded to the stainless steel tube plate. Macroscopic and microscopic studies reveal defect-free joints. The presence of copper interlayer and intermetallics was evident from X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) studies. The microhardness survey was presented across and along the interface. A novel test procedure called “plunge shear test” was developed to evaluate the joint properties of the welded joints. The highest shear fracture load of 31.58 kN was observed on the sample having petals as flash trap profile. The sheared surfaces were further characterized using SEM for fractography.

A Study of the Welding Parameters for High Frequency Welded Pipes

In cold roll forming, steel pipes are welded with different technology parameters in order to improve the steel pipe＇s quality, thus we should optimize the technology parameters for producing steel pipes. By means of metallographic examination, scanning electron microscope examination, hardness test, impact test, bend test, tensile test and so on, the microstructure and mechanical properties of the steel pipes were investigated. The test results show that welding defects such as crack and blowholes are not found. The microstructure of the welded metal is Widmanstatten ; the microstructure of the heat affected zone is Widmanstatten, pearlite and proeutectoid ferrite, and the base metal is pearlite and ferrite. The highest of the metal Brinell hardness is in the weld seam, followed by the heat affected zone, and the lowest is in the base metal. The microstructure of the weld metal is coarse, which results in that the toughness of the weld is the lowest, but the hardness of the welds is the highest in the weld zone. The bend angles of the weld metal present a mountainous shape with the surface energy. Only when the surface energy is of the best value, the mechanical properties of the weld metal is the best.

爆炸焊接铜/钢复合管界面组织表征与性能研究

为了研究应用于压力容器的管道或承压部件的铜/钢双金属复合管材料中晶粒存在形式和力学性能之间的关系,通过爆炸焊技术获得了T2铜/316L不锈钢复合管,并对其界面形貌与微观组织进行分析。结果表明,T2铜/316L不锈钢复合管结合界面处呈现平直界面和周期性波状界面,波形结合区域的平均波长203μm、波高58μm。复合管结合界面两侧的元素发生互扩散,扩散层厚度为1μm。界面处Fe侧晶粒尺寸较小,随着结合界面距离的增加晶粒尺寸逐渐变大。通过纳米压痕试验发现,波峰处界面的纳米压痕结果达到了3.16 GPa,波谷处的纳米压痕结果达到了2.44 GPa,同时波峰处界面附近区域的纳米压痕结果均高于波谷处,Fe侧纳米压痕结果均高于Cu侧。纳米压痕试验获得的力学性能分布规律和微观组织的分布规律相一致。

轴力作用下焊接方管Π型节点的极限承载力分析

目前规范中还未规定Π型构造形式的方管节点承载力计算公式。该文在经过试验验证有限元分析准确性的基础上,基于两种方管不同区域的材料本构关系模型,利用Abaqus软件对85组在轴力作用下的节点进行了数值模拟,得到了方管Π型节点在轴力作用下的极限承载力。随后,通过参数化分析和多元回归,得出影响Π型节点极限承载力的因素以及修正的承载力计算公式。结果表明,支管-主管宽度比β对节点极限承载力和初始刚度影响较大,增大支管宽度,能够显著提高节点的极限承载力,支管上施加的荷载由主管上表面的抗弯、抗剪作用和主管侧壁共同承担,节点的破坏模式也取决于β;主管宽厚比2γ越大,意味着主管上翼缘和支管连接区域变得更加细长,降低了主管上翼缘的抗弯刚度,节点承载力和初始刚度因此降低;支管-主管高宽比η和支管间距g对节点极限承载力有一定影响,增大支管截面的高度和支管间隙,即增大了沿主管纵向方向的支管、主管相交区域,使得支管在主管翼缘更宽的区域传递荷载,节点的塑性区域更大,材料利用更充分,因此提高了节点的承载能力;支管-主管厚度比τ对节点极限承载力和初始刚度影响不大,支管的壁厚增加,提高了支管的承载力,但节点最终破坏是主管上翼缘达到屈服破坏而并非支管破坏,因此支管厚度的变化对节点承载能力影响不明显。根据有限元模型的分析结果,通过曲线拟合提出了计算方管Π型节点极限承载力的参数方程,并对该方程的准确性进行了评价,为这类节点的进一步研究和工程应用提供了参考。

钯合金阵列管束气密性焊接工艺方法研究

采用预先高频钎焊钯合金管过渡接头,再使用脉冲激光焊的方法,对钯合金扩散室密排列钯合金管束与不锈钢法兰进行了密封焊接工艺研究,通过对激光焊接接头的观察和气密性检测分析,确定了激光焊接功率、离焦量、脉冲频率、脉冲宽度及焊接速度等主要焊接参数。正式样件经气密性检测和氦质谱检漏达到了氢纯化分离用钯扩散装置的使用要求,从而确定激光焊技术可推广应用于钯合金扩散室密集阵列管束批量焊接生产。

CT70低合金高强度油管用钢激光焊接接头残余应力有限元模拟

针对CT70级连续管用钢激光焊焊接接头,考虑试板、焊缝、热源的轴对称性,应用有限元软件建立了1/2轴对称有限元分析模型,对激光焊接接头的温度场、变形场与应力场进行了模拟分析。结果表明,有限元模拟焊缝尺寸与实际基本一致;残余应力主要集中在焊缝周围,在远离焊缝区域残余应力逐渐减小,且焊缝中心为拉应力;变形在焊缝周围最大,距离焊缝越远变形越小。将有限元模拟结果与实际测试结果对比,激光焊焊缝中心为拉应力,与有限元计算结果相同。

深孔焊结构喷泉式管束装配工艺技术研究

深孔焊技术广泛应用于石油化工领域中的重要换热设备,可有效减少间隙腐蚀、应力腐蚀、疲劳破裂等问题。本文针对深孔焊结构喷泉式管束,进行装配工艺技术的研究。

双相不锈钢换热管与管板的焊接

换热管与管板的焊接是换热器质量控制的重点。双相不锈钢焊接的目标是获得平衡的铁素体(δ)和奥氏体(γ)。采用手工钨极氩弧焊,使用Φ1.6 mm的ER2209焊丝,以0.54 kJ/mm的热输入焊接Φ25 mm×2 mm的S32205双相不锈钢换热管与管板试件。经取样检测,角焊缝厚度均值2.88 mm;焊缝维氏硬度均值255.8 HV;按ASTM E562测定铁素体含量,焊缝铁素体含量均值59.3%,管侧熔合线57.3%,管侧热影响区58%,板侧熔合线58.7%,板侧热影响区58.2%;按ASTM A923的方法A检测,5区的金相组织相界和晶界平滑,无有害沉淀相析出,评定为未受影响的金相组织;按GB/T 4334的方法E试验,无晶间腐蚀现象。以上各项检测指标均符合相应标准和技术协议要求,说明焊接工艺适用。

小径管X射线焊缝图像缺陷识别算法

针对小径管X射线焊缝图像缺陷检测精确率低的现状,通过对图像进行特征分析并结合稀疏字典学习,提出一种基于图像分割的小径管焊缝图像缺陷检测算法.首先,对小径管焊缝图像进行两步图像分割获得感兴趣区域;其次,提取焊缝缺陷,得到缺陷疑似局部图像;最后,提出以不同类型原子间相关性最小为目标的小径管焊缝缺陷字典矩阵数学模型并使用K-SVD算法进行求解,利用该字典矩阵实现圆形缺陷、线形缺陷和噪声的分类鉴别.为提高系统实时性,使用并行编程对图像分割算法进行加速.结果表明,改进后缺陷字典矩阵对圆形缺陷识别成功率为0.974,线形缺陷识别成功率为0.967,且具有较快的识别速度,实现了小径管焊缝图像缺陷的有效识别.

高压液氨预热器管板环焊缝主副加热局部热处理

管板环焊缝局部热处理是影响高压液氨预热器服役安全的关键制造技术,传统局部热处理时温度分布不均匀、管板约束大,导致残余应力难以消除。对此,采用主副加热局部热处理方法,并验证该方法在高压液氨预热器局部热处理时的有效性。计算与测试结果表明,传统局部热处理仅可降低外表面的轴向和环向残余应力,而内表面轴向应力会略微增大,环向应力降幅较小;主副加热局部热处理使内表面轴向应力由283 MPa降低至100 MPa以下,降幅约64%,环向应力由324 MPa降低至206 MPa,降幅约37%,显著降低了设备内表面应力腐蚀开裂的敏感性。

焊接工艺对钢管混凝土拱桥拱肋相贯节点残余应力的影响

为研究焊接工艺对钢管混凝土拱桥拱肋相贯节点残余应力的影响,基于建立的热力顺序间接耦合的有限元分析方法,对拱肋相贯节点的焊接温度场和残余应力场进行数值模拟,结合文献试验结果验证了有限元分析方法的准确性。然后对湘渝高速双堡桥拱脚处拱肋相贯节点进行焊接温度场和残余应力场的数值模拟。在此基础上,通过参数分析研究对比了不同焊接热输入和焊接速度以及进行焊前预热和焊后热处理等不同焊接工艺对拱肋相贯节点不同位置的残余应力影响。结果表明:不同焊接热输入和焊接速度下拱肋相贯节点的焊接残余应力分布规律基本一致,变化规律表现为焊接残余应力与焊接热输入呈正相关关系,与焊接速度呈负相关关系;随着焊接热输入的减小和焊接速度的提高,拉压残余应力整体减小,拱肋相贯节点经过焊前预热150~200℃以后,残余应力的峰值应力总体降低4%以上,但焊前预热对残余应力分布基本没有影响,更高的焊前预热温度能更有效地降低残余应力的峰值应力;拱肋相贯节点经过550~650℃保温温度下保温4 h的焊后热处理以后,焊接残余应力总体降低幅度在40%以上,更高的保温温度能更有效地降低焊接残余应力;钢管混凝土拱桥拱肋相贯节点可通过减小焊接热输入和提高焊接速度的焊接工艺、焊前预热处理和焊后热处理来减小焊接残余应力。

锆合金压力电阻焊接头热影响区中第二相的组织特征

采用热模拟试验机分别对Zr-4合金管和锆锡铌(Zr-Sn-Nb)系锆合金管与Zr-4合金柱进行压力电阻焊连接,研究了接头热影响区的第二相形貌、成分和晶体结构,并与母材进行对比。结果表明:在压力电阻焊的热力耦合作用下,Zr-4合金接头热影响区近熔合线区的第二相粒子发生完全溶解,近母材区的密排六方结构Zr(Fe,Cr)_(2)Laves第二相颗粒的数量相比母材显著减少,平均直径增大。Zr-Sn-Nb系合金接头热影响区近熔合线区的第二相颗粒数量很少,以直径小于50nm的体心立方结构β-Nb相为主,近母材区的第二相颗粒数量介于母材与热影响区近熔合线区之间,由细小的体心立方结构β-Nb相以及粗大的面心立方结构(Zr,Nb)Fe_(2)相组成。

细长焊接圆钢管轴心受压稳定承载力研究

为研究细长焊接圆钢管轴压稳定性能,对30根试件进了轴压试验,分析了试件失稳变形的特征,比较了试件的稳定系数与我国规范中稳定曲线的关系,并考虑钢管几何初始缺陷和残余应力对其稳定承载力进行了有限元分析。研究表明:细长焊接圆钢管的几何初始缺陷具有较大离散性,与我国规范规定值不同,正则化长细比在1.0~1.3区间时,试验得到的稳定系数低于规范值,最大相差-24.4%;几何初始缺陷小于1/500杆长时,可采用规范值进行设计;而几何初始缺陷大于1/500杆长时,建议重新制定压杆曲线。最后,给出了细长焊接圆钢管在8种初始缺陷下的压杆稳定曲线。

锅炉水冷壁管泄漏事故失效分析

针对某电厂锅炉水冷壁管泄漏事故进行分析,对泄漏失效管子进行宏观检测、化学成分分析、力学性能测试,同时对管子及其角焊缝进行金相组织观察和断口形貌分析。结果表明:引起水冷壁管泄漏的主要原因是水冷壁管子与鳍片角焊缝的焊接质量不良,在水冷壁管运行过程中,角焊缝的裂纹从外向内不断沿晶扩展、穿透管壁,最终引起水冷壁管泄漏。