Recently, Dr. Glyn M. Evans posted a large shielded metal arc (SMA) weld metal (WM) database on the ResearchGate website (researchgate.net). This database contains more than 950 WM compositions, along with their respective WM tensile and Charpy V-notch (CVN) impact properties. In particular, the CVN impact properties list the test temperatures that achieved 28 and 100 J impact energy for each WM composition. While the availability of this SMA WM database is a valuable and rare gift to the welding community, how could the welding community analyze this database to gain valuable insights? This paper utilizes a constraints-based model (CBM) as a simple and effective framework to organize and analyze this very large Fe-C-Mn SMA WM database. A CBM is built on the metallurgical principle that one needs to lower relevant solid-state phase transformation (i.e., austenite decomposition) temperatures to improve WM strength and fracture toughness while simultaneously reducing carbon content and Yurioka’s carbon equivalent number (CEN) to improve the weldability of high-strength steels. To this end, a CBM identifies and simultaneously solves several statistical (regression) equations that relate the chemical composition of high-strength steel WM with Yurioka’s CEN and selected solid-state phase transformation temperatures related to austenite decomposition. The results of the current effort demonstrate that the analysis of Evans’s shielded metal arc welding database using a CBM as a framework reaffirms that controlling carbon content, the value of the CEN, and calculated solid-state phase transformation temperatures, particularly the difference between the calculated Bs (bainite-start) and Ms (martensite-start) temperatures, is critical to developing and identifying high-performance, high-strength steel welding electrodes. A dual approach that manipulates the contents of principal alloy elements such as C, Mn, Ni, Cr, Mo, and Cu, and adds controlled amounts of Ti, B, Al, O, and N, appears to offer the best means to lower relevant solid-state phase transformation temperatures to produce high-strength and high-toughness WMs.
最近，Glyn M. Evans博士在ResearchGate网站(researchgate.net)上发布了一个大型屏蔽金属电弧(SMA)焊接金属(WM)数据库。该数据库包含950多种WM成分，以及它们各自的WM拉伸和夏比v型缺口(CVN)冲击性能。特别是，CVN冲击性能列出了每种WM成分达到28和100 J冲击能量的测试温度。虽然这个SMA WM数据库的可用性对焊接界来说是一个宝贵而罕见的礼物，但焊接界如何分析这个数据库以获得有价值的见解呢?本文利用基于约束的模型(CBM)作为一个简单有效的框架来组织和分析这个非常大的Fe-C-Mn SMA WM数据库。CBM建立在冶金原理的基础上，即需要降低相关的固相转变(即奥氏体分解)温度，以提高WM强度和断裂韧性，同时降低碳含量和Yurioka碳当量数(CEN)，以提高高强度钢的可焊性。为此，CBM识别并同时求解了几个统计(回归)方程，这些方程将高强度钢WM的化学成分与Yurioka的CEN和与奥氏体分解相关的选定固相转变温度联系起来。目前的研究结果表明，使用CBM作为框架对Evans的屏蔽金属电弧焊数据库进行的分析再次表明，控制碳含量、CEN值和计算的固态相变温度，特别是计算的Bs(贝氏体开始)和Ms(马氏体开始)温度之间的差异，对于开发和确定高性能、高强度钢焊条至关重要。控制主要合金元素(如C、Mn、Ni、Cr、Mo和Cu)的含量，并添加一定量的Ti、B、Al、O和N的双重方法，似乎是降低相关固相转变温度以生产高强度和高韧性WMs的最佳方法。
{"title":"Analysis of a High-Strength Steel SMAW Database","authors":"K. Sampath","doi":"10.29391/2022.101.036","DOIUrl":"https://doi.org/10.29391/2022.101.036","url":null,"abstract":"Recently, Dr. Glyn M. Evans posted a large shielded metal arc (SMA) weld metal (WM) database on the ResearchGate website (researchgate.net). This database contains more than 950 WM compositions, along with their respective WM tensile and Charpy V-notch (CVN) impact properties. In particular, the CVN impact properties list the test temperatures that achieved 28 and 100 J impact energy for each WM composition. While the availability of this SMA WM database is a valuable and rare gift to the welding community, how could the welding community analyze this database to gain valuable insights? This paper utilizes a constraints-based model (CBM) as a simple and effective framework to organize and analyze this very large Fe-C-Mn SMA WM database. A CBM is built on the metallurgical principle that one needs to lower relevant solid-state phase transformation (i.e., austenite decomposition) temperatures to improve WM strength and fracture toughness while simultaneously reducing carbon content and Yurioka’s carbon equivalent number (CEN) to improve the weldability of high-strength steels. To this end, a CBM identifies and simultaneously solves several statistical (regression) equations that relate the chemical composition of high-strength steel WM with Yurioka’s CEN and selected solid-state phase transformation temperatures related to austenite decomposition. The results of the current effort demonstrate that the analysis of Evans’s shielded metal arc welding database using a CBM as a framework reaffirms that controlling carbon content, the value of the CEN, and calculated solid-state phase transformation temperatures, particularly the difference between the calculated Bs (bainite-start) and Ms (martensite-start) temperatures, is critical to developing and identifying high-performance, high-strength steel welding electrodes. A dual approach that manipulates the contents of principal alloy elements such as C, Mn, Ni, Cr, Mo, and Cu, and adds controlled amounts of Ti, B, Al, O, and N, appears to offer the best means to lower relevant solid-state phase transformation temperatures to produce high-strength and high-toughness WMs.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2021-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47628492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Advanced high-strength steels (AHSS) such as complexphase (CP) and high-formability (HF) steel offer weightsaving advantages for automotive applications such as chassis and frame applications. To prevent material oxidation, materials are often galvanized to protect the substrate from corrosion. However, the weldability of coated AHSS becomes challenging due to the trapping of zinc in the weld molten pool, which could lead to weld defects such as porosity and liquid metal embrittlement cracks. This work focused on the weldability of AHSS (CP800 and 980HF) using the gas metal arc welding process. The roles of both galvanized iron coating and filler material on weld strength were investigated. The welds were performed using two different filler materials: a low-strength filler (ER70S-6) and a high-strength filler (ER100S-6) material. In addition, two different joint configurations were studied: lap joints and butt joints. The results showed that the butt joint had a higher strength compared to the lap joints. Furthermore, the strength of the butt joint overmatched the base material strength in all of the tested materials (both in galvanized and uncoated). In general, lap joint strength undermatched the base material strength, which was attributed to the rotation during tensile testing that induced unaccounted bending stress on the lap joint, while using a higherstrength welding wire improved the tensile strength material in the lap joint configuration. The hardness profiles in the 980HF steel also showed a significant hardness mismatch due to the formation of a fully martensitic microstructure in the heat-affected zone, which led to suppressing the deformation across the lap joint.
{"title":"Effect of Coating and Welding Wire Composition on AHSS GMA Welds","authors":"A. Midawi, E. Biro, Srinath R. Kistampally","doi":"10.29391/2021.100.035","DOIUrl":"https://doi.org/10.29391/2021.100.035","url":null,"abstract":"Advanced high-strength steels (AHSS) such as complexphase (CP) and high-formability (HF) steel offer weightsaving advantages for automotive applications such as chassis and frame applications. To prevent material oxidation, materials are often galvanized to protect the substrate from corrosion. However, the weldability of coated AHSS becomes challenging due to the trapping of zinc in the weld molten pool, which could lead to weld defects such as porosity and liquid metal embrittlement cracks. This work focused on the weldability of AHSS (CP800 and 980HF) using the gas metal arc welding process. The roles of both galvanized iron coating and filler material on weld strength were investigated. The welds were performed using two different filler materials: a low-strength filler (ER70S-6) and a high-strength filler (ER100S-6) material. In addition, two different joint configurations were studied: lap joints and butt joints. The results showed that the butt joint had a higher strength compared to the lap joints. Furthermore, the strength of the butt joint overmatched the base material strength in all of the tested materials (both in galvanized and uncoated). In general, lap joint strength undermatched the base material strength, which was attributed to the rotation during tensile testing that induced unaccounted bending stress on the lap joint, while using a higherstrength welding wire improved the tensile strength material in the lap joint configuration. The hardness profiles in the 980HF steel also showed a significant hardness mismatch due to the formation of a fully martensitic microstructure in the heat-affected zone, which led to suppressing the deformation across the lap joint.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":"1 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2021-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41881486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Gould, L. Lindamood, J. Malpica, P. Lester, Dewei Zhu
A major challenge for high-volume resistance spot welding of aluminum sheet is durability of the electrodes themselves. In production today, electrodes have total anticipated lives (including dressing) on the order of 1000 welds. This is largely related to the use of medium-frequency direct current (MFDC) power. The single-polarity orientation of MFDC welding results in excessive heating of one electrode (anode) and accelerated wear rates. Recently, technology employing capacitor discharge (CD) welding in conjunction with polarity switching has been developed. This work is the first effort in examining the response of resistance spot welding on aluminum sheet using this power source. Part 1 of this research (Ref. 1) described basic process robustness in spot welding with CD power systems. Part 2 addresses electrode life response. Duplicate electrode life tests were completed for 2000 welds without failure. These results were related to the polarity switching and short time that produced balanced and minimized wear. Additional testing was done without the use of electrode-cooling water. A limited test (500 welds) largely paralleled the ones done with cooling, suggesting that long-term spot welding with polarity-switching CD power and no water was possible.
{"title":"Capacitor Discharge Spot Welding of Aluminum, Part 2: Electrode Life Assessments","authors":"J. Gould, L. Lindamood, J. Malpica, P. Lester, Dewei Zhu","doi":"10.29391/2022.101.031","DOIUrl":"https://doi.org/10.29391/2022.101.031","url":null,"abstract":"A major challenge for high-volume resistance spot welding of aluminum sheet is durability of the electrodes themselves. In production today, electrodes have total anticipated lives (including dressing) on the order of 1000 welds. This is largely related to the use of medium-frequency direct current (MFDC) power. The single-polarity orientation of MFDC welding results in excessive heating of one electrode (anode) and accelerated wear rates. Recently, technology employing capacitor discharge (CD) welding in conjunction with polarity switching has been developed. This work is the first effort in examining the response of resistance spot welding on aluminum sheet using this power source. Part 1 of this research (Ref. 1) described basic process robustness in spot welding with CD power systems. Part 2 addresses electrode life response. Duplicate electrode life tests were completed for 2000 welds without failure. These results were related to the polarity switching and short time that produced balanced and minimized wear. Additional testing was done without the use of electrode-cooling water. A limited test (500 welds) largely paralleled the ones done with cooling, suggesting that long-term spot welding with polarity-switching CD power and no water was possible.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46148254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Q. Zhi, X. Tan, Wenhui Liu, Yang Liu, B. Ou, Hongwei Zhao, Zhongxia Liu, P. Wang
In this study, the effect of the fixture configuration on ultrasonic welding of 4-mm-thick carbon-fiber-reinforced polyamide 66 (CF/PA66) composite with 30% mass fiber was evaluated. An analytical model to estimate the energy dissipation in the welding zone of lapped CF/PA66 samples was derived. Calculation analyses showed the energy dissipation at the faying interface of joints made from hollow-fixture ultrasonic welding (HFUSW) was about 25% higher than those made from conventional ultrasonic welding (CUSW) under the given process variables. This was primarily attributed to the almost total reflection at the workpiece-to-fixture interface in HFUSW. Experimental results indicated that the HFUSW joints exhibited a greater peak load and weld area than CUSW joints when the weld time was less than 2.1 s. The optimal weld time for CUSW and HFUSW processes were 2.1 and 1.7 s. When the weld time exceeded the optimal time, the joints occurred with a porous region, which was caused by thermal decomposition of the material, resulting in the decrease in peak load. Experimental and simulation results demonstrated the HFUSW process changed the propagation behavior of the ultrasonic wave and enhanced the energy dissipation at the faying interface. This study enriched the understanding of energy dissipation during ultrasonic welding of polymers.
{"title":"The Effect of a Hollow Fixture on Energy Dissipation of Ultrasonic Welded Carbon Fiber/Polyamide 66 Composite","authors":"Q. Zhi, X. Tan, Wenhui Liu, Yang Liu, B. Ou, Hongwei Zhao, Zhongxia Liu, P. Wang","doi":"10.29391/2021.100.033","DOIUrl":"https://doi.org/10.29391/2021.100.033","url":null,"abstract":"In this study, the effect of the fixture configuration on ultrasonic welding of 4-mm-thick carbon-fiber-reinforced polyamide 66 (CF/PA66) composite with 30% mass fiber was evaluated. An analytical model to estimate the energy dissipation in the welding zone of lapped CF/PA66 samples was derived. Calculation analyses showed the energy dissipation at the faying interface of joints made from hollow-fixture ultrasonic welding (HFUSW) was about 25% higher than those made from conventional ultrasonic welding (CUSW) under the given process variables. This was primarily attributed to the almost total reflection at the workpiece-to-fixture interface in HFUSW. Experimental results indicated that the HFUSW joints exhibited a greater peak load and weld area than CUSW joints when the weld time was less than 2.1 s. The optimal weld time for CUSW and HFUSW processes were 2.1 and 1.7 s. When the weld time exceeded the optimal time, the joints occurred with a porous region, which was caused by thermal decomposition of the material, resulting in the decrease in peak load. Experimental and simulation results demonstrated the HFUSW process changed the propagation behavior of the ultrasonic wave and enhanced the energy dissipation at the faying interface. This study enriched the understanding of energy dissipation during ultrasonic welding of polymers.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42984874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hui Huang, Jian Chen, Zhili Feng, Hui-Ping Wang, W. Cai, B. Carlson
The computational design of industrially relevant welded structures is extremely time consuming due to coupled physics and high nonlinearity. Previously, most welding distortion and residual stress simulations have been limited to small coupons and reduced order (from three-dimensional [3D] to two-dimensional [2D]), or inherent strain approximations were used for large structures. In this current study, an explicit finite element code based on a graphics processing unit was utilized to perform 3D transient thermomechanical simulation of structural components during welding. Laser brazing of aluminum alloy panels as representative of automotive manufacturing scenarios was simulated to predict out-of-plane distortion under different clamping conditions. The predicted deformation pattern and magnitude were validated by laser scanning data of physical assemblies. In addition, the code was used to investigate residual stresses developed during multipass arc welding of a nuclear industry pressurizer surge nozzle and subsequent welding repair where a 3D simulation was necessary. Taking the experimental data as reference, the 3D model predicted better residual stress distribution than a typical 2D asymmetrical model. Stress evolution in welding repair was also presented and discussed in this study. The efficient numerical model made it feasible to use integrated computational welding engineering to simulate welding processes for large-scale structures.
{"title":"Large-Scale Welding Process Simulation by GPU Parallelized Computing","authors":"Hui Huang, Jian Chen, Zhili Feng, Hui-Ping Wang, W. Cai, B. Carlson","doi":"10.29391/2022.101.032","DOIUrl":"https://doi.org/10.29391/2022.101.032","url":null,"abstract":"The computational design of industrially relevant welded structures is extremely time consuming due to coupled physics and high nonlinearity. Previously, most welding distortion and residual stress simulations have been limited to small coupons and reduced order (from three-dimensional [3D] to two-dimensional [2D]), or inherent strain approximations were used for large structures. In this current study, an explicit finite element code based on a graphics processing unit was utilized to perform 3D transient thermomechanical simulation of structural components during welding. Laser brazing of aluminum alloy panels as representative of automotive manufacturing scenarios was simulated to predict out-of-plane distortion under different clamping conditions. The predicted deformation pattern and magnitude were validated by laser scanning data of physical assemblies. In addition, the code was used to investigate residual stresses developed during multipass arc welding of a nuclear industry pressurizer surge nozzle and subsequent welding repair where a 3D simulation was necessary. Taking the experimental data as reference, the 3D model predicted better residual stress distribution than a typical 2D asymmetrical model. Stress evolution in welding repair was also presented and discussed in this study. The efficient numerical model made it feasible to use integrated computational welding engineering to simulate welding processes for large-scale structures.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43975007","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Kumar, P. Ganesh, V. Sharma, M. Manekar, R. Gupta, R. Singh, M. Singh, G. Mundra, R. Kaul
Austenitic stainless steel is often used as the construction material for particle accelerator vacuum chambers. It is also a strong candidate construction material for helium vessels of superconducting radiofrequency cavities of highenergy, high-power particle accelerators. One of the major limitations of austenitic stainless steels for their application in particle accelerators is the relatively higher magnetic permeability of its welds. The present paper describes an experimental study to obtain a low-magnetic-permeability gas tungsten arc weld of 316L stainless steel while using ER 316L stainless steel filler metal through controlled addition of nitrogen in the argon shielding gas. It was demonstrated that 316L stainless steel welds, made with the addition of 1.5% nitrogen in the argon shielding gas, were associated with magnetic permeability close to that of the base metal. The welds exhibited good strength and ductility in addition to qualifying the impact test requirement of the American Society of Mechanical Engineers Boiler & Pressure Vessel Code (BPVC) for operation at room temperature and liquid helium temperature (4 K). The technique is important for the fabrication of BPVC-compliant 316L stainless steel vacuum chambers and pressure vessels of particle accelerators, including helium vessels of superconducting radiofrequency cavities.
{"title":"Development of Low-Magnetic-Permeability Welds of 316L Stainless Steel","authors":"A. Kumar, P. Ganesh, V. Sharma, M. Manekar, R. Gupta, R. Singh, M. Singh, G. Mundra, R. Kaul","doi":"10.29391/2021.100.029","DOIUrl":"https://doi.org/10.29391/2021.100.029","url":null,"abstract":"Austenitic stainless steel is often used as the construction material for particle accelerator vacuum chambers. It is also a strong candidate construction material for helium vessels of superconducting radiofrequency cavities of highenergy, high-power particle accelerators. One of the major limitations of austenitic stainless steels for their application in particle accelerators is the relatively higher magnetic permeability of its welds. The present paper describes an experimental study to obtain a low-magnetic-permeability gas tungsten arc weld of 316L stainless steel while using ER 316L stainless steel filler metal through controlled addition of nitrogen in the argon shielding gas. It was demonstrated that 316L stainless steel welds, made with the addition of 1.5% nitrogen in the argon shielding gas, were associated with magnetic permeability close to that of the base metal. The welds exhibited good strength and ductility in addition to qualifying the impact test requirement of the American Society of Mechanical Engineers Boiler & Pressure Vessel Code (BPVC) for operation at room temperature and liquid helium temperature (4 K). The technique is important for the fabrication of BPVC-compliant 316L stainless steel vacuum chambers and pressure vessels of particle accelerators, including helium vessels of superconducting radiofrequency cavities.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2021-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48666359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The extent of the heat-affected zone (HAZ) in welding is typically estimated from thermodynamic considerations of austenization; however, thermodynamics are a poor predictor of the HAZ location in microalloyed steels. This work addresses the problem through the study of austenite formation during continuous heating on a grade X80 pipeline steel with an initial ferritic and bainitic microstructure. The methodology involved dilatometry, electron microscopy, and thermodynamic calculations. A continuous heating transformation diagram was developed for heating rates varying from 1˚ to 500˚C/s. For the slower heating rates, austenite start-transformation temperature was higher than the one dictated by the equilibrium, while for the faster heating rates, start-transformation temperature gradually approached the theoretically calculated temperature at which the ferrite can transform (possibly through a massive transformation) without a long-range diffusion into austenite. Partial-transformation experiments suggested that austenite formation occurs in the following two stages: 1) the transformation of bainitic zones into austenite, and later, 2) the transformation of polygonal ferritic grains.
{"title":"Effect of the Heating Rate on Austenite Formation","authors":"Alejandro HINTZE CESARO, P. Mendez","doi":"10.29391/2021.100.030","DOIUrl":"https://doi.org/10.29391/2021.100.030","url":null,"abstract":"The extent of the heat-affected zone (HAZ) in welding is typically estimated from thermodynamic considerations of austenization; however, thermodynamics are a poor predictor of the HAZ location in microalloyed steels. This work addresses the problem through the study of austenite formation during continuous heating on a grade X80 pipeline steel with an initial ferritic and bainitic microstructure. The methodology involved dilatometry, electron microscopy, and thermodynamic calculations. A continuous heating transformation diagram was developed for heating rates varying from 1˚ to 500˚C/s. For the slower heating rates, austenite start-transformation temperature was higher than the one dictated by the equilibrium, while for the faster heating rates, start-transformation temperature gradually approached the theoretically calculated temperature at which the ferrite can transform (possibly through a massive transformation) without a long-range diffusion into austenite. Partial-transformation experiments suggested that austenite formation occurs in the following two stages: 1) the transformation of bainitic zones into austenite, and later, 2) the transformation of polygonal ferritic grains.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2021-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42625785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Gould, L. Lindamood, J. Malpica, P. Lester, Dewei Zhu
A key aspect of integrating automotive sheet into automotive production are the costs associated with joining. While the majority of sheet steel assembly is done with resistance spot welding, that has not readily translated to aluminum. Resistance spot welding of aluminum sheet is challenged by high current demand as well as reduced electrode life. In the latter case, direct current (DC) power supplied by state-of-the-art systems has exacerbated the problem. Recently, technology employing capacitor discharge (CD) welding in conjunction with polarity switching has been developed. This work is a first effort in examining the response of resistance spot welding on aluminum sheet to polarity-switching CD power. In this paper, the current range response between medium-frequency DC (MFDC) and polarity-switching CD was investigated. It was found that polarity-switching CD welding offered improved current ranges over MFDC. In addition, replicate mechanical testing cross-tension results were similar, but tensile shear strengths improved nominally 20–25%. Finally, some limited tests were done to assess the suitability of CD resistance spot welding in the presence of an adhesive. Current range tests with and without a prepulse were done, and both showed excellent weldability.
{"title":"Capacitor Discharge Spot Welding of Aluminum, Part 1: Weldability Assessments","authors":"J. Gould, L. Lindamood, J. Malpica, P. Lester, Dewei Zhu","doi":"10.29391/2021.100.028","DOIUrl":"https://doi.org/10.29391/2021.100.028","url":null,"abstract":"A key aspect of integrating automotive sheet into automotive production are the costs associated with joining. While the majority of sheet steel assembly is done with resistance spot welding, that has not readily translated to aluminum. Resistance spot welding of aluminum sheet is challenged by high current demand as well as reduced electrode life. In the latter case, direct current (DC) power supplied by state-of-the-art systems has exacerbated the problem. Recently, technology employing capacitor discharge (CD) welding in conjunction with polarity switching has been developed. This work is a first effort in examining the response of resistance spot welding on aluminum sheet to polarity-switching CD power. In this paper, the current range response between medium-frequency DC (MFDC) and polarity-switching CD was investigated. It was found that polarity-switching CD welding offered improved current ranges over MFDC. In addition, replicate mechanical testing cross-tension results were similar, but tensile shear strengths improved nominally 20–25%. Finally, some limited tests were done to assess the suitability of CD resistance spot welding in the presence of an adhesive. Current range tests with and without a prepulse were done, and both showed excellent weldability.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2021-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47630864","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In Ni-based alloys, precipitates that form along grain boundaries (GBs) during terminal solidification have been shown to pin GBs and resist GB sliding, which can cause ductility-dip cracking (DDC). As a result, it is often suggested that the stainless steel skeletal/lacy in a matrix resists DDC because it pins GBs. In the present study, austenitic stainless steels 304, 316, 310, and 321 were quenched with liquid Wood’s metal (75˚C) during welding. Quenching captured the elevated-temperature micro-structure and simultaneously induced cracking, thus revealing the mechanisms of the resistance to DDC. In addition, DDC was much higher in 310 than 304, 316, and 321, which is consistent with results of conventional tests. Both 304 and 316 solidified as columnar grains, with continuous formed along GBs soon after solidification to resist DDC along the GBs. 321 solidified as equiaxed grains of instead of columnar, and the tortuous GBs associated with equiaxed grains resisted DDC. 310, however, solidified as coarse, straight grains with little along the GBs, and solidification GBs migrated to become locally straight. The resulting GBs were long, straight, and naked, which is ideal for DDC. In 304, 316, or 321, skeletal/lacy in a matrix did not exist in the fusion zone near the mushy zone, where DDC occurs. This proved skeletal/lacy cannot resist DDC as often suggested. Instead, the present study identified two new mechanisms of resistance to DDC: 1) formation of continuous or nearly continuous along boundaries of columnar grains and 2) solidification as equiaxed grains.
{"title":"Resistance of Austenitic Stainless Steels to Ductility-Dip Cracking: Mechanisms","authors":"P. Yu, J. Morrow, S. Kou","doi":"10.29391/2021.100.026","DOIUrl":"https://doi.org/10.29391/2021.100.026","url":null,"abstract":"In Ni-based alloys, precipitates that form along grain boundaries (GBs) during terminal solidification have been shown to pin GBs and resist GB sliding, which can cause ductility-dip cracking (DDC). As a result, it is often suggested that the stainless steel skeletal/lacy in a matrix resists DDC because it pins GBs. In the present study, austenitic stainless steels 304, 316, 310, and 321 were quenched with liquid Wood’s metal (75˚C) during welding. Quenching captured the elevated-temperature micro-structure and simultaneously induced cracking, thus revealing the mechanisms of the resistance to DDC. In addition, DDC was much higher in 310 than 304, 316, and 321, which is consistent with results of conventional tests. Both 304 and 316 solidified as columnar grains, with continuous formed along GBs soon after solidification to resist DDC along the GBs. 321 solidified as equiaxed grains of instead of columnar, and the tortuous GBs associated with equiaxed grains resisted DDC. 310, however, solidified as coarse, straight grains with little along the GBs, and solidification GBs migrated to become locally straight. The resulting GBs were long, straight, and naked, which is ideal for DDC. In 304, 316, or 321, skeletal/lacy in a matrix did not exist in the fusion zone near the mushy zone, where DDC occurs. This proved skeletal/lacy cannot resist DDC as often suggested. Instead, the present study identified two new mechanisms of resistance to DDC: 1) formation of continuous or nearly continuous along boundaries of columnar grains and 2) solidification as equiaxed grains.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46249446","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Welder-dependent manufacturing is no longer suitable for the modern production of a high-performance nuclear pressure container. The high-quality root pass welding of medium-thick steel plates is the main challenge to obtain a sturdy reactor vessel, especially to generate one-sided welding with back-formation bead without a backing. Herein, low frequency and large duty-cycle pulsed gas tungsten arc welding (GTAW) was employed to weld the medium-thick steel plates with a 5-mm root face and 2-mm root opening. The arc characteristic and weld pool dynamic behavior in the proposed GTA root pass welding was investigated by a high-speed camera, and a deflection phenomenon of arc tail flame was first found. The correlations of the characteristic parameters of the arc tail flame, including the deflected angle and length, with the weld joint penetration and welding speed were also analyzed in detail. The results showed a negative correlation to the welding speed and a positive correlation with the weld joint penetration. A sound weld bead was formed at a range from 15 deg and 20 mm to 19 deg and 27mm. Based on the above relationship, a new method using these two characteristic parameters was proposed to identify the weld joint penetration in the root pass welding, and its fundamentals were completely demonstrated by the dynamic change of the keyhole. Its feasibility was also demonstrated by the experiment combined with the weld pool dynamic-dependent theoretical analysis.
{"title":"Joint Penetration Monitoring in Low-Frequency Pulsed GTA Root Pass Welding of Medium-Thick Steel Plates","authors":"Zhengwen Zhu, Gang Zhang, K. Wang, Yu Shi, M. Zhu","doi":"10.29391/2021.100.025","DOIUrl":"https://doi.org/10.29391/2021.100.025","url":null,"abstract":"Welder-dependent manufacturing is no longer suitable for the modern production of a high-performance nuclear pressure container. The high-quality root pass welding of medium-thick steel plates is the main challenge to obtain a sturdy reactor vessel, especially to generate one-sided welding with back-formation bead without a backing. Herein, low frequency and large duty-cycle pulsed gas tungsten arc welding (GTAW) was employed to weld the medium-thick steel plates with a 5-mm root face and 2-mm root opening. The arc characteristic and weld pool dynamic behavior in the proposed GTA root pass welding was investigated by a high-speed camera, and a deflection phenomenon of arc tail flame was first found. The correlations of the characteristic parameters of the arc tail flame, including the deflected angle and length, with the weld joint penetration and welding speed were also analyzed in detail. The results showed a negative correlation to the welding speed and a positive correlation with the weld joint penetration. A sound weld bead was formed at a range from 15 deg and 20 mm to 19 deg and 27mm. Based on the above relationship, a new method using these two characteristic parameters was proposed to identify the weld joint penetration in the root pass welding, and its fundamentals were completely demonstrated by the dynamic change of the keyhole. Its feasibility was also demonstrated by the experiment combined with the weld pool dynamic-dependent theoretical analysis.","PeriodicalId":23681,"journal":{"name":"Welding Journal","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43879061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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