Influence of heat treatment on microstructure,mechanical and corrosion behavior of WE43 alloy fabricated by laser-beam powder bed fusion

Magnesium(Mg)alloys are considered to be a new generation of revolutionary medical metals.Laser-beam powder bed fusion(PBF-LB)is suitable for fabricating metal implants withpersonalized and complicated structures.However,the as-built part usually exhibits undesirable microstructure and unsatisfactory performance.In this work,WE43 parts were firstly fabricated by PBF-LB and then subjected to heat treatment.Although a high densification rate of 99.91%was achieved using suitable processes,the as-built parts exhibited anisotropic and layeredmicrostructure with heterogeneously precipitated Nd-rich intermetallic.After heat treatment,fine and nano-scaled Mg24Y5particles were precipitated.Meanwhile,theα-Mg grainsunderwent recrystallization and turned coarsened slightly,which effectively weakened thetexture intensity and reduced the anisotropy.As a consequence,the yield strength and ultimate tensile strength were significantly improved to(250.2±3.5)MPa and(312±3.7)MPa,respectively,while the elongation was still maintained at a high level of 15.2%.Furthermore,the homogenized microstructure reduced the tendency of localized corrosion and favoredthe development of uniform passivation film.Thus,the degradation rate of WE43 parts was decreased by an order of magnitude.Besides,in-vitro cell experiments proved their favorable biocompatibility.

Respiratory Flow Rates of Metal Welders Compared to a Population Not Exposed to Metal Welding Dust

Background: The welding trade includes many industrial activities in both the formal and informal sectors. Workers in this professional environment do not have access to individual and collective means of protection adapted to the activity, which exposes them to the dust emitted during their activity and therefore contributes to increasing the risk of developing respiratory disorders in this population. Objective: Our study aimed to evaluate the ventilatory function of metal welders in the city of Dakar. Method: This was a comparative study based on the analysis of the spirometric parameters of metal welders working in the city of Dakar (Senegal) with those of a control group of the same kind, selected from the general population. Measurements of forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), peak expiratory flow (PEF) and maximum mid expiratory flow (MMEF) were measured. Results: A total of 75 men between the ages of 19 and 61 were recruited and divided into two groups (43 controls and 32 welders). The welding population had more frequent distal and central obstructions and pulmonary restriction compared to the control group. The metals most commonly used by welders were aluminum for welders who had an obstruction, while for those who had a restriction, iron was the most used metal. Signs of metal fever were frequently found in welders, especially those with ventilatory disorders. Conclusion: The prevalence of respiratory disorders observed is close to that observed in industrial environments, where exposure levels are the highest. The lack of personal protective equipment could also be a significant risk factor in the development of these disorders.

闪光焊机硅钢焊接时影响焊缝稳定性因素分析

针对酒钢碳钢冷轧的闪光焊机在开发无取向硅钢50JW800存在焊接后焊缝稳定性差,频繁断带原因进行了分析。以酒钢碳钢薄板厂2022年1月发生的多起硅钢焊缝断带事件为攻关对象,通过大量实测数据统计分析,总结出硅钢生产时焊缝断带原因,并提出影响焊缝稳定性的因素及控制措施,为闪光焊机生产硅钢过程中稳定焊缝质量,保障生产顺行提供了有效指导。

窄搭接电阻缝焊过程中焊轮打火的解决方法

连续热镀铝锌生产线的窄搭接电阻缝焊过程中常出现焊轮打火问题,导致焊缝质量下降造成断带,从而引发产线停机,因此需要对电阻焊过程中焊轮打火的原因进行分析。主要针对焊接电流、焊轮与钢带之间的接触电阻、钢带与钢带之间的接触电阻等因素进行探讨。分析发现,焊轮与钢带之间的接触电阻增大是导致焊轮打火的主要原因:焊轮表面的污染物会显著增加接触电阻,导致热量过大,烧穿焊缝;钢带表面的清洁度也对接触电阻有显著影响,导致电流分布不均,产生打火。此外,根据钢带厚度选择合适的焊接电流对于控制焊接过程中的打火现象也至关重要。

负载持续率对手工弧焊机空闲损耗的控制研究

焊接是一种常见的金属连接方法,焊接过程中会产生大量的损耗,焊接结束后也会产生空闲损耗。本文旨在研究焊接负载持续率对焊机空闲损耗的有效控制,以优化焊接过程,降低焊接空闲损耗,提高焊接质量。文章依据标准GB 28736—2019的试验方法对焊接电流500 A以下的手工弧焊机进行试验验证,通过固定焊接周期对焊接时间进行调整,最终得出10分钟为一周期的手工弧焊机在保证正常焊接质量前提下在63%~64%负载持续率时一分钟的平均空闲损耗获得最低值。

特种设备钢种类常用焊接方法考核项目优化

为了优化特种设备行业焊接作业人员的考核项目,减少企业资源浪费和经济损失,提高焊接作业效率和质量。针对当前焊接作业人员考核中存在项目重叠和无证上岗的问题提出优化方案。通过分析TSG Z6002—2010《特种设备焊接操作人员考核细则》和实际生产需求,对手工焊焊工和焊机操作工的考核项目进行了系统梳理,考虑了焊接方法、金属材料类别、接头形式、试件位置、焊缝金属厚度、管材试件外径、填充金属类别、焊接工艺因素等多个要素,对SMAW、GMAW(含FCAW)、GTAW、SAW等常用焊接方法的考核项目进行具体优化。结果表明,通过选择合适的考核项目,可以覆盖更广泛的焊接作业需求,同时减少考核项目的数量,降低企业的考核成本;企业应根据自身的焊接作业特点和实际生产需求,制定最优化、经济、适用范围广的考核项目,提升焊接作业人员的专业技能,确保特种设备的焊接质量。

铝电解阳极导杆组钢爪头半自动电渣焊机的研发与应用

阳极导杆组是铝电解槽阳极的金属结构件,在铝电解槽生产过程中,阳极导杆组会因为导杆缺陷、焊接缺陷、钢爪头缺陷、外观几何尺寸、表面质量等质量因素下线,下线后的导杆组经维修合格后进入下一个循环周期。钢爪头的修复是导杆修理过程中的重要环节,原有修复工艺是将报废的钢爪头切割,锯切新钢爪头,对结合面开坡口并打磨,再组对焊接。这种工艺生成的焊缝压降较大,焊接质量难以保证。钢爪头半自动熔铸技术,成功的解决了阳极钢爪头焊接的难题,有效的提高了焊接质量,降低了焊缝压降,提高了劳动效率,降低了维修成本。

GHG-800固定式闪光焊机脉动闪光焊接工艺试验及接头性能分析

采用GHG-800直流固定式闪光焊机脉动焊接工艺对鞍钢U71MnG钢轨进行焊接试验。对焊接设备、工艺和焊接质量进行分析,通过优化部分工艺参数,可有效改善GHG-800固定式闪光焊机脉动闪光焊轨底角灰斑的面积和尺寸,同时改善轨底角断口形貌,从而获得焊接接头良好的力学性能。同时,研究发现工艺调整前后灰斑出现的位置呈现一定的规律,检验了GHG-800固定式闪光焊机工艺的稳定性。合理的GHG-800固定式闪光焊机脉动闪光焊工艺可以通过型式检验的落锤、断口、晶粒度、静弯和探伤检验。

Digital Twin for Human-Robot Interactive Welding and Welder Behavior Analysis

This paper presents an innovative investigation on prototyping a digital twin(DT)as the platform for human-robot interactive welding and welder behavior analysis.This humanrobot interaction(HRI)working style helps to enhance human users'operational productivity and comfort;while data-driven welder behavior analysis benefits to further novice welder training.This HRI system includes three modules:1)a human user who demonstrates the welding operations offsite with her/his operations recorded by the motion-tracked handles;2)a robot that executes the demonstrated welding operations to complete the physical welding tasks onsite;3)a DT system that is developed based on virtual reality(VR)as a digital replica of the physical human-robot interactive welding environment.The DT system bridges a human user and robot through a bi-directional information flow:a)transmitting demonstrated welding operations in VR to the robot in the physical environment;b)displaying the physical welding scenes to human users in VR.Compared to existing DT systems reported in the literatures,the developed one provides better capability in engaging human users in interacting with welding scenes,through an augmented VR.To verify the effectiveness,six welders,skilled with certain manual welding training and unskilled without any training,tested the system by completing the same welding job;three skilled welders produce satisfied welded workpieces,while the other three unskilled do not.A data-driven approach as a combination of fast Fourier transform(FFT),principal component analysis(PCA),and support vector machine(SVM)is developed to analyze their behaviors.Given an operation sequence,i.e.,motion speed sequence of the welding torch,frequency features are firstly extracted by FFT and then reduced in dimension through PCA,which are finally routed into SVM for classification.The trained model demonstrates a 94.44%classification accuracy in the testing dataset.The successful pattern recognition in skilled welder operations should benefit to accelerate novice welder training.

Heat source analyses of dual laser-beam bilateral synchronous welding for T-joint

The DLBSW（ dual laser-beam bilateral synchronous welding） technology of T-type joint has been widely used for the connection of skins and stringers in airplane industry. To understand the thermodynamic and mechanical behavior of this process, it is necessary to establish a reasonable heat source model. Two different surface-body combination heat source models are adopted in this paper. Both models use the Gaussian surface heat source model and one is combined with the cone body heat source model and the other is combined with Gaussian rotator body heat source model. The simulation results of these two different models are investigated. And the temperature field results of DLBSW process for T-joint with two different heat sources are discussed. It is indicated that the combination heat source model is effective to simulate the DLBSW process and the current study is useful for more profound research in this field.

A high precision electron beam welder power supply based on buck-boost converter using fuzzy PID control

A novel electron beam welder （ EBW） power supply was developed. Compared with the traditional 3-phase contrail 12-pulse rectifying supplies, it requires a much lower step-up ratio transformer, but a much less output ripple voltage can be obtained. The design of the main circuit of this new power supply is based on PWM buck-boost converter topology. In developing the system a fuzzy PID control method is adopted because of the strong non-linearity and big signal working conditions of the circuit system. The SABER-MATLAB models and fuzzy algorithm were used in developing the fuzzy PID controller. The co-simulation and experimental results displayed that the unit introduced herein has the characteristics of high control precision and antinterference capability.

Occupational Hearing Hazards among Informal Sector Welders in Lubumbashi, Democratic Republic of Congo

Introduction: Noise, an undesirable sound which is found in all areas of occupational activity, is still a matter of concern given the damage it causes. Various machines and tools, from simple to sophisticated ones, produce several types of noise in the workplace. The purpose of this study was to assess the current status of occupational hearing loss among informal sector welders in the city of Lubumbashi, in the Democratic Republic of Congo. Methods: This was a descriptive cross-sectional study which was conducted among 122 informal sector welders over a period of five months. The study used an anonymous questionnaire on noise exposure in the workplace and collected audio-metric data of welders. The survey collected data on welders who had a minimal three-year duration of employment without the morbidity associated with the Ear Nose Throat (ENT) region. Socio-professional data (age, duration of employment, sex, education), noise exposure, awareness of hazards and audiometric data were taken into account. Results: 122 questionnaires were completed by male subjects, or 100% (n = 122). The mean age of welders was 36.37 ± 11.91 years with extremes being 20 and 63 years. The mean duration of employment was 11.51 ± 9.6 years with extremes being 3 and 44 years. Audiometric data have shown 37.96% (n = 41) of occupational hearing loss. Three degrees of hearing loss were recorded, notably mild hearing loss standing at 80.49% (n = 33);moderate and severe hearing loss standing at 2.44% (n = 1). Ninety-six percent (n = 117) of welders reported not using personal protective equipment (PPE) and 1% (n = 111) were aware of the hazard associated with noise exposure in the workplace. A correlation was found between welders with an advanced age (p < 0.001;RP = 3.66 (2.16 - 6.22)) and hearing loss, and between the duration of employment and hearing loss (p < 0.001;RP = 6.48 (3.32 - 12.65)). Conclusion: In the study area, occupational hearing loss among welders is a relevant fact. Three degrees of hearing loss were identified. Most of those suffering from it have developed a mild type of hearing loss whose continued development can be stopped. Despite the fact that welders are aware of the hazards associated with noise exposure in the workplace, they hardly protect themselves. Lack of a culture of prevention and poor enforcement of the existing laws could account for such a situation. There seems to be a crucial need to put in place a program for protecting the welders’ auditory organs in the workplace.

Early diagnosis of health damage in arc welders based on their serum ferritin level

To develop a method for the early diagnosis of health damage due to arc welding, we measured serum ferritin in 96 general employees and 320 arc welders in Company A. A positive correlation was observed between age and the serum ferritin level in the young group (age, 20 - 44 years) among the general employees. The mean serum ferritin level in the general employees was 119 ± 56 ng/ml. When the mean ± 2.5 SD was used as the standard value, ferritin levels > 260 ng / ml could be regarded as high. Based on this standard value, high ferritin levels were observed in 7 (6.6%) of 106 young arc welders in Company A but none of the general employees. Chest X-ray films showed minimal abnormality in one of 7 young arc welders who showed high ferritin levels. These results suggest that the determination of the serum ferritin level is useful for the early diagnosis of health damage due to arc welding.

State of Eye Protection for Metal Welders in the Workshops of Conakry

Introduction: Welders are an occupational group at high risk for eye injuries. The aim of this study was to investigate the state of eye protection of metal welders in the workshops of Conakry. Material and Methods: The study was cross-sectional, descriptive, and included 180 welders from 45 welding workshops in the city of Conakry for a period of three months. It involved all welding professionals working in an informal unit selected by the study and who had agreed to participate in the study. Results: The average age of the participants was 33.9 ± 13.4 years, with extremes of 15 and 68 years. The study found that 99% of the welders owned glasses, 27% owned face shields, and 49% owned welding masks. Goggles were used regularly by 86% of the welders but were not suitable for welding (98%). All welders had reported having had an eye injury at least once. Foreign bodies were cited in 81%, arc strike in 65%;eye burns in 61%. However, approximately 81% of welders did not have first aid kits at their work sites. Conclusion: The use of protective equipment during welding remains very low in the workshops of Conakry, which is the cause of great ocular morbidity among welders.

Situation on welder training in China

The state of welders training in China is introduced in this paper.There are different specifications because of variable examining organizations,as the deeping of reform and openning in China, welders are trained according to variable specification to fit specific requirement.

国际焊工考试标准或规程的分析与应用

焊工的技能水平直接决定焊接产品质量,焊工技能操作水平的评定通常是通过焊工资格考试来进行的。目前国际上焊工考试标准或规程针对于不同的产品类型及结构特点考虑有所不同,同时标准或规程的具体内容结合产品或体系的特点也有所差异,通过对国际上典型的、应用较多的焊工考试标准或规程进行分析,了解不同焊工考试标准或规程之间存在的差异以及各自的适用范围,合理选择焊工考试标准及项目,建立完善的焊工培训考核体系,强化焊接产品质量的同时提高焊工的个人素质,保证安全生产,达到最佳的经济性。

焊接服新旧标准对比分析

解析GB 8965.2—2022《防护服装焊接服》标准。将该标准与GB 8965.2—2009《防护服装阻燃防护第2部分:焊接服》之间的差异进行了对比和分析,列出了技术要求和测试方法的改变,并提出了合理化建议。指出:新标准完善了熔融金属防护服的标准体系,进一步提高了焊接服的质量控制水平,体现了标准的连续性、合理性和先进性。认为:补充检验规则,规范耐久性标识的评价指标,更有利于新标准的实施和推广。

新版《国家职业资格培训教程•焊工系列》编写概况

以2018版焊工标准为基础介绍了新版《国家职业资格培训教程·焊工系列》编写原则、结构内容及质量控制方法,同时对比了新旧版教程的差异。新版教程以“焊工标准”为依据,以“职业等级制划分”为基础,以“职业活动”为导向,以“职业功能”为核心进行编写,更加模块化,结构清晰明了,是对构建我国焊工人才体系的进一步完善,能够加快提高焊工(电焊工、气焊工、钎焊工、焊接设备操作工)理论知识与技能水平,为焊工队伍的规范化和科学化鉴定提供支撑。

电焊工尘肺CT表现分析

目的:分析电焊工尘肺CT表现,提高对电焊工尘肺的诊断水平。方法:回顾性分析2015年1月-2020年12月按职业病诊断标准诊断为Ⅰ期及Ⅱ期的电焊工尘肺患者共103例。对其临床资料及影像特征进行总结分析。结果:本组电焊工尘肺CT表现为小叶中心磨玻璃密度微小结节影44例,小叶分支线状影63例,其中小叶分支线状影合并小叶中心磨玻璃密度微小结节影共20例;腺泡磨玻璃结节影7例,弥漫性磨玻璃改变10例,致密微小结节影6例,伴有肺间质纤维化6例、纤维灶10例、肺结核6例、肺气肿15例、肺大泡14例、支气管扩张1例、淋巴结肿大9例、胸膜增厚19例。结论:电焊工尘肺的CT具有特征性的影像表现,小叶中心磨玻璃密度微小结节影及小叶分支线状影为其特征的CT表现,结合职业病史,可做出明确诊断。

滚焊机调压轮H62黄铜极片13工步级进模设计

针对滚焊机调压轮H62黄铜极片批量生产的要求,设计了一副13工步连续级进模用于该制件的成形生产。采用简单工序集中和复杂工序分散成形的办法,将制件的冲压成形的工步优化为13个工步,分别为:①定位孔+切边成形➝②冲孔成形➝③切定位槽成形➝④切筋条➝⑤切筋条➝⑥切边➝⑦切连接筋➝⑧一次翻边➝⑨切边+折弯➝⑩切边+180°折弯➝(11)180°折弯➝(12)切断➝(13)制件落料。模具中,针对折弯A特征的成形实用先折弯后翻边的办法成形,针对贴紧的180°折弯成形,分散为4个工位进行成形;针对带一定间距的180°折弯E的成形,分散为2个工位进行折弯成形,先通过凸模将板料筋条进行圆弧预弯,然后再使用2个滑块进行挤压弯曲成形。模具成形工艺设计合理,模具结构简单实用,较好地实现了制件的自动化生产。