微Ti处理380CL车轮钢闪光对焊工艺与组织调控

为解决轮辋闪光对焊(FBW)后微裂纹率和炸裂率偏高的问题,选取6.75 mm厚380CL车轮钢为研究对象,通过研究一元化闪光对焊参数对接头硬度的影响规律,建立闪光对焊温度场控制机制. 通过Ti微合金化技术思路进一步降低380CL闪光对焊焊缝的硬化倾向. 结果表明,为保证380CL闪光对焊后的成材率,需采取温度梯度较大的焊接规范,配合合理的顶锻量,从而获得最优的焊接接头. 在烧化量19 mm,钳口距离36 mm,烧化速度1.2 mm/s,带点顶锻时间0.5 s,顶锻量7 mm的闪光对焊参数下,6.75 mm厚380CL车轮钢可获得最低的硬度值140HV2. 对微Ti处理的380CL车轮钢进行了焊接热模拟,在1 000 ℃以上时的顶锻变形抗力降低,组织晶粒细化,显著降低了380CL闪光对焊后微裂纹率和炸裂率. 以上研究具备向高强度轮辋用钢的闪光对焊做进一步推广和应用示范.     

焊接名词术语(九)

3.40 顶锻留量 upset allowance 考虑焊件因顶锻缩短而预留的长度。 3.41 顶锻速度 upset speed 闪光对焊和电阻对焊过程中,顶锻阶段动夹的移动速度。 3.42 工作行程 operational stroke     

闪光对焊参数微机测判装置

本文研制了由单片机的闪光对焊参数测试及质量判定装置。本装置通过采集对焊过程的位移，电流和油压等数据，再经过数据处理，能够打印输出闪光留量，闪光速度、顶锻留量，有电要面锻留量、顶锻速度及顶锻压强等参数，并能判上述参数合理与否，如果需要还能打印出过程的焊接电流与位移的变化曲线。     

铝铜异种材料线性摩擦焊接头的微观组织与力学性能

采用不同的顶锻力对AA5083-H112铝合金和T2纯铜进行了线性摩擦焊接,获得了无明显缺陷的焊接头,并通过扫描电镜、硬度、力学性能试验等方法研究了线性摩擦焊铝铜接头的微观组织和力学性能。结果表明,随着顶锻力的减小,摩擦效应增加,更多的铜颗粒渗入铝基体中;而随着顶锻力的增加,拉伸力学性能明显下降,这是由于较大的顶锻力会使摩擦过程的热输入量增大,从而在铝铜结合处生成层状的第二相Al_2CuMg,使焊接头的力学性能降低。     

汽车齿轮用20CrMnTiH钢顶锻裂纹产生原因及改进措施

汽车齿轮用20GrMnTiH钢热顶锻时产生表面裂纹,对存在缺陷的钢材进行高低倍检验及对生产过程工艺参数进行分析,连铸过程产生的皮下气孔和皮下裂纹是造成热顶锻裂纹的主要原因,通过改进保护渣的理化指标,避免连铸结晶器保护渣结壳,可以消除热顶锻裂纹的发生。     

45圆钢热顶锻裂纹原因分析

针对45圆钢热顶锻开裂问题,从宏观和微观两方面对裂纹原因进行分析,结果表明圆钢折叠缺陷是引起热顶锻裂纹的主要原因,同时局部脱碳加剧了顶锻开裂。可以通过严格执行检修和轧制制度,同时配合优化轧钢加热制度来消除热顶锻裂纹的发生。     

Q235钢筋闪光对焊工艺

全面研究Q235钢筋棒材闪光对焊工艺及其组织性能,通过改变伸出长度、顶锻留量、顶锻力等工艺参数,测定其对抗拉强度的影响。分析了焊缝及热影响区的组织和硬度变化规律。结果表明,采用合适的工艺参数进行焊接,能够获得强度高于母材的焊接接头。     

磁控旋转电弧管板对焊装置的研制

根据磁控旋转电弧的工作原理,设计了一种新型磁控旋转电弧管板对焊装置。该装置由机械机构和电气控制两部分组成,满足了焊件夹紧、定位、顶锻等功能,提供了对焊所需的电源、磁场及其逻辑控制系统等。其中,顶锻机构采用了电磁和弹簧加压方式代替液压顶锻,简化了设备构成;励磁电源具有恒电流和恒电压外特性,可方便控制磁感应强度,改变电弧旋转速率。实现了焊接过程中引弧、旋弧、顶锻的自动控制,操作简单方便。电弧形态试验表明,通过焊接参数的调节该装置可产生稳定的旋转电弧,焊件端面金属熔化均匀,可以满足对焊工艺的需求。     

钢轨压焊顶锻变形热/力模拟研究

采用美国先进的Gleeble-2000热模拟试验机,对高速铁路轨道用U71Mn钢轨的对焊顶锻变形过程进行了热力模拟试验。研究了不同加热条件下,钢轨顶锻所需压力的大小;探索了在相同加热条件下,钢轨钢在顶锻变形过程中的顶锻量、顶锻速度以及带电顶锻时间对接头焊接质量的影响规律。实验结果为合理制定钢轨对焊工艺,有效控制焊轨质量,为列车安全运行提供了试验数据和理论依据。     

铝合金薄壁管焊接区开裂分析

通过宏观及微观检测,分析了6061铝合金管及A7003铝合金薄壁管经TIG(氩弧)焊后的焊接区开裂的原因.分析结果表明,虽然具体铝合金牌号的焊接性能不尽相同,但造成这类铝合金薄壁管焊接开裂的主要原因是焊接中线能量控制不平稳,局部能量过大造成焊接塌陷突起而引发热裂纹.     

Study on lamellar tearing generated by corner joint welding in box column of ultrathick plate

Abstract

In an attempt to reduce the risk of lamellar tearing during welding of ultrathick plates, the present study has evaluated the susceptibility to lamellar tearing of steel structures in relation to welding stress rather than metallurgical properties, and eventually attempted to determine the optimum groove shape and welding procedure by computer simulation based on the finite element method. Based on the simulation, it has been identified that controlling the shape of the deposited weld metal in the anticipated position of the occurrence of lamellar tearing is the most favourable method of preventing lamellar tearing by minimising welding residual stress and strain. Owing to the difference in weld deposited area, the cooling rate for the partial penetration condition is more rapid than for full penetration. Furthermore, in terms of welding residual stress, the full penetration condition is preferable to the partial penetration condition.     

Lamellar tearing

Lamellar tearing is a type of weld cracking which occurs in a joint on which a large restraint stress acts in the direction of the plate thickness (hereafter referred to as Z-direction) of a steel plate. The term 'lamellar tear' was first used by J E Jubb¹, D M Nicholls² and others of Cranfield University, UK in 1968 and means tearing in a lamellar form.     

中间包层状撕裂产生的原因及预防措施

针对中间包焊接时产生层状撕裂问题，从产品结构、焊接工艺等方面分析了层状撕裂的原因，并制定相应的工艺措施，避免了层状撕裂的产生。     

Weldability and toughness evaluation of pressure vessel quality steel using the shielded metal arc welding (SMAW) process

The present study was carried out to assess the weldability properties of ASTM A 537 Cl. 1 pressure-vessel quality steel using the shielded metal arc welding (SMAW) process. Implant and elastic restraint cracking (ERC) tests were conducted under different welding conditions to determine the cold cracking susceptibility of the steel. The static fatigue limit values determined for the implant test indicate adequate resistance to cold cracking even with unbaked electrodes. The ERC test, however, established the necessity to rebake the electrodes before use. Lamellar tearing tests carried out using full-thickness plates under three welding conditions showed no incidence of lamellar tearing upon visual examination, ultrasonic inspection, and four-section macroexamination. Lamellar tearing tests were repeated using machined plates, such that the central segregated band located at the midthickness of the plate corresponded to the heat-affected zone (HAZ) of the weld. Only in one (no rebake, heat input: 14.2 kj cm^-1, weld restraint load: 42 kg mm^-2) of the eight samples tested was lamellar tearing observed. This was probably accentuated due to the combined effects of the presence of localized pockets of a hard phase (bainite) and a high hydrogen level (unbaked electrodes) in the weld joint. Optimal welding conditions were formulated based on the above tests. The weld joint was subjected to extensive tests and found to exhibit excellent strength (tensile strength: 56.8 kg mm^-2, or 557 MPa), and low temperature impact toughness (7.4 and 4.5 kg-m at-20 °C for weld metal, WM, and HAZ) properties. Crack tip opening displacement tests carried out for the WM and HAZ resulted in δ_m values 0.36 and 0.27 mm, respectively, which indicates adequate resistance to brittle fracture.     

硬质合金/钢钎缝中的夹杂物及其对接头力学性能的影响

以YG8硬质合金与45钢的钎焊接头为研究对象,选用BCu54ZnMnNiSn钎料钎焊。借助金相显微镜(OM)、扫描电镜(SEM)、能谱分析仪(EDS)、MTS万能力学试验机等手段分析了钎焊接头夹杂物与力学性能的关系。结果表明钎焊接头的夹杂物有氧化物、硫化物、磷化物、硅酸盐、硼化物等。剪切断口观察到大范围的层状撕裂和局部的小韧窝,说明断裂为韧-脆混合型断裂。在裂纹发源处很容易观察到Fe-Co-O,MnO,FeS-MnS,FeP,2MnO·SiO_2等非金属夹杂物。由于非金属夹杂物的熔点、沸点较高,与钎料基体的热膨胀系数差别较大,容易成为裂纹萌发并扩展的区域,宏观表现为剪切强度降低。     

120mm大厚度Q390GJC Z35高层建筑用钢的研制

针对大厚度高层建筑用钢生产难度大、产量少等问题,通过优化成分、轧制及热处理工艺,试制了120mm大厚度Q390GJC Z35高强度钢板。结果表明,产品组织均匀、韧窝细小,力学性能及抗层状撕裂性能均满足国家标准要求。     

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 中厚板拉伸试样出现了延伸率不合问题，并且拉伸试样断口出现了层状撕裂现象。通过对试样断口形貌、试样变形区和未变形区金相组织的研究，认为：中厚板中心区域珠光体比例高是层状撕裂试样厚度中心呈现脆性的原因，这种脆性区导致在拉伸过程中最先萌生裂纹，并最终导致拉伸试样延伸率不合；出现层状撕裂的试样在拉伸之前并不存在结构上的分层和断口分层，在断口上出现的平行于轧制方向的裂纹是在拉伸过程中形成的；当珠光体带的宽度超过25 μm时，试样在拉伸过程中在珠光体带中易出现裂纹并导致断口出现层状撕裂。     

Characterisation of hot tearing in Al cast alloys: methodology and procedures

Abstract

Hot tearing is perhaps the pivotal issue defining castability. It is affected by alloy composition as well as processing conditions and variables. Hot tearing is a complex phenomenon in that it lies at the intersection of heat flow, fluid flow and mass flow. Over the years, many theories and models have been proposed, and accordingly, many tests have been developed. Unfortunately, many of the tests that have been proposed are qualitative in nature. The need exists for a simple, reliable and repeatable quantitative test to evaluate hot tearing. The Metal Processing Institute and the CANMET‐Materials Technology Laboratory, both members of the Light Metal Alliance, joined forces to address this need. A quantitative hot tearing test was developed, and the methodology is presented and discussed. The test has been applied to study hot tearing of A356 and M206 alloys. The results are presented and discussed. Protocol and standardised procedures that can be adapted by the metal casting industry is presented.     

抽油杆用非调质钢摩擦焊的组织与力学性能

以材料型超高强度抽油杆用钢FG - 2 0为研究对象 ,进行了摩擦焊工艺参数与接头力学性能关系的研究和探讨。以便为采用摩擦焊工艺生产制造超高强度抽油杆提供理论依据和实用工艺参数。试验采用正交试验结合相关力学性能评定和组织分析 ,确定了摩擦焊主要工艺参数的适用范围和优化方向。结果表明 ,由于FG - 2 0钢强度高 ,与其它钢材比较 ,应采用较小的摩擦工进速度和较大的顶锻压力 ;另外 ,对于FG -2 0钢 ,由于摩擦焊过程中 ,热影响区组织性能发生变化 ,因此采用焊后局部回火处理用以改善接头力学性能是非常必要的。