基于BP神经网络薄板P-PAW搭接的间隙自适应工艺参数优化

对大型LNG燃料薄膜舱中1.2 mm厚SUS304L不锈钢板薄板的搭接焊,存在的搭接间隙会带来焊缝成形不良等严重影响船舱安全性的问题。本文通过激光传感器检测搭接间隙变化,设计了不同的峰值电流和焊接速度在不同间隙下的工艺实验,研究了间隙对焊缝成形质量的影响机制;基于BP神经网络建立不同间隙下的脉冲等离子弧焊(P-PAW)的工艺参数和间隙及焊缝成形尺寸之间的拓扑关系模型,通过工艺实验获取模型的训练样本,实现了基于BP神经网络的间隙自适应工艺参数优化系统。结果表明,该系统实现了不同搭接间隙下进行实时工艺参数优化的功能,并对搭接间隙在0～0.6 mm变化时所带来的空洞等缺陷起到了有效的抑制作用,实现了良好的焊接成形一致性控制,提高了在LNG薄膜舱中不锈钢板焊接的自适应能力。     

薄板TIG焊熔池谐振法熔透自适应控制

在直流电流上附加正弦波焊接电流,诱发熔池金属振荡,通过电弧电压检测熔池谐振信号,此谐振信号与熔池尺寸有良好对应关系。实验研究了影响熔池谐振信号产生的电弧因素,通过建立以直流变动电流电源、步进电弧、微计算机数据采集和反馈控制为主体的焊接熔透控制系统,实现了薄板对接焊缝熔宽的实时控制,获得良好焊缝成形。在有意识地改变外部影响因素条件下,取得了满意的自适应控制效果。     

电弧电流对AZ31B/DP980激光诱导电弧焊接接头成形及力学性能的影响

采用激光诱导钨极惰性气体保护(tungsten inert gas, TIG)电弧焊接技术,在未添加任何夹层和镀层的条件下,通过优化工艺,获得了AZ31B镁合金和DP980高强钢高质量搭接焊接头,重点研究TIG电弧电流对焊接接头成形和力学性能的影响规律。结果表明：电弧电流的增大会提高镁合金在高强钢的润湿铺展能力,提升焊缝宽度的同时减小润湿角。镁合金/钢焊接接头的最大拉伸载荷随着电弧电流的增大先升高后降低,接头断裂模式由沿界面断裂转变为沿焊缝断裂。当TIG电流为80 A、激光功率为350 W时,焊接接头最大平均拉伸载荷达到279 N/mm。焊缝宽度和界面层厚度的增大以及激光匙孔的钉扎作用共同提升了镁合金/钢的接头性能。     

钛及钛合金真空等离子焊箱枪体的改造

为了满足大尺寸钛及钛合金电极的焊接要求,宝钛集团有限公司依据等离子弧的压缩效应原理及电弧的稳定性原理,对从德国引进的钛及钛合金真空等离子焊箱枪体的阴极和喷嘴进行了技术改造.改造后,不仅提高了电弧的稳定性,而且也扩大了电极的焊接尺寸.焊缝宽度可达50 mm～60 mm,深度达20 mm～30 mm,可焊电极的最大长度为6 m,直径为0.6 m,满足了钛及钛合金大规模化的生产要求.     

刍议单面焊双面成型焊接的工艺缺陷和控制切入点

单面焊双面成形焊接的工艺缺陷主要表现在焊接电流、焊速、焊条类型及焊条直径的影响等方面,以及焊接层数选择不当、电弧电压上,这些缺陷一旦形成,不仅要增加消耗,降低结构的质量和使用寿命,而且还会给结构的安全生产带来威胁,引起安全事故。业已引起了业界的高度重视。     

双丝单弧气保焊熔滴过渡及焊缝成形

双丝单弧气保焊是一种新型熔化极焊接方法,系统由单电源、单送丝机构和单焊枪组成,双丝共用一个具有两孔的导电嘴,单电源通过导电嘴同时向双丝输出电流形成单个电弧,双丝末端熔滴相互吸引形成共熔滴并稳定过渡到熔池。采用高速摄像、信息同步采集及焊接电源等装备,开发双丝单弧气保焊熔滴过渡试验系统,研究了不同焊接电流参数对熔滴大小、过渡行为及焊缝形貌的影响,并阐明了双丝单弧气保焊熔滴过渡机理。结果表明：随着焊接电流的增大,熔滴过渡形式依次为多脉一滴、一脉一滴、射流过渡和潜弧射流过渡四种模式,过渡频率逐渐增大,熔滴体积逐渐减小。焊缝形貌研究表明,随着焊接电流增大,焊缝熔深逐渐增大,熔宽先增大后减小,当焊接电流为570 A时,焊缝截面成形质量最佳,此时熔敷速度为15.8 kg/h。     

铝锂合金YAG-MIG复合焊缝成形特征及性能研究

对5A90铝锂合金薄板YAG-MIG复合焊缝成形特征及性能进行了研究.结果表明:YAG-MIG复合焊可以显著改善5A90铝锂合金激光焊缝下塌、咬边等现象,扩大激光焊的最大间隙容许裕度,使之可达1.0mm.复合焊接头的主要组织特征为细晶层和焊缝区大范围等轴晶,与激光焊接头类似.而不同之处表现为复合焊接头的显微组织相对粗化...     

船用高强钢薄板焊接成形研究

探究了不同焊接工艺对3 mm船用高强钢薄板焊接成形质量的影响.结果表明:3 mm对接试板经不同方法焊接后均呈马鞍形变化.焊条电弧焊和手工气保焊焊接的试板变形严重,且两者变形量和残余应力基本相当,药芯焊丝CMT(cold metal transfer)自动焊接试板的焊缝内部存在夹渣缺陷.利用实心焊丝CMT自动焊接试板的焊缝均匀、内部无缺陷,焊缝中心残余应力明显降低,其变形量平均值比焊条电弧焊减小37.8%,且线能量仅为焊条电弧焊的22.4%.焊接试板变形量与其线能量大小的变化趋势一致.     

双面双弧焊对高强钢焊接效率和质量影响分析

对高强钢10CrNi3MoV钢厚板进行了双面双弧焊接试验研究。结果表明,焊接长2 m、厚50 mm的钢板,双面双弧焊与传统单弧MAG焊相比,生产效率提高1.4倍,焊接接头力学性能满足指标要求;双面双TIG打底的热影响区金相组织为板条状马氏体,焊缝区为板条马氏体+针状铁素体。     

窄间隙P-GMAW多信息融合侧壁熔合状态识别研究

窄间隙焊缝坡口间距小且焊道较深,摆动中心与焊缝中心偏差较大时,坡口两侧侧壁受热不良,易发生未熔合缺陷。为了及时了解窄间隙侧壁熔合情况,掌握侧壁内部焊接质量,本文提出了一种基于BP神经网络和D-S证据理论的多信息融合方法,预测侧壁熔合状态。对窄间隙焊接未熔合缺陷产生机制进行了分析,研究发现焊接电弧信号和熔池变化与侧壁成形质量存在密切关系,为此进行了一系列偏差实验,建立了电弧电信号和电弧熔池图像信号的实时采集系统,采用批量特征提取算法,提取了与侧壁熔合状态密切关联的峰值电流、峰值电压、电弧弧长、熔池长宽比、熔池面积和熔池周长等特征参量。采用BP算法训练神经网络,在此基础上通过D-S证据理论进行决策级融合。实验结果表明,该模型识别率可达96.667%,避免了神经网络识别时的误诊,获得了比单一传感信息更好的预测结果,提高了熔合状态识别的准确度和可靠度。     

Phase formation in selected surface-roughened plasma-nitrided 304 austenite stainless steel

Abstract

Direct current (DC) glow discharge plasma nitriding was carried out on three selected surface-roughened AISI 304 stainless steel samples at 833 K under 4 mbar pressures for 24 h in the presence of N₂:H₂ gas mixtures of 50 : 50 ratios. After plasma nitriding, the phase formation, case depth, surface roughness, and microhardness of a plasma-nitrided layer were evaluated by glancing angle x-ray diffractogram, optical microscope, stylus profilometer, and Vickers microhardness tester techniques. The case depth, surface hardness, and phase formation variations were observed with a variation in initial surface roughness. The diffraction patterns of the plasma-nitrided samples showed the modified intensities of the α and γ phases along with those of the CrN, Fe₄N, and Fe₃N phases. Hardness and case depth variations were observed with a variation in surface roughness. A maximum hardness of 1058 Hv and a case depth of 95 μm were achieved in least surface-roughened samples.     

Phase formation in selected surface-roughened plasma-nitrided 304 austenite stainless steel

Direct current (DC) glow discharge plasma nitriding was carried out on three selected surface-roughened AISI 304 stainless steel samples at 833 K under 4 mbar pressures for 24 h in the presence of N₂:H₂ gas mixtures of 50 : 50 ratios. After plasma nitriding, the phase formation, case depth, surface roughness, and microhardness of a plasma-nitrided layer were evaluated by glancing angle x-ray diffractogram, optical microscope, stylus profilometer, and Vickers microhardness tester techniques. The case depth, surface hardness, and phase formation variations were observed with a variation in initial surface roughness. The diffraction patterns of the plasma-nitrided samples showed the modified intensities of the α and γ phases along with those of the CrN, Fe₄N, and Fe₃N phases. Hardness and case depth variations were observed with a variation in surface roughness. A maximum hardness of 1058 Hv and a case depth of 95 μm were achieved in least surface-roughened samples.     

Super304H奥氏体耐热钢微观组织研究

为了深入认识新型奥氏体耐热钢Super304H(0.1C-18Cr-9Ni-3Cu-Nb,N)的微观组织,利用光学显微镜、扫描电子显微镜、电子探针和X射线衍射等手段,研究了Super304H钢合金元素的分布和析出相的组成及分布形态.试验结果表明,Super304H钢在供货状态下的显微组织由γ-基体和析出相组成.与传统的18-8不锈钢相比,这种奥氏体钢晶粒均匀细小,晶粒尺寸约46μm.析出相主要由Nb(C,N)和富铜相组成,Nb(C,N)有呈方向性分布的条块状和呈弥散分布的细小颗粒状两种形态,条块状的Nb(C,N)是软化过程中残留下来的,而弥散分布的是固溶处理及冷却过程中析出形成的.其中弥散分布的Nb(C,N)与富铜相对细化晶粒和改善钢的高温强度起重要作用,而多种复合强化机制使得Super304H钢具有优异的高温性能.     

The role of retained austenite in hydrogen embrittlement of supermartensitic stainless steel

Retained austenite may play a role in the hydrogen embrittlement process because austenite has much higher hydrogen solubility than martensite has. The effect of the retained austenite on hydrogen cracking was investigated by tensile testing of standard round bar specimens that had been heat treated in order to achieve different levels of retained austenite. A significant effect of the retained austenite was observed. Samples with high amounts of retained austenite experienced a much higher reduction in ductility after hydrogen charging than samples with low amounts of retained austenite. In order to explain this effect, the hydrogen solubility of samples containing different levels of austenite and precipitates was measured. This was achieved by charging the samples to saturation in an electrolyte and performing hydrogen analysis.     

Selective dissolution of austenite in AISI 304 stainless steel by bacterial activity

Selective attack in an AISI 304 stainless steel weld metal has been developed after three months in service in well water. Welding zones showed a severe corrosive attack that in some cases led to the steel perforation. Optical and scanning electron microscopy (SEM/EDX) revealed a selective attack. An in-depth analysis showed indications of microbiological activity which could be responsible of the severe attack.     

Dynamic recrystallisation of as cast austenite in 18–8 stainless steel

Abstract

Dynamic recrystallisation behaviour of an as cast 0Cr18Ni9Ti stainless steel during hot deformation was investigated by hot compression test at a temperature range of 950–1200°C and strain rate of 5 × 10^-3–1 × 10^-1 s^-1. Change of austenite grain size owing to dynamic recrystallisation was also studied by microstructural observation. The experimental results showed that the hot deformation conditions, such as temperature, strain, and strain rate determine the dynamic recrystallisation behaviour for the as cast stainless steel, and the dynamically recrystallised grain size is determined by the deformation conditions and is independent of the strain.     

大型奥氏体不锈钢应变强化真空粉末绝热贮槽轻量化设计

以实际产品设计为例,将大型真空粉末绝热贮槽的传统设计与采用应变强化技术的设计进行比较,得出应变强化技术可实现压力容器的轻量化设计。对于应变强化型大型容器,为了较容易实现内、外筒体的套装,采用多种方法有效地控制了强化后的应变,其中控制原材料的屈服强度是最直接有效且不增加成本的控制强化后应变的方法。     

Effects of annealing temperature on nano/ultrafine-grained structure in austenite stainless steel

A nano/ultrafine-grained (NG/UFG) structure was obtained by heavy cold deformation (80%) and annealing in the range between 700 and 950°C for 60?s to explore the effects of temperature on the development of NG/UFG structures in austenitic stainless steel. Results showed that martensite was reversibly transformed to austenite, with the accumulation of twins, dislocations and subgrain boundaries. At 700°C, the microstructure exhibited low elongation and consisted of 65% austenite. Above 750°C, the amount of reversed austenite was nearly 100%. The tensile strength of the sample decreased slightly, whereas the elongation increased further, showing co-dependent strengthening and toughening. At 850°C, micrometre-sized grains were embedded in the nanocrystalline/ultrafine grains. In this case, both the microstructure and mechanical properties were optimal.     

含铜奥氏体抗菌不锈钢抗菌性能和机理初步研究

考察了含铜奥氏体抗菌不锈钢的抗菌性能，并对其抗菌机理进行了初步探讨。方法：覆膜法测定杀菌率；透射电镜观察E．coli细胞形态；考马斯亮蓝法测定细胞漏出液中可溶性蛋白含量；琼脂糖凝胶电泳检测菌体基因组DNA考察抗菌不锈钢对DNA的剪切作用。结果：除产气肠杆菌外，奥氏体抗菌不锈钢对其它供试的16种常见微生物均显示较强的抗菌活性，具有广谱抗菌性．在作用9h时可将1×10^7cfu／ml的E．coli全部杀灭，对浓度≤1×10^7cfu／ml的E．coli液在24h内杀灭率达到99．5％。透射电镜结果显示，与奥氏体抗菌不锈钢作用后的E．coli细胞壁和细胞膜破裂，核区不明显；作用后的菌液中可溶性蛋白质含量增加；实验中未检测到有明显的菌体DNA断裂现象．结论：奥氏体抗菌不锈钢具较强的抗菌性能和广谱抗菌性。其作用机理可能为使菌体细胞壁和细胞膜因氧化而破裂，胞内可溶性蛋白漏出，最终导致菌死亡。