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Development of a chromium-free consumable for joining stainless steels.

机译：开发用于连接不锈钢的无铬易损件。

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摘要

Government regulations in the United States (OSHA Standards: 1910; 1915; 1917; 1918; 1926) and abroad are decreasing allowable exposure levels of hexavalent chromium to welding related personnel. The latest OSHA ruling in 2006 reduced the permissible exposure limit of airborne hexavalent chromium from 52 to 5 mug m-3. Achieving the new level may not be practical from an engineering controls standpoint during the fabrication of tightly enclosed stainless steel components such as the inside of ship hulls and boiler vessels. One method of addressing this problem is to implement a chromium-free welding consumable that provides equivalent mechanical performance and corrosion characteristics to current stainless steel welding consumables. This project was aimed at developing such a consumable and evaluating its suitability for replacement of current stainless steel consumables such as E308L-16. A new shielded metal arc welding (SMAW) consumable based on the Ni-Cu-Ru system was developed for austenitic stainless steel welding. The focus of this work was evaluating the mechanical properties, weldability, and fume formation characteristics of the various iterations of consumables developed. Welds deposited on Type 304 stainless steel were evaluated with weldability tests including: mechanical testing, hot ductility testing, Strain-to-fracture testing, Transverse Varestraint testing, and button melting.;Mechanical properties of weld deposits of each consumable were found to exceed minimum values of Type 304 stainless steel based on tensile testing. Guide bend testing showed that weld deposits met minimum weld ductility requirements for stainless steel consumables, such as E308-16.;Hot ductility testing revealed a narrow crack susceptible region (33 to 54°C) indicating a low susceptibility to weld metal liquation cracking. GTA welds exhibited superior ductility when compared to SMA welds. This was attributed to a lack of slag inclusions in the weld deposit, which are effective weld strengtheners.;Varestraint testing revealed that weld deposits have a higher solidification cracking susceptibility than stainless steel consumables used to join Type 304. Higher cracking susceptibility was attributed to austenitic solidification of the weld metal resulting in increased weld segregation and stabilization of a TiC eutectic reaction at the end of solidification. No solidification cracks were observed in actual weld deposits.;Evaluation of weld microsegregation patterns showed higher dilutions of Type 304 increased segregation of Ti, promoting a TiC eutectic reaction at the end of solidification. Thermodynamic modeling techniques were used to describe the solidification the Ni-Cu weld deposits as a function of dilution with Type 304. Solidification cracking susceptibility was shown to increase with dilution during evaluation with the Cast Pin Tear Test indicating high dilution welds should be avoided to minimize solidification cracking during welding.;The Strain-to-fracture test was used to examine DDC cracking susceptibility, and revealed that this alloy has a higher susceptibility to solid-state weld cracking than austenitic stainless alloys such as 304. Threshold strain levels necessary to initiate cracking in the weld deposits were in the range of 2 to 3%. These values are comparable to other Ni-base alloys with a moderate to high susceptibility to DDC.;Fume generation rates (FGR) of the new consumable were measured and bulk fume phases were analyzed with X-ray diffraction. FGR values were found to be similar to current SMAW and flux cored arc welding consumables. No chromium bearing compounds were observed during X-ray diffraction measurements, and the bulk fume consisted primarily of halides and metallic-oxides. Fume generated by the new consumable was subjected to colorimetric testing showing hexavalent Cr content (0.02 wt-%) was reduced by two orders of magnitude compared to E308-16 (2.6 wt-%). The source of this hexavalent chromium was from evaporation of the base metal due to the welding heat source.;The consumable developed in this study, having a nominal composition of Ni-7.5Cu-1Ru-0.5Al-0.5Ti-0.02C, met virtually all the design criteria that were initially established. Work performed by the Fontana Corrosion Center showed that the weld deposits met corrosion design criteria to prevent localized attack of the weld metal. Work performed in this study showed that mechanical properties were comparable to stainless steel consumables, and weld cracking susceptibility was comparable to Ni-base welding consumables. The consumable was also found to have good operability characteristics. (Abstract shortened by UMI.)
机译：美国政府的法规（OSHA标准：1910； 1915； 1917； 1918； 1926）和国外正在降低焊接相关人员的六价铬容许暴露水平。 OSHA在2006年的最新裁定将机载六价铬的允许暴露极限从52降低到5杯m-3。从工程控制的角度来看，在制造紧密密封的不锈钢部件（例如船体和锅炉船的内部）时，达到新的水平可能不切实际。解决此问题的一种方法是实现无铬焊接材料，该材料可提供与当前不锈钢焊接材料相同的机械性能和腐蚀特性。该项目旨在开发这种易损件并评估其是否适合替代当前的不锈钢易损件，例如E308L-16。开发了一种基于Ni-Cu-Ru系统的新型屏蔽金属电弧焊（SMAW）消耗品，用于奥氏体不锈钢焊接。这项工作的重点是评估所开发的各种消耗品迭代的机械性能，可焊性和烟雾形成特性。用可焊性测试对沉积在304型不锈钢上的焊缝进行了评估，包括：机械测试，热延展性测试，应变断裂测试，横向变应变测试和纽扣熔化;发现每种易损件的焊缝机械性能均超过最小值304型不锈钢的拉伸试验值。引导弯曲测试表明焊缝沉积物满足不锈钢耗材的最低焊接延展性要求，例如E308-16 .;热延展性测试显示狭窄的裂纹敏感区（33至54°C）表明对焊接金属液化裂纹的敏感性较低。与SMA焊缝相比，GTA焊缝具有出色的延展性。这归因于焊缝中没有熔渣夹杂物，它们是有效的焊缝强化剂。Varestraint测试表明，焊缝中的焊缝凝固性比用于加入304型不锈钢的不锈钢易损件要高。开裂敏感性高的原因是奥氏体焊接金属的凝固导致增加的焊接偏析和凝固结束时TiC共晶反应的稳定性。在实际的焊缝中没有观察到凝固裂纹。焊缝微观偏析的评估显示，较高的304型稀释度会增加Ti的偏析，从而在凝固结束时促进TiC共晶反应。使用热力学建模技术描述了304型镍-铜焊缝熔敷随稀释量的变化。在铸针撕裂试验评估过程中，随着稀释量的增加，凝固裂纹敏感性增加，这表明应避免高稀释度的焊缝以最大程度地减少应变断裂试验用于检验DDC裂纹敏感性，结果表明该合金比304等奥氏体不锈钢具有更高的固态焊接裂纹敏感性。焊缝中的开裂在2％到3％的范围内。这些值可与其他对DDC具有中等到高度敏感性的镍基合金相媲美。;测量了新消耗品的烟气生成率（FGR），并通过X射线衍射分析了烟气相。发现FGR值类似于当前的SMAW和药芯焊丝电弧焊耗材。在X射线衍射测量过程中未观察到含铬化合物，并且大烟主要由卤化物和金属氧化物组成。新消耗品产生的烟气经过比色测试，显示六价铬含量（0.02 wt％）与E308-16（2.6 wt％）相比减少了两个数量级。该六价铬的来源是由于焊接热源而导致的贱金属蒸发。本研究开发的消耗品，其标称成分为Ni-7.5Cu-1Ru-0.5Al-0.5Ti-0.02C，满足几乎所有最初建立的设计标准。丰塔纳腐蚀中心进行的工作表明，焊缝符合腐蚀设计标准，可以防止焊缝金属局部腐蚀。在这项研究中进行的工作表明，其机械性能与不锈钢材料相当，并且焊接裂纹敏感性与镍基焊接材料相当。还发现该消耗品具有良好的可操作性特征。 （摘要由UMI缩短。）

著录项

  • 作者

    Sowards, Jeffrey William.;

  • 作者单位

    The Ohio State University.;

  • 授予单位 The Ohio State University.;
  • 学科 Engineering Metallurgy.;Engineering Materials Science.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 262 p.
  • 总页数 262
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 冶金工业;工程材料学;
  • 关键词

  • 入库时间 2022-08-17 11:38:10

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