ESR Refining Potential for Titanium Alloys using a CaF2‐based Active Slag

Since the end of the Cold War and due to the needs to produce titanium more cost‐efficient and thus more attractive for its civilian use, the electroslag remelting (ESR) process has become an increasingly important topic of international research programmes, because titanium and titanium aluminides can be chemically refined by ESR in some degree. Using ESR, titanium turnings from machining steps and scrap from foundries can be remelted, refined and provided as secondary titanium for the market at relatively favourable prices. This article investigates the removability of the main impurities out of titanium and titanium‐aluminium alloys by electroslag remelting using the active slag system CaF₂‐Ca‐(CaO). Thermochemical and kinetic aspects of the ESR process are considered.     

全封闭Ar气保护电渣重熔GH4169合金

上海五钢采用ALD 5t全封闭Ar气保护电渣重熔炉 ESR(Ar)冶炼了GH4 16 9合金锭 ,分析结果表明 ,ESR(Ar)电渣锭氧、硫含量和锭头尾碳、铝、钛之差远低于一般ESR工艺 ;VIM(真空感应熔炼 ) +ESR(Ar)工艺冶炼合金中平均氧含量 6× 10 - 6 远低于VIM +VAR(真空电弧重熔 )工艺冶炼合金中平均氧含量 13× 10 - 6 ,所以ESR(Ar)工艺脱氧效果优于VAR工艺     

电渣炉渣参数的优化选择

本文论述了电渣冶炼渣参数优化选择的理论与实践。大生产应用表明,在保证电渣钢质的同时,渣量可减少45％,电耗降低19.4％,具有较显著的经济效益。     

电渣溶炼浇铸法制备金属模具

本文简述了用电渣炼浇铸法制备金属模具的工艺原理和该方法的应用前景。     

电渣熔铸中渣池深度对渣池温度场影响的模拟研究

渣池深度是电渣熔铸过程中重要的工艺参数,它直接影响到熔铸过程的稳定、熔铸效率和产品质量.本文在对渣池温度场和电场耦合模拟的基础上,研究了不同渣池深度条件下渣池温度场的变化情况,为实际生产中优化工艺参数和提高生产效率提供了理论依据.     

重熔与时效工艺对ZL101铝合金组织与抗拉强度的影响

ZL101铝合金重熔后,浇注时间和浇注位置对其组织与性能影响很大。从ZL101铝合金不同浇注时间、不同浇注的位置取样,对铸态和时效后的试样进行抗拉强度性能测试,用光学显微镜观察其微观组织,研究重熔与时效工艺对ZL101铝合金组织与性能的影响规律。结果表明,在浇注过程中,试样的晶粒先发生粗化,随着浇注时间的延长,晶粒又发生细化。其抗拉强度也是先降低而后又升高。随着浇注位置的变化,由下向上晶粒逐渐粗化,共晶硅的分布逐渐变得不均匀,且抗拉强度逐渐降低。合金的时效与铸态的组织、性能的变化规律一致。     

Feasibility of laser surface treatment of pearlitic and bainitic ductile irons for hot rolls

The effects of laser surface treatment on the microstructure, crackability and stresses generated on laser hardened layers produced in several ductile cast iron materials were investigated. Two kinds of alloys having pearlitic (SGP) and acicular (SGA) matrix microstructures were selected. Hardened layers with thicknesses ranging from 1.5 to 2.5 mm were obtained by means of laser remelting (LSRm) or laser hardening (LSH). Thermal stresses generated upon laser processing have been estimated by a simple thermal model. For energy densities delivered onto the material at above 40 J/mm², extensive cracking was developed in SGA and SGP irons due to the contribution of thermal stresses. By lowering the energy density, crack formation was avoided in SGP irons only. At low energy densities, crack formation is controlled by the generation of transformational stresses due to excessive austenite retention. An increase of the surface temperature or the alloying content gave rise to an increase of the retained austenite and the formation of lower bainite at the remelted zone and the heat affected zones, respectively. K_C fracture toughness of Fe₃C carbides embedded in pearlitic and acicular matrixes was measured by means of the nano-indentation technique. Fracture toughness of cementite in SGP irons was slightly higher than in SGA irons, which can help to reduce the crackability of LSH layers.     

Al2O3 loss prediction model of selective laser melting Al2O3–Al composite

The element/phase loss is undesirable but existing during selective laser melting (SLM) of materials with volatile element/phase, which not only changes the material composition but also affects the molten pool flow. In the previous researches, the effect of remelting on the element/phase loss was neglected during the SLM process, instead, laser energy density was thought to be uppermost. In fact, the SLM process fabricates the parts in a manner of line by line and layer by layer, i.e., additive character, and the remelting in the overlap zone occurs during the SLM process. In this paper, three different Al₂O₃ loss prediction models of SLM Al₂O₃–Al composite by considering the additive character of SLM and the distribution of the Al₂O₃ associated with the different molten pool driving forces were developed. By comparing with the experimental results and predicted results, it is found that the Al₂O₃ is distributed on both sides of the molten pool under the combined action of the Marangoni flow and the evaporation recoil pressure. This kind of Al₂O₃ distribution enhances the effect of the remelting on the Al₂O₃ loss, i.e., the remelting brings a logarithmic increase in the Al₂O₃ loss rate. This determines the final Al₂O₃ loss rate of the SLMed 3D samples. During this study, although the Al₂O₃ loss rate of the single-track is only 33%, the loss rate of SLMed 3D samples increases significantly to 97% when the hatching space of 60 μm and scanning speed of 200 mm/s are utilized, i.e., almost no Al₂O₃ in the 3D sample. Thus, it is more important to reduce the remelting, i.e., overlap rate for reducing the element/phase loss. This study is a benefit for understanding and reducing the element/phase loss in SLM.     

20#钢激光熔覆-重熔Ni基涂层及其高温磨损行为

应用激光熔覆法,采用镍基NiCrSiB粉末,在20#钢表面制备了熔覆涂层,并用激光重熔涂层。观察了熔覆-重熔层的形貌,检测了其相组成和高温耐磨性能,结果表明:所制得熔覆-重熔层组织均一、致密,与基体形成了良好的冶金结合;经重熔处理后,熔覆层表面的裂纹显著减少;熔覆-重熔层的硬度提高到基体的5倍,高温磨损率约为基体的1/3。熔覆-重熔层耐磨能力的增强除因其与基体形成了良好的冶金结合和硼化物、硼碳化物等析出相的强化作用外,也是重熔减少微裂纹的结果。     

电渣用碳质引弧剂的试制及应用

攀钢集团长钢公司标准Ti≤0．03％的低钛钢在电渣重熔过程中由于使用钛质引弧剂作为电渣导电引弧，导致电渣成品钢锭大头Ti高而产生大量废品。我们研制出一种碳质引弧剂代替钛质引弧剂用于电渣引燃渣料进行重熔生产，通过试验证明，采用碳质引弧剂引燃渣料进行重熔生产，电渣锭大头增Ti得以解决。