钢中残余元素在连铸坯和热轧板中的富集行为

通过扫描电镜和X射线能谱分析仪(X-EDS)分析,对低合金钢种连铸板坯和热轧板中Cu、As和Sn的富集行为进行了研究.实验结果表明:连铸坯中氧化层和氧化层/基体层界面存在Cu、As和Sn元素同时富集现象;热轧板氧化层/基体层界面存在Cu、As和Sn元素富集相,基体层中Cu、As和Sn含量高于氧化层;热轧板晶界处Cu、As和Sn含量明显高于热轧板晶内;Cu、As和Sn在γ晶界偏聚和Fe的优先氧化造成连铸坯中Cu、As和Sn富集,加热炉的二次加热加剧Cu、As和Sn的富集程度,引起Cu、As和Sn向钢材基体渗透扩散,使钢的塑性恶化,导致中板大量表面微裂纹缺陷.分析了Cu、As和Sn富集相对表面微裂纹的影响机理.     

残余元素对低合金钢连铸坯高温延塑性的影响

 采用Gleeble 1500热模拟试验机测试了含有一定量残余元素Cu、As和Sn的低合金钢连铸坯的高温延塑性。低合金钢的第Ⅰ脆性温度区在ts～1340 ℃之间,第Ⅲ脆性温度区在920～730 ℃之间。由于钢中Cu、As和Sn等残余元素含量比较高,因此第Ⅲ脆性温度区比较宽,深度比较大。     

Cu、As和Sn对低合金钢连铸坯第Ⅲ脆性区的影响

为了研究残余元素Cu、As和Sn对钢高温延塑性的影响,采用Gleeble-1500热模拟试验机测试了含有一定量Cu、As和Sn低合金钢连铸坯的高温延塑性,得到了低合金钢第Ⅲ脆性温度区在920~730℃之间.结果表明:第Ⅲ脆性温度区脆化的主要原因是奥氏体单相区低温域钢中Cu、As和Sn等残余元素在奥氏体晶界的偏聚削弱晶界结合能,导致试样沿晶脆性断裂;奥氏体和铁素体两相区在原奥氏体晶界析出的网状铁素体导致试样沿晶开裂.钢中的Cu、As和Sn元素增加第Ⅲ脆性温度区的宽度和脆性凹槽的深度,同时提高第Ⅲ脆性温度区的上限临界温度.     

钢中残余元素对连铸圆坯纵裂的影响

使用Gleeble机测定了不同残余元素含量的连铸圆坯试样的高温力学性能,结果表明:Cu当量(Cu+10Sn)＝0.32 %的试样在925～1 000 ℃,特别是在950 ℃的热塑性显著降低;扫描电镜和俄歇检验发现,此温度下试样为沿晶断裂,在奥氏体晶界有Sn偏析.分析连铸生产条件认为,如拉速较低,结晶器内初生坯壳温度处于此高温脆性区,圆铸坯将可能产生纵裂.     

含砷/铜砷C-Mn钢的高温氧化行为

利用热重分析仪、扫描电镜和电子探针研究了含As或者Cu+As的C-Mn钢的高温氧化特性.1050℃氧化初期约500 s内,As钢和Cu-As钢为线性氧化阶段,随后转为抛物线氧化,两种钢的抛物线氧化速率均高于C-Mn钢.因氧化层分离,1150℃氧化增重小于1050℃氧化增重.钢中Cu和As的存在促进了固相Fe₂SiO₄层的生长.由于As在氧化层/基体界面的富集,1050℃氧化时,As钢中存在明显的条带状内部氧化粒子层;C-Mn钢中加入Cu和As后,其氧化层/基体界面变得崎岖不平,内部氧化粒子的数量随着氧化时间及氧化温度的增加而增加.1050℃氧化时氧化层/基体界面处Cu和As的富集程度高于1150℃氧化.     

SPAH钢集装箱板连铸坯加热氧化特性

通过实验室箱式电阻炉对SPAH钢(%:0.05C、0.25Cu、0.12Ni、0.41 Cr)连铸坯试样进行900～1 250℃,20 min氧化试验,并用扫描电镜和X-射线能谱仪观察和分析了试样氧化层的组织和成分。结果表明,随加热温度增加,钢的氧化速度急剧增加,同时氧化层中的Cu富集相增加;≤1 000℃加热时,晶界氧化占主导,1 000℃以上加热,晶内氧化占主导。因此SPAH钢集装箱板连铸坯加热时,应减少高温段的加热时间,以便减少氧化烧损。     

残余元素对连铸坯和热轧板表面质量的影响

 通过扫描电镜、透射电镜和EDS分析,对残余元素对连铸坯和热轧板表面质量的影响进行了研究。试验结果表明,连铸坯氧化层中存在铜、砷和锡同时富集。热轧板基体层与氧化层界面存在铜、砷和锡富集,基体层铜、砷和锡含量高于氧化层铜、砷和锡含量。铜、砷和锡在γ晶界偏聚和铁优先氧化造成连铸坯中铜、砷和锡富集,加热炉二次加热加剧铜、砷和锡富集,铜、砷、锡向钢基体渗透扩散,恶化钢的塑性,导致中板表面微裂纹缺陷,分析了铜、砷和锡富集相对表面微裂纹的影响机理。     

Cu、As、Sn对C-Mn钢热轧板表面质量的影响

通过扫描电子显微镜和X-射线能谱分析研究了C-Mn钢(%:0.13～0.20C、1.00～1.60Mn、0.09Cu、0.07As、0.05Sn)连铸坯热轧的25 mm板表面微裂纹。结果表明,热轧板表面裂纹两侧存在薄的氧化脱碳层,裂纹沿晶界开裂,裂纹附近的基体处存在Cu、As、Sn低熔点富集相。实际生产中当钢中的Cu、As、Sn含量分别控制≤0.02%,可基本消除热轧板表面网状裂纹。     

中板表面微裂纹缺陷研究

通过金相观察、扫描电镜和XEDS分析,对低合金钢连铸板坯轧制中板出现的表面微裂纹进行研究,发现裂纹附近存在Cu和As元素,裂纹沿晶界延伸,确定钢中的Cu、As和Sn等元素在γ晶界偏聚和选择氧化在钢基体和氧化铁层间形成含Cu、As和Sn的富集相,钢的塑性恶化是导致中板表面微裂纹的主要原因.分析了Cu、As 和Sn对表面微裂纹的影响机理,提出了相应的防止措施.     

残余元素对涟钢CSP热冷轧卷质量的影响

钢中的残余元素问题是钢铁冶金面临的重要问题之一,高性能新钢种必须考虑残余元素的有害影响.涟钢矿石来源多而杂,导致铁水中As,Cu,Pb,Sn,Sb等残余元素增加.从残余元素(As,Cu,Pb,Sn,Sb等)对涟钢热轧卷、冷轧卷表面质量和力学性能的影响进行分析.分析结果表明:送检的热轧卷发现表面氧化铁与试样基体的界面有铜的富集;晶界处铜的富集会成为热轧卷产生裂纹的原因之一;冷轧卷酸洗后表面有黑点,黑点处发现有Cu,As,Sn,Sb等残余元素的富集;对特定时期的热轧卷力学性能进行多次逐步回归分析发现Sb对屈服强度有显著的负相关.     

Cu enrichment behavior at steel-scale interface during high temperature oxidation of Cu containing steel

In order to suppress the surface cracking induced by Cu during reheating and hot rolling process,Cu enrichment and its migration at the steel-scale interface was investigated during heating of steel cast at temperatures between 1000℃and 1200℃in N₂-O₂ and N₇-H₂O atmospheres.For oxidation of Cu containing steel,Cu enriched phase was formed by the preferential oxidation of Fe and the enrichment and migration behavior of Cu depends on the oxidation temperature,steel chemistry and atmosphere condition.Ni in steel induced the formation of solid Cu and Ni enriched phase at steel/scale interface and in scale layer and the formation of uneven steel/scale interface, which suppresses the Cu enrichment because of extrusion of Cu enriched region before the formation of liquid phase.On the other hand,Sn addition promotes the liquid Cu formation at steel/scale interface and penetration into grain boundary of Cu enriched phase by decreasing solidus temperature and solubility limit.In addition,for oxidation at 1 200℃,the behavior of Cu at and around the steel-scale interface was found dependent to a large extent on morphology of the oxide scale formed during oxidation.At the early stage of oxidation,Cu-rich phase formed and accumulated at the steel scale interface under both O₂-N₂ and H₂O-N₂ atmospheres.As the oxidation proceeded,however,Cu enrichment at and its migration from the steel-scale interface were vastly different for different oxidizing atmospheres.In the case of O₂-N₂ oxidation,an oxide layer formed initially at the steel surface, but soon after a gap was developed at the steel-scale interface and grew in its size,which practically separated the scale from the steel substrate.The scale layer formed under this condition was porous.The Cu-rich phase initially formed at the interface was found migrating to the scale layer,leaving no Cu-rich phase at the interface.In the case of H₂O-N₂ oxidation,however,the scale layer formed was dense and tightly attached to the steel surface,and the Cu rich-phase continued to accumulate at the interface.Regarding the behavior of Cu-rich phase formed at the interface,it is proposed with experimental evidences that,when a gap forms at the steel-scale interface,it is the vaporization of Cu in the Cu-rich phase through the gap that brings Cu to the scale.     

机械合金化法制备(Ag-Cu28)-xSn合金的结构和性能研究

利用机械合金化法制备(Ag-Cu28)-xSn系合金粉末,借助差示扫描量热仪、X-射线衍射仪、扫描电镜等,研究了Sn含量对合金熔化温度、球磨时间对合金粉末的物相组成及显微结构的影响。研究表明:Sn对合金的熔化温度有显著影响,随Sn含量增加合金熔化温度下降趋势减缓;当Sn含量为30%时,合金熔化温度最低为539.3℃。球磨40 h时,(Ag-Cu28)-30Sn粉料合金化完全,其物相组成为Ag4Sn、Cu3Sn和Cu6Sn5。球磨初始阶段(Ag-Cu28)-30Sn粉料颗粒异常长大,球磨至40 h时合金化完成,颗粒断裂和焊合达到平衡,合金粉末粒度均匀,平均粒径约为5~10μm。     

HRB400螺纹钢的高温氧化行为及动力学

为了优化HRB400螺纹钢氧化皮结构,以提高耐蚀性能,采用热重法研究了试验钢空气条件下在800、850、900、950、1000和1050℃温度下的氧化行为,建立了氧化动力学模型,计算出试验钢的氧化激活能,借助扫描电镜(SEM)分析和确定氧化皮结构和组成.结合螺纹钢的实际生产情况讨论了螺纹钢氧化皮形成规律,建立了螺纹钢...     

Effect of Aging Temperature on the Microstructure and Shear Strength of SAC0307-0.1Ni Lead-Free Solders in Copper Joints

This paper presents an investigation of the effects of aging temperature on the microstructure and shear strength of SAC0307-0.1Ni/Cu solder joints. Single-overlap shear solder joints were aged for 1 h at 80, 130, and 180°C. The microstructure of the interface between the solder and the Cu substrate contained phase of the intermetallic compounds (IMCs) (Cu,Ni)6Sn5 formed along the interface. The shape of scallop-like (Cu,Ni)6Sn5 IMCs changed to the long dendrite and grew larger at the interface of solder joints after increased aging temperature. In addition, a phase of particle-like Ag3Sn IMCs was formed in the solder matrix. The growth of the interfacial IMC layer in the solder joints increased with increasing the aging temperature. The thickness of this layer was controlled by diffusion mechanism. The shear strength of the as-reflowed solder joints was greater than that of the aged solder joints, and the shear strength of all the aged solder joints decreased with increasing the aging temperatures. Therefore, the aging temperature mainly affected the thickness of the interfacial layer of IMCs and the shear strength of the solder joints.     

The growth of Cu-Sn intermetallics at a pretinned copper-solder interface

This article reports a comparative study of the formation and growth of intermetallic phases at the interface of Cu wetted with a thick solder joint or a thin, pretinned solder layer. The η phase (Cu₆Sn₅) forms when Cu is wet with eutectic solder at temperatures below 400 °C. The intermetallic layer is essentially unaffected by aging at 70 °C for as long as 13 weeks. On aging a eutectic joint at 170 °C, the η-phase intermetallic layer thickens and ε phase (Cu₃Sn) nucleates at the Cu/intermetallic interface and grows to a thickness comparable to that of the η phase, while a Pb-rich boundary layer forms in the solder. The aging behavior of a thin, pretinned eutectic layer is qualitatively different. At 170 °C, the Sn in the eutectic is rapidly consumed to form η-phase intermetallic, which converts to ε phase. The residual Pb withdraws into isolated islands, and the solderability of the surface deteriorates. When the pretinned layer is Pb-rich (95Pb-5Sn), the Sn in the layer is also rapidly converted into η phase, in the form of dendrites penetrating from the intermetallic at the Cu interface and discrete precipitates in the bulk. How ever, the development of the intermetallic largely ceases when the Sn is consumed; ε phase does not form, and the residual Pb remains as an essentially continuous layer, preserving the solderability of the sample. These observations are interpreted in light of the Cu-Sn and Pb-Sn phase diagrams, the temperature of initial wetting, and the relative diffusivities of Cu and Sn in the solder and intermetallic phases. A.J. SUNWOO, Formerly with the Lawrence Berkeley Laboratory, Berkeley, CA,     

蒸汽温度对G115钢氧化行为的影响

研究了马氏体耐热钢G115在600～700℃的蒸汽氧化行为。通过对氧化增重的测量得到了不同温度下的氧化动力学曲线。采用扫描电镜(SEM)和透射电镜(TEM)及其附带的能谱仪(EDS)对氧化皮的形貌和结构进行了分析。氧化增重结果表明,G115钢600℃的氧化速率显著低于650和700℃。650℃前150 h的氧化增重比700℃低,后期反而比700℃的氧化增重更高。氧化皮形貌和结构的观察结果表明,600℃形成的氧化皮由氧化皮外层、氧化皮内层和内氧化区组成,氧化皮中无明显的富Cr层。在650和700℃氧化时,早期的氧化皮中含有内氧化区,但内氧化区随着氧化时间延长而逐渐消失,外氧化的富Cr在氧化皮/基体界面附近形成。700℃时内氧化区向外氧化层的转变比650℃更快。升高温度一方面使扩散系数提高而加速整体氧化速率,另一方面降低了外氧化转变所需的Cr临界值而促进外氧化富Cr层形成,进而延缓氧化。总的来说温度对G115钢的蒸汽氧化行为具有复合影响。