Microstructure and mechanical properties of dissimilar joint between aluminum and aluminum-coated steel by cold metal transfer process

Two dissimilar materials, aluminum alloy and aluminum-coated steel, were joined by cold metal transfer process using AlSi5 filler wire. To this end, the steel was coated with Al-Si. The steel did not melt and aluminum was melt to form the joint during the process, it was actually cold metal transfer welding-brazing. The macrostructure, microstructure, alloy element distribution, and inter-metallic compounds were analyzed by optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy. It was found that the Al-Si coating dissolved into the weld metal. The pre-existing thin Fe-Al- Si ternary inter-metallic compounds in the interface between the Ak-Si coating layer and base metal steel also partially dissolved into the weld zone, tending to reduce the thickness of inter-metallic compounds. Approximate 3 μm thick undissolved intermetallic compound was found at the interface after welding which could guarantee sound bonding strength in dissimilar materials joining. The sample was fractured at the fusion zone near the aluminum side in the tensile test. The ultimate tensile strength was about 156 MPa, and the fracture mode is ductile failure in nature according to its morphology.

Deformation prediction of porcelain-enameled steels with strain history by press forming and high-temperature behavior of coating layer

Porcelain enamel coatings were widely applied for the protection of steel products because they offered high corrosion protection,resistance to heat and abrasion,high hardness,hygiene and ease of cleaning.The typical process to produce enameled steels is roughly divided into two stages:the first stage consists of a forming process to give the desired shape to a steel substrate,and the second stage consists of a firing process to bond enamel frits on the substrate.This firing process requires a high temperature above 800 °C,which may lead to austenitic transformation and severe thermal deformation of the steel substrate.The aim of this study is to develop a finite element analysis (FE analysis) technique to predict the mechanical and thermal deformations of the enameled steels during forming and any further enameling process,including firing.The FE analysis involves analyzing the strain history of the steel substrate,which comprises the stress and thickness distributions of the substrate and its deformed shape,and the high-temperature behavior of the enamel coating layer.The validity of the FE analysis is verified through the U-bending test and firing test with various numbers and positions of enamel coating layers on the substrate.The results reveal that the FE analysis results agree well with the experimental results with 8% error.

Effect of Coiling Temperature on Ti(C,N) Precipitation and Properties of Batch Annealed DC06EK Enamel Steel

The effects of hot-strip coiling temperature on Ti（C,N） precipitation, texture and hydrogen permeation behavior in DC06 EK enamel steel were investigated by TEM, EBSD test and electrochemical hydrogen permeation experiment. It was found that the Ti（C,N） particles in hot-strip coarsened with increasing coiling temperature, whereas after cold-rolling and annealing, the size difference of Ti（C,N） particles was lessened. The hot-strip coiling temperature has a significant impact on the recrystallized texture in the subsequent cold-rolled and annealed sheet. Hot-strip using high temperature（700 ℃） coiling leads to strong {111} recrystallized texture in annealed sheet, with peak intensity 9.2. On the contrary, in annealed sheets using hot-strip coiling at 650 ℃, their {111} recrystallized textures were weaker, which was also reflected in their rmvalues. Even though the hydrogen diffusion coefficient is slightly lower（7.76×10^（-5） mm^2/s） in annealed sheet using low temperature coiling（600 ℃）, appropriately higher coiling temperature is more suitable for DC06 EK enamel steel combining both good drawability and fish-scale resistance.

Microstructure and properties of Ti-bearing hot-rolled high-strength steel plates for two-sided enameling

The composition and production technology of the type of hot-rolled steel plate used in two-sided enameling were briefly described. The microstructure and mechanical properties before and after enameling were contrastively investigated,and the precipitates in the samples were analyzed using transmission electron microscope and energy dispersive spectrometer. The results show the ferrite grain size of the steel plate after high-temperature enamel firing to be fine,with a large number of TiC and Ti;C;S;precipitates dispersed throughout the ferrite matrix. After two rounds of enamel firing at a temperature range of 800-890 ℃,its yield strength can still reach342 MPa. The results of a hydrogen permeation test show that the hydrogen storage properties of the steel plate are much better than those of ordinary structural carbon steel. A better bubble structure in the enamel layer can be obtained by this steel plate,with no fish-scale defects on the enameled steel-plate surface.

Study on microstructure and properties of cold-rolled high strength steel for enameling

With its superior comprehensive properties, cold-rolled enameling steel is widely applied in many fields. However, its low yield stress greatly limits its application. This study aims to improve the yield stress of cold-rolled enameling steel under the premise of meeting formability and enameling properties by strengthening the ferrite matrix via solid strengthening of Mn. The grain size of ferrite before and after enameling,mechanical properties of annealed steel, and precipitation behavior of second-phase precipitates are obtained through studying the microstructure and properties of enameling steel at different stages. The microstructure of the steel investigated at room temperature is found to contain equiaxial ferrite and bunchy cementite particles;the ferrite grains have grown to some extent after enameling. The fine dispersed TiC particles and cementite particles contained in the annealed steel are the main factors improving the hydrogen storage capability. Finally, the result of a falling-ball impact test shows that the steel has achieved excellent adherence.

酸洗搪瓷钢密着性能影响关键因素研究

为提高酸洗搪瓷钢的密着性能,研究了酸洗搪瓷钢密着性能的影响因素,包括烧搪时间、脱脂效能、表面色差和表面粗糙度,对不同脱脂程度、表面状态及粗糙度的试样进行涂搪和烧搪,并采用落球冲击法对密着性能评级。结果表明:在850℃进行烧搪时,烧搪时间从5 min延长至10 min,密着等级从2.0级提高至1.0级。同时,烧搪5 min时,脱脂不充分、保护渣增碳所致色差和降低粗糙度都会降低钢板和瓷釉之间的密着性能,其中脱脂不充分和色差的影响可通过延长烧搪时间至10 min进行改善,但延长烧搪时间后,粗糙度对密着性能仍存在显著影响。

等离子喷涂硅酸盐搪瓷涂层及其热循环行为研究

[目的]硅酸盐搪瓷涂层在冷热循环过程中的失效行为很少受到关注。[方法]采用喷雾造粒与烧结相结合的方式制备了多组分硅酸盐团聚烧结喷涂粉末材料,随后采用大气等离子喷涂技术在12CrMoV合金钢表面制备了SiO_(2)-Al_(2)O_(3)-Na_(2)CO_(3)-CaO基硅酸盐搪瓷涂层,研究了该涂层的微观组织和在700℃下的水淬热震循环行为。[结果]硅酸盐团聚烧结喷涂粉末材料呈球形,粒径分布在20~60μm之间。等离子喷涂硅酸盐涂层呈明显的堆叠层状铺展沉积,表面较为粗糙,其内部虽然存在一定数量的闭孔,但整体较为致密,除了含有一定数量的非晶相,还有SiO_(2)、Al_(2)SiO_(5)和Ca_(2)MgSi_(2)O_(7)晶相。该涂层在700℃水淬热震循环145次后发生部分脆性剥落。[结论]热震循环过程中发生的金属基体氧化、晶相分解,以及冷热交变循环等因素产生的热应力可能是导致涂层失效的原因。

铸坯火焰清理深度对超低碳冷轧搪瓷钢搪瓷性能的影响

通过研究调整铸坯火焰清理深度,验证超低碳冷轧搪瓷钢的抗鳞爆性、密着性以及氢渗透性的变化情况。研究结果表明,铸坯火焰清理深度从4mm降低至2mm,超低碳冷轧搪瓷钢没有出现鳞爆现象,密着等级无变化。氢渗透试验结果显示,降低铸坯火焰清理深度至2mm后,氢渗透时间和抗鳞爆敏感性TH值无明显变化,且TH值均>10min/mm^(2),抗鳞爆性能优良。

提高高钛超低碳搪瓷钢可浇性生产实践

针对高钛超低碳搪瓷钢可浇性差、水口易结瘤情况,对水口结瘤物和结瘤原因进行了机理分析。后续通过强化钢包顶渣改质,降低了顶渣氧化性。全工序低氧位控制,减少氧化铝夹杂物的产生。合理地控制RH循环时间和精炼后钢水镇静时间,严格执行保护浇注和控制大包下渣等措施,钢水可浇性大幅提高,实现搪瓷钢连浇炉数由原来3炉提高至6炉。

Causes of the formation of pit defects on the surface of the enamel layer

During the production of the inner walls of ovens,pit defects were formed on the surface of the enamel layer that was enameled on the cold-rolled steel via electrostatic powder spraying and sintering.The paper elaborates on the microstructure and element distribution of the enamel-steel interface and the enamel layer.Optical microscopy,scanning electron microscopy,and energy-dispersive spectroscopy were adopted to investigate the microstructure of a longitudinal section of the defect,and the pit-forming causes were analyzed.The results show that rusty spots lead to pit defects.During high-temperature firing,there is an inadequate fusion and reaction between iron oxides of the rusty spots and the enamel glaze.The rusty spots are closely related to pretreatment process;thus,to avoid their occurrence,electrostatic powder spraying and sintering should be performed timely after forming,degreasing,and thorough drying of the metal sheets.

低碳冷轧搪瓷钢DC01EK研发及抗鳞爆性能研究

通过安钢1780 mm热连轧-1550 mm冷轧生产线研发了1.8 mm的低碳冷轧搪瓷钢DC01EK(/%:C≤0.06,Si≤0.03,Mn:0.15~0.25,P≤0.015,S:0.010~0.020,Alt:0.020~0.040,B:0.0010~0.0020)和抗鳞爆性能研究。热轧采用直接热装工艺,终轧温度890℃,卷取温度720℃,控制BN、MnS和Fe_(3)C第二相粒子析出,以提高抗鳞爆性能,采用810℃退火温度,提高了低碳冷轧搪瓷钢DC01EK的冲压性能。结果表明:低碳冷轧搪瓷钢DC01EK屈服强度在208~239 MPa,抗拉强度在333~348 MPa,伸长率>36%,其金相组织为铁素体和珠光体,能够满足冲压成形要求。并通过氢渗透试验,研究了硼元素及第二相粒子对低碳冷轧搪瓷钢抗鳞爆性能影响。

高强度冷轧双面搪瓷用钢的显微组织和性能

采用光学显微镜、扫描电子显微镜和拉伸试验机研究了屈服强度为360 MPa级高强度冷轧双面搪瓷用钢搪烧前后的显微组织和力学性能,应用氢渗透实验评价了实验钢的抗鳞爆性能,并在实验室进行了湿法和静电干法涂搪实验。研究结果表明:搪烧前后实验钢的显微组织均为铁素体,经过搪烧,铁素体由扁平状变为等轴状,平均晶粒尺寸由5.47μm增大至7.07μm,搪烧前后实验钢的析出相主要是C、S和Ti的析出相及部分C、S和Mn、Ti的复合析出相,搪烧后晶粒内析出物数量明显变少。实验钢搪烧前的屈服强度、抗拉强度和伸长率分别为382 MPa、469 MPa和34.5%;搪烧后的屈服强度降低至355 MPa,抗拉强度降低至405 MPa,伸长率增加至38%。强度的降低是由于铁素体平均晶粒尺寸增大、第二相析出物密度降低导致的。实验钢的氢渗透时间为9.68 min,经湿法和静电干法双面涂搪、烧成后无鳞爆,密着性能良好。

新型搪瓷拼装罐在垃圾渗滤液处理中的应用

搪瓷拼装罐是目前处理垃圾渗滤液最佳选择之一。用于垃圾渗滤液处理的搪瓷拼装罐需要有优良的耐渗滤液腐蚀性能,因此需对钢板进行高温热退火处理以消除厚钢板内部压力,通过喷砂等表面预处理及机械喷搪的方法将搪瓷釉喷涂在钢板表面,经过烘干和烧成,釉层与钢板密着强度高,形成耐渗滤液腐蚀性能优良的搪瓷釉层。

热水器内胆用高强度搪瓷钢的研制

研究了合金元素对热水器内胆用高强度搪瓷钢微观组织、力学性能及抗鳞爆性的影响。分析了热轧工艺(如终轧温度与卷取温度)、冷轧连续退火工艺对微观组织及力学性能的作用机制。试制结果表明,冷轧高强度搪瓷钢屈服强度为245~272 MPa,抗拉强度为362~386 MPa,延伸率为39.0%~41.0%,能够满足热水器内胆的制作要求。其显微组织主要由铁素体和珠光体组成,并弥散分布着少量MnS、TiN颗粒。通过抗鳞爆敏感性测试及终端用户检测,进一步验证了开发的高强度搪瓷钢具有良好的抗鳞爆性。

马氏体不锈钢表面氧化铝颗粒增强搪瓷涂层的制备及抗高温氧化性能

以马氏体不锈钢为基体,硅铝酸盐搪瓷作为成膜物质,氧化铝作为填料,制备了氧化铝−搪瓷高温防护涂层,并研究了复合涂层的高温氧化行为。在650℃下,马氏体不锈钢基体会被氧化,表面生成氧化物Cr_(2)O_(3),氧化100 h后的增重为0.2 mg/cm^(2)。施加搪瓷涂层会显著降低马氏体不锈钢的氧化速率,提升基体的抗高温氧化性能达一个数量级。在搪瓷中加入氧化铝颗粒后形成的复合涂层在抗高温氧化能力方面得到明显提高,其微观机理为:溶解的氧化铝以铝氧四面体的形态补全了硅氧网络和未溶解的氧化铝镶嵌在空间网络中,阻碍O^(2−)的传输,令O^(2−)的传输路径更长。

双曲面搪瓷钢板幕墙生产工艺质量控制研究

双曲面搪瓷钢板幕墙工艺是国内建筑领域的首创。结合建筑幕墙生产工艺质量控制的内涵,确定双曲面搪瓷钢板幕墙加工精度、加工方法、外观质量和性能等生产工艺质量要求,通过完善先进的质量控制体系,应用现代技术优化来料检验方法,采用高端高精密生产设备加强钣金过程管控,从表面处理、喷涂处理、烧成处理、压板处理和密封包装处理等环节严把搪烧过程质量关,实现双曲面搪瓷钢板幕墙的材质、外观、颜色和亮度与设计要求的完美契合,从而推动我国建筑幕墙工程的创新性发展。

深冲搪瓷钢成形性与抗鳞爆分析

深冲搪瓷钢板不同于其他钢板,不仅要具有良好的塑韧性,还必须具备抗鳞爆性。要防止鳞爆,钢中必须含有一定量的第二相和空穴。因此,主要分析了搪瓷钢中获得合适的第二相种类、体积百分比及大小,使搪瓷钢在使用中既有良好的成形性能,又有良好的抗鳞爆性能。

冷轧超低碳搪瓷钢板的开发

简要介绍了冷轧超低碳搪瓷钢板的成分特点及工艺要求 ,分析了钢板的组织结构及析出相 ,研究了冷变形对氢在钢板中扩散系数和穿透时间的影响。实际批量生产结果表明 ,以超低碳为基础、添加适量的合金元素 ,采用合适的工艺制度生产的冷轧钢板既具有优良的成形性能 ,又具有优良的抗鳞爆性能。

退火温度对DC05EK搪瓷用钢贮氢性能的影响

研究rDC05EK冷轧搪瓷用钢板贮氢能力随退火温度的变化规律，分析了析出物对氢渗透时间的影响．结果表明：随着退火温度的升高，小尺寸析出物数量减少，降低了实验钢的贮氢能力，氢渗透时间缩短．退火温度在730～850℃之间，随着退火温度的提升，1mm厚实验钢板的氢渗透时间从16．5min下降到11．9min；退火温度升高至870℃，由于细小弥散析出物的反向溶解，导致氢渗透时间急剧缩短为3．6min，贮氰能力不足；DC05EK冷轧搪瓷用钢合适的连续退火温度范围是730—850℃．

Ti对DC01EK冷轧搪瓷用钢组织性能的影响

针对部分普通钢涂搪后由于H原子扩散导致鳞爆现象,在DC01EK钢中添加Ti元素,研究了Ti对钢板退火过程的再结晶行为及其贮氢性能的影响。结果表明,Ti的添加可形成大量粗大、弥散的第二相粒子Ti4C2S2,阻碍了再结晶过程,改变了钢板的再结晶温度范围,形成了大量的贮氢陷阱,有效提高了钢板的贮氢性能。