Electron Brush-plating Technique of Cr12MoV Die Steel and Its Wear Resistance

The paper is mainly about electron brush-plating technique of Cr12MoV die steel and its wear resistance.Through using different parameters of brushing plating for making the coating,the coating with better wear resistance was selected.The results indicate that the coating of Ni and Ni-W are better at the voltage of 15 and 10 V.For the same plating time of Ni and Ni-W coating,the wear-resistance of the Cr12MoV die steel can be improved by 6.4 and 3.9 times,respectively.

Improvement of center segregation in high-carbon steel billets using soft reduction

Center segregation is the main reason for cup fracture of high-carbon wire rod during drawing. Therefore, to continuously produce cast billets with very low center segregation is an important objective. The soft reduction technology is considered to be an effective method to minimize center segregation. To elucidate the effect of soft reduction on the internal quality of high-carbon steel billets, soft reduction was applied with different solid fractions in the core area of billets in a laboratory casting machine. A coupled temperature/displacement finite element model was developed to calculate the solid fraction using the commercial software ABAQUS. Center segregation, center porosity, homogeneity of elements, and equiaxed crystal zone were obviously improved by applying soft reduction, especially when the solid fraction was less than 1.0. The optimal results were obtained when the solid fraction was approximately 0.9.

Application of Low Temperature Liquid Sulfurization Catalyzed with Rare Earth on Cr12 Impacting Die

One kind of quenched Cr12 steel dies for impacting stainless steel wire rope （SSWR） was treated by low temperature liquid sulfurization catalyzed with rare earths, in order to extend their service life for assuring the continuity of production line, and simultaneously improve the surface quality of SSWR obtained. After immerged into the melting sulphur containing 4 % （mass fraction） of LaF3 and 1% of CeCl3 at 463 K for 4 h, the sulfurized dies were very smooth and black, with little distortion and hardness loss. They exhibited a certain extent of corrosion-resistance in air due to the coexisting rare earths in the sulfurized layer. Optical observations showed that the sulfurized layer was uniform and had scale-like structure. The trail of machined SSWR indicated that the production capacity of sulfurized dies had been doubled and the replacing period on line was postponed. SEM morphology also proved that the wear extent of cavities on sulfurized dies decreased greatly and the surface quality of SSWR obtained was improved markedly.

Effect of anions on stress corrosion cracking behaviors of ultra-high strength steel 23Co14Ni12Cr3Mo

The effects of chloride,sulfate and carbonate anions on stress corrosion behaviors of ultra-high strength steel 23Co14Ni12Cr3Mo were studied by stress corrosion cracking(SCC)test method using double cantilever beam(DCB)specimens.The SCC morphology was observed by using scanning electron microscopy(SEM)and the composition of corrosion products was analyzed by using energy dispersive spectrometer(EDS).The results show that the crack propagates to bifurcation in NaCl and Na2SO4 solution,while the crack in Na2CO3 solution propagates along the load direction.The SCC rate in NaCl solution is the highest,while lower in Na2SO4 solution and little in Na2CO3 solution.From the SEM morphologies,quasi-cleavage fracture was observed in NaCl and Na2SO4 solutions,but intergranular features in Na2CO3 solution.The mechanism of anion effect on SCC of steel 23Co14Ni12Cr3Mo was studied by using full immersion test and electrochemical measurements.

Cr12型模具钢锻造内部裂纹产生的原因及预防

基于Cr12型钢种的特点,归纳了Cr12钢锻造时内部裂纹的类型,分析了内部裂纹产生的原因并提出了相应的预防措施。

9％-12％Cr高等级耐热钢的IV型开裂研究进展

9%～12%Cr高等级耐热钢因其性能优势在超超临界机组中有良好的应用前景,但这些钢在高温、低应力长时间运行时其焊接接头的细晶区有出现IV型开裂的可能性。介绍国外研究机构对铁素体耐热钢IV型开裂的研究成果,分析了IV型开裂的试验应力该如何确定,我国目前投产运行的超超临界机组P92钢焊接接头的服役参数是否会导致IV型开裂从而引起部件失效等,从而为试验研究新型耐热钢的IV型开裂提供依据。

超超临界机组耐热钢高温短时持久性能影响因素研究

某超超临界机组叶片使用的12%Cr系耐热钢调质处理后,常温力学性能及金相组织满足规范要求,但高温短时持久性能出现明显的分散性。为提高和稳定材料的高温持久性能,对典型的同炉次持久试样进行试验分析,以研究短时持久性能差异的影响因素。研究表明:材料短时持久断裂属于典型的蠕变断裂方式,短时持久强度下降与持久试验温度下板条间和晶界的碳化物粗化有密切关系,能谱分析进一步发现孔洞处脱落物B元素含量较高,达到19.98%,说明晶界的B在高温持久过程中开始向晶内迁移并形成含B的第二相质点,晶界强度明显削弱,在高温持久试验中会造成高温强度的迅速下降并快速断裂,断裂的位置大多是沿晶的,个别会在夹杂物或第二相造成的孔洞处萌生发展。

9%～12% Cr钢Ⅳ型开裂与软化区对比实验

选用SA335-P92钢管,采取GTAW+SMAW+SAW的焊接方法获取焊接接头,利用SAW的较大热输入,获得了具有较宽热影响区的试验接头。通过高温低应力的持久试验获取发生Ⅳ型开裂的试样,在扫描电镜下确定蠕变孔洞的出现位置,并通过测试整个热影响区显微硬度找出了软化区,比较了二者位置关系。试验表明:高温低应力下产生的Ⅳ开裂主要发生在热影响区的细晶区,其直接原因为蠕变孔洞,与热影响区的软化区没有直接关系。

12%Cr耐热钢裂纹萌生临界变形量

以12%Cr耐热钢为研究对象,基于Gleeble-3800D热模拟试验机进行高温拉伸实验,得到不同变形温度和应变速率下的高温拉伸真应力-真应变曲线。结果显示:应变速率越大、温度越低时材料的抗拉强度及屈服强度越大;由高温拉伸断口微观组织可知,温度越高、应变速率越小,材料的塑性越好。结合高温拉伸实验与数值模拟方法确定了12%Cr耐热钢热锻过程中的临界损伤值,并进一步将裂纹萌生临界损伤值转化为实际热锻的临界变形量,建立了12%Cr耐热钢在给定变形温度和应变速率条件下热锻成形过程中的临界变形量模型,并在500 N液压机上进行了镦粗工艺验证,为超超临界转子锻造成形工艺提供了理论参考。