真空脱气轴承钢的研究

本文对采用真空处理冶炼轴承钢的RH法、VArD法和碱性电炉钢进行了试验研究。结果表明:破坏概率在50％的情况下,采用RH真空处理轴承钢的疲劳寿命是碱性电弧炉钢的1.8倍和1.2倍。采用VArD法真空处理轴承钢的疲劳寿命和电炉钢相近,没有明显提高。经RH法真空处理轴承钢的疲劳寿命之所以得到提高,是因为钢中非金属夹杂物分布弥散,夹杂物为Al和Si氧化物类型组成,并具有硫化物包围氧化物的趋势。而经VArD法真空处理的轴承钢和电炉钢非金属夹杂物分布集中并多为Al和Ca的铝酸钙类型夹杂物组成,而铝酸钙盐所形成的点状夹杂物是降低钢材疲劳寿命的主要原因。钢中非金属夹杂物至工作表面的远近直接影响钢材的疲劳寿命,距工作表面越近其疲劳寿命越低。     

高洁净轴承钢GCr15滚动接触疲劳机制研究

通过对真空脱气工艺制备的高洁净轴承钢的化学成分、低倍组织、碳化物不均匀性、非金属夹杂物等冶金质量进行标准检测及评级，并利用Aspex扫描分析仪对钢中的非金属夹杂物的数量、类型、尺寸及洁净度指数等进行定量分析，结合滚动接触疲劳寿命试验结果，建立了非金属夹杂物与轴承钢接触疲劳寿命的关系。研究结果表明，高洁净轴承钢的w[O]≤0.000 5%,w[Ti]≤0.000 8%，大颗粒夹杂物DS≤0.5级，但仍是以夹杂物为主导的接触疲劳破坏机制，其中，氧化物类夹杂尺寸较大，并在夹杂物周围存在孔洞缺陷，易于造成应力集中形成疲劳裂纹。高洁净轴承钢中氧化物类夹杂的最大尺寸控制在10μm以下，4.5 GPa高接触应力下的额定寿命L10达到1×107次以上，有望取代电渣重熔轴承钢用于高铁、高速机床主轴、风电主轴等高端装备领域。     

82A和82B高强钢疲劳性能的试验研究

对某钢厂生产的82A和82B高强钢进行了高周疲劳性能试验研究,得到了这两种钢的疲劳应力-寿命曲线(S-N曲线)及疲劳强度。用扫描电镜对试样的疲劳断口进行了观察。结果显示,对夹杂物进行变性处理后的82A钢的疲劳裂纹大多从表面缺陷处萌生,而夹杂物没有变性处理的82B钢的疲劳裂纹则从非金属夹杂物及表面缺陷处萌生,且从内部非金属夹杂物处萌生的疲劳断口呈"鱼眼"特征。讨论了非金属夹杂物对高强钢疲劳性能的影响。     

一种提高轴承钢接触疲劳寿命的精炼法

本文讨论了用三种不同冶炼工艺生产的轴承钢中氧含量、非金属夹杂物对接触疲劳寿命的影响。结果表明,用低碱度渣-吹氩处理工艺生产的轴承钢具有较高的接触疲劳寿命。该工艺已应用于生产。     

高疲劳寿命轴承钢洁净度现状及研究进展

对比了国内外高疲劳寿命轴承钢主要杂质元素、主要夹杂物特征等冶金性能的差异，并对比了不同冶金质量下，轴承钢的疲劳性能及诱发疲劳断裂的因素，总结了国产轴承钢洁净度现状及与国外优质轴承钢的差距。在此基础上，围绕高疲劳寿命轴承钢，以进一步提高国产轴承钢质量为目的，分析梳理了国产轴承钢冶炼技术及夹杂物控制方法的发展轨迹，探讨了国产轴承钢进一步提高疲劳寿命及质量的发展方向。      

Ca—RE复合处理55SiMnVB汽车弹簧钢的研究

电、平炉冶炼不同硫含量的55SiMnVB汽车弹簧钢,经Ca-RE复合处理控制非金属夹杂物形态,都能明显提高单片弹簧的疲劳寿命。并且发现平炉钢中硫含量较高、其处理效果更好。     

钙处理对硅脱氧弹簧钢55SiCr氧化物夹杂的影响

摘要：为了将硅脱氧弹簧钢中SiO2类高熔点硬质夹杂改性成低熔点夹杂物,在炼钢生产中进行了钙处理试验。利用FEI Explorer 4自动扫描电镜对硅脱氧弹簧钢55SiCr在正常工艺与钙处理工艺处理后的铸坯、盘条中氧化物夹杂的成分、尺寸、数量、形貌进行检测,统计分析2种工艺下夹杂物尺寸、夹杂物轧制变形性的差异,并通过弹簧钢丝Nakamura旋转弯曲疲劳测试对比2种工艺下夹杂物控制水平。分析结果表明：硅脱氧弹簧钢55SiCr钙处理工艺后氧化物夹杂主要为CaO SiO2 (CaS)类,尺寸较大,且此类夹杂物在盘条轧制过程中不易变形细化,最终恶化弹簧钢疲劳性能;正常工艺处理后氧化物夹杂尺寸随着夹杂物中Ca含量升高有增大倾向,CaO SiO2 Al2O3系相图中方石英、磷石英与莫来石交界区的夹杂物轧制变形性优于假硅灰石和钙长石共熔区的夹杂物。     

汽车悬架弹簧用55CrSi盘条-火成材工艺的开发

介绍了杭州钢铁集团公司采用电炉一连铸一高线轧制一火成材新工艺开发汽车悬架弹簧用55CrSi盘条的情况。对该盘条的化学成分、表面质量、金相组织、夹杂物含量和力学性能等指标检测结果表明，盘条的表面质量、脱碳层、力学性能等指标达到了国产同类产品的先进水平，可满足不同制簧工艺的要求，弹簧疲劳寿命达到汽车悬架弹簧国家标准规定。     

宝钢高速线材硬线钢夹杂物处理技术探讨

概述了高碳硬线钢夹杂物处理的几种工艺情况,通过从钢坯取样,对夹杂物尺寸,组成和形态及钢坯中夹杂物总量进行分析测定,并对几种工艺处理夹杂物效果进行评价,其结果表明：常规真空处理及喷吹高碱度粉剂可满足一般要求高碳钢丝的生产要求,采用RH和Ca处理工艺,可提高高碳钢丝的疲劳寿命,对高碳钢丝中夹杂物进行无害化处理,可满足高品质的钢丝生产要求。     

钙处理对硅脱氧弹簧钢55SiCr氧化物夹杂的影响

为了将硅脱氧弹簧钢中SiO_2类高熔点硬质夹杂改性成低熔点夹杂物,在炼钢生产中进行了钙处理试验。利用FEI Explorer 4自动扫描电镜对硅脱氧弹簧钢55SiCr在正常工艺与钙处理工艺处理后的铸坯、盘条中氧化物夹杂的成分、尺寸、数量、形貌进行检测,统计分析2种工艺下夹杂物尺寸、夹杂物轧制变形性的差异,并通过弹簧钢丝Nakamura旋转弯曲疲劳测试对比2种工艺下夹杂物控制水平。分析结果表明:硅脱氧弹簧钢55SiCr钙处理工艺后氧化物夹杂主要为CaO-SiO_2-(CaS)类,尺寸较大,且此类夹杂物在盘条轧制过程中不易变形细化,最终恶化弹簧钢疲劳性能;正常工艺处理后氧化物夹杂尺寸随着夹杂物中Ca含量升高有增大倾向,CaO-SiO_2-Al_2O_3系相图中方石英、磷石英与莫来石交界区的夹杂物轧制变形性优于假硅灰石和钙长石共熔区的夹杂物。     

A Fatigue Life Model for Predicting Crack Nucleation at Inclusions in Ni-Based Superalloys

Engineering alloys such as Ni-based alloys, Al-alloys, and steels often contain non-metallic inclusions in their microstructures. These inclusions, which include oxide particles, carbides, and intermetallic particles, are introduced during component manufacturing processes such as casting, powder-metallurgy, or additive manufacturing methods. The presence of inclusions in the microstructure can promote fatigue crack nucleation by competing against slipband nucleation and reduce fatigue life performance of an engineering component. While it has been reported in many occasions, the competition between fatigue crack nucleation at inclusions and slipbands is still not well understood. In this article, the conditions for the concurrent occurrence of fatigue crack nucleation at inclusions and slipbands are analyzed theoretically. The analysis indicates that there exists a critical inclusion size (diameter) below which there is no fatigue life debit due to crack initiation at inclusions and above which a transition from slip-induced to inclusion-induced crack nucleation occurs. The low-cycle fatigue life model is applied to Ni-based superalloys and the model predictions are compared against experimental data from the literature to assess the dependence of the critical inclusion size on the slip morphology, grain size of the matrix, and the shear modulus of the inclusion.     

Theory and Practice of Oxide Inclusion Composition and Morphology Control in Spring Steel Production

Theoxideinclusionsinspringsteelcomemainlyfromtheproductsofdeoxidizationofmoltensteel .Ifthemoltensteelisalloyedwithferrosiliconandfinal lydeoxidizedwithaluminum ,thepropertiesofde oxidization productsarenotdeterminedbythechemicalcompositionofmoltensteel,butbythepropertiesofalloysanddynamicconditionsofdeoxi dization .Forspringsteel ,theoriginaldeoxidizationproductsfoundinfinishedproductsaretridymite ,a luminumsilicateandalumina[1] .Inordertoreducetheamountandthesizeofinclusionswhichdeterio rate…     

超低氧钢中复合夹杂物形成的实验室研究简

 通过实验室真空感应炉试验,研究了超低氧条件下钢中复合非金属夹杂物的形成。研究发现：在含有一定硫的超低氧钢中高熔点氧化物夹杂很少,大部分为MnS。钢中Al2O3的尺寸较MgO-Al2O3系夹杂要大。以高熔点夹杂物为异质形核核心析出的MnS能显著提高钢材的疲劳寿命,此种复合夹杂物的形成与钢液成分、高熔点夹杂物的尺寸有关。     

疲劳性能不合格的38Si7弹簧钢夹杂物分析

  针对工业生产38Si7弹簧钢疲劳强度不合格的问题,借助光学显微镜和扫描电镜,并结合数学理论模型,从夹杂物的角度分析38Si7弹簧钢疲劳强度不合格的原因。研究结果表明：工业生产38Si7弹簧钢中的夹杂物主要组成为CaO(MgO) Al2O3 SiO2三元复合夹杂物,而且圆截面上中心区域复合夹杂物中Al2O3的含量明显低于外层复合夹杂物中Al2O3的含量;根据夹杂物等效投影面积模型得出,当疲劳失效为内部起裂时,临界夹杂物尺寸大约为6.5μm,当疲劳失效为表面起裂时,临界夹杂物尺寸大约为5.5μm。当弹簧钢中的夹杂物尺寸大于临界夹杂物尺寸时,容易造成疲劳强度失效。     

Inclusion modification in Al-killed valve spring steel by Na2CO3 addition

Hard inclusions with high melting temperatures such as Al₂O₃ (2054°C) and MgO·Al₂O₃ (2135°C) generate nozzle blockage problems during continuous casting of Al-killed valve spring steel and are very detrimental with respect to fatigue properties. In the present paper, inclusion modification in Al-killed valve spring steel by Na₂CO₃ addition was investigated in the laboratory using a graphite tube resistance furnace. The results show that inclusions with high melting temperature can be successfully modified into Na₂O-containing inclusions with lower melting temperatures by the addition of Na₂CO₃. The effectiveness of inclusion modification can be enhanced by increasing the Na₂CO₃ addition and/or decreasing the amount of Al. This suggests that Na₂CO₃ addition could possibly be a substitute for Ca treatment as a method for preventing nozzle blockage during continuous casting of Al-killed steel.     

Gigacycle Fatigue Behavior of 1800 MPa Grade High Strength Spring Steel for Automobile Lightweight

Gigacycle fatigue behavior of 60Si2CrVA high strength spring steel was investigated by ultrasonic fatigue test machine. Fatigue fractography was observed by scanning electron microscopy （SEM）. Maximum inclusion sizes and fatigue strength in different volumes were estimated by statistics of extreme values （SEV） and generalized Pareto distribution （GPD） methods. The results showed that S N curves of 60Si2CrVA spring steels for two rolling processes were not horizontal asymptotes but a gradient in a regime of 109 cycles, and traditional fatigue limits were eliminated. Surface machined topography and inclusions in steel were major factors that led to elimination of fatigue limit for 60Si2CrVA spring steel. The SEV and GPD methods could effectively predict size of the maximum inclusion and fatigue strength in different volumes of 60Si2CrVA spring steel. Predicted fatigue strength was in accordance with experimental results by ultrasonic fatigue testing.     

不同生产工艺对高强度弹簧钢夹杂物尺寸分布及疲劳性能的影响

采用两种不同的生产工艺生产弹簧钢以控制氧化物夹杂的性质和尺寸分布。研究发现，钢中酸溶铝含量的高低并不影响弹簧钢的奥氏体晶粒度，但明显影响钢材中的非金属夹杂物尺寸分布，从而影响高强度弹簧钢的疲劳性能。     

Microstructural Inclusion Influence on Fatigue of a Cast A356 Aluminum Alloy

We examine the dependence of fatigue properties on the different size scale microstructural inclusions of a cast A356 aluminum alloy in order to quantify the structure-property relations. Scanning electron microscopy (SEM) analysis was performed on fatigue specimens that included three different dendrite cell sizes (DCSs). Where past studies have focused upon DCSs or pore size effects on fatigue life, this study includes other metrics such as nearest neighbor distance (NND) of inclusions, inclusion distance to the free surface, and inclusion type (porosity or oxides). The present study is necessary to separate the effects of numerous microstructural inclusions that have a confounding effect on the fatigue life. The results clearly showed that the maximum pore size (MPS), NND of gas pores, and DCS all can influence the fatigue life. These conclusions are presumed to be typical of other cast alloys with similar second-phase constituents and inclusions. As such, the inclusion-property relations of this work were employed in a microstructure-based fatigue model operating on the crack incubation and MSC with good results.     

Inclusion-controlled fatigue properties of 1800 MPA-class spring steels

Fatigue tests were conducted on a series of 1800 MPa-class spring steels whose fatigue properties were inclusion controlled. The fatigue tests were conducted on billets and on hot-rolled bars, taking into account the elongation of the oxide-type composite inclusions that were deformed during hot rolling, i.e., controlled inclusions. Anisotropy of the fatigue properties due to the slender shape of the elongated inclusions was also discussed. Fatigue tests were then conducted for both the rolling direction (RD) and transverse direction (TD) in the case of the billets. The fatigue test results in the RD showed a slight difference between billets and bars. The inclusions that were deformed during hot rolling were sufficiently elongated, even for the billet specimens, and differences in the effective inclusion sizes between the billets and their hot-rolled bars for the RD were small. However, there were marked differences in fatigue strength between the RD and TD in the billet specimens: the fatigue strength was almost half in the TD due to the presence of fish-eye fractures originating in large and slender MnS inclusions. In these fatigue tests, the two types of deformable inclusions revealed remarkably different effects on fatigue strength: the deformable oxide-type inclusions never caused fish-eye fracture, although the MnS inclusions found in the billets were extremely detrimental to fatigue strength when stress was applied in the TD.