Evaluation of Mechanical Properties of Medium Carbon Steel Quenched in Water and Oil

Samples of medium carbon steel were examined after heating between 900℃ - 980℃ and soaked for 45 minutes in a muffle furnace before quenching in palm oil and water separately. The mechanical behavior of the samples was investigated using universal tensile testing machine for tensile test and Vickers pyramid method for hardness testing. The microstructure of the quenched samples was studied using optical microscope. The tensile strength and hardness values of the quenched samples were relatively higher than those of the ascast samples, suggesting improved mechanical properties. However, samples quenched in palm oil displayed better properties compared with that of water-quenched samples. This behavior was traced to the fact that the carbon particles in palm oil quenched samples were more uniform and evenly distributed, indicating the formation of more pearlite structure, than those quenched in water and the as-received samples.

Cold extrusion deformation behavior of medium carbon steel after quenching and tempering

By taking 40Cr as a specific object, cold extrusion deformation behavior of medium carbon steel after quenching and tempering was studied by experimental works. The influence of deformation extent (10%-50%), cone angle of die (90 °-120 °), hardness after quenching and tempering (HRC21-29) and lubricated condition on the forming load was analyzed. The results show that there is no central bursting and micro crack in the inner of the extruded specimen, and the forming quality is good. The double-peak phenomenon takes place at the front-end of the specimen; the double-peak index increases with deformation extent, and larger deformation can avoid the double-peak phenomenon. The deformation extent is the most important influencing factor, and the lubricated condition almost has no influence, which means that the phosphate coating plus soap process is still a proper lubrication method for cold extrusion of medium carbon steel after quenching and tempering. By investigating the microscopic structure before and after deformation, the initial equiaxed grain is elongated in the extrusion direction, and this feature is more significant at the front-end of specimen.

45钢链轮淬火裂纹常见原因分析与预防

45钢链轮在调质处理或感应淬火时,表面时常出现淬火裂纹。对淬火裂纹产生原因进行分析,提出了预防淬火裂纹的措施。应根据链轮化学成分、原材料金相组织、链轮结构复杂程度和表面状态等进行分析,制定合理的热处理工艺,采取预防措施,减小链轮淬火时热应力和组织应力。还需要加强现场工艺操作管理,增强责任心,避免45钢链轮淬火裂纹产生。

Microstructural Characteristics and Mechanical Properties of Low-Alloy, Medium-Carbon Steels After Multiple Tempering

The microstructure and mechanical properties of NiCrMoV-and NiCrSi-alloyed medium-carbon steels were investigated after multiple tempering. After austenitising, the steels were hardened by oil quenching and subsequently double or triple tempered at temperatures from 250 to 500 °C. The samples were characterised using scanning electron microscopy and X-ray diffraction, while the mechanical properties were evaluated by Vickers hardness testing, V-notched Charpy impact testing and tensile testing. The results showed that the retained austenite was stable up to 400 °C and the applied multiple tempering below this temperature did not lead to a complete decomposition of retained austenite in both steels. It was also found that the microstructure, hardness and impact toughness varied mainly as a function of tempering temperature,regardless of the number of tempering stages. Moreover, the impact toughness of NiCrMoV steel was rather similar after single/triple tempering at different temperatures, while NiCrSi steel exhibited tempered martensite embrittlement after single/double tempering at 400 °C. The observed difference was mainly attributed to the effect of precipitation behaviour due to the effect of alloying additions in the studied steels.

植酸添加量对硅烷锆盐植酸复合膜耐腐蚀性能的影响

为提高40Cr钢的耐蚀性,采用双-[γ-(三乙氧基硅)丙基]-四硫化物(BTESPT)、硝酸锆和植酸按照一定比例配制成处理液,在其表面制备了硅烷锆盐植酸复合膜。采用扫描电子显微镜(SEM)及其配套的能谱仪(EDS)对膜层进行微观形貌和元素分析,采用X射线光电子能谱(XPS)对膜层进行表面结构分析,采用电化学方法和盐水浸泡试验考察了不同植酸添加量的复合膜的耐蚀性。结果表明:硅烷锆盐植酸复合膜表面Si、Zr和P元素分布均匀,含PO_(4)^(3-)基团的絮状螯合物能较好地填补膜层孔隙。在硅烷体积分数5%、硝酸锆质量分数0.75%和植酸质量分数0.75%的条件下制备的膜层耐蚀性最好。

浅析中碳Cr-Mo钢的淬火开裂倾向

42CrMo钢是常用的中碳合金钢。生产中发现,42CrMo钢工件淬火易开裂。为能制定合理的42CrMo钢的淬火工艺,减少因工件淬火开裂而造成的经济损失,系统分析了影响42CrMo钢工件淬火开裂倾向的因素,包括原材料的冶金缺陷、原始组织、工件结构、化学成分和淬火工艺等。

矿用齿辊破碎机齿环热处理脆性研究

针对当前国产齿辊破碎机齿环制造开裂问题,在不改变破碎机齿环整体硬度和韧性的前提下,基于中碳合金钢热处理第一类回火脆性特征,通过调整材质元素含量区间和重复试验,找到最合理的铸件淬火温度和低温回火温度,从而解决整个制造过程中局部开裂缺陷,降低制造成本,提升齿环整体可靠性。

冷线入口开卷机芯轴楔形块焊接修复探讨

本文介绍了酒钢不锈钢分公司冷轧分厂冷线入口开卷机芯轴楔形块断裂后所进行的应急检修焊接的方法及其原理,重点对楔形块材料的焊接性、焊接变形控制进行了分析,根据分析结果探讨了楔形块断裂的检修方法,在今后维修积累经验。

Influence of on-line tempering parameters on microstructure of medium-carbon steel

A new process involving ultra-fast cooling（UFC）and on-line tempering（OLT）was proposed to displace austempering process,which usually implements in a salt/lead bath and brings out serious pollution in the industrial application.The optimization of the new process,involving the evolution of the microstructure of medium-carbon steel during various cooling paths,was studied.The results show that the cooling path affected the final microstructure in terms of the fraction of pearlite,grain size and distribution of cementite in pearlite.Increasing the cooling rate or decreasing the OLT temperature contributes to restraining the transformation from austenite to ferrite,and simultaneously retains more austenite for the transformation of pearlite.It is also noted that bainite was observed in the microstructure at the cooling rate of 45℃/s and the OLT temperature of 500℃.Through either increasing the cooling rate or decreasing the OLT temperature,the distribution of cementite in pearlite is more dispersed and grain is refined.Taking the possibility of industrial applications into account,the optimal process of cooling at 45℃/s followed by OLT at 600℃ after hot rolling was determined,which achieves a microstructure containing nearly full pearlite with an average grain size of approximately 7μm and a homogeneously dispersed distribution of cementite in pearlite.

一种中碳非调质钢锻件的控温冷却工艺研究

锻后冷却工艺对中碳非调质钢锻件的性能与组织有重要影响,为研究适合中碳非调质钢46MnVS5的冷却工艺,本文将连杆锻件在三种不同的工艺条件下进行冷却,取样分析冷却速度对连杆力学性能及显微组织的影响。三种冷却条件下得到的连杆金相组织均为铁素体—珠光体,并且随着冷却速度的增加,连杆晶粒尺寸减小、强度升高、韧性降低。结果表明,在速冷工艺下冷却的锻件综合性能最优,各项指标均满足产品要求。

TGOG13Cr-1超级马氏体不锈钢的组织和性能

采用SEM、金相、Gleeble 3800观察和分析了TGOG13Cr-1超级马氏体不锈钢在不同热处理制度下的组织转变和力学性能的变化情况。试验结果表明,TGOG13Cr-1室温下的显微组织为低碳回火马氏体,其Ac1为720℃、Ac3为860℃、Ms为281℃、Mf为157℃;在相同的淬火温度和回火工艺下,采用水淬较空冷更容易实现对力学性能的控制;随着回火温度的升高,合金的强度、硬度越低,塑性、韧性越好。

热处理对中碳低合金耐磨钢组织与耐磨性的影响

研究了水冷、风冷、空冷3种冷却方式和200、250、300、350、400℃5种回火温度对中碳低合金耐磨钢的组织和耐磨粒磨损性能的影响。结果表明,经不同的冷却方式,可依次得到单相马氏体和马氏体加贝氏体的复相组织。含有贝氏体的复相组织在低温回火后有较好的抗回火软化能力和韧性,有助于耐磨性的提高。用SEM观察磨损表面,结果表明:在磨粒磨损情况下,实验用钢的磨损机理主要为塑性变形犁机制和显微切削机制。

调质状态下30CrMnSiA钢的激光焊接

探讨了调质状态下 30CrMnSiA钢的激光焊接性、焊缝成形及焊后残余变形 ;研究了调质状态下激光焊接30CrMnSiA钢时焊缝及热影响区的金相组织 ;提出了调质状态下 30CrMnSiA钢在焊深≥ 1.5mm时的激光焊接规范参数。结果表明 ,采用激光焊接调质状态下的 30CrMnSiA钢 ,易获得质量优良的焊缝 ,不会出现常见的焊接裂纹和明显的热影响区性能变化 ;工件加工误差对焊缝成形的影响可通过一定的措施加以改善 。

淬火及回火工艺对中锰钢组织和性能的影响

通过热处理工艺实验及SEM与TEM组织观察,研究了不同淬火及回火工艺对碳锰钢与中锰钢组织和性能的影响。结果表明,提高锰含量显著降低了实验钢的Ac1和Ac3温度,缩小了两相区范围;随着淬火温度的升高,实验钢的屈服强度、抗拉强度有所降低;随着回火时间的增加,实验钢的冲击功升高;碳锰钢与中锰钢最优淬火温度分别为800~900℃和750~800℃,其屈服强度、抗拉强度分别为818、847和820、878 MPa,-40℃的冲击功在200 J左右,均具有良好的综合性能,中锰钢具有低成本、高强度及高韧性的综合优势。两种实验钢均可获得细小均匀的马氏体组织,马氏体板条束交错分布,随着回火时间的增加,实验钢中大尺寸碳化物的数量有所降低。

硼对刃具钢组织与性能的影响

为研制开发适合水淬的新型刃具钢,采用显微组织观察、力学性能测试、热处理试验和磨粒磨损试验等技术手段,对比研究了含硼中碳钢与不含硼的65Mn钢热轧后与热处理后的显微组织和应用性能.结果表明:热轧态中碳含硼钢中存在较多铁素体相,强硬性更低,韧塑性更好;中碳含硼钢水淬回火后组织为回火马氏体,硬度可达50 HRC以上,高于油淬回火的65Mn钢,韧塑性和耐磨性也明显好于65Mn钢.中碳含硼钢完全适合水淬工艺,减少了工业污染,符合环保要求.

30CrMnSiA调质钢的激光焊接性研究

探讨了调质状态下 30CrMnSiA钢的激光焊接性、焊缝成形及焊接变形 ;研究了调质状态下激光焊接30CrMnSiA钢时焊缝的金相组织及热影响区性能变化 ;提出了焊深≥ 1 .5mm的调质状态下 30CrMnSiA钢激光焊接规范参数。结果表明 ,采用激光焊接调质状态下的 30CrMnSiA钢 ,易获得质量优良的焊缝 ,不会出现常见的焊接裂纹和明显的热影响区性能变化 ;工件加工误差对焊缝成形的影响可通过一定的措施加以改善 。

1.41%C超高碳钢淬火高温回火球化组织的研究

采用淬火+高温回火热处理对碳的质量分数为1.41%超高碳钢进行球化处理,研究碳化物超细化的机理,确定最佳的球化工艺参数。结果表明:在850～1100℃范围内淬火时,随着温度的上升,碳化物不断溶入奥氏体,使粗大碳化物颗粒变小,回火后不仅从针状马氏体中析出均匀细小的碳化物,同时在残余奥氏体中也析出大量均匀细小的碳化物,碳化物数量增加。钢中含有抑制碳化物长大的Al和Cr元素,在550～750℃高温回火时,温度越高球化效果越好,即使在1100℃淬火+750℃回火后碳化物颗粒尺寸仍然保持在0.1～0.3μm。

磷在钢回火脆性发展时的非平衡偏聚及钼的影响

用俄歇能谱仪和扫描电镜研究了中碳钢和含钼中碳钢在回火脆性发展过程中Ｐ在晶界上的偏聚。发现在４８０ ℃回火时，两种钢均在晶界出现Ｐ的浓度峰值。含钼中碳钢中的Ｍｏ 减小了晶界断裂比例，但并不改变Ｐ的浓度峰值。同时还观察了Ｓ、Ｃ、Ｍｏ 等组元在晶界的偏聚。Ｐ在晶界的浓度峰值可以用磷－空位复合体的非平衡偏聚机制加以解释。

V-N对中碳SiMn非调质钢显微组织的影响

用光学显微镜和透射电镜研究了0.130%V-0.021 5%N、0.130%V-0.0304%N和0.001%V- 0.020 7%N三种V-N含量的(%)0.37～0.38C、0.82～0.92Si、1.78～1.81Mn、0.06 Ti、0.015Nb非调质钢的组织,用Gleeble 1500热模拟机测定了该钢的应力-应变曲线,并用JMatPro4.1软件计算了该钢的CCT曲线以及900℃和600℃平衡状态下钢中各相的含量。结果表明,该钢的组织为珠光体+先共析铁素体,随氮含量增加,珠光体增多,晶界铁素体变粗;随钒含量减少,珠光体数量显著增加,贝氏体及铁素体变粗;共析铁素体和先共析铁素体中的析出物尺寸≤3 nm;V和/或N含量高的钢,应变时应力大。

组织细化对中碳Cr-Mo钢力学性能的影响

通过循环热处理和改变奥氏体化温度两种方法获得不同的原奥氏体晶粒尺寸,研究了不同晶粒尺寸对高温回火中碳Cr-Mo钢力学性能的影响。结果表明,当奥氏体化温度低于1 050℃时,实验钢的强度随奥氏体化温度的升高而提高。在相同的奥氏体化温度下,强度随着晶粒的细化而上升。在整个研究范围内,随着晶粒的细化,实验钢的韧性有一定的提高,塑性略有下降。晶粒细化显著提高了钢的低温冲击韧性。