链板失效分析

借助硬度计、直读光谱仪、金相显微镜对失效链板进行检测和分析.结果表明:链板原材料中存在条状夹杂物和带状组织,链板冲压成形时产生了表面裂纹,已有的裂纹在随后的淬火处理时产生的应力作用下,沿着夹杂物和带状组织提供的应力"通道"扩展,最终导致链板发生突然断裂.     

51CrV4钢链板断裂分析

经等温淬火的发动机齿形链,材料为51CrV4钢,在装配过程中发现有断裂现象。对断裂的齿形链进行了化学成分分析、显微组织检验和硬度测试,以揭示其断裂产生的原因。结果表明,齿形链属于脆性断裂,主要是由于链板在网带炉内等温淬火时发生了增碳,使脆性增大,导致在链板台阶处由于应力集中而断裂。     

链板自动送料多排级进模

<正> 1 概述 链板是滚子链条上的主要承载元件,它承受交变的动载荷,链条的疲劳失效也主要发生在链板元件上。因而为了提高链板的疲劳强度,以保证链条工作时不致过早疲劳破坏,通常链板材料采用优质碳素结构钢45钢、40Mn或合金结构钢40Cr。例如08A外链板材料为40Mn,板厚为1.6mm,具体形状及尺寸见图1。一般链板采用精加工工艺,以     

齿形链板冲裁模优化设计

针对齿形链板在级进模成形时,存在冲裁光亮带和链板平面度达不到要求的问题,对零件排样和模具结构进行了优化。优化后的零件排样采用双排齿尖部交错排列方案,可同时成形内接触内链板和外接触内链板。零件外形冲裁和落料采用镶嵌式结构,便于通过更换模具部件生产不同尺寸的链板零件。实践证明,模具结构设计合理,生产效率高,满足客户的要求。     

65Nb钢链板冲裁模具热加工工艺试验

讨论了链板冲裁模选材、锻加工、球化退火、热处理工艺,重点讨论了6Cr4W3Mo2VNb(65Nb钢)热处理工艺参数对钢的性能和组织的影响.结果表明:通过改进热加工工艺,可改善冷冲模钢的强韧性,大幅度提高链板冲裁模(凸模、凹模、凸凹模)的使用寿命.     

平顶链链板卷圆冲压成形模具的设计与仿真北大核心CSCD

为提高平顶链链板卷圆工序的成形精度,根据工艺要求设计了一套平顶链链板卷圆冲压成形模具,该模具的上、下模均采用拼接式结构,上、下模间设有校孔装置,对该模具的关键参数进行了初步设计。利用Abaqus软件对链板的卷圆成形过程进行仿真,分析链板所受的等效应力及其成形精度,并根据仿真结果,对模具的关键参数进行修正。仿真结果表明:工件所受的最大等效应力位于链板左右两侧形成的卷圆处,符合链板卷圆成形的实际受力情况;且当卷圆销孔上模的圆角半径为6.12 mm、铰孔上模的圆角半径为6.35 mm、销孔下模的圆角半径为6.14 mm、铰孔下模的圆角半径为6.28 mm时,仿真后的链板的成形精度高。最后,制作模具样机并进行卷圆冲压成形实验。结果表明,卷圆冲压成形后工件的合格率达到98%。     

石油链的链板冲孔模

介绍了侧压定位装置、弹性送料装置和小间隙冲裁工艺等在链板生产中的应用，较好地解决了链板冲孔问题。     

平顶链链板自动冲压成形系统设计北大核心CSCD

为提高平顶链链板精度和生产效率,根据平顶链链板冲压成形工艺,以及生产效率要求,设计了一套多工位自动冲压成形系统,其中包括冲压模具结构设计以及送料系统设计。冲压模具结构设计包括预弯模具、折弯模具以及卷圆模具的结构设计,并利用ABAQUS有限元分析软件进行冲压模拟仿真,改进模具尺寸,提高链板成形精度。送料系统设计包括储料装置、自动送料装置结构设计及相关设备选型。为了实现自动化冲压生产,自动送料装置采用的是三自由度横杆式结构。最后,完成了样机制作和实验,试生产出的平顶链链板合格率达到97.83%,生产效率达每分钟9件,结果表明,所设计的平顶链链板自动冲压成形系统达到了链板的生产精度和生产效率要求。     

链板精密级进模设计

设计了1副链板无搭边分体式准高速精密级进模。介绍了链板外形无搭边模具结构形式、打印模结构、模具导向方式和卸料方式、废料处理等,介绍了模具制造要点。经长期使用证明,材料利用率大幅提高,提高了模具寿命和链板质量。     

新颖的铸造链板传送带式热处理电炉

一种适用于轴承行业、标准件行业、五金工具行业、汽车拖拉机行业中的中小型零件在通气氛条件下或不通气氛条件下进行热处理的新颖的铸造链板传送带式电炉——SL88-286型传送带式热处理生产线,在上海电炉厂研制成功。一九九○年十二月已通过了技术鉴定。所谓铸带炉生产线是:淬火加热炉的传送带是用结构特殊的铸造链板组成的传送带式炉,称铸造链板传送带式炉,简称铸带炉。也有人简称铸链炉或铸链板炉。再根据热处理工艺的需要,配置传送带式淬火槽,传送带式清洗机,传送带式回火炉,上料机等组成的连续式热处理生产线。     

600 MPa级汽车桥壳钢生产实践

介绍了河北普阳钢铁有限公司生产600 MPa级汽车桥壳钢板600QK的生产工艺及产品性能特点,研究了不同未再结晶区开轧温度和待温厚度对600QK钢板的组织和力学性能的影响。结果表明：铌、钛微合金元素的复合添加,有助于细化铁素体晶粒,提高钢材的强度和韧性。通过控制成品氮含量不大于50×10-6,未发现大尺寸TiN夹杂物。采用两阶段控轧工艺,随未再结晶区开轧温度的降低和待温厚度的增加,组织更加细化,钢板的抗拉强度及伸长率变化不大,但屈服强度及-20 ℃冲击功显著增加。产品各项性能良好且稳定,满足了用户的需求。     

Influence of slab reheating practice on the microstructural evolution and toughness behavior of quenched and tempered plates of medium carbon microalloyed steel

In the current study, granular bainite was found to be the major component in the microstructure of air cooled 80 mm thick plates of medium carbon microalloyed steel. The second constituent in this granular bainite was identified as cementite. It was further observed that (1) ferrite lath size and (2) amount of cementite in granular bainite varied with slab reheating time before plate rolling. Smaller ferrite laths and a lesser amount of cementite were found in the plate processed with the longer slab reheating time of 26 h. Contrary to this, very large sized ferrite laths and a larger population of cementite were formed in the plate processed with the shorter slab reheating time of 4 h. Subsequent quenching and tempering of these plates favored the formation of lower bainite and tempered martensite in the plate with 26 h slab reheating time. On the other hand, upper bainite and coarser cementite were formed after the quenching and tempering of the plate with 4 h of slab reheating time. The influence of different microstructures, formed due to varied slab reheating time, on the toughness property of tempered plates was evaluated under different test conditions. In tensile test and fracture toughness testing of thinner specimens, a ductile mode of fracture was observed, irrespective of varied microstructures in the tempered plates. However, in the three-point bend test of full thickness specimens, the mode of fracture was ductile in the tempered plate with 26 h slab reheating time, while the tempered plate from the slab with 4 h reheating time gave rise to a predominantly brittle mode of fracture. These observations showed that the toughness property of these tempered plates was sensitive to the microstructure only under the specific condition, which prevailed during the three-point bend test of full thickness specimens. Under this condition, coarse cementite and upper bainite became prone to cracking resulting in a lower toughness of the tempered plate associated with lower slab reheating time.     

铁素体轧制工艺条件下边部缺陷控制方法研究

研究了在铁素体区轧制条件下热轧带钢边部翘皮的宏观分布规律和微观缺陷形貌,分析了该工艺下缺陷形成的原因,粗轧段板坯边角部进入两相区,同时生产线的立辊和侧导板等接触设备的表面质量不良,造成了边角部变形不均,在精轧过程中最终形成边部翘皮。结合现场工艺,探讨了缺陷的改善措施,通过优化粗轧立辊辊型,提升轧制过程中坯料边角部温度,以及通过设备功能精度管理提升粗轧、精轧的侧导板和立辊辊面质量,最终消除了铁素体轧制超低碳钢的边部质量问题。     

铁素体不锈钢连铸板坯宽度尺寸的控制

铁素体不锈钢由于高温强度低,直弧型连铸机生产的板坯宽度尺寸难以满足公差要求.本文对铁素体不锈钢板坯宽度不合公差要求的原因进行了分析,并提出相应的工艺措施.     

石墨砂轮精密磨削铁氧体的实验研究

本试验使用石墨白刚玉砂轮精密磨削铁氧体,可实现简化工艺的目的。实验结果表明:在磨削速度24 m/s、工件速度1~10 m/min、切深2.5~7.5 μm的普通磨削工艺条件下,铁氧体零件的表面粗糙度值均达到R_a 0.18 μm以下。最小的表面粗糙度值可以达到R_a 0.09 μm,磨削表面呈镜面。因此,该磨削工艺可以完全满足铁氧体零件的表面加工质量要求。      

着色法区分铁素体球墨铸铁中的渗碳体与铁素体

采用不同的侵蚀剂,进行了铁素体球墨铸铁中铁素体和游离态渗碳体的金相显示和区分试验。结果表明,采用常规腐蚀剂(2%~5%的硝酸酒精),难以有效地分辨在铁素体球墨铸铁工件铸造过程中非常容易出现的游离态渗碳体,借助显微硬度也只能解决部分问题。在2%~5%的硝酸酒精预蚀后,采用碱性苦味酸钠溶液沸浸5~15 min,根据不同物相的着色效果,可以完美呈现铁素体球墨铸铁中的不同物相及成份偏析;也可以在样品预蚀后,采用苦味酸水溶液,同样根据着色效果的不同,实现快捷、有效的物相区分及评级。     

薄板坯连铸连轧生产中的铁素体轧制工艺

介绍了薄板坯连铸连轧生产中铁素体轧制工艺的特点及其理论依据，以及铁素体轧制工艺在超薄热带项目中的应用。     

X60钢在CSP热轧过程中的组织演变与混晶现象

研究包钢CSP生产线上同一X60钢轧件经不同道次变形后,其不同部位的金相组织,结果表明:连轧前铸坯的室温组织为粗大的针状或块状铁素体,少量的珠光体沿铁素体晶界不均匀分布。空冷到室温的轧件具有铁素体 珠光体组织。在CSP薄板轧制过程中,晶粒明显细化但出现混晶现象。前面道次中边部晶粒尺寸和表面晶粒尺寸比心部晶粒尺寸细小均匀,在终轧后差异变小。同时分析了微观组织演变特点和混晶产生的原因。     

Microscopic phase-dependent residual stresses in the machined surface layer of two-phase alloy

Residual stresses in the machined surface layer, which affect fatigue crack nucleation and stress corrosion cracking especially in aerospace engines and gas turbines for power generation, depend on microstructures in case of machining a multiple-phase alloy. Hence, the microscopic phase-dependent residual stresses should be known when a machined part is used under critical stress conditions and circumstances. In the present paper, finite element modeling of machining two-phase alloys has been developed for obtaining the residual stresses in the machined surface layer. Iron and steels, which consist of different volume fractions of ferrite and eutectoid pearlite, were selected as work materials to be machined. First, it was confirmed that the calculated results agree well in chip formation and cutting forces with experimental ones. Then, residual stresses in the machined surface layer were obtained for different carbon contents and regular/random arrangements of microstructure. As a result, it is found that the microstructure of the workpiece has a great influence on the residual stress distribution on the machined surface and that tensile surface residual stress on pearlite is much larger than that on ferrite. Finite element machining of the work material with stripe arrangement of ferrite and pearlite revealed that the peak of residual stress would be reduced by decreasing the width of stripes of ferrite and pearlite.     

Control of Transverse Corner Cracks on Low-Carbon Steel Slabs

In this article, the formation mechanism of transverse corner cracks on a low-carbon steel continuous-casting slab was investigated. The factors influencing the transverse corner cracks were discussed. The hot ductility of the low-carbon steel within 600°C and 1250°C was detected using a thermal simulator Gleeble 1500 (Dynamic Systems, Inc., Poestenkill, NY) to determine the embrittling temperature range of the steel. The temperature of the slab varied with time, especially at the slab corner, and it was calculated and discussed. It was found that transverse corner cracks were generated on the ferrite films along grain boundaries, and there was little decarburization layer near the cracks. According to the calculated temperature at slab corner, the cooling water flow rate and cooling strategy were optimized by adjusting the cooling water flow rate at each spray cooling zone to avoid the embrittling temperature range at the bending and straightening segments of the caster. As a result, the transverse corner cracks were successfully weakened.