Study of the surface layer of ground high strength steels

Grinding is one of the most widely used finishing operations to obtain close tolerances and a reasonably good surface finish. The effects of rough grinding on different types of steels both hardened and unhardened have been studied. Most of the surface defects caused by extremely abusive conditions were produced by rough grinding. The effects of gentle and conventional conditions of grinding were also studied for comparative data.     

EAF-CSP工艺低碳高强钢中沉淀相的TEM观察

Compact Strip Production(CSP)is a new process for production of hot strips from continuously casting thin slabs by direct charging.The hot strips produced by CSP process undergo different thermo-mechanical process compared with the conventional cold charging process.Supersaturation of microalloy elements in the solid solutions is obvious higher than that in the snips produced by conventional process[1].     

Tool wear mechanisms in the machining of steels and stainless steels

In this article, we study the effects of the temperature control on a dehydration tomato slices process when two control strategies are considered: PID controller and optimal linear control when inherent input time delay is considered. The first controller is tuned by D-partitions method and a numerical procedure in order to minimize a quadratic performance index, the second one considers a state predictor to compensate the effects of the input delayed. The energy savings and the intrinsic characteristics in the tomato slices (vitamin C, total phenols, and lycopene levels) are quantified in order to conclude advantages of the two controllers under study.     

高强钢管板单面电阻点焊工艺实验研究

针对高强钢管板单面电阻点焊工艺,通过实验研究,分析了接头熔核形态,揭示了焊接电流、电极压力、管材半径和电极错位等参数对焊接变形和拉剪强度的影响规律.研究结果可为管板单面点焊焊接质量监控方法研究提供参考.     

高压离心式氧压机的结构强度分析及优化

离心式氧气压缩机正常工作状态时需承载高内压栽荷,高强度承压机壳的设计是其结构设计问题中的难点.文中完成了三万等级离心氧压机在高内压条件下的仿真分析,考虑了上下机壳之间的接触问题和螺栓预紧力对结构强度的影响,重点计算了氧压机机壳、底座装配体的强度,并对氧压机整机进行了必要的模态分析.同时,完成了在水压试验时的氧压机上机壳的内压分析,得到了氧压机机壳可以承受的极限水压力.在满足设计、制造的安全性和合理性前提下,对机壳结构进行了优化,改善了机壳的应力分布,并在制造过程中节省超过7%的材料.     

Wear mechanisms of structural steels and effect of wear on their mechanical and acoustic properties during tension

Optical and scanning electron microscopy have been used to study the wear mechanisms of structural steels with various structures and strengths, as well as to assess their mechanical and acoustic properties after friction. The prevailing wear mechanisms have been revealed; they are governed by the strength and structure of the steels and involve the refinement and rotation of grains, the formation of parallel rows of microcracks, the strain dissolution of cementite, and martensitic transformation, as well as the formation of seizure sites in the friction contact zone, shear and intergranular pores, and microcracks. The low-carbon steel with a ultrafine-grained structure has demonstrated a high wear resistance. Friction for 3000 h had a weak effect on the mechanical properties of the steels during tension.     

Adhesive mechanisms in the wear of some tool steels

The adhesive wear properties of a number of tool steels have been investigated, with special emphasis on the formation and action of prows. The test pieces were worn by dry sliding in a pin-on-ring machine. A special specimen preparation technique made it possible to study the internal structure of wear fragments and prows as a function of depth under the external surface. It was found that prows form in successive steps. The initial step has been reported earlier for pure metals and low carbon steel.A detailed explanation of material deterioration in adhesive wear has been worked out. The dominating mechanism was found to be an abrasive dead zone action, rather than the shearing off or destruction of prows.Investigations by X-ray and electron microscope techniques revealed extensive transformations between the austenite and martensite phases, an extremely fine grain size and a redistribution of carbide and oxide particles during the formation of prows. Correspondingly high microhardness values, up to 1600 HV_0.15N, were measured in the transformed material. Distortion of the retained austenite lattice contributes to the high hardness.     

The sliding wear mechanisms of metals, mainly steels

Early studies of the dry and boundary lubricated wear of metals concentrated on the most catastrophic wear conditions, severe wear and scuffing. It was established how these states could be avoided by protective film formation. Subsequently studies away from these conditions have shown wear either by the removal of surface reaction films or by metal surface fatigue. This review traces these developments and places them in perspective.     

Tribo-electrification mechanisms for self-mated carbon steels in dry severe wear process

The tribo-electrification mechanisms and wear behavior are investigated for self-mated metal pairs of iron and carbon steels (0.2% C, 0.45% C, 0.7% C) under the dry severe wear condition in the reciprocating friction tester. Results show that with increasing the carbon percentage of the steels, the formation mechanism of the wear particle varies from the macro-asperity removal of the slip-tongue to the micro-asperity removal of the wedge. Meanwhile, the variation of tribo-electrification with the sliding time appears to be more serious. The polarity of tribo-electrification is significantly influenced by the difference between the wear losses of the plate and pin specimens. This means the tribo-electrification is mainly caused by the effect of the material transfer for self-mated carbon steels. Under the higher surface hardness, the mean amplitude of the friction coefficient is decreased and the mean amplitude of tribo-electrification is increased. Results also show that the mean amplitude of tribo-electrification for self-mated carbon steels is linearly proportional to the electric resistivity and the relative wear rate, but inversely to the dynamic real contact area.     

低碳结构钢热处理强化应用探讨

阐述低碳结构钢（主要是Q235-A钢）的热处理强化机理,经强化后的低碳结构钢的机械性能明显提高,某些方面甚至超过了调质后的中碳钢。同时对其在机械行业中的应用,及部分取代中碳钢的可行性进行探讨。     

Summarized criterion for evaluating wear resistance and strength of steels

The article deals with basic questions of the prospects of development of high-strength and wear-resistant steels. The paper notes that in steels production a considerable time already is used a broad range of steels with little differences of strength characteristics. The authors developed a generalized criterion for evaluating the wear resistance of steels without wear testing, which can serve as a reliable guide for choosing high-strength steels for different operating conditions.     

Corrosion-wear mechanisms of hard coated austenitic 316L stainless steels

Austenitic stainless steels like 316L are amongst the most commonly selected structural alloys for use in corrosion environments. Unfortunately, their resistance to surface degradation caused during sliding contacts with other materials, in such environments is poor. Here, a synergistic combination of mechanical (wear) and chemical (corrosion) processes, known as corrosion-wear processes, are responsible for causing surface material loss. Accordingly, efforts are being made to identify surface treatments that can enhance the corrosion-wear resistance of 316L and similar alloys. One plausible solution is to apply thin hard coatings (∼5-10 μm thick) using various plasma-based technologies. In practice, this is often fraught with difficulty because of the complex nature of the pervading corrosion-wear mechanisms. This paper presents our recent work that has identified three major corrosion-wear mechanisms that must be minimised if a successful surface engineering design is to be achieved for corrosion-wear protection. These are: Type I—the removal of the coating passive film during sliding contact; Type II—galvanic attack of the substrate resulting in blistering of the coating and; Type III—galvanic attack of the counterface material leading to abrasion of the coating during subsequent sliding contact.     

工程结构钢疲劳寿命分散性评价方法

随着可靠性应用研究工作的深入,材料试验结果不可避免存在的分散性处理日益受到人们的重视,特别是工程结构钢的疲劳寿命数据的可靠性评价已经引起人们的关注。本文针对常见的工程结构材料的疲劳寿命数据,采用威布尔三参数法进行处理并对数据处理中的问题进行探讨,得到了一种快速计算材料疲劳寿命可靠性评价方法,该方法有助于小样本试样结果的精度提高,从而可以节省试验时间和费用。     

Predicting the fatigue strength of structural elements

The development of models relating the fatigue strength of materials to their static strength and plasticity is considered. Statistical strength theories were developed to describe the results of fatigue tests and to predict the strength of machine components with variable loads. Experiments show that the strength of materials depends significantly on structural defects, and the limiting stress is a statistical quantity.     

在役门座式起重机结构强度有限元分析方法

采用有限元分析软件MSC．PATRAN／NASTRAN对一在役门座式起重机建立整体结构计算分析有限元模型,模型中考虑了腐蚀对结构的影响,进行了两种危险工况下的应力计算,并给出结构中应力值较大的几个典型位置作为应力测试位置,进行应力现场测试。通过将有限元计算结果与实测应力结果进行比较,验证了有限元计算结果的可靠性,为在役门座式起重机的有限元强度分析提供了可行的参考方法。     

大型真空罐的结构强度与稳定性分析

进行环境气候实验时,可以将实验室设计为大型钢制真空罐,其设计既要满足强度的要求,也要满足稳定性的要求.在对其进行强度的有限元分析后,其罐体的一次总体薄膜应力强度和一次薄膜加一次弯曲应力强度满足JB4732-1995要求,同时可以得出罐上各部分横、纵加强筋的承载状况;在对其进行特征值的屈曲有限元分析和施加初始几何缺陷后的非线性屈曲有限元分析后,所计算出的临界压力满足GB150的要求,同时可以得出大型真空罐的稳定对几何缺陷很敏感.     

高速铣削淬硬钢的研究进展

对国内外高速铣削淬硬钢的研究成果进行评述.讨论高速切削的概念和特点、切削力、金属软化效应、涂层刀具加工淬硬钢的切削性能、切屑形成机理、冷却方式以及对加工表面的影响,并提出高速铣削淬硬钢研究中的热点问题.