H13圆盘剪剪刃裂纹、崩刃原因分析及改进措施

圆盘剪是中厚钢板纵向剪切的一种主要设备,在使用过程中剪刃裂纹及崩刃是主要的失效形式,通过对H13剪刃裂纹、崩刃原因的分析,指出剪刃热处理硬度偏高是导致剪刃失效的原因,提出了在制造和实际使用过程中相应的改进措施.     

H13钢芯棒淬火裂纹分析及防止措施

采用宏观断口检查、金相分析、化学成分分析等方法对H13钢芯棒淬火裂纹成因进行了具体分析,结果表明芯棒裂纹是由于芯棒本体存在带状组织、疏松、夹杂等缺陷,同时淬火冷却不均匀从而导致淬火过程中应力过大使芯棒失稳开裂,并提出了改进措施.     

低碳含铌钢表面裂纹的研究与改进措施

 主要研究了低碳含铌钢的表面裂纹形成的原因。通过对表面裂纹缺陷部位进行金相组织观察、SEM(EDS)、金属原位分析,得知低碳含铌钢表面裂纹附近存在夹杂物,铌元素的含量富集。钢水中的氮过高、连铸二冷水强度是影响铌提前凝固析出富集的主要原因。通过降低钢水的氮含量,适当提高热矫温度等工艺的优化措施,明显降低了低碳含铌钢的表面裂纹。     

CSP热轧板卷边部裂纹成因及控制

为了抑制CSP热轧板卷边部裂纹,对CSP热轧板卷边部裂纹的成因进行了研究.CSP热轧板卷边部裂纹缺陷主要有3类:边部横裂纹、边部纵裂纹、边部烂边或掉块等.板卷产生边部裂纹的主要原因是:连铸坯表面边部横裂纹(包括深的振痕)和边部的细小纵裂纹,在加热和轧制过程中不断扩展;钢液在凝固以及铸坯在冷却、均热、轧制、层流冷却和卷取等过程中的热应力、机械应力以及相变应力等作用力超过钢的塑性变形抗力.抑制CSP热轧板卷产生边部裂纹的主要措施是:控制好合适的钢水成分;制定有效的工艺参数,如结晶器热流密度、结晶器振动参数、二冷冷却强度等.工业试验结果表明,CSP热轧板卷边部裂纹率由7.93%降低到1.81%.     

320MPa级高强度船板表面微裂纹形成原因的分析

采用金相、扫描电镜对320 MPa级高强度船板表面微裂纹的形成原因进行了研究,发现铸坯表面微裂纹是造成板材表面微裂纹的主要原因,并进一步分析了铸坯表面微裂纹的成因。通过铸坯冷、热装对比试验,指出采取堆垛缓冷的措施可以有效降低板材表面微裂纹的产生。     

圆盘剪H13剪刃裂纹及崩刃分析

圆盘剪是中厚钢板纵向剪切的一种主要设备,在使用过程中剪刃裂纹及崩刃是主要的设备事故,通过对H13试验剪刃裂纹、崩刃原因的分析,找出因剪刃热处理硬度偏高导致剪刃损坏的原因,提出了在制造和实际使用过程中相应的改进措施.     

转炉45热轧圆钢裂纹原因分析

对转炉生产45热轧圆钢轧材裂纹、热顶锻裂纹形成的主要原因进行了分析,指出轧制过程中导卫、轧辊表面附着物是产生圆滑形裂纹和热顶锻裂纹的主要原因。通过采取加强铸坯夹杂物控制、加强导卫、轧辊维护等手段解决45热轧圆钢裂纹的问题。     

H13模块锻造裂纹分析

本文通过对H13钢模块的化学成分、金相组织及硬度进行检验，对其锻造裂纹的形成原因进行了分析和讨论，得知模块的化学成分和组织偏析以及主裂纹区域沿晶分布的低熔点相是造成锻造开裂的直接原因，     

316H不锈钢表面等离子粉末堆焊Tribaloy~?T400涂层的性能研究

采用等离子粉末堆焊工艺在316H不锈钢表面堆焊Tribaloy~?T400 (T400)合金涂层,研究焊接时不同焊接热输入对堆焊件表面形貌、成分、维氏硬度、摩擦因数以及磨损质量的影响。结果表明:当焊接热输入为840 J/mm时,堆焊件表面没有明显的缺陷,维氏硬度以及耐磨性能达到最佳,且Cr元素含量最低;对316H不锈钢和堆焊件的磨损机制进行研究发现,316H不锈钢的磨损机制主要为剥层磨损,伴随有少量氧化磨损,堆焊件的磨损机制主要为磨粒磨损,伴随有黏着磨损。对焊接热输入为840 J/mm的堆焊件在700℃的环境中进行时效实验,堆焊件的维氏硬度随着时效时间的延长而增大,堆焊件经1 000 h时效后,维氏硬度由原来的528增加到602,堆焊层具有较高的高温力学稳定性。     

H13型热作模具钢表面改性技术研究进展

 在工业中,模具的变形、磨损和疲劳失效普遍存在,严重影响了生产效率和产线安全。为了更好地了解和分析模具失效的原因,改善模具的性能,提高其使用寿命,通过介绍国内外H13型热作模具钢的表面改性技术及研究现状,总结了激光加热处理、热喷涂处理、化学热处理3类表面改性技术的特点及在改善热作模具钢表面性能方面的研究成果。探讨了不同表面处理工艺对该热作模具钢表面性能的影响,对不同处理技术应用于该热作模具钢表面改性的优缺点进行了分析,并对该热作模具钢表面改性技术的发展方向进行了展望。     

Characterization of laser-beam surface treated cold and hot working steels

In order to increase the wear resistance of metal forming tools, four different cold and hot working steels were laser-beam surface melted and alloyed with titanium carbide and vanadium carbide. The layers were investigated concerning chemical composition, microstructure, hardness profiles, wear behaviour measured by pin-on-disk-tests with different counterbodies and plastic behaviour of the surface by a new developed repeated impact testing machine. It turned out to be more useful to take a substrate which is already quenched and tempered prior to the laser-beam surface treatment than to carry out the tool hardening heat treatment afterwards. A tempering step after the laser-beam alloying offers the advantage of carbide precipitates in the layer connected with an increase in the hardness and a reduction of residual stresses. By means of laser-beam surface alloying the wear protection of the layer can be increased while the alloying content of the substrate is reduced with respect to the core fracture toughness. The optimal alloying addition depends on the demands of the envisaged application.     

White-Etching Matter in Bearing Steel. Part I: Controlled Cracking of 52100 Steel

Although most of the research performed in bearing steel metallurgy aims to prevent crack nucleation and propagation, some applications require the exact opposite in order to study the role that disconnected surfaces inside the bulk material play when load is applied, or when fluids entrapped in surface cracks propagate tensile stresses or exacerbate corrosion. Four heat treatments have been designed to create controlled arrays of crack types and distributions in quenched and untempered steel normally used in the manufacture of bearings. The varieties of cracks studied include sparsely distributed martensite-plate cracks, fine-grain-boundary cracks, abundant martensite-plate cracks, and surface cracks. The intention was to create samples which can then be subjected to appropriate mechanical testing so that phenomena such as the appearance of “white-etching areas” or “white-etching cracks,” crack-lubricant interactions, or hydrogen trapping can be studied further.     

狄舍尔轧管机限动芯棒选材与应用研究

鞍钢无缝钢管厂狄舍尔轧管机的限动芯棒消耗量大，主要的失效形式为热磨损与热疲劳，具体表现为磨损和网裂，为改善芯棒的抗热损伤性能，根据理论计算及实际工况、重新选择芯棒钢材质，经模拟和工业性试验表明，试验钢的耐热疲劳性比原材质４２ＣｒＭｏ钢高３倍左右，芯棒一次性单耗由３．３ｋｇ／ｔ降至１ｋｇ／ｔ以下。     

热处理对Ni-W-GO复合镀层组织及性能的影响

氧化石墨烯（GO）因其独特的结构和特性引起了广泛研究.论文以GO纳米片为硬质相,采用直流电沉积方法在45#钢基体上制备了Ni-W-GO复合镀层,并对其进行不同温度下的真空热处理,通过SEM、XRD、显微硬度计及摩擦磨损试验机等分析了热处理前后复合镀层的组织结构、物相、力学性能及摩擦磨损性能,分析磨损机理.结果表明:热处理过程使复合镀层晶粒尺寸逐渐增大,并伴随有微裂纹出现和中间相颗粒析出;随着热处理温度的升高,复合镀层的显微硬度及磨损性能呈现出先增大后减小的趋势,且当热处理温度为350 ℃时,维氏硬度最高达840.      

高应力冲击磨损的白层剥落机制

研究了贝氏体钢经高应力冲击磨损后，试样表层内的组织变化及裂纹形成与扩展特征。实验发现，高应力冲击磨损后，磨损试样表层形成高硬度的白层与变形层。在白层与变形层内均产生不同程度的损伤裂纹。受力后损伤裂纹将向基体内和白层内扩展。裂纹在白层内的快速扩展造成表面白层的脆性剥落。在实验的基础上，作提出了高应力冲击磨损的白层剥落机制模型。     

钢管在线加速冷却技术开发

研究了化学成分和生产工艺参数对钢管在线加速冷却后组织、性能的影响.结果表明,材料经过穿孔工序或连轧工序后,为奥氏体完全动态再结晶组织;经过张减工序后,为加工硬化状态的奥氏体组织.采用轧后余热和水气复合冷却方式对钢管外表面加速冷却,可以保证钢管轴向、周向、径向3个方向上的强度和硬度均匀性.采用25MnVN或25MnMoVN之类微合金钢,经过轧后加速冷却,可以不经过调质热处理,生产出性能完全满足要求的N80钢级石油套管.     

Residual Stress Measurement and Fatigue Crack Growth Prediction after Cold Expansion of Cracked Fastener Holes

The cold expansion technique is often used to introduce beneficial compressive stress at fastener holes, and can be used for remedial work where cracks already exist. In this paper, results are presented showing the effect of preexisting cracks on the residual stress field produced by cold expanding a fastener hole, and on subsequent fatigue crack growth. The effect on the residual stresses was experimentally evaluated in two ways: indirectly, in terms of retained expansion and directly, by measurement of the stresses using the X-ray and neutron diffraction techniques. The retained expansion ratio showed that cold expansion is more sensitive to the existence of precracks at lower levels of applied interference, and the inlet and outlet faces have different behavior. The stress measurements showed that preexisting cracks reduce the compressive residual stresses more on the mandrel inlet face than on the outlet face and in the middle of the specimen. The effect on fatigue crack growth rates was modeled using a linear-elastic fracture mechanics approach. It was found that cold expansion of a hole containing a preexisting crack longer than 1 mm introduces little benefit for subsequent fatigue crack growth behavior.     

Effect of heat treatment process on impact wear property and mechanism of SKD11 steel

The microstructure, mechanical property, phase of SKD11 steel after vacuum heat treatmentor deep cryogenic heat treatment were studied by means of OM, hardness tester, impact tester and XRD.The impact wear properties of SKD11 steel under the two heat treatments were tested by MLD- 10 dynamic load- bearing wear tester. The impact wear mechanism was also analyzed. The results show that the microstructures of SKD11 steel after the two heat treatmentsare composed of tempering martensite, retained austenite and carbide. The hardness after cryogenic treatment is 1HRC higher than that of the vacuum treatment and impact toughness decreases lightly. Under impact wear conditions, the weight loss of the sample during deep cryogenic treatment is lower than that of the vacuum treatment, which shows better wear resistance. In the studied wear time, the wear mechanism of the sample after vacuum treatment is high stress surface fatigue and abrasive wear, and the wear mechanism of the sample after cryogenic treatment is slight abrasive wear.     

异型坯表面纵向微细裂纹研究

通过对异型坯腹板表面纵向微细裂纹宏观和显微特征的研究、保护渣性能检验、连铸二冷段铸坯表面温度测定和连铸设备的检查等,确定了异型坯腹板表面纵向微细裂纹的产生原因主要有结晶器保护渣性能波动大、连铸冷却工艺不合理、设备状况差及连铸操作不规范等.根据分析结果,同时结合异型坯连铸温度场、应力场数值模拟结果,提出了改进措施,使异型坯表面纵向裂纹发生率由10%下降到1.5%以下.     

Cu–(Fe–C)合金中Fe–C相的固态转变对其摩擦磨损行为及机理的影响

采用光学显微镜（OM）、扫描电子显微镜（SEM）、纳米力学探针、力学性能测试以及室温摩擦磨损实验研究了Cu–(Fe–C)合金的铸态组织、形变态组织、Fe–C相形貌、力学性能和摩擦磨损行为。结果表明，Cu–(Fe–C)合金中弥散分布着微米级和纳米级的Fe–C相，其中微米级的Fe–C相在淬火和回火过程中发生了固态转变，这种固态转变与钢中的马氏体转变和回火转变类似。合金先在850 ℃淬火，然后在200、400和650 ℃回火，Fe–C相由针状马氏体逐渐向颗粒状回火索氏体转变，Fe–C相纳米硬度分别为9.4、8、4.2和3.8 GPa，实现了对强化相硬度的控制。室温摩擦磨损实验结果表明，随着回火温度升高，合金的磨损机制逐渐由犁削向黏着磨损和大塑性变形转变，导致合金的耐磨损性能降低。这一结论可以为通过Fe–C相的固态转变的方法调控Cu–(Fe–C)合金的摩擦磨损性能提供参考作用。