Microstructure and Impact Wear Resistance of TiN Reinforced High Manganese Steel Matrix

 A high-manganese austenitic steel matrix (Mn13) composite reinforced with TiN ceramic particles was synthesized by means of Vacuum-Evaporation Pattern Casting (V-EPC). The composite microstructure and interface bonding of TiN/matrix were analyzed utilizing optical microscope (OM) and X-ray diffraction (XRD). The effects of different volume fraction of TiN on impact wear resistance were evaluated by MLD-10 impact wear test.The results showed that TiN was evenly distributed in composite layer and had a good interface bonding with matrix when the volume fractions of TiN were 27% and 36%, respectively. However, cast defects and TiN agglomeration occurred when the TiN volume fraction increased to 48%. Compared with high-manganese austenitic steel (Mn13), the impact wear resistance of the TiN-reinforced composite is better. In small impact load conditions, composite layer can effectively resist abrasives wear and TiN particles played an important role in determining impact wear resistance of composite layer. In large impact load, the synergistic roles of spalling of TiN particles and the increase of work hardening of Mn13 based material are responsible for impact wear resistance.     

稀土金属对纯镍铸铁焊条抗热裂性影响的研究

采用HRL-1型热裂纹试验机测试焊缝临界变形速度的方法，研究了常用稀土金属镧、铈、镨、钇及钕在纯镍铸铁焊条冷焊时。对焊缝临界变形速度VBL、焊缝微观组织以及热裂敏感性的影响规律。试验结果表明：焊缝中加入适量的稀土镧、铈、钇和镨。有脱硫、脱磷、去除晶界杂质的作用，每种稀土金属，偏离该最佳值都会使焊缝抗热裂性降低。纯镍铸铁焊条中加入稀土钕会增加焊缝热裂敏感性。稀土镧、铈、钇和镨能在一定范围内显著提高焊缝临界变形速度VBL，改善纯镍铸铁焊缝抗热裂性能。     

Evaluation of Cracking Resistance of Copper-Bearing Age Hardening Steel Weldment

The weldability of a low-carbon copper-bearing age hardening steel was evaluated using cracking suscepti- bility calculation, HAZ maximum hardness measurement, and Y-groove cracking evaluation test. The results show that the hardenability characteristics and cold cracking susceptibility of the steel are very low. The results also indicate that a crack-free weldment can be obtained during the welding of this type of steel even at an ambient temperature as low as -5 ℃ as well as in an absolute humidity lower than 4 000 Pa without any preheat treatment. A slight preheat treatment can prevent the joint from cracking when welding is carried out at lower ambient temperature or higher absolute humidity.     

薄板坯连铸连轧低合金耐磨钢磨料磨损特性

 研制了30CrMo,50CrV4两种牌号的薄板坯连铸连轧低合金耐磨钢板,对试验钢板进行淬火和低温回火热处理,并且与传统热轧工艺生产的热轧态的45,16Mn,Q235钢对比进行低应力磨料磨损试验,研究其磨损特性。结果表明,淬火低温回火态薄板坯连铸连轧30CrMo,50CrV4钢的相对耐磨性都达到了热轧Q235钢的1.6倍以上。在低应力磨料磨损下,显微切削机制为主要磨损机制,淬火回火态薄板坯连铸连轧低合金耐磨钢具有高硬度因而具有较好的耐磨性能,并在试验钢板硬度高于450HBW以后相对耐磨性明显提高。对比两种牌号的薄板坯连铸连轧低合金耐磨钢的显微组织、硬度、韧性及耐磨性能,30CrMo钢的综合性能较好。50CrV4钢耐磨性能较好,但其冲击韧性较低。     

Effect of Welding Processes and Consumables on Tensile and Impact Properties of High Strength Quenched and Tempered Steel Joints

Quenched and tempered steels are prone to hydrogen induced cracking in the heat affected zone after welding. The use of austenitic stainless steel consumables to weld the above steel was the only available remedy because of higher solubility for hydrogen in austenitic phase. In this investigation, an attempt was made to determine a suitable consumable to replace expensive austenitic consumables. Two different consumables, namely, austenitie stain less steel and low hydrogen ferritic steel, were used to fabricate the joints by shielded metal are welding （SMAW） and flux cored arc welding （FCAW） processes. The joints fabricated by using low hydrogen ferritic steel consumables showed superior transverse tensile properties, whereas joints fabricated by using austenitic stainless steel consumables exhibited better impact toughness, irrespective of the welding process used. The SMAW joints exhibited superior mechanical and impact properties, irrespective of the consumables used, than their FCAW counterparts.     

不同冲击载荷下10Mn钢和NM500的磨损性能及机理

为了给不同类型耐磨钢的实际使用环境提供可靠试验依据,研究不同微观组织的磨损性能和机理,分别在低载荷2 J和高载荷5 J下测试NM500马氏体钢和10Mn奥氏体钢的冲击磨损性能。NM500马氏体耐磨钢以板条状马氏体为主,板条内部存在高密度位错亚结构,同时存在少量残余奥氏体和一些棒状碳化物(TiC);奥氏体10Mn耐磨钢以奥氏体为主,还有少量马氏体和碳化物(NbC、VC)。结果表明,在低冲击载荷(2 J)下,NM500耐磨性高于10Mn钢(160 min的磨损量分别为109和181 mg),归因于NM500比10Mn钢具有更高的硬度,磨料对表面的破坏更小;在高冲击载荷(5 J)下,磨损初期,NM500耐磨性高于10Mn钢(120 min的磨损量分别为140和145 mg),但长时间磨损,NM500耐磨性低于10Mn钢(160 min的磨损量分别为222和173 mg),归因于10Mn钢发生了充分加工硬化,具有更优异的耐磨性。10Mn钢磨损后亚表面微观形貌中存在大量的高密度位错、形变孪晶、应变马氏体,优异的加工硬化能力使10Mn在5 J冲击载荷下更耐磨。     

海洋平台用S355G10+M厚钢板的焊接性研究

按照EN10225标准要求,对75 mm厚度规格海洋平台用S355G10+M钢板进行了堆焊硬度试验(BOP)、可控热拘束试验(CTS)以及热输入50 k J/cm埋弧焊对接接头系列力学性能试验,研究了钢板焊接热影响区(HAZ)的淬硬倾向、HAZ冷裂纹敏感性、焊接接头各部位抗拉强度、冲击韧性和裂纹尖端张开位移(CTOD)值的变化情况。结果显示S355G10+M厚钢板的HAZ最高硬度、焊接钢板冷裂纹、埋弧焊对接接头抗拉强度、低温冲击功均值、CTOD值等各项性能指标良好,满足海洋平台的焊接生产要求。     

热轧带钢冷弯开裂原因分析

冷弯性能是衡量钢材塑性好坏的一项重要的力学性能指标,并且直接影响产品质量和经济效益。针对某厂Q235B、SS400钢种出现的冷弯不合格情况,通过采用金相分析和扫描电镜检测,认为热轧带钢冷弯开裂与钢材中心存在偏析带、团状珠光体和大量的魏氏体组织有关。严格控制连铸钢水过热度在20~30℃以内,铸坯入炉温度500℃,在炉时间≤180 min等工艺参数后,基本消除了热轧带钢冷弯开裂现象。     

Effects of heat treatment on wear resistance and fracture toughness of duo-cast materials composed of high-chromium white cast iron and low-chromium steel

The objective of this study is to investigate effects of heat treatment on wear resistance and fracture toughness in duo-cast materials composed of a high-chromium white cast iron and a low-chromium steel as a wear-resistant part and a ductile part, respectively. Different size, volume fraction, and distribution of M₇C₃ carbides were employed in the wear-resistant part by changing the amount of chromium, and the volume fraction of martensite in the austenitic matrix was varied by the heat treatment. In the alloys containing a small amount of chromium, an interdendritic structure of eutectic M₇C₃ carbides was formed, and led to the improvement of wear resistance and fracture toughness. After the heat treatment, the selective wear of the matrix and the cracking or spalled-off carbides were considerably reduced since the hardness difference between carbides and matrix decreased by the increase in the matrix hardness, thereby leading to the improvement of the wear resistance. However, the fracture toughness of the heat-treated alloys was lower than that of the as-cast alloys because the matrix containing a considerable amount of martensite did not effectively prevent the crack propagation.     

Influence of Alloying and Heat Treatment on the Abrasive and Impact–Abrasive Wear Resistance of High-Manganese Steel

The basic factors that affect the wear resistance of high-manganese steel are considered. The literature on this topic is reviewed. Conclusions are formulated regarding the materials used in existing studies. Research topics of interest to enterprises that manufacture and employ Hadfield steel are identified. Materials used in the machining of liquid steel are considered. Production technology for experimental high-manganese steel parts is discussed. The composition of the alloy employed as the base is analyzed. The procedure and equipment used to determine the cooling rate of alloys in the mold and to study the wear resistance in conditions of abrasive and impact–abrasive wear are outlined, as well as methods of thermal analysis. Results are presented for the alloying of Hadfield steel by nitrided ferroalloys and other alloys. The coefficients of abrasive and impact–abrasive wear resistance are plotted for different alloying conditions. In addition, the influence of the alloying elements on the wear resistance of high-manganese steel in different wear conditions is studied. The concentrations of the alloying elements corresponding to maximum abrasive and impact–abrasive wear resistance are established. In addition, the results of thermal analysis are presented. The heating of Hadfield steel castings prior to quenching is considered. The temperature ranges corresponding to processes such as excess-phase deposition, the solution of cementite in austenite, and complete solution of phosphide eutectic and metal carbides are established. The temperature limits of oxidation and decarburization of the steel are also determined. On the basis of the results, recommendations are made with a view to increasing the wear resistance of castings made from high-manganese steel for different operating conditions and also to selecting the heat-treatment temperature for such castings.     

新型节镍奥氏体不锈钢的成分设计及生产试制

综合传统AISI300系奥氏体不锈钢和高氮奥氏体不锈钢的优缺点,开发一种新型节镍奥氏体不锈钢.为了研究其最优成分和工业试制工艺,通过Thermo-Calc热力学计算软件设计成分、热轧试生产试验钢和微观测试方法分析试验钢.结果 表明,新型节镍奥氏体不锈钢最优的成分范围(质量分数)为N0.2％～0.3％o、C小于0.1％、...     

A Comparison of Creep Rupture Strength of Ferritic/Austenitic Dissimilar Weld Joints of Different Grades of Cr-Mo Ferritic Steels

Evaluations of creep rupture properties of dissimilar weld joints of 2.25Cr-1Mo, 9Cr-1Mo, and 9Cr-1MoVNb steels with Alloy 800 at 823 K were carried out. The joints were fabricated by a fusion welding process employing an INCONEL 182 weld electrode. All the joints displayed lower creep rupture strength than their respective ferritic steel base metals, and the strength reduction was greater in the 2.25Cr-1Mo steel joint and less in the 9Cr-1Mo steel joint. Failure location in the joints was found to shift from the ferritic steel base metal to the intercritical region of the heat-affected zone (HAZ) of the ferritic steel (type IV cracking) with the decrease in stress. At still lower stresses, the failure in the joints occurred at the ferritic/austenitic weld interface. The stress-life variation of the joints showed two-slope behavior and the slope change coincided with the occurrence of ferritic/austenitic weld interface cracking. Preferential creep cavitation in the soft intercritical HAZ induced type IV failure, whereas creep cavitation at the interfacial particles induced ferritic/austenitic weld interface cracking. Micromechanisms of the type IV failure and the ferritic/austenitic interface cracking in the dissimilar weld joint of the ferritic steels and relative cracking susceptibility of the joints are discussed based on microstructural investigation, mechanical testing, and finite element analysis (FEA) of the stress state across the joint.     

Investigation of the Effect of Tungsten Substitution on Microstructure and Abrasive Wear Performance of In Situ VC-Reinforced High-Manganese Austenitic Steel Matrix Composite

Particulate VC-reinforced high-manganese austenitic steel matrix composites with different vanadium and tungsten contents were synthesized by conventional alloying and casting route. Microstructural characterizations showed that the composites processed by in situ precipitation of the reinforcements were composed of V₈C₇ particulates distributed in an austenitic matrix. It was observed that addition of tungsten to austenite increases work-hardening rate of subsurface layer during pin-on disk wear test. The maximum abrasive wear resistance was achieved at tungsten content equal to 2 wt pct. However, excessive addition of tungsten promoted the formation of W₃C phase and reduced the abrasive wear resistance because of decrease in distribution homogeneity and volume fraction of the reinforcing VC particles.     

Relation between microstructure, composition, and hot cracking in Ti-stabilized austenitic stainless steel weldments

A stabilized, fully austenitic alloy D9, a 15Cr-15Ni-2Mo stainless steel with a titanium addition corresponding to UNS 38660, is a candidate material for the fuel-clad and wrapper applications of the Prototype Fast Breeder Reactor (PFBR). The fully austenitic microstructure and the presence of titanium in this alloy lead to high susceptibility to hot cracking during welding. The fusion-zone and the heat-affected zone (HAZ) cracking susceptibility of alloy D9 was studied at three titanium levels, 0.22, 0.32, and 0.42 pct, all other elements remaining constant. The longitudinal and transverse Varestraint (Transvarestraint) hot-cracking tests were used to evaluate fusion-zone and HAZ cracking. The results showed that titanium increases cracking in the fusion zone by 15 to 20 pct in the range of Ti levels studied. The microanalysis of fusion-zone hot cracks using electron probe microanalysis (EPMA) showed an enrichment of Ti, C, N, and S along cracks and in the interdendritic regions. The corresponding phases were identified as TiC, TiC_0.3N_0.7, and the carbosulfides Ti₂CS and Ti₄C₂S₂, which are believed to form eutectics with austenite to produce cracking. The amounts of these phases increased with increasing Ti content. In the HAZ, a similar relation between titanium level and cracking was found. The comparison of the weldability of the D9 with an FA mode type 321 revealed that Ti-bearing eutectics were responsible for a high degree of cracking irrespective of the solidification mode. The results show that in the D9, the ratio of Ti to C and N must be controlled to minimize cracking.     

Development and application of a new hot-work die steel for hot stamping

A new hot-work die steel for hot stamping was developed, and used the die for mass production. The produced die showed good performance owing to its high heat conductivity and wear-resistant characteristics. Two different benchmarking hot-work die steels were investigated, and then compared in terms of their impact ductility,temper characteristics, heat conductivity, and thermal stability. The result of the high-temperature friction wear test indicated that oxidative wear was the main mode in high temperature. On the basis of the comparison and test results, the alloying composition of the new hot-work die steel was especially designed. The new die steel showed good performance with good wear-resistant quality, as well as temper hardness and heat conductivity of HRC 50 and34.3 W/(m·K), respectively. Furthermore,without surface plasma nitriding, the die made of the new steel had no obvious galling with 6142 strokes. After surface plasma nitriding, the die completed 40000 strokes with good surface. The die life is expected to exceed 200000 strokes.     

低碳低合金钢的热延性及表面裂纹

本文介绍近年来有关低碳低合金钢的热延性、与热延性相关的表面裂纹以及裂纹形成机制等方面的研究结果。     

影响奥氏体热作模具钢性能的因素

 在700 ℃下,马氏体型热作模具钢难以工作,奥氏体型热作模具钢具有良好的高温强度。基于均匀设计方法,设计了6种不同成分的试验钢及相应的热处理工艺。试验测定了6种钢的硬度、室温冲击韧性、热稳定性,利用二次型逐步回归分析方法对试验结果进行了建模,得出了三者与成分、工艺之间的回归方程,并与H13钢和DIEVAR钢对比。结果表明：增加Si、Mn、V含量,降低Cr、Mo含量可以提高钢的韧性;同时在所设计的热处理工艺范围内可以使钢的室温冲击功达到300 J;在700 ℃保温20 h,硬度HRC减少1~3。     

Weldability of 1 000 MPa Grade Ultra-low Carbon Bainitic Steel

Maximum hardness test in weld heat-affected zone(HAZ),oblique Y-groove cracking test and mechanical property test of welding joint of 1 000 MPa grade ultra-low carbon bainitic steel were carried out,so as to research the weldability of the steel.The results show that the steel has lower cold cracking sensitivity,and preheating temperature of 100 ℃ can help completely eliminate cold cracks,generating good process weldability.The increase of preheating temperature can reduce the hardening degree of heat-affected zone.The strength of welding joint decreases and hardness reduces when heat inputs increase,and excellent mechanical properties can be obtained when low welding heat inputs are used.Fine lath bainites of different orientations combined with a few granular bainites that effectively split the original coarse austenite grains are the foundation of good properties.     

600 MPa级高能量输入焊接压力钢管用钢的研制

经过系列技术攻关,改进了武钢专用钢板冶炼及连铸过程中一些工艺,形成了一套自主操作技术模式,生产的微合金化低合金高强钢中杂质含量显著降低,钢板性能稳定性明显提高.利用武钢新改进的冶炼技术研制了一种600 MPa级低焊接裂纹敏感性高能量输入焊接水电站压力钢管用钢,研究了该钢的力学性能、微观组织结构以及焊接粗晶热影响区(CGHAZ)的组织特征及力学性能.结果表明,研制的新钢种集高强度、高韧性、优异的焊接性能于一体,且能承受大线能量焊接,焊前不预热,焊后不热处理.CGHAZ中弥散分布的复合氧化物夹杂促使针状铁素体的形成,提高了CGHAZ的力学性能.     

09CuPCrNi-A热轧钢板剪切后开裂原因分析

通过扫描电镜、能谱分析、金相检验等手段,分析了造成09CuPCrNi-A钢板剪切后横断面上出现中心开裂及钢板冲击韧性波动的原因。确认钢板剪切后中心开裂是由P及S偏析所致,这也是导致钢板冲击韧性波动的原因。