Effect of RE-Modifier on Microstructure and Mechanical Property of High-Carbon Medium-Manganese Steel

The effect of RE-modifier on the microstructure and mechanical properties of high carbon-medium manganese steel has been investigated in present work.The results showed that the RE-modifier can refine the crystalline grain of high-carbon medium-manganese steel.The shape and distribution of carbides are improved and the columnar grains and phosphide in grain boundary are eliminated.Consequently,the impact toughness of the steel is increased by more than one time,compared with no addition of RE-modifier.

MICROSTRUCTURE OF LASER MELTED-RESOLIDIFIED LAYER ON HIGH SPEED TOOL STEEL

The laser melted-resolidified processing on W18Cr4V high speed tool steel has been made us- ing a 1 kW CO_2 continuous wave laser device.The microstructure of the laser melted- resolidified layer has been examined by optical microscopy and transmission electron microscopy(TEM).It was characteristic of extremely fine dendrite in the laser melted- resolidified layer and δ-ferrite in bulk form in the center of dendrite.The predominant twin martensite and a little dislocation martensite existed in the dendrite.The thin plate-like M_(213)C_6 carbide precipitated coherently on the twin martensites along their twin plane.There were both austenite rich in W,V and Cr and M_6C carbide in the interdendritic regions.

Influence of carbon content on microstructure and mechanical properties of Mn13Cr2 and Mn18Cr2 cast steels

In this paper, a comparison study was carried out to investigate the influence of carbon content on the microstructure, hardness, and impact toughness of water-quenched Mn13Cr2 and Mn18Cr2 cast steels. The study results indicate that both steels' water-quenched microstructures are composed of austenite and a small amount of carbide. The study also found that, when the carbon contents are the same, there is less carbide in Mn18Cr2 steel than in Mn13Cr2 steel. Therefore, the hardness of Mn18Cr2 steel is lower than that of Mn13Cr2 steel but the impact toughness of Mn18Cr2 steel is higher than that of Mn13Cr2 steel. With increasing the carbon content, the hardness increases and the impact toughness decreases in these two kinds of steels, and the impact toughness of Mn18Cr2 steel substantially exceeds that of Mn13Cr2 steel. Therefore, the water-quenched Mn18Cr2 steel with high carbon content could be applied to relatively high impact abrasive working conditions, while the as-cast Mn18Cr2 steel could be only used under working conditions of relatively low impact abrasive load due to lower impact toughness.

Microstructure and Mechanical Properties of High Manganese TRIP Steel

Microstructure evolution and mechanical properties of newly designed 0.1C-6Mn-0.5Si-1Al TRIP-aided steels under different annealing conditions and the effects of matrix microstructure before intercritical annealing on the final microstructure were studied by means of X-ray diffraction（XRD）,scanning electron microcopy（SEM）,dilatometric simulation,optical microstructure（OM） and tensile testing in this work.The experimental results indicate that the TRIP steel with Mn of 6% could form a considerable amount of retained austenite with good TRIP effect after a simple intercritical annealing treatment,and the matrix microstructure before intercritical annealing treatment can greatly affect the final microstructure.The original microstructure of the ferritic matrix steel was eliminated,while annealed martensite was remained from the martensite matrix steel under the same intercritical annealing conditions

Rietveld refinement, microstructure and high-temperature oxidation characteristics of low-density high manganese steels

Three forged low-density high manganese steels Mn28Al10,Mn28Al8 and Mn20Al10 were used as experimental materials in this study.The forged microstructure and external oxidation characteristics at 1323 K and 1373 K for 5-25 h in air were investigated by microstructural observation and X-ray diffraction（XRD）technique.The phase compositions and abundance in the forged and oxidized samples were quantitatively obtained by Rietveld method on the basis of XRD pattern analysis.The results showed that an austenitic microstructure formed in steels Mn28Al10 and Mn28Al8,and 18.02 wt%ferrite could be found in Mn20Al10.The relative amount of ~5.28 wt%-carbide（Fe_3AlC_（0.5））in Mn28Al10 was far greater than that in Mn28Al8 and Mn20Al10.The oxidation kinetics of forged steels oxidized at 1323 K for 5-25 h had two-stage parabolic rate laws;and the oxidation rate of the first stage was lower than that of the second stage.When they were oxidized at 1373 K for 5-25 h,the oxidation kinetics followed only a parabolic law and the oxidation rates were respectively greater than those at 1323 K for 5-25 h.When they were oxidized at 1323 K for 25 h,detached external scales contained Fe_2MnO_4and-Fe_2O_3oxides.-Al_2O_3and（Fe,Mn）_2O_3oxides could only be indexed in steels Mn28Al8 and Mn28Al10,respectively.When they were oxidized at 1373 K for 25 h,Fe_2MnO_4,Fe_3O_4,-Fe_2O_3 and-Al_2O_3oxides could all be indexed in the external detached scales.The main phase of detached external scales was Fe_2MnO_4;and the relative amount of-Al_2O_3in steel Mn28Al8 was higher than that in steels Mn28Al10 and Mn20Al.The external oxidation layers of these three forged steels oxidized at 1323 K and 1373 K for 25 h were essentially followed the sequence of-Al_2O_3,Fe_2MnO_4,Fe_3O_4,FeMnO_3,and Fe_2O_3from the substrate to the outside surface.The forged Mn28Al10 steel with austenitic microstructure and a certain amount of-carbide（~5.28 wt%in the present work）possessed a better combination of strength,ductility,specific strength,and oxidation rate when compared to that of the forged Mn28Al8 and Mn20Al10 steels.

Hot workability of high manganese transformation induced plasticity steel

The hot deformation behavior and microstructure evolution of high manganese transformation induced plasticity steel(Fe - 20Mn - 3Si - 3Al) were investigated by using hot compression test in a temperature range from 800℃to 1 050℃and strain rate ranging from 0.01 s^(-1) to 5.0 s^(-1).The effects of temperature,strain rate,and true strain on the flow behavior and microstructures of high manganese transformation induced plasticity steel were discussed.The results show that the dynamic recrystallization occurs only at higher temperature and lower strain rate.Hot deformation behaviors of high manganese transformation induced plasticity steel were sensitive to temperature and strain rate.The apparent stress exponent and the apparent activation energy of the investigated steel were about 4.280 and 463.791 kJ/mol, respectively.The apparent activation energy of the high manganese transformation induced plasticity steel was approached to the austenitic stainless steel(400 -500 kJ/mol).The hot working equation is obtained. Hot deformation peak stress increased with increasing of the value of lnZ.Peak stress and InZ exhibits a linear variation,the linear correlation coefficient was 0.988 9.The results show that the dynamic recrystallization was prone to occur when lnZ≤43.842 26 and Z≤1.098×10^(19),and better hot deformation properties would be obtained under this condition.

Characterizing modified surface layer of 316L stainless steel treated by high current pulsed electron beam

High current pulsed electron beam(HCPEB) is now developing as a useful tool for surface modification of materials.When concentrated electron flux transferring its energy into the surface layer of target material within a short pulse time,coupled thermal and stress processes would lead to the formation of metastalbe microstructure with improved properties.In the present work,HCPEB treatment of 316L stainless steel(SS) was carried out and the microstructural changes in modified surface layer were characterized with optical microscopy,X-ray diffractometry and electron backscatter diffractometry(EBSD) techniques.The corrosion resistance of modified surface was measured in a 5wt.% salt solution.The evolution regularity of surface craters and grain refinement effect,as well as the preferred orientation of(111) crystal plane occurring in the HCPEB treatment under different working parameters were discussed along with their influence on corrosion resistance.

Hot deformation behavior and hot-metal-gas-forming process of V micro-alloyed high manganese steel

The hot deformation behavior of a newly designed V micro-alloyed high manganese steel(HMnS)was investigated in order to guide the development of the hot-metal-gas-forming process.Single-pass hot compression experiments were conducted in the temperature range of 950–1100℃ and the strain rate range of 0.05–10 s^(−1),and the stress–strain curves and the corresponding softening mechanism of the V micro-alloyed HMnS were analyzed.Results show that two types of stress–strain curves,representing the work hardening(WH)-dynamic recovery(DRV)-dynamic recrystallization(DRX)mechanism and the WH–DRV mechanism,respectively,occur during the deformation process.Moreover,the WH–DRV–DRX mechanism gradually transforms into the WH–DRV mechanism with the increasing strain rate and decreasing deformation temperature.Two types of constitutive models considering the softening mechanism difference were established and verified by additional hot-deformation experiments.Hot processing map of the HMnS was established and correlated well with the microstructure evolution result.Based on the constitutive models and processing map,the optimal processing parameter range and flow stress of HMnS for the hot-metal-gas-forming were determined.

Casting properties of ASTM A128 Gr.E1 steel modified with Mn-alloying and titanium ladle treatment

This work aims to produce a high manganese steel with more refined austenite grains and better wear resistance without sacrificing the toughness and tensile properties by Mn alloying and Ti ladle treatment in comparision to ASTM A128 Gr.E1 steel (1.0C-13Mn) that is mostly used in the mining industry.The 1.0C-17Mn-xTi alloys (x=0,0.05 and 0.1,in wt.%) were prepared.A relationship was established between the microstructures and mechanical properties of the as-cast and solution annealed alloys.Increasing Ti content increases the stable Ti(CN) phase on and beside the grain boundaries and decreases up to 37% the austenite grain size of the as-cast alloy with 0.10wt.% Ti.Correspondingly,after solution annealed,optimized titanium content (0.05wt.%) results in significant improvements in wear resistance,hardness,elongation,yield and tensile strengths by 44%,31%,30%,8% and 12%,respectively,except 9% decrease in impact toughness compared to ASTM A 128 Gr.E1 steel without modification.These results show that 1.0C-17Mn-0.05Ti alloy can be used for parts exposed to high load wear and applied in conditions where relatively high tensile properties with sufficent ductility is needed.

激光送丝熔覆高锰钢涂层的显微组织及超声滚压硬化机理

为了维持高锰钢部件优异的形变硬化能力,提出了高锰钢涂层的激光送丝熔覆技术。使用激光送丝熔覆技术在Mn13钢板上制备了高锰钢涂层,并通过超声滚压技术对熔覆层表面进行形变硬化处理。分析了超声滚压前后高锰钢熔覆层的显微组织、相组成和力学性能,揭示了高锰钢熔覆层的超声滚压硬化机理。研究结果表明,激光送丝熔覆高锰钢涂层的显微组织为枝晶结构,且在枝晶间存在Mn、C元素的成分偏析;超声滚压过程中未出现相变,超声滚压后涂层的硬度、耐磨性均大幅提高;初始高锰钢涂层内部存在的C、Mn的枝晶偏析、位错和孪晶在超声滚压过程中严重阻碍了位错的运动,从而增大了位错的密度;由于高锰钢的孪晶诱导塑性变形效应,超声滚压后涂层内部会产生大量的形变孪晶,形变孪晶之间的相互作用进一步增强了高锰钢熔覆层的形变硬化能力。激光送丝熔覆为大型高锰钢部件表面的高性能修复提供了技术基础。

High-temperature Oxidation Behavior of a High Manganese Austenitic Steel Fe–25Mn–3Cr–3Al–0.3C–0.01N

In this paper, a Fe-Mn-Al-C austenitic steel with certain addition of Cr and N alloy was used as experimental material. By using the SETSYS Evolution synchronous differential thermal analysis apparatus, the scanning electron microscope （SEM）, the electron microprobe （EPMA） and the X-ray diffraction （XRD）, the high-temperature oxidation behavior microstructure and the phase compositions of this steel in air at 600-1,000 ℃ for 8 h have been studied. The results show that in the whole oxidation temperature range, there are three distinct stages in the mass gain curves at temperature higher than 800 ℃ and the oxidation process can be divided into two stages at temperature lower than 800 ℃. At the earlier stage the gain rate of the weight oxidized in temperature range of 850 ℃ to 1,000 ℃ are extremely lower. The oxidation products having different surface microstructures and phase compositions were produced in oxidation reaction at different temperatures. The phase compositions of oxide scale formed at 1,000 ℃ are composed of Fe and Mn oxide without Cr. However, protective film of Cr oxide with complicated structure can be formed when the oxidation temperature is lower than 800 ℃.

固溶处理对新型全奥氏体高锰低温钢微观组织、力学性能及摩擦性能的影响

针对新型奥氏体高锰低温钢在LNG (Liquefied natural gas)储罐应用中的磨损问题,本文中研究了不同固溶处理温度对微观组织、力学性能和耐磨性能影响以及三者之间的关联性.将25Mn高锰钢分别在950、1 000、1 050以及1 100℃下固溶处理0.5 h,并采用光学显微镜、白光干涉仪、扫描电子显微镜及能谱仪对试样的微观组织、磨损轮廓和磨痕形貌进行了表征.结果表明:随着固溶处理温度的升高,高锰钢的表面硬度逐渐下降,1 100℃固溶处理后钢材硬度降到最低,约为261 HV.另外,钢材的抗拉强度随固溶温度升高先增大后减小,其中在1 000℃下展现出最优的抗拉强度、屈服强度及应变硬化速率.在摩擦性能测试结果中可以看出,高锰钢表面平均摩擦系数随着固溶处理温度先增大后减小再增大,在1 000℃时因发生氧化摩擦而降到最低,约为0.39,磨损率为0.49‰,表现了最优的耐磨性能.这主要是由于1 000℃热处理后的高锰钢磨痕表面密布颗粒均匀的碳化物,导致磨损后的硬度增大近50.6%,磨损机理从颗粒磨损与疲劳磨损结合转变为黏着磨损为主,颗粒磨损为辅.

Surface effect induced phase transformation by Mn removal during annealing and its textures in cold-rolled high manganese transformation-induced plasticity steel

The surface effect induced transformation texture during vacuum annealing of cold-rolled high manganese transformation-induced plasticity(TRIP)steels was studied.Due to Mn removal occurring at the surface layer,γ→δdiffusional phase transformation leads to the formation of hard pancake-shaped ferrite grains due to solution strengthening at the surface and the centre layer remains as austenite+martensite after annealing.In the case of slow heating,{112}/{111}<110>textures for the surface ferrite were strengthened with the increase in temperature and holding time,indicating an inheritance of rolling textures.By increasing the heating rate of annealing,the rotated cube texture was developed in surface ferrite.This kind of multiphase sandwich structure with hard ferrite surface layer and tough austenite dominant centre can increase tensile strength and should also improve deep drawing properties,therefore providing new possibility of controlling properties for the application of high manganese TRIP steel.

TiN纳米陶瓷对ZGMn13微观组织和力学性能影响

为细化ZGMn13的组织,并提升其使用效果。采用TiN纳米陶瓷作为添加剂,以ZGMn13为基体材料,采用吹氩法制备了添加TiN纳米陶瓷的ZGMn13试样,并对试样进行了固溶处理;使用扫描电子显微镜观察了TiN纳米陶瓷对ZGMn13试样微观组织的影响;使用布氏硬度、冲击和磨粒磨损等试验设备,对试样的力学性能、摩擦磨损性能进行测试与研究。结果表明:通过吹氩法加入的TiN纳米陶瓷对ZGMn13的晶粒起到了明显的细化作用,同时组织中的连续网状碳化物也被明显地分散和隔断。添加TiN纳米陶瓷的ZGMn13试样的冲击吸收能量和硬度均有所提升。在试验条件下,添加TiN纳米陶瓷的ZGMn13试样的磨损量降低21.1%,耐磨性明显提高,摩擦磨损性能得到改善。

焊接工艺对LNG储罐用高锰钢焊接接头组织和性能的影响

为了推动新型国产低温高锰钢及相应焊材在LNG储罐国产化中的应用,利用扫描电子显微镜、光学显微镜并通过常温拉伸、弯曲、低温冲击以及显微硬度等试验,研究了熔化极气体保护焊(GMAW),埋弧焊(SAW)和焊条电弧焊(SMAW)3种不同的焊接工艺对LNG储罐用低温高锰钢焊接接头组织和性能的影响。结果表明,3种焊接工艺的热影响区组织为奥氏体与少量夹杂物颗粒,熔合线附近晶粒粗大且狭长,焊缝组织为柱状晶。硬度最低值均位于焊缝中心,拉伸试验断裂位置均为焊缝部位。3种焊接工艺焊接接头抗拉强度分别为839.2,863.8,675.2 MPa,拉伸和弯曲性能均能满足要求。-196℃时的焊缝冲击吸收能量值分别为123,100,83.7 J,冲击断口均为韧性断裂。在焊接低温高锰钢时应严格控制热输入,从而保证低温高锰钢的焊接质量。

高锰钢显微组织的显示方法

介绍了两种锰元素含量不同的高锰钢显微组织显示方法。采用草酸+硝酸+偏重亚硫酸钠+无水乙醇溶液作为腐蚀液,在室温下对锰元素质量分数为11%~14%的耐磨高锰钢进行腐蚀,可获得清晰完整、色彩艳丽的显微组织形貌;采用硝酸+无水乙醇溶液和盐酸+无水乙醇溶液复合的方法对锰元素质量分数为22%~28%的超低温环境用高锰钢进行腐蚀,可获得清晰的显微组织形貌。

高锰钢在模拟海洋环境中的应力腐蚀行为

以低温高锰钢为研究对象,采用光学显微镜、扫描电镜、透射电镜、X射线能谱分析仪等设备对高锰钢进行微观观察,采用恒载荷应力腐蚀试验研究其在人工海水溶液中的应力腐蚀行为,采用电化学手段测试其腐蚀性能。结果表明:低温高锰钢晶粒度大小不一,显微组织主要为形变奥氏体,试样内存在位错及孪晶,晶界上未见明显析出物;在低温高锰钢的使用过程中,其缺陷部位优先发生腐蚀,在恒定应力条件下,材料表面局部生成微裂纹,且扩展速率较慢,材料对应力腐蚀不敏感;当应力发生变化时,试样中微裂纹与应力的平衡被打破,加速了裂纹的扩展和新微裂纹的萌生,材料在腐蚀环境下易发生应力腐蚀开裂。

变质处理对超高锰钢铸态和热处理组织的影响

通过显微组织观察、成分分析和热力学计算，研究了变质处理对超高锰钢铸态和热处理组织的影响。结果表明，变质处理可使铸态组织中的奥氏体晶粒明显细化，晶界碳化物的网状特征消失；使热处理组织中的夹杂物球化，碳化物细化，且分布更加均匀弥散；超高锰钢凝固时的形核次序为ＣａＳ（ＣｅＳ）→ＴｉＣ→Ｆｅ３Ｃ（奥氏体），它们可通过两次匹配异质形核的方式提高形核率，增强变质效果。

高锰钢衬板的研究及应用

综述了国内外高锰钢衬板的研究开发和应用现状。近年来对高锰钢衬板的研究主要包括合金化、热处理和表面预硬化处理等。分类介绍了改性高锰钢、超高锰钢和爆炸硬化处理高锰钢在衬板方面的应用,并分析今后高锰钢衬板的发展方向:减少贵重金属的使用,降低衬板成本;添加铝元素,降低衬板密度和生产能耗。

稀土变质处理及合金化对高锰钢组织结构的影响

对高锰钢进行稀土变质处理 ,并加入 5%Cr ,有效改变了析出碳化物的形态 ,获得了以M2 3C6为主 ,弥散分布的颗粒状碳化物。通过组织、结构及微区成分分析 。