热处理工艺对100mm特厚07MnCrMoVR水电钢板组织性能的影响

对07MnCrMoR水电钢板的淬透性曲线进行了测定,利用淬火机和热处理炉对100 mm厚试验钢板进行了淬火和回火试验,并对试验钢进行了组织观察和力学性能测定。结果表明,随着试验钢距水冷端的距离增大,淬火组织由马氏体转变为粒状贝氏体,距离端部50 mm处转变为铁素体和粒状贝氏体的混合组织。试验钢板利用淬火机淬火后得到板条贝氏体+粒状贝氏体+先共析铁素体,回火后转变为铁素体+粒状贝氏体,同时大量的碳化物在铁素体基体和晶界处析出。试验钢最合理的热处理工艺为930℃ 30min水冷淬火,660℃ 60min空冷回火。     

卷取机夹送辊表面堆焊层组织性能研究

采用埋弧堆焊工艺在Q235B表面堆焊8-10mm的Cr8系列新型熔覆材料,测定其耐磨性和硬度变化,分析熔覆金属的组织形貌和高温工况下的合金元素扩散。研究结果表明,熔覆金属打底层主要是以铁素体为主,伴随着少量的贝氏体。盖面层的焊态组织主要为马氏体和残余奥氏体,伴有少量的回火马氏体,同时在枝晶马氏体间可见少量较小的碳化物。经550℃回火后其盖面层组织为回火马氏体和残余奥氏体,碳化物析出相均布较焊态呈增多趋势。焊态硬度值为530-580HV300,回火后硬度值为720-830HV300,磨损失重是45#淬火钢的0.31倍。在使用3个月后发现在熔覆层表面出现了元素偏移并形成了由Cr2O3、WO等组成的氧化膜,降低了夹送辊的粘钢倾向,提高使用寿命。     

38CrMoAl钢表面超细贝氏体组织的研究

研究了38CrMoAl钢表面获得超细贝氏体组织的热处理工艺及其组织结构特征。首先利用自行设计的滴注式可控气氛全自动渗碳炉,在930℃对该钢渗碳8h,使钢表面的碳的质量分数达到0．85％,渗层深度为2mm。将经过渗碳热处理的试样加热到930℃保温20min进行奥氏体化处理。然后直接淬入温度分别为230、255和280℃的...     

Selection of Heat Treatment Process and Wear Mechanism of High Wear Resistant Cast Hot-Forging Die Steel

 Dry sliding wear tests of a Cr-Mo-V cast hot-forging die steel was carried out within a load range of 50-300 N at 400 ℃ by a pin-on-disc high-temperature wear machine. The effect of heat treatment process on wear resistance was systematically studied in order to select heat treatment processes of the steel with high wear resistance. The morphology, structure and composition were analyzed using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS); wear mechanism was also discussed. Tribo-oxide layer was found to form on worn surfaces to reduce wear under low loads, but appear inside the matrix to increase wear under high loads. The tribo-oxides were mainly consisted of Fe3O4 and Fe2O3, FeO only appeared under a high load. Oxidative mild wear, transition of mild-severe wear in oxidative wear and extrusive wear took turns to operate with increasing the load. The wear resistance strongly depended on the selection of heat treatment processes or microstructures. It was found that bainite presented a better wear resistance than martensite plus bainite duplex structure, martensite structure was of the poorest wear resistance. The wear resistance increased with increasing austenizing temperature in the range of 920 to 1120 ℃, then decreased at up to 1220 ℃. As for tempering temperature and microstructure, the wear resistance increased in following order: 700 ℃ (tempered sorbite), 200 ℃ (tempered martensite), 440 to 650 ℃ (tempered troostite). An appropriate combination of hardness, toughness, microstructural thermal stability was required for a good wear resistance in high-temperature wear. The optimized heat treatment process was suggested for the cast hot-forging steel to be austenized at 1020 to 1120 ℃, quenched in oil, then tempered at 440 to 650 ℃ for 2 h.     

Low Cost High Performance Steel Plate With Superior HAZ Toughness for Large Heat Input Welding

In this paper, a laboratory study has been made to develop low cost high performance steel plates with superior HAZ toughness for large heat input welding. Simulated results show that the absorbed impact energy of heat-affected zone (HAZ) at -20℃reaches above 200J when large heat inputs of 100 to 400kJ/cm were applied, suggestive of superior HAZ toughness for large heat input welding of developed steel plate. The microstructures in HAZ are transformed from mainly fine ferrite and bainite at 100kJ/cm, through an intermediate stage of ferrite, bainite and pearlite at 200 and 300kJ/cm, to nearly fine ferrite and pearlite at 400kJ/cm. The prior austenite grain size and ferrite grain size in HAZ are controlled to ～50 and ～20μm, respectively. The high HAZ toughness is due to the inhibition of prior austenite grain size at high temperatures and the formation of beneficial microstructures to HAZ toughness during continuous cooling.     

�ȴ����ն�����ģ�߸�P20��ʴ��Ϊ��Ӱ��

Effect of heat treatment process on corrosion performance of plastic die steel P20 and mechanism for corrosion were studied by electrochemical test, electrochemical impedance spectrum test, weight loss test, neutral salt spray test, SEM, EDS and XRD. It is found that the steels with bainite/martensite quenched at 860?? by air cooling or martensite quenched at 860?? by oil cooling have better corrosion resistance than the steel with ferritic/martensitic quenched at 785?? by oil cooling. After the samples with bainite/martensite or martensite are tempered at 450 and 620?? respectively, martensite and bainite decompose and a lot of carbides precipitate, leading to a poor corrosion resistance. After electrochemical test, the outer layer of corrosion product on the surface of the samples is loose FeOOH and the inner layer is relatively dense Fe3O4. The anode reaction is mainly dissolution of Fe and the cathode reaction is generation of hydrogen. Pitting mainly occurs around inclusions in NaCl solution of 0. 5mol/L.     

Microstructure and Mechanical Properties of Martensitic Stainless Steel 6Crl5MoV

 Martensitic stainless steel containing Cr of 12% to 18% (mass percent) are common utilized in quenching and tempering processes for knife and cutlery steel. The properties obtained in these materials are significantly influenced by matrix composition after heat treatment, especially as Cr and C content. Comprehensive considered the hardness and corrosion resistance, a new type martensitic stainless steel 6Cr15MoV has been developed. The effect of heat treatment processes on microstructure and mechanical properties of 6Cr15MoV martensitic stainless steel is emphatically researched. Thermo-Calc software has been carried out to thermodynamic calculation; OM, SEM and TEM have been carried out to microstructure observation; hardness and impact toughness test have been carried out to evaluate the mechanical properties. Results show that the equilibrium carbide in 6Cr15MoV steel is M23C6 carbide, and the M23C6 carbides finely distributed in annealed microstructure. 6Cr15MoV martensitic stainless steel has a wider quenching temperature range, the hardness value of steel 6Cr15MoV can reach to HRC 608 to HRC 616 when quenched at 1060 to 1100 ℃. Finely distributed carbides will exist in quenched microstructure, and effectively inhabit the growth of austenite grain. With the increasing of quenching temperature, the volume fraction of undissolved carbides will decrease. The excellent comprehensive mechanical properties can be obtained by quenched at 1060 to 1100 ℃ with tempered at 100 to 150 ℃, and it is mainly due to the high carbon martensite and fine grain size. At these temperature ranges, the hardness will retain about HRC 592 to HRC 616 and the Charpy U-notch impact toughness will retain about 173 to 20 J. A lot of M23C6 carbides precipitated from martensite matrix, at the same time along the boundaries of martensite lathes which leading to the decrease of impact toughness when tempered at 500 to 540 ℃. The M3C precipitants also existed in the martensite matrix of test steel after tempered at 500 ℃, and the mean size of M3C precipitates is bigger than that of M23C6 precipitates.     

W9Mo3Cr4V/45钢复合轧辊的液 固结合界面

 采用重力铸造液 固结合的方法对高速钢复合轧辊结合界面进行了研究,并对切取的小试样进行了完全退火、高温焠火+3次550 ℃×1 h回火处理。利用金相显微镜、扫描电镜、能谱分析、X射线衍射仪以及显微硬度计对试样进行了金相组织观察、结合面附近合金成分线扫描、组织成分能谱分析、显微硬度测试和X射线衍射相分析。结果表明：在辊芯45号钢表面电磁感应预热到1 270~1 300 ℃,外层W9Mo3Cr4V高速钢钢液浇铸温度为1 550~1 600 ℃的情况下,两者之间以熔合扩散方式形成了牢固的冶金结合;在铸态下结合界面宽度为40~50 μm,碳及合金元素明显向45号钢侧扩散,通过退火及淬回火处理后,高速钢中的碳及合金元素向45号钢侧进一步扩散,结合界面宽度扩大了100 μm左右,45号钢侧得到细片状索氏体组织,高速钢侧为回火马氏体+残余奥氏体+碳化物组织。     

Microstructure of welded and weld-simulated 3Cr-1.5Mo-0.1V ferritic steel

Ferritic steels are often used in thick-plate form. The feasibility of electron-beam welding such thick plates and the mechanical properties of these welds were examined in a recent study. In this investigation, the microstructures of these thick-plate, electron-beam welds were evaluated. The study was carried out on a 3Cr-1.5Mo-0.1V steel. Weld simulations were used to aid in the study of the heat-affected zone (HAZ) microstructure. Such simulations allowed for a more reliable and detailed evaluation of the variation in microstructure with distance from the fusion line. The structures were related to microhardness measurements made across the width of the weld and the HAZ. The fusion zone and the immediately adjacent HAZ consisted of bainite platelets with narrow films of retained austenite at many of the bainite platelet boundaries. Farther away from the fusion zone, the structure was a two-phase mixture of bainitic platelets and ferrite produced by heating base metal between theAc ₁ and theAc ₃ temperatures. Still farther from the weld, the structure consisted of tempered bainite, with the degree of tempering decreasing with distance from the fusion line. The bainite plus ferrite region and the tempered bainite section are associated with a soft zone in the hardness profile across the weld. A postweld heat treatment (PWHT) was found to reduce the hardnesses of the fusion zone, HAZ, and base material to relatively uniform levels. The structure across the weld and HAZ after a PWHT is tempered bainite except in one section of the HAZ in which tempered bainite and ferrite coexist.     

In-situ Corrosion Characterization of API X80 Steel and Its Corresponding HAZ Microstructures in an Acidic Environment

During heat treatment processing,microstructures of heat affected zone(HAZ)were formed in X80 pipeline steel.After observation by optical microscopy,scanning electron microscopy and transmission electron microscopy,microstructure of the as-received X80 steel was confirmed to be acicular ferrite,while the microstructures of quenched,normalized and annealed X80 steels were lath bainite,granular ferrite and quasi-polygonal ferrite,respectively.After immersion in the simulated acidic soil solution for 48 h,corrosion rates of these four steels were determined by mass loss measurements and corrosion products were examined by Raman spectroscopy and X-ray photoelectron spectroscopy.Scanning vibrating electrode technique was used to characterize the micro-galvanic corrosion behaviors of the synthetic bimetallic electrodes which were formed by coupling each of the simulated HAZ microstructures with the as-received steel in direct physical and electric contact.It is demonstrated that the as-received steel acts as cathode in the as-received/quenched and as-received/normalized couples,while the annealed steel acts as cathode when coupling with the as-received steel.The distinction of current density between the galvanic couples reduces with prolonging the immersion time.     

组织形态对718塑料模具钢切削性能的影响

通过热处理制备出具有回火马氏体组织、下贝氏体组织以及粒状贝氏体组织的718钢,利用光学显微镜、扫描电子显微镜、X射线衍射仪、万能拉伸实验机比较其显微组织及力学性能。同时借助高速铣削实验及光学轮廓仪,研究力学性能以及组织结构对切削性能的影响。结果表明,当切削速度低于145 m·min?1时,贝氏体组织类型比回火马氏体组织更易切削,切削贝氏体组织比切削回火马氏体组织的刀具使用寿命高30%～40%。当切削速度高于165 m·min?1时,马氏体组织发生了加工软化现象,刀具使用寿命提高,切削性能上升。粒状贝氏体组织加工表面因为严重的刀具黏附而出现背脊纹路,马氏体组织具有最佳的切削表面粗糙度。综合考虑之下,三种组织的综合切削性能从高到低排序为:下贝氏体组织、马氏体组织、粒状贝氏体组织,采用300 ℃等温淬火工艺可以有效提升718塑料模具钢的综合切削性能。      

Q690q耐候桥梁钢免预热焊接热影响区的组织性能

针对Q690q耐候桥梁钢,利用MMS-300热模拟试验机进行焊接热循环过程模拟试验,研究了10.5～114.9 kJ/cm热输入下粗晶热影响区(CGHAZ)、细晶热影响区(FGHAZ)和不完全相变热影响区(ICHAZ)的微观组织以及冲击韧性、硬度的变化情况,并观察了冲击断口形貌,然后采用优选的焊接热输入,进行了免预热的药芯焊丝熔化极气体保护焊(FCAW)和埋弧焊(SAW)的焊接工艺评定试验。结果表明,热输入较低时,CGHAZ和FGHAZ主要生成板条马氏体组织、ICHAZ出现岛状的M/A组元,其冲击韧性低、硬度高;热输入较高时,CGHAZ主要生成大尺寸的粒状贝氏体、准上贝氏体或上贝氏体组织,同时大尺寸的块状M/A组元数量不断增加、尺寸变大,其冲击韧性显著降低。FGHAZ生成较多多边形或准多边形铁素体、珠光体等高温转变组织,其硬度降低明显。ICHAZ除生成准多边形铁素体、无碳化物贝氏体和退化珠光体外,回火索氏体基体组织中的碳化物颗粒尺寸不断变大,其强韧性不断降低;热输入为18.2～25.7 kJ/cm时,CGHAZ以板条束细小且异向的板条贝氏体为主、FGHAZ形成细小均匀的板条贝氏体和粒状...     

Effect of Strengthening Phase on Deformation Behaviour during Uniaxial Tension of Hot-rolled Dual Phase Steel

Two kinds of C-Si-Mn-Cr series tested steels were designed to obtain dual phase microstructures of ferrite （F） ＋martcnsite （M） or ferrite （F）-bainite （B） with different mechanical properties. Effects of strengthening phase on yielding and fracture behaviours during uniaxial tension of dual phase steel were discussed. Compared with hot-rolled martensite dual phase steel, ferrite-bainite dual phase steel has high ratio of yield strength to tensile strength （YS/TS） and low elongation. During necking process of uniaxial tension, microvoids of ferrite-martensite steel are generated by fracture of ferrite/martensite boundary or martensite islands with irregular shape. But ferrite matrix elongated remarkably along deformation direction, and strengthening phase also coordinated with ferrite matrix. Compatible de formation between ferrite and bainite is distinct. Ferrite-bainite dual phase steel has fine and less microvoid, and phase boundary of ferrite and bainite is beneficial for restraining generation and extending of microvoid.     

Effect of Microstructure on Hydrogen Induced Cracking Behavior of a High Deformability Pipeline Steel

The hydrogen induced cracking(HIC) behavior of a high deformability pipeline steel was investigated with three different dual-phase microstructures,ferrite and bainite(F+B),ferrite and martensite/austenite islands(F+M/A) and ferrite and martensite(F+M),respectively.The HIC test was conducted in hydrogen sulfide(H2S)-saturated solution.The results showed that the steels with F+B and F+M/A dual-phase microstructures had both higher deformability and better HIC resistance,whereas the harder martensite phase in F+M microstructure was responsible for the worst HIC resistance.The band-like hard phase in dual-phase microstructure was believed to lead to increasing susceptibility to HIC.     

Effect of Heat Treatment on Microstructure and Property of Cr13 Super Martensitic Stainless Steel

 The microstructures and mechanical properties of Cr13 super martensitic stainless steel after different heat treatments were studied. The results show that the structures of the steel after quenching are of lath martensite mixed with a small amount of retained austenite. With the raising quenching temperature, the original austenite grain size increases and the lath martensite gradually becomes thicker. The structures of the tempered steel are mixtures of tempered martensite and reversed austenite dispersed in the martensite matrix. The amount of reversed austenite is from 754% to 2249%. After different heat treatments, the tensile strength, the elongation and the HRC hardness of the steel are in the range of 813-1070 MPa, 101%-212% and 2133-3237, respectively. The steel displays the best comprehensive mechanical properties after the sample is quenched at 1050 ℃ followed by tempering at 650 ℃.     

Si-Mn系超高强度热成形淬火钢板的点焊性能

 采用不同的点焊工艺参数对研发的1700MPa级Si-Mn系热成形淬火钢板与低碳钢板DC04进行异种材料之间点焊,并对焊接接头的拉伸性能、显微硬度分布及微观组织特征等进行了分析。结果表明,焊接电流对点焊接头熔核直径和抗剪强度具有显著的影响,而焊接时间的影响相对较小。超高强度钢板侧的热影响区存在两个明显的软化区和硬化区,即在靠近母材处存在一个硬度明显低于母材的软化区,其组织为回火马氏体;在靠近熔核处存在一个硬度明显高于母材的硬化区,其组织为细小的马氏体。点焊接头熔核部位为柱状粗大马氏体组织,其硬度明显低于超高强度钢板母材且远高于低碳钢板母材。低碳钢板热影响区低的硬度和明显粗化的铁素体组织,使得点焊接头单向拉伸时均从低碳钢板的热影响区一侧破断。     

Microstructure,Composition, and Impact Toughness Across the Fusion Line of High-Strength Bainitic Steel Weldments

This paper analyzed the evolution of microstructure, composition, and impact toughness across the fusion line of high-strength bainitic steel weldments with different heat inputs. The main purpose was to develop a convenient method to evaluate the HAZ toughness quickly. The compositions of HAZ were insensitive to higher contents of alloy elements (e.g., Ni, Mo) in the weld metal because their diffusion distance is very short into the HAZ. The weld metal contained predominantly acicular ferrite at any a heat input, whereas the main microstructures in the HAZ changed from lath martensite/bainite to upper bainite with the increasing heat input. The evolution of HAZ toughness in relation to microstructural changes can be revealed clearly combined with the impact load curve and fracture morphology, although the results of impact tests do not show an obvious change with heat input because the position of Charpy V notch contains the weld metal, HAZ as well as a part of base metal. As a result, based on the bead-on-plate welding tests, the welding parameter affecting the HAZ toughness can be evaluated rapidly.     

Short‐term Creep Behavior of an X 37 Cr Mo V 5‐1 Hot‐work Tool Steel with almost Bainitic and fully Martensitic Microstructures

In this study two different heat treatments were conducted on an X 37 Cr Mo V 5‐1 hot‐work tool steel, resulting either in a tempered fully martensitic matrix or a matrix almost consisting of tempered bainite. Short‐term creep tests were performed at a high stress level of 800 MPa and at temperatures in the range from 450 °C to 500 °C. Creep specimens consisting of a tempered fully martensitic microstructure exhibited a three times longer creep‐to‐rupture time, than those consisting of a tempered almost bainitic microstructure. Microstructural investigations of creep specimens were performed by transmission electron microscopy. Results of these investigations revealed that due to a lower cooling rate, which is necessary to form bainite, the tempered bainitic microstructure consists of large former bainitic plates, whereas tempered martensite shows fine former martensitic laths. Tempered bainite also exhibits a higher number density of large M₃C, M₇C₃ and MC carbides than tempered martensite. Small M₂C carbides appear in both microstructures in the same quantity, however, nanometer‐sized MC carbides could only be found in tempered martensite. Thus poor short‐term creep behavior of the tempered almost bainitic microstructure can be explained by the lesser amount of strengthening relevant precipitates, a smaller size‐effect due to distance of bainitic interfaces as well as lower solid solution hardening.     

Use of the nanoindentation technique for studying microstructure/crack interactions in the fatigue of 4340 steel

The objectives of this research are to study the influence of microstructure on the fatigue crack growth behavior in 4340 steel and to explore the application of the nanoindentation technique for determining the plastic deformation zone at a fatigue crack tip. Two heat treatment conditions were chosen for the steel: annealed and quenched plus tempered. The annealed steel consists of coarse pearlite and proeutectoid ferrite, while the quenched and tempered steel consists of fine tempered martensite. Fatigue crack propagation tests were conducted on disklike compact (DCT) specimens. Subsequently, the nanoindentation technique was applied to quantitatively determine the plastic deformation zone at fatigue crack tips. The plastic deformation zone size determined by the nanoindentation test seems larger than the cyclic deformation zone calculated using the fracture mechanics equation, which involves many assumptions. The fatigue crack growth test results show that the annealed steel has a higher resistance to crack growth than the quenched and tempered steel. The fatigue crack in the annealed steel tends to grow along pearlite domain boundaries, or the cementite/ferrite interfaces within a pearlite domain. In contrast, the fatigue crack in the quenched and tempered steel tends to traverse the fine martensite laths. Consequently, the actual crack path in the annealed steel is rougher than in the quenched and tempered steel and more secondary cracks are observed in the annealed steel.     

淬火-配分马氏体钢的组织特征

淬火-配分(Quenching and Partitioning,简称QP)工艺是针对马氏体钢提出的热处理新工艺。利用QP工艺处理40Si2Ni2钢,并通过扫描电镜观察其微观组织特征。结果表明,与传统淬火+回火工艺得到的组织不同,QP组织为低碳(回火态)和高碳马氏体(淬火态)共存,其中高碳马氏体呈现为有规则几何形状、边界清晰、无析出物析出的块状组织,淬火温度(QT)对高碳马氏体(淬火态)量有影响。