热形变和钒微合金化对高碳钢组织转变的影响

通过在Gleeble1500热模拟试验机上的热形变和冷却试验,研究了热形变及钒微合金化对高碳钢连续冷却后显微组织及硬度的影响。研究结果表明：未形变的含钒试验钢在5和9℃/s冷速下出现了中低温组织贝氏体和马氏体,950℃变形后的含钒钢,在同样冷速下相变后得到的组织全为珠光体。随钒含量的增加,珠光体转变后的片层间距变小,硬...     

低合金高强钢形变奥氏体相变行为及其模型

 为了研究低合金高强钢的形变奥氏体连续冷却转变行为及组织变化规律,利用Gleeble-3800热力模拟试验机对试验钢进行了多道次轧制工艺模拟试验,并根据试验所得相变温度和各冷却速度下的室温组织相对量,回归出相变模型。结果表明,试验钢在变形后的连续冷却过程中发生铁素体、珠光体、贝氏体和马氏体转变,基于对各转变的温度和组织相对量得到的相变模型分析,证实了模型的可靠性。     

钒微合金化低碳贝氏体钢的连续冷却相变特性

 采用热膨胀法测定6种不同成分低碳贝氏体钢的连续冷却转变(CCT)曲线。CCT曲线表明,加入微量硼能使含钒低碳贝氏体钢在大于03℃/s的冷速下获得贝氏体组织,而V-N微合金化的低碳贝氏体获得全贝氏体的临界冷速要高于V-B钢,且贝氏体转变的开始温度也要较V-B钢高20℃左右。在含钒、氮低碳贝氏体钢中加入钼、铬将会促进钢的贝氏体相变,但钼的作用要优于铬;钼、铬的加入可使含钒、氮低碳贝氏体钢的贝氏体转变温度降低至少30℃,且贝氏体组织得到了细化,钢的维氏硬度也提高了HV10~30。     

硅质量分数对CSP生产DP600相变规律及工艺的影响

基于C Si Mn Cr Mo系600 MPa级热轧双相钢的组分,设计了不同硅质量分数(0.55%和1.17%)的两种试验钢。采用Gleeble 3500热模拟试验机测定了两种试验钢的连续冷却转变曲线,分析了硅质量分数对试验钢连续冷却过程中组织转变的影响,并研究了硅质量分数对短流程生产中温卷取型热轧双相钢生产工艺的影响。结果表明,相对于w(Si)=1.17%,w(Si)=0.55%使铁素体开始转变温度降低40~50 ℃,明显缩短了铁素体转变的孕育期,并增加了铁素体的体积分数。在CSP线上生产时,低硅钢的终轧温度可控制为820~830 ℃,低的终轧温度使铁素体相变时间增加2.2 s左右,铁素体转变量增加,且后续相变过程中可避免非马氏体组织的出现。因此,低硅钢适合在CSP短流程线上生产中温卷取型热轧双相钢。     

含钒超级贝氏体钢组织和性能研究

设计并在实验室冶炼了一种低碳、低合金含量的新型含钒贝氏体钢,在Gleebe - 1500热模拟实验机上进行模拟空冷相变实验,根据冷却过程中的热膨胀曲线和冷却后的金相组织,确定出贝氏体转变温度区间.在此基础上,选择不同的热处理温度对实验钢进行等温处理,检验热处理后的组织,根据不同温度热处理后的组织和贝氏体转变温度区间,在...     

980MPa级复相钢热处理工艺优化及组织性能研究

利用Gleeble-3500热模拟试验机、光学显微镜研究了热处理工艺对980MPa级复相钢显微组织和力学性能的影响。结果显示:钢的显微组织为贝氏体、铁素体及马氏体三相,且加热温度越高,贝氏体及马氏体硬相组织越多,铁素体含量越少,组织均匀性显著提高。钢的屈服强度也随加热温度的提高而逐渐增高,但抗拉强度保持不变。随着缓冷温度的降低,钢中贝氏体及马氏体组织减少,铁素体含量增加,同时力学性能降低。相变-位移曲线显示加热过程中试验钢在730°C左右开始发生奥氏体相变,在860°C左右完成全奥氏体化。在降温过程中试验钢在456°C左右进行贝氏体相变,在244°C至165°C较宽的温度范围内进行马氏体相变,且均热温度越高,贝氏体相变量越大,马氏体量越少。     

17MnNiVNbR钢的连续冷却转变行为研究

利用Formastor-FII型膨胀仪和Gleeble-3800热模拟试验机,结合显微组织观察和硬度测试,研究了压力容器用钢17MnNiVNbR的静态和动态连续冷却转变行为,并分析了热变形对相变行为的影响。实验结果表明:冷却速率较低时,17MnNiVNbR钢的相变组织为先共析铁素体和珠光体;随着冷却速率的增加,依次出现贝氏体和马氏体。热变形能提高铁素体、珠光体和贝氏体的相变温度,并使连续冷却转变曲线向左上方移动。     

Q345E钢冷却过程中相变的研究

通过模拟试验,测定了Q345E钢的CCT图,确定了不同冷却条件下钢中相变的开始点和终了点,研究了变形量对转变开始点的影响,发现高于再结晶温度时转变开始温度随着变形量的增加而升高,这是变形诱导相变影响的结果。文中还用CCT图曲线对现场冷却过程的相变进行了模拟分析。     

变形温度对45#精冲钢组织演变的影响

利用热模拟单道次压缩实验研究了45#钢在不同温度变形过程中微观组织的演变规律。通过对变形过程中组织形貌的观察和应力-应变曲线的分析，讨论了变形过程中的相变行为和软化过程。结果显示，实验钢在热变形过程发生铁素体(DIF)和珠光体(DIP)两种形变诱导相变，Ar3温度以上变形时，主要发生形变诱导铁素体相变，伴随少量珠光体生成，并且随着变形温度的降低铁素体增加，珠光体略微降低；Ar3温度以下变形时，形变诱导珠光体逐渐取代铁素体，且随温度的变化趋势相反。低温变形时，形变诱导相变是软化的主要原因，高温变形时主要发生动态再结晶，导致软化，并且动态再结晶的软化作用要比形变诱导相变的好。     

过共析钢线材组织与性能的控制

采用热／力物理模拟和微观分析相结合的方法研究了过共析钢在连续冷却过程中的固态相变和热加工工艺对钢的组织性能影响。结果表明：降低变形温度引起相变温度升高：加快冷却速度,使得相变温度下降;提高变形温度有利于增加抗拉强度,但断面收缩率下降。试验结果用于生产过程优化和控制,使线材的合格率达到95％以上。     

Experimental Research of Vanadium-Microalloyed X100 Pipeline Steels

In order to develop X100 pipeline steels with high strength and low temperature toughness,the steel bearing vanadium has been studied in the laboratory.The continuous cooling phase transformation behavior of the steel under deforming condition was investigated.The microstructure of the steel at different cooling rates was observed by microscope.Finally,by proper producing processes,the X100 pipeline steel was developed successfully in lab.The composition,processes,microstructure and properties have been analyzed and discussed.Experimental research results showed that the strength of X100 steel can be improved by reducing the cooling stop temperature.The tempering treatment after TMCP can improve the strength of vanadium-microalloyed X100 steel too,without change of the impact toughness.     

钒对耐火钢显微组织及高温性能的影响

 通常采用控轧控冷方式生产耐火钢Mo-Nb复合合金化。采用电子显微镜、相分析和三维原子探针等方法,研究了不同热轧工艺条件下钒对含钒耐火钢的室温和600 ℃拉伸性能的影响,探讨了微观组织与力学性能之间的关系。结果表明,添加钒后能形成细小弥散分布的析出物,配合控制贝氏体比例后能有效地提高室温和高温力学性能;钒在热轧态耐火钢中主要固溶于先共析铁素体内,再加热至600 ℃时热轧态被“隐藏”的钒存在明显的析出,进一步提高了含钒耐火钢的高温性能。     

Effect of Microalloying Additions on the Microstructure and Mechanical Properties of Low Carbon Steel

Low carbon steels are characterized by good weldability,formability and fracture toughness properties.However,the low strength levels of these steel grades limit their wide applications.On the other hand,increasing the strength by increasing the carbon content and alloying elements deteriorates the other properties.In this study,the microalloying technique was used to examine the possibility of attaining low carbon steels with good combination of strength,ductility and impact properties.A low carbon steel microalloyed with single addition of vanadium and another one microalloyed with combined addition of vanadium and titanium were used in this investigation and their properties were compared with non-microalloyed low carbon steel having the same base composition.Furthermore,other two nonmicroalloyed and V-microalloyed steels with higher carbon,silicon and manganese contents were also investigated to reveal the effect of base composition.Tensile,hardness,room and zero temperature Charpy V-notch impact tests were conducted to evaluate the variations in the mechanical properties of low carbon hot forged steel containing vanadium and combinations of vanadium and titanium.In addition,the microstructures of the different investigated steels were observed using both optical microscope and scanning electron microscope.Furthermore,the hardness of the ferrite phase was also determined using micro-hardness technique.The results showed improvement of the mechanical properties of the investigated steels by both single V-and combined V + Ti-microadditions.Tensile,hardness and impact tests results indicated that good combinations of strength,ductility and impact properties can be achieved by V-microalloying addition.Steel with combination of V and Ti microaddition has much higher hardness,yield strength,ultimate tensile strength and impact energy at both room and zero temperatures compared with non-microalloyed and single Vmicroalloyed steels.Higher C,Si and Mn contents result in increasing the strength accompanied with decrea     

快冷条件下钒对中低氮钢晶粒尺寸的影响

通过实验室轧制试验,研究了中低氮含钒钢在轧后快速冷却条件下的铁素体晶粒尺寸和屈服强度的变化规律.结果表明,加入钒能够细化铁素体晶粒,原因是在快速冷却条件下中低氮含钒钢中的钒全部固溶在基体中,固溶的钒降低铁素体的实际相变温度,从而细化了铁素体晶粒.     

Properties and application of TRIP‐steel in sheet metal forming

A further development of dual‐phase‐steels are represented by TRIP (transformation induced plasticity) ‐steels. TRIP‐steels contain austenite, which is metastable at room temperature. It transforms to martensite during straining (TRIP effect). This process improves the strength‐ductility balance of these steels. Two types of TRIP‐steels, low alloyed (L‐TRIP) and high alloyed (H‐TRIP), can be applied in sheet forming processes and exhibit different forming characteristics. Basing on results of uniaxial tensile tests and the evaluation of Young's modulus the forming limits in deep drawing processes and the component properties of deep drawn parts are discussed. The Young's modulus decreases significantly with increasing pre‐strain, especially demonstrated for the L‐TRIP material TRIP700. Forming limit curves determined at different forming temperatures indicate its influence on the forming limits. Martensite transformation is suppressed at a temperature of approximately T = 200 °C and therefore the major strain ?₁ decreases significantly. For the investigated stainless steel AISI304 (H‐TRIP) different lubricant types in comparison to chlorinated paraffins have been tested. Lubricants consisting of sulphur additives led to good forming conditions in forming processes, even better than lubricants based on chlorinated paraffins. The evaluation of component properties, compared between L‐TRIP and H‐TRIP, was done based on the analysis of springback and dent resistance. The L‐TRIP material TRIP700 shows higher springback angles than AISI304 resulting from higher yield strength and decreased Young's modulus, resulting from the forming process. The dent resistance of TRIP‐steel was exemplarily demonstrated for AISI304. Uniaxial pre‐strained sheet specimen were analysed to show the dent resistance depending on dent depth. During elastic denting pre‐strain has no influence on dent resistance. Further increasing dent depth lead to increased dent forces for pre‐strained specimens.     

The effect of heat treatment on the properties and structure of molybdenum and vanadium dual-phase steels

A systematic study was made of the effect of the heat treating parameters,(i.e., temperature, time, and cooling rate) on the properties and structure of molybdenum and vanadium bearing dual-phase steels. The volume percent martensite was found to be the major structural factor that controls the strength and ductility of these steels. The relationship between strength and ductility was independent of alloy addition for the alloys studied. Annealing temperature was shown to be very important in these alloys, especially at high quench rates. The molybdenum alloy exhibited better hardenability than the vanadium alloy for equivalent heat treating conditions. Therefore, for a given set of annealing conditions the molybdenum alloy generally had the highest tensile strength and lowest total elongation. A minimum in the 0.2 pct yield strength was found at a specific volume fraction martensite. The increase in yield strength at the lowest volume fraction studied can be related to a jog or discontinuity in the stress-strain curve during tensile testing. This jog was found to be the result of the lack of a sufficient amount of free dislocations. The causes of this deficiency of the dislocations may be: 1) an insufficient amount of transformed martensite, 2) a large martensite interparticle spacing, 3) dynamic recovery of dislocations during cooling, and 4) pinning of dislocations by precipitates during cooling.     

Effect of copper on microstructure and strength and ductility of low alloy wear resistance steel

The effect of copper on the microstructure and strength and ductility of low alloy wear resistance steels without copper and copper bearing was studied. The CCT curve was calculated by JmatPro software. The microstructure was analyzed by OM and TEM and the mechanical properties and ductility were tested by universal tensile testing machine and impact testing machine. The results show that the element of copper increases the stability of austenite and the transformation of ferrite and pearlite is postponed for the copper bearing steel. The microstructure is composed of matensite and lower bainite for the experimental steels and the content of martensite of the steel bearing copper is higher than the steel without copper. There are nano- size precipitations of (Nb,Ti)C and (Nb,Ti,Mo)C in the matrix of the two steels. The yield strength and the impact energy at -60?? of the steel with 0. 49 mass% copper is higher than that of the steel without copper. The element of copper is benefit to improve strength and low temperature ductility for the low alloy resistant steel.     

合金元素对机械合金化和放电等离子烧结Ti-Nb基合金显微组织的影响

β-Ti型结构的钛基材料在生物材料领域具有广泛的应用前景。本文采用机械合金化法和放电等离子烧结制备β-Ti型Ti-Nb基合金,研究不同Nb,Fe含量对合金显微组织及力学性能的影响。利用扫描电镜(SEM)、X射线衍射仪(XRD)和透射电镜(TEM)等手段分析合金的显微组织变化情况。结果表明:机械合金化过程中,粉末的平均粒度减小,当球磨时间超过60 h时粉末易发生团聚。当球磨转速为300 r/min,球料比为12:1,Ti和Nb的质量分数分别为64%和24%时,球磨100 h后制备的粉体材料中具有一定体积的非晶相。该粉末在1 000℃下通过放电等离子烧结(SPS)制备具有均匀细小的球状晶粒组织的Ti-Nb合金,其强度、伸长率和弹性模量分别为2 180MPa,6.7%和55 GPa。通过控制Nb,Fe的含量,可以促进β-Ti相形成,获得高强度和低杨氏模量的Ti-Nb合金。     

超级贝氏体钢的现状和进展

超级贝氏体钢的基本合金元素为C-Mn-Si,通过300～500℃低温相变得到超细贝氏体、马氏体和残余奥氏体组织。为减小临界冷却速度、促进贝氏体转变,部分超级贝氏体钢中添加Cr、Ni、Mo等合金元素,并降低C、Mn含量以改善钢材的焊接性能。超级贝氏体钢具有超高强度和良好的塑性,其屈服和抗拉强度分别达～1 200MPa和1 600～1 700 MPa,总伸长率为～15%。新一代超级贝氏体钢的屈服强度可达1 300 MPa以上,抗拉强度超过1 700 MPa。     

Heat Treatment of Cold-Rolled Low-Carbon Si-Mn Dual Phase Steels

 The effects of over aging (OA) and vanadium on microstructure and properties of cold-rolled low-carbon Si-Mn vanadium-bearing and traditional dual-phase steel sheets are studied. The results show that the microstructure and mechanical properties of DP steels are greatly affected by over-ageing temperature. When OA below 250℃, the elongation rate increases sharply whiles both the yield strength and tensile strength decrease slightly, this is favorable to the increase of all over mechanical properties. After OA above 300℃, elongation does not increase much, but the yield strength increases and tensile strength decreases, which deteriorate the mechanical properties of the steel. Finally, the results also show that both the hardenability and the tempering stability of steel can be significantly improved by vanadium micro-alloying.