钒对YQ450NQR1高强度耐候钢组织与性能的影响

以含钒YQ450NQR1高强度耐候钢为研究对象,通过光学显微镜、高分辨率电镜、相分析等方法,研究了不同钒含量试验钢的金相组织、钒析出行为,探讨了钒析出量与力学性能之间的关系.结果表明,试验钢热轧态组织为块状铁素体 珠光体;钒在钢中明显析出,析出相以VN或V(C,N)为主; 钒在YQ450NQR1钢中起明显的强化作用,并且钒的作用与氮密切相关.只要获得了较高的VN析出比例,试验钢的钒含量可以得到降低.     

Effect on Manufacturing Conditions on Mechanical Properties of Super Formable IF High Strength Steels

There have been increasing demands for improving safety, fuel economy and dent resistance in the automotive industry. To meet these demands, a super‐formable high strength steel with excellent formability was investigated. The mechanical properties and precipitation behaviour of Ti‐Nb bearing Interstitial Free (IF) steels with various contents of Ti and P were studied. In addition, the effect of processing conditions such as the cold reduction ratio and the annealing temperature on the formability was analysed. Improved mean r‐value was obtained in Ti‐0.01Nb steels with Ti content ranging from 0.015% to 0.025%. This improvement was due to non‐scanvenging effect and FeTiP precipitates. Furthermore, with an increase in P content, the mean r‐value was increased because of grain refinement in the hot rolled strip.     

氮对高强度耐候钢钒析出行为的影响

在普通耐候钢的基础上采用单独添加或复合添加微合金元素的方法生产高强度耐候钢,并结合攀枝花现有资源特点,针对性地进行了不同氮含量含钒高强度耐候钢的研究。采用Glbeele-3500热模拟试验机、相分析等方法,研究了含钒高强度耐候钢在不同变形程度及变形温度条件下的钒析出-温度-时间关系(PTT曲线),探讨了氮含量、变形量对钒析出行为的影响。试验表明,试验钢的PTT曲线为典型的C曲线形状,在一定的奥氏体化条件下,钒析出过程存在所需时间最短的析出温度;增加氮含量会使PTT曲线明显向左移动;增加变形量可以加快V(C,N)在奥氏体中的析出过程,使PTT曲线向左移动;变形量越大,析出开始时间越短。通过研究,为进一步产品开发提供了技术支持。     

Effect of Vanadium Microalloying on the HAZ Microstructure and Properties of Low Carbon Steels

Four Steels,C-Mn-0.05V,C-Mn-0.11V,C-Mn-0.03Nb and C-Mn were subjected to heat treatment to simulate the microstructure of a coarse grained heat affected zone (CGHAZ) and an intercritically reheated coarse grained heat affected zone (ICCGHAZ).This involved reheating to 1350°C,rapid cooling (Δt 8/5 =24s) to room temperature and then reheating to either 750°C or 800°C.The toughness of the HAZs was assessed using both Charpy and CTOD tests.Microstructural features were characterised by optical,scanning` and transmission electron microscopy.Fractographic examinations of the Charpy and CTOD specimens were carried out to understand the micromechanism of fracture under different microstructural and test conditions.The CGHAZ toughness was similar for the steels except that Steel C-Mn-0.05V had a slightly lower ITT compared to the others.The toughness deteriorated in the ICCGHAZ for all the steels,again Steel C-Mn-0.05V had a superior toughness compared to the other three steels in both ICCGHAZ conditions.Raising the level of vanadium to 0.11% caused a decrease in ICCGHAZ toughness.Steel C-Mn-Nb exhibited a greater degradation of impact toughness after the intercritical cycles.The presence of M-A constituents was the dominant factor in determining the toughness of the ICCGHAZs.The size and area fraction of the M-A constituents were the smallest in Steel C-Mn-0.05V.Increasing vanadium level to 0.11% resulted in a greater area fraction of the M-A constituents,larger average and maximum sizes of M-A particles,and significantly more fields containing the M-A.The addition of 0.031% Nb produced the largest M-A particles and the greatest area fraction for the steels tested.     

Effect of Small Cold-Reductions on Mechanical Properties of Sintered Steels

Abstract

The mechanical properties, particularly strength and toughness, of sintered steels are improved considerably by surface densifying treatments consisting of small reduction extrusion and rolling and subsequent full annealing. It has been found that a reduction of about 11% is most effective for extrusion and a reduction of about 0·2 mm, by a small reduction per pass with a small diameter roll, is most effective for rolling. The toughening mechanism may be ascribed mainly to an appropriate density gradient which is given by the small cold-reduction in forming. Also the collapsed pores in the surface layers are reduced in size and spheroidized, and the interparticle bonding is increased by the subsequent full annealing.     

Evolution of Phases and Mechanical Properties of Thermomechanically Processed Ultra High Strength Steels

The present study concerns the development of two low carbon microalloyed ultra high strength steels on a pilot scale. This recent endeavour has been made towards the reduction of weight by achieving high strength to weight ratio together with improved weldability for the various prospective high performance defence applications such as explosive ammunition, gun barrel, missile skins, light-weight military bridges etc. These steels were thermomechanically processed and finished at different finish rolling temperatures followed by water quenching. Variation in microstructure and mechanically properties at different finished rolling temperatures was studied. The experimentally determined continuous cooling transformation diagrams have revealed that adequate hardenability is achievable in these steels usually at a cooling rate >5 °C/s. Lath martensite along with the microalloy (Ti, Nb) CN precipitate particles are the characteristic microstructural feature of the investigated steels. The high strength value obtained in the present steels is due to the accumulated contribution of fine grained pan-caked austenite, highly dislocated lath martensite along with the presence of tiny precipitates of microalloy carbide/carbonitride and Cu rich precipitates. The good combination of strength (1,364–1,538 MPa) and ductility (11–16 %) has been achieved for the selected range of finish rolling temperature. The Charpy impact toughness values (30–80 J) reveal approximately consistent fall with the lowering of testing temperature.     

Effect of Aluminum Content on the Microstructure and Mechanical Properties of Hypereutectoid Steels

Hypereutectoid steels with 0, 0.69, 1.29, and 1.95 wt pct aluminum were prepared. The samples were hot rolled at 1100 °C followed by cooling in air. The microstructure of the as-rolled samples was characterized using field emission–scanning electron microscopy (FE-SEM). The electron backscattered diffraction (EBSD) technique was used to identify the grain boundary phases. The steels have a pearlitic microstructure with different amounts of grain boundary cementite. A continuous grain boundary cementite network is present in the 0 wt pct Al steel. Grain boundary cementite formation is completely suppressed in the 1.29 wt pct Al steel. Phase diagram calculations show that aluminum increases the eutectoid temperature. However, the interlamellar spacing and pearlite colony size decrease with increase in aluminum content. Dilatometry measurements show that aluminum addition increases the undercooling below the eutectoid temperature. The yield strength increases with the decrease in interlamellar spacing and colony size. Very high ultimate tensile strengths (1200 to 1400 MPa) and improved elongations to failure (7 to 9 pct) are achieved in the as-rolled condition.     

The Effect of Nb on Mechanical Properties of Quenching and Partitioning Steels

In order to study the effect of alloy elements on mechanical properties of quenching and partitioning steels,the Q and P heat treatments on different chemical composition steels were carried on in lab.The tensile test results indicated the strength of Nb+Ti-bearing steel was not increasing as expected,but lower than that of the Nb+Ti-free steel,and the elongation was raised to 26% from 9%.The Nb+Ti-bearing steel microstructures after tensile test were detected by TEM and found a certain amount of twins in the deformed microstructure while the deformed microstructure mainly was lath martensite in Nb+Ti-free steel,which means the addition of Nb and Ti elements could cause the twinning induced plasticity by inhibiting the phase transformation from austenite to martensite.Based on above analysis,adding trace Nb element could greatly increase the stacking fault energy of the retained austenite,which is beneficial to the formation of twins,and the formation of twins would lower the strength slightly and raise the elongation drastically.     

碳、钒含量对高钒高速钢组织和力学性能的影响

在ωv/ωc≈3与ωv≈10%的条件下,研究了钒、碳含量对高钒高速钢组织和力学性能的影响.结果表明：高钒高速钢的耐磨性决定于硬度与组织.硬度低于HRC 57时,耐磨性主要决定于硬度;硬度超过HRC 57之后,耐磨性主要决定于碳化钒的数量、形态、分布与基体组织.ωv=8.15%～10.20%、ωc=2.70%～3.15%时,经适当变质处理和热处理,可使团球状或团块状的碳化钒均匀分布在经1 050 ℃淬火,550 ℃回火的坚硬基体上,从而获得优良的耐磨性能.     

Nb对超低碳钢机械性能的影响

1　前言众所周知 ,合金化元素 Nb可提高钢的强度 ,是因为它形成一种 Nb(C,N)微细沉淀物 ,还可用来改善许多钢的机械性能。就 Fe原子和 Nb原子之间原子大小的差异来看 ,Nb被置于 Fe晶格位置内 ,与运动位错发生很强的相互作用。通过固溶强化 ,Nb能提高钢的强度。高温下铌在移动相界处或晶界处有很强的偏析趋势 ,并且这种偏析趋势对于运动位错同样适用 ,因此估计铌在高温下也可以提高流变应力。Nb在运动位错中的偏析会因溶质拖曳作用而消耗某部分动力 ,从而提高流变应力。本文研究了 Nb在室温和高温下对超低碳钢机械性能的影响。2　试验步…     

Effect of Sulfur and Zirconium on the Machinability and Mechanical Properties of AISI 1045 Steels

The effects of small increases of sulfur and addition of zirconium in conjunction with sulfur on the machinability and mechanical properties of laboratory-produced AISI 1045 steels have been investigated. Machinability was measured in terms of cutting energy per unit volume of metal machined. With increasing sulfur, there is a linear increase in sulfide volume fraction and improvement in machinability. Ductility parameters such as tensile reduction in area and impact shelf energy, however, significantly decrease with sulfur, particularly in the transverse direction. Addition of zirconium causes formation of manganese-zirconium sulfides and increased globularity. Although further improvement in machinability by zirconium addition is not evident, there is a significant improvement in transverse impact properties by zirconium addition for steels containing high sulfur. The study suggests that an optimum combination of higher sulfur for improved machinability and zironium for better impact properties yields a steel with acceptable machining and ductility criteria.     

碳含量对Fe-Mn-Cu-C系TWIP钢组织和力学性能的影响

 采用真空熔炼法制备Fe-20Mn-3.0Cu-XC系高强度高塑性合金钢,通过X射线衍射（XRD）、光学显微镜（OM）和透射电子显微镜（TEM）观察方法研究了碳含量对该系列合金微观组织和力学性能的影响,分析了合金的拉伸变形微观机制。结果表明：Fe-20Mn-3.0Cu-XC系合金拉伸变形前后均为单相奥氏体组织,未发生马氏体相变。随着碳质量分数的增加,合金的屈服强度、抗拉强度和伸长率均显著提高。Fe-20Mn-3.0Cu-1.41C合金的屈服强度为501.62MPa,抗拉强度为1178.4MPa,具有优异的综合力学性能。Fe-20Mn-3.0Cu-XC系合金具有优异的应变硬化能力。随着碳质量分数增大至1.41%,最大应变硬化指数n值达到0.782。Fe-20Mn-3.0Cu-XC系合金拉伸变形过程中,TWIP效应是主要的塑性变形机制,大量位错的塞积、形变孪晶的形成以及位错与孪晶间的交互作用共同引起材料强度和塑性的提高。     

卷取温度对钒微合金化耐候钢力学性能的影响

 在实验室制备了钒微合金化高强耐候钢,通过拉伸试验、冲击试验、扫描电镜、透射电镜对试验钢的组织结构、力学性能以及第二相粒子析出行为进行了研究,分析了不同卷取温度对耐候钢显微组织和力学性能的影响。研究结果表明：随着卷取温度的降低,试验钢在550℃获得最佳力学性能,晶粒尺寸细小,细晶强化效果明显,但是钒的析出数量减少,析出强化作用减弱。试验钢在550℃卷取时组织为铁素体、珠光体以及部分针状铁素体,针状铁素体组织以及细晶强化共同作用不但弥补了该卷取温度下析出强化的不足,而且使得试验钢的力学性能有了明显提高。     

Effect of Chemical Composition and Structure on Mechanical Properties of High-Strength Welding Steels

Metallurgist - Based on the analysis of the Russian-made 4 to 16 mm thick rolled products produced by thermomechanical rolling from high-strength (yield point: 433 to 828 MPa) low-alloyed welding...     

Effect of Microadditives on Center Segregation and Mechanical Properties of High-Strength Low-Alloy Steels

Metallurgist - One of the main tasks of steelmaking is to obtain the necessary thermodynamic conditions that ensure fine and homogeneous solidified microstructure. The relatively economical...