低碳中合金钢破碎机锤头的研制

研究了一种新型的破碎机锤头,对其采用合金化处理并经过热处理,实验表明:该低碳中合金耐磨钢的硬度大于51HRC,冲击韧性大于141J/cm2。经热处理后的显微组织为回火马氏体+残余奥氏体+弥散的碳化物,比高锰钢破碎机锤头性能有很大提升。     

Fabrication of Ti–Nb–Ag alloy via powder metallurgy for biomedical applications

Ti and some of its alloys are widely used as orthopedic implants. In the present study, Ti–26Nb–5Ag alloys were prepared by mechanical alloying followed by vacuum furnace sintering or spark plasma sintering (SPS). The microstructure and mechanical properties of the Ti–Nb–Ag alloys were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDX), compressive and micro-hardness tests. The effect of different sintering methods on the microstructure and properties of Ti–Nb–Ag alloy was discussed. The results showed that the titanium alloy sintered by vacuum furnace exhibited a microstructure consisting of α, β and a small amount of α″ martensite phase; whilst the SPS sintered alloy exhibited a microstructure consisting of α, β and a small amount of α″ martensite phase, as well as a nanostructured Ag homogeneously distributed at the boundaries of the β phases. The Ti–Nb–Ag alloy sintered by SPS possessed fracture strength nearly 3 times of the alloy sintered by vacuum furnace.     

Nb、Ti微合金钢中碳氮化物固溶与再析出的研究

利用光学显微镜(OM)、透射电子显微镜(TEM)研究了再加热温度、奥氏体区变形温度和组织转变温度的变化对Nb、Ti微合金钢组织性能及其碳氮化物固溶与再析出行为的影响.结果表明:钢中加入铌,主要利用铌的碳氮化物在奥氏体形变过程中的再析出,抑制形变奥氏体的再结晶,在随后的组织演变过程中细化了组织;而钢中加入较高含量的钛,主要利用钛的碳化物在铁素体中的析出,产生明显的沉淀强化作用.这主要是铌、钛的碳氮化物固溶后,在奥氏体和铁素体中再析出的不同所造成的.钢中复合加入Nb-Ti后既起到细化晶粒的作用,又起到析出强化的作用.细晶强化既提高钢的强度又提高钢的韧性,但沉淀强化在大幅提高钢的强度的同时恶化了钢的韧性.     

高锰钢合金化的组织及加工硬化性能

研究了高锰钢合金化对组织的影响。指出:Nb或Ti并吹N_2净化了钢液,细化了奥氏体组织,形成了一定数量的硬质点相;硬相的大量存在,促进了形变过程中γ诱发转变,提高了锰钢的强韧性。     

轧制工艺对低碳中锰钢微观组织和力学行为的影响

目的 研究热轧和温轧两种轧制工艺对低碳中锰钢的微观组织演变和力学性能的影响规律,阐明两种轧制工艺对马氏体转变和应变硬化行为的影响.方法 通过对热轧和温轧两种轧制工艺得到的实验钢进行拉伸性能测试,分析温轧后实验钢强塑性同步提升的现象,通过EBSD数据分析,测量热轧和温轧实验钢中马氏体的转变量,并对两种轧制工艺拉伸后实验钢...     

Effects of Alloying Elements on Microstructure and Erosion Resistance of Fe—C—Cr Weld Surfacing Layer

Effects of alloying elements on microstructure and erosion resistance of Fe-C-Cr weld surfacing layer have been studied. The experimental results show that increasing C and Cr content favors improving the erosion resistance of the layer, and the excessive C and Cr result in decreasing the erosion resistance at 90 deg. erosion. That Mo, Nb or Ti improves the erosion resistance of Fe-C-Cr weld surfacing layer is mainly attributed to increasing the amount of M7C3 and forming fine NbC or TiC in austenite matrix, but the excessive Mo, Nb or Ti is unfavorable. The addition of Mo, Nb and Ti in proper combination possesses stronger effect on improving the erosion resistance and the erosion resistance (εA) of Fe-C-Cr weld surfacing layer with fine NbC, TiC and M7C3 distributing uniformly in austenite matrix obviously increases to 2.81 at 15 deg. erosion and 2.88 at 90 deg. erosion when the layer composition is 3.05C, 20.58Cr, 1.88Mo, 2.00Nb and 1.05Ti (in wt pct).     

Structure,mechanical properties and grindability of dental Ti–10Zr–X alloys

This study aimed to investigate the structure, mechanical properties and grindability of a binary Ti–Zr alloy added to a series of alloying elements (Nb, Mo, Cr and Fe). The phase and structure of Ti–10Zr–X alloys were evaluated using an X-ray diffraction (XRD) for phase analysis and optical microscope for microstructure of the etched alloys. Three-point bending tests were performed using a desk-top mechanical tester. Grindability was evaluated by measuring the amount of metal volume removed after grinding for 1 min at each of the four rotational speeds of the wheel (500, 750, 1000 or 1200 m/min). Results were compared with c.p. Ti, which was chosen as a control. Results indicated that the phase/crystal structure, microstructure, mechanical properties and grindability of the Ti–10Zr alloy can be significantly changed by adding small amounts of alloying elements. The alloying elements Nb, Mo, Cr and Fe contributed significantly to increasing the grinding ratio under all grinding conditions, although the grinding rate of all the metals was found to be largely dependent on grinding speed. The Ti–10Zr–1Mo alloy showed increases in microhardness (63%), bending strength (40%), bending modulus (30%) and elastic recovery angle (180%) over those of c.p. Ti, and was also found to have better grindability. The Ti–10Zr–1Mo alloy could therefore be used for prosthetic dental applications if other conditions necessary for dental casting are met.     

Mechanical properties and hot-rolled microstructures of a low carbon bainitic steel with Cu-P alloying

A low carbon bainitic steel with Cu-P alloying was developed. The new steel aims to meet the demand of high strength, high toughness and resistance to chloride ion corrosion for the components used in the environment of sea water and oceanic atmosphere. Mechanical properties of the steel were tested and strengthening and toughening mechanisms were analyzed by comparing hot-rolled microstructures of the low carbon bainitic steels with and without Cu-P alloying. The results show that Cu-P alloying provided strong solution strengthening with weak effect on ductility. The toughness loss caused by Cu-P alloying could be balanced by increasing the amount of martensite/remained austenite (M/A island) at lower finishing temperature. The static recovery process during rolling interval was delayed by the interaction of phosphorous, copper atoms with dislocations, which was favorable to the formation of bainitic plates. Super-fine Nb(C, N) particles precipitated on dislocations had coherency with bainite ferrite at 830 °C finishing temperature. Raising finishing temperature to 880 °C, Nb(C, N) particles were prone to coarsening and losing coherency. It was also found that no accurate lattice match relationship among retained austenite, martensite and bainite in granular bainitic microstructure.     

原位观察稀土镧对低合金高强度钢焊接热影响区晶粒细化的影响

使用高温激光共聚焦扫描显微镜原位观察了含0.016％(质量分数,下同)的La和不含La的低合金高强钢模拟焊接热影响区中高温阶段奥氏体的长大和组织转变行为,并使用光学显微镜和电子扫描显微镜对比分析了添加0.016％的La对粗晶热影响区晶粒细化的影响.结果 表明:添加0.016％的La使低合金高强钢中的夹杂物由Al-Mg-...     

Microstructures and Mechanical Properties of Si-Al-Mn TRIP Steel with Niobium

Microstructure consisting of ferrite, bainite and retained austenite can be obtained through intercritical annealing and isothermal treatment in bainite transformation region for low silicon TRIP (transformation induced plasticity) steel containing niobium. Effects of strain rate, Nb content and soaking temperature in bainite region on microstructure and mechanical properties of test steels were investigated. It is shown that as strain rate ranges from 10-2 to 10-4 s-1, the volume fraction of transformed martensite from retained austenite,as well as tensile strength, elongation rate and strength-ductility product, increases. When Nb is added, the volume fraction of retained austenite decreases, but tensile strength and yield strength increase. While Nb content reaches 0.014%, the steel exhibits high elongation and combination of strength and ductility. Higher retained austenite volume fraction and good mechanical properties are obtained in the test steels when the soaking temperature in bainite region is 400℃. The maximum values of tensile strength, total elongation rate and strength-ductility product can reach 739 MPa, 38% and 28082 MPa%, respectively.     

AUSTEMPERING OF A SILICON MANGANESE CAST STEEL

The influence of austempering on the microstructure and mechanical properties of an alloyed cast steel containing high silicon (3.00%) and high manganese (2.00%) was studied. The influence of microstructure on the plain strain fracture toughness of this new steel was also examined. The test results show that by using a suitable austempering process, i.e., by austenitizing at 1010°C (1850°F) for 2 hr and then subsequently austempering at 316°C (600°F) for 6 hr, it is possible to produce more than 80% austenite in the matrix of the material. Such a large percentage of austenite in the matrix made the steel almost nonmagnetic. Austempering resulted in a significant improvement in mechanical properties as well as fracture toughness of the material. The potential applications of this steel are in naval structural components, aircraft, and automotive components.     

Microstructures and Mechanical Properties of Si-AI-Mn TRIP Steel with Niobium

Microstructure consisting of ferrite, bainite and retained austenite can be obtained through intercritical annealing and isothermal treatment in bainite transformation region for low silicon TRIP （transformation induced plasticity） steel containing niobium. Effects of strain rate, Nb content and soaking temperature in bainite region on microstructure and mechanical properties of test steels were investigated. It is shown that as strain rate ranges from 10^-2 to 10^-4 s^-1, the volume fraction of transformed martensite from retained austenite, as well as tensile strength, elongation rate and strength-ductility product, increases. When Nb is added, the volume fraction of retained austenite decreases, but tensile strength and yield strength increase. While Nb content reaches 0.014%, the steel exhibits high elongation and combination of strength and ductility. Higher retained austenite volume fraction and good mechanical properties are obtained in the test steels when the soaking temperature in bainite region is 400℃. The maximum values of tensile strength, total elongation rate and strength-ductility product can reach 739 MPa, 38% and 28082 MPa%, respectively.     

Mechanisms of Solidification Structure Improvement of Ultra Pure 17 wt% Cr Ferritic Stainless Steel by Ti,Nb Addition

The grain structures and the precipitates in the solidification microstructure of the ultra pure 17 wt% Cr ferritic stainless steels with different Ti and/or Nb micro-alloying were investigated both experimentally and theoretically.It was found by the grain structure observation that the addition of Ti or Nb to the steel reduced the grain size (D) and elongation factor (E),and improved the equiaxed grain proportion (P) and globularity factor (ξ).Among the four steels studied,the minimum grain size and maximum equiaxed grain proportion were obtained by jointly adding both Ti and Nb to the steel.The SEM observation indicated that several kinds of precipitations,such as TiN,MC (rich in Nb),Laves phase (Fe2Nb) and so on,formed in the corresponding steels.In addition,the results calculated using the Thermo-Calc software illustrated that TiN precipitates in the liquid at proper Ti and N contents.Meanwhile,the solidification interval (△T) was enlarged by the addition of Ti or Nb,and the effectiveness of Nb was stronger than Ti.Based on the experimental and calculation results,the mechanisms of grain refinement and increment in equiaxed grain proportion were discussed.     

基于S35140钢的超低碳成分设计和力学性能研究

S35140钢是一种基于25Ni-20Cr的奥氏体耐热钢,为了获得高强度,通常会提高碳含量,但碳含量较高不利于高温时效稳定性和长期耐腐蚀性能.本文在S35140钢的基础上,大幅度降低碳含量,并通过调控N和Nb等微合金元素含量,以及加入Ti元素,促使析出新的强化相,弥补减少碳含量所导致的强度降低.同时引入一定量的Al元素...     

Microstructure and properties of Ti–Nb–V–Mo-alloyed high chromium cast iron

The correlations of microstructure, hardness and fracture toughness of high chromium cast iron with the addition of alloys (titanium, vanadium, niobium and molybdenum) were investigated. The results indicated that the as-cast microstructure changed from hypereutectic, eutectic to hypoeutectic with the increase of alloy contents. Mo dissolved in austenite and increased the hardness by solid solution strengthening. TiC and NbC mainly existed in austenite and impeded the austenite dendrite development. V existed in multicomponent systems in forms of V alloy compounds (VCrFe₈ and VCr₂C₂). With the increase of alloy additions, carbides size changed gradually from refinement to coarseness, hardness and impact toughness were increased and then decreased. Compared with the fracture toughness (6 J/cm²) and hardness (50·8HRC) without any alloy addition, the toughness and hardness at 0·60 V–0·60Ti–0·60Nb–0·35Mo (wt%) additions were improved and achieved to 11 J/cm² and 58·9HRC, respectively. The synergistic roles of Ti, Nb, V and Mo influenced the solidification behaviour of alloy. The refinement of microstructure and improvement of carbides morphologies, size and distribution improved the impact toughness.     

终冷温度对高强度抗震钢筋组织和性能的影响

用Gleeble-3800热模拟机进行高强度抗震钢筋的热模拟实验,使用金相显微镜(OM)、场发射扫描电子显微镜(SEM)、高分辨透射电子显微镜(TEM)和万能拉伸试验机等手段表征其微观结构、第二相、力学性能和断口形貌,研究了终冷温度对高强度抗震钢筋的组织和性能的影响并揭示微合金元素细化晶粒的机理。结果表明：实验钢的显微组织主要为铁素体和珠光体,随着终冷温度的降低铁素体晶粒细化。终冷温度为650℃时实验钢中分布在铁素体基体上的主要析出相 (Nb, Ti, V)C和(V, Nb, Ti)C的平均粒径约为2 nm和5 nm。随着终冷温度的降低实验钢的抗拉强度和屈服强度都增加,终冷温度为650℃时其抗拉强度和屈服强度分别为638.75 MPa和467 MPa,强屈比为1.37。在不同终冷温度实验钢的拉伸断口主要为等轴韧窝,其尺寸和深度不同。     

Microstructure and properties of Nb-bearing high-strength low-alloy surfacing layers

Based on Q345 steel, high-strength low-alloy surfacing layers with Nb content ranging from 0.0041 to 0.26?wt-% were prepared by adding Nb element into electrode coating and manual electric arc welding, the microstructure as well as mechanical properties of surfacing layers were evaluated and analysed. The experimental results show that with the increasing of Nb content, the grain size becomes smaller meanwhile the microstructure distribution is more uniform, the size of hard phase martensite/austenite gradually decreases and the NbC precipitates increases. The yield and tensile strength greatly increase for the fine-grain strengthening of Nb and the precipitation strengthening of NbC, moreover, the impact toughness is significantly improved due to the microstructure variation and obvious grain refinement.     

钛对非调质塑料模具钢奥氏体晶粒长大规律的影响

汽车和家电行业对高品质大截面塑料模具钢的需求量逐渐增大,但随着塑料模具钢截面厚度的增大,其出现粗晶的可能性也增大,这使得合理的热处理工艺设计显得尤为重要。通过添加钛来抑制高温处理过程中奥氏体晶粒的长大行为,并着重研究微合金钛元素对非调质塑料模具钢奥氏体晶粒长大的影响规律。研究发现,含0.03%钛的非调质塑料模具钢在均质化温度高于1 050℃时具有较好的抗晶粒粗化能力,原因是组织中晶界附近存在一定量的以Ti(C,N)为主的析出相。通过以上研究建立了奥氏体晶粒长大模型,该模型可有效预测非调质塑料模具钢高温均质化过程中的奥氏体晶粒长大规律。     

正火型V-N-Ti和Nb-V-Ti海工钢焊接粗晶热影响组织和韧性研究

用焊接热模拟方法研究了V-N-Ti和Nb-V-Ti微合金化正火型海工钢模拟粗晶热影响区(CGHAZ)组织和韧性的变化规律。结果表明,组织的不同使V-N-Ti设计正火型海工钢的模拟CGHAZ韧性比Nb-V-Ti钢的好。对于V-N-Ti钢,较高的N含量提高了富Ti(Ti, V)(C, N)粒子析出温度和铁素体形核能力,使模拟CGHAZ原始奥氏体晶粒和(取向差角为15°)晶粒细化,并生成能阻止或使解理裂纹的偏转细小多边形铁素体,因此具有良好的低温韧性。而Nb-V-Ti钢模拟CGHAZ原奥氏体晶界上的链状M-A、粗大的原始奥氏体晶粒和有效晶粒尺寸,是模拟CGHAZ韧性差的原因。     

Effect of Microstructure Refinement on the Strength and Toughness of Low Alloy Martensitic Steel

Martensitic microstructure in quenched and tempered 17CrNiMo6 steel with the prior austenite grain size ranging from 6 μm to 199 μm has been characterized by optical metallography （OM）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The yield strength and the toughness of the steel with various prior austenite grain sizes were tested and correlated with microstructure characteristics. Results show that both the prior austenite grain size and the martensitic packet size in the 17CrNiMo6 steel follow a HalI-Petch relation with the yield strength. When the prior austenite grain size was refined from 199 μm to 6 μm , the yield strength increased by 235 MPa, while the Charpy U-notch impact energy at 77 K improved more than 8 times, indicating that microstructure refinement is more effective in improving the resistance to cleavage fracture than in increasing the strength. The fracture surfaces implied that the unit crack path for cleavage fracture is identified as being the packet.