复合轧制220mm特厚S355NL钢板的组织性能分析

复合连铸坯轧制技术是生产特厚钢板的一项创新工艺,主要对连铸坯进行真空电子束焊接而组合制成复合连铸坯,再轧制成大单重特厚钢板。对采用这种新工艺生产的特厚钢板典型产品进行了评价分析,包括轧制结合面处的低倍组织、金相显微组织、横纵向拉伸性能、全厚度Z向拉伸、横纵向弯曲、性能均匀性、剪切试验等。结果显示该工艺生产的特厚钢板各项组织性能优良,完全满足标准和使用要求。     

Al元素对建筑用含B特厚钢板力学性能的影响

研究了建筑用含B特厚钢板的显微组织和力学性能。结果表明,特厚钢板中的B元素可以提高钢基体的淬透性,并能对特厚钢基体的内部低温抗冲击韧度和拉伸性能起到有效的改善作用。Al元素的添加会使含B钢的淬透性增强,从而进一步提高特厚钢板的力学性能。     

特厚钢板复合轧制工艺的实验研究

采用连铸坯直接轧制生产特厚钢板时,由于压缩比的限制,成品的厚度受到极大限制,很难生产产品厚度超过100mm的高质量特厚钢板。文中介绍了复合轧制生产特厚钢板的实验方法、工艺过程以及实验分析结果,包括复合界面金相组织观察、Z向抗拉强度及拉伸曲线、拉伸样断面收缩率、断口扫描分析、超声波探伤等。从金相组织看,界面结合率约99%~100%,从金相图片上已经找不到复合界面;Q345复合钢板的Z向平均抗拉强度为445MPa,平均断面收缩率为54.13%,拉伸试样在微观上表现为韧性断裂。从超声波探伤结果看,未出现明显缺陷回波。     

采用新型差温轧制工艺生产Q690级特厚钢板

为了实现在厚度方向上具有优异强度均匀性的Q690级特厚钢板的研发,采用一种新型的差温轧制工艺进行了实验室轧制,并研究了差温轧制工艺对钢板显微组织、厚度方向上强度均匀性和力学性能的影响。结果表明:差温轧制工艺能够显著细化钢板芯部和1/4厚度处的原始奥氏体组织,增加芯部和1/4厚度处淬火组织中的两相区铁素体体积分数。通过差温轧制工艺生产的Q690级钢板具有优异的力学性能,钢板的伸长率和-40℃冲击功分别大于16%和60J,从表面到芯部,钢板屈服强度差异小于10 MPa。     

特厚钢板射流冲击淬火过程厚向冷速试验研究

利用开发的特厚钢板射流淬火试验装置及多通道温度记录仪,测试了射流速度14.0~23.5 m/s、射流压力0.4~1.0 MPa条件下,84 mm、170 mm厚大断面钢板淬火温降曲线,采用有限元方法建立了三维反传热导热模型和表面换热系数模型,对比分析了射流参数和换热区分布对钢板厚向温降、温度梯度和冷速的影响。结果表明:84 mm厚钢板断面冷速与表面换热系数近似正比关系,射流速度为23.5 m/s时钢板心部冷速达3.7℃/s;170 mm厚钢板表面换热对厚向冷速影响减弱,相应的温度遗传效应和断面厚向温度梯度的影响增强。     

极限模焊工况下大厚度SA387Gr11CL2钢板的力学性能

针对设计院和制造厂提出的越来越严格的模焊工艺要求,结合136 mm厚钢板研究了极限模焊工况对大厚度SA387Gr11CL2钢力学性能的影响。结果表明,在保温温度690 ℃、保温时间24 h、装出炉温度200 ℃、升降温速率30 ℃/h的极严格模焊工艺制度下,钢的全厚度(表面下1.6 mm、板厚1/4处及板厚1/2处)室温拉伸性能尚可,但0 ℃及以下随着冲击温度的降低,相应冲击吸收能量逐渐下降,板厚1/2处-20 ℃冲击吸收能量已经接近标准要求的下限,富余量很小,结合金相和扫描电镜进行组织分析,表明过分加严模焊工艺会引起显微组织中碳化物沿晶界偏聚并长大,使钢板韧性明显变差。     

应用连铸坯生产特厚钢板技术

鞍山钢铁股份有限公司通过合理的成分及工艺设计,解决了连铸坯生产特厚钢板因压缩比小所造成的偏析、疏松等同题.采用300mm铸坯可以生产最大厚度为150mm的特厚钢板,最小压缩比为2:1,生产的特厚钢板探伤合格、性能稳定,各项指标均符合国家标准.     

特厚超高强海工钢表面回火马氏体组织对冲击韧性的影响

320 mm厚度连铸坯采用控轧-控冷轧制成100 mm钢板,通过淬火-回火热处理制备690 MPa级特厚超高强海工钢,研究了表面和1/4厚度处的回火马氏体对系列低温冲击性能的影响。结果表明:特厚钢板表面奥氏体晶粒均匀细小,回火后获得几乎为全回火马氏体组织,其低温冲击韧性比较低。淬火过程中,过快的冷却速度提高了钢板表面马氏体转变的过冷度,引起马氏体转变的形核率降低,导致特厚板表面马氏体板条束、板条块等亚结构的相对粗大,造成冲击韧性低下,尤其降低-60℃和-80℃低温冲击韧性。     

低屈强比特厚钢板的控制轧制和正火工艺研究

采用连铸—控轧—正火工艺试制了90 mm特厚钢板,研究了不同控制轧制和正火工艺对组织和力学性能的影响。结果表明:在奥氏体未再结晶区轧制时,减少道次数,单道次采用大压下率,有利于细化特厚钢板中心的晶粒,提高轧态厚板中心强度和韧性,而对珠光体的片层间距和体积分数影响不大;正火后,组织带状特征减轻,分布均匀,晶粒和珠光体团得到细化,使伸长率、低温冲击功及z向断面收缩率提高,能够得到抗拉强度为550 MPa级的低屈强比、高韧性和良好抗层状撕裂的特厚钢板。     

辊模拉伸Ti6A14V钛合金丝材的力学性能分析

研究辊模拉伸TC4钛合金丝材的组织和性能,并与传统拉伸工艺相比较。结果表明:由于二者拉伸过程中丝材所受的摩擦力大小及摩擦力形式不同,使得经过辊模拉伸生产的丝材表面光亮,内部组织更加均匀、细小;而传统工艺生产的丝材表面易出现划伤、粘模等加工缺陷,其内部的晶粒较大。将两种不同拉伸工艺生产出的产品经过再结晶退火后处理,发现辊模拉伸生产出的丝材具有强度高、塑形好等优点,其力学性能远远高于采用传统工艺生产的同规格丝材。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.