Development in high-grade dual phase steels with low C and Si design

Cold rolled dual phase steels with low C and Si addition were investigated in terms of combination of composition and processing in order to improve mechanical properties and workability including welding and galvanizing. Mo and Cr could be used as alloying elements to partially replace C and Si to assure enough hardening ability of the steels and also give solute-hardening. Mo addition is more effective than Cr addition in terms of obtaining the required volume fraction of martensite and mechanical strength. The ferrite grain was effectively refined by addition of Nb microalloying, which gives optimized mechanical properties. The experimental results show that it is possible to obtain the required mechanical properties of high grade 800 MPa dual phase steel, i.e., tensile strength > 780 MPa, elongation > 15%, and yield/tensile strength ratio < 0.6 in the condition of low carbon (C < 0.11 wt.%) and low silicon design (Si < 0.05 wt.%) through adequate combination of composition and processing.     

Development in high-grade dual phase steels with low C and Si design

Cold rolled dual phase steels with low C and Si addition were investigated in terms of combination of composition and processing in order to improve mechanical properties and workability including welding and galvanizing. Mo and Cr could be used as alloying elements to partially replace C and Si to assure enough hardening ability of the steels and also give solute-hardening. Mo addition is more effective than Cr addition in terms of obtaining the required volume fraction of martensite and mechanical strength. The ferrite grain was effectively refined by addition of Nb microalloying, which gives optimized mechanical properties. The experimental results show that it is possible to obtain the required mechanical properties of high grade 800 MPa dual phase steel, i.e., tensile strength>780 MPa, elongation>15%, and yield/tensile strength ratio<0.6 in the condition of low carbon (C<0.11 wt.%) and low silicon design (Si<0.05 wt.%) through adequate combination of composition and processing.     

304不锈钢消音蜂窝钎焊工艺、组织及力学性能分析

采用镍基BNi2钎料钎焊制备了304不锈钢消音蜂窝,对蜂窝芯体与面板钎焊界面组织和蜂窝的力学性能进行了分析和测试,并研究了钎焊热循环次数对钎焊界面组织和蜂窝拉伸力学性能的影响,为实际工程应用确定未焊合缺陷补焊次数提供了依据。液态钎料的毛细作用使钎料沿蜂窝芯箔材表面铺展并与箔材发生显著的元素扩散反应,蜂窝芯与面板之间的钎缝由Ni、Cr、Si等互溶而成的Ni基固溶体组织组成,未生成脆性共晶组织或金属间化合物。钎料中的B和Si元素显著扩散于面板材料中,形成钎料-面板反应区,因B元素的沿晶界快速扩散效应,面板侧组织呈现晶界元素渗入特征。随着钎焊次数增加,钎料对母材的溶解和晶界渗透增加,钎焊界面组织发生显著变化。制备的304不锈钢消音蜂窝拉脱强度为7.21MPa,呈现板/芯界面附近蜂窝芯破坏特点,多次钎焊时蜂窝拉脱强度呈下降趋势。制备的304不锈钢消音蜂窝平压、侧压和弯曲力学性能测试过程均经历弹性变形、塑性变形和失稳三个阶段,强度值分别为5.67MPa、33.85MPa和105.87MPa,平压和弯曲失效模型为蜂窝失稳,侧压破坏除蜂窝失稳外,发生穿孔面板与蜂窝芯体剥离的现象。鉴于多次钎焊热循环对蜂窝拉脱强度的不利影响,建议304不锈钢蜂窝钎焊缺陷的最大补焊次数为一次。     

6.5 wt% Si high silicon steel sheets prepared by composite electrodeposition in magnetic field

A new preparation method of near-net-shape 6.5?wt% Si high silicon steel sheets was proposed by combining composite electrodeposition (CED) and diffusion annealing under magnetic field. The obtained sheets were characterized by scanning electron microscopy, energy dispersive spectrometry, analytical balance and a silicon steel material measurement system. The results show that the surface morphology, the elemental distribution, the cathode current efficiency and the silicon content of coatings were obviously influenced by the micro and macro magnetohydrodynamics (MHD) flows under magnetic field. With the effect of magnetic field, the silicon particles content of coatings showed an increasing trend and the diffusion process showed that an approximately uniform 6.5?wt% silicon steel sheet has been successfully obtained. The magnetism measurement showed that the high silicon steel sheet has the lower iron loss, and the iron loss further decreased under magnetic field. The new method proposed in this article, which is more environmentally friendly and low energy consumption, is feasible to prepare high silicon steel sheets.     

Fe3Si基合金的制备及应用研究进展

Ｆｅ３Ｓｉ基合金具有优异的软磁性能,不仅有希望硅钢片（在高频信息领域）,而且还广泛用作音几视频磁头材料和卡片阅读器用磁头材料。本文综述了Ｆｅ３Ｓｉ基合金的制备工艺及应用,并结合我们的研究工作,分析了其研究现状,简要论述了其发展前景。     

Formation of ultrafine-grained microstructure in HSLA steel profiles by linear flow splitting

Linear flow splitting is a new cold forming process for the production of branched sheet metal structures in integral style. It induces extremely high deformation degrees without formation of cracks in the split sheets due to hydrostatic compressive stresses. Investigations on a HSLA steel (ZStE 500) show the formation and fragmentation of a dislocation cell structure in the severely deformed regions of the steel sheet. This results in ultrafine-grained microstructures and improved mechanical properties, similar to SPD processes as Equal Channel Angular Pressing (ECAP) or High Pressure Torsion (HPT). EBSD measurements reveal a gradient in grain size with an increase in direction perpendicular to the surface, whereas micro hardness decreases in the same direction. Based on these results, basic principles of linear flow splitting and its expected potential are discussed.     

Analysis of sheet steel fracture during deep drawing

Low-carbon steel sheet used for the fabrication of automotive brake components was tearing during deep drawing. The associated mill certificates revealed that the coil met the specified chemical composition and mechanical properties. Metallographic evaluation revealed a severe variation with respect to grain size through the thickness of the steel sheet, as well as a slight segregation of pearlite. Insufficient temperature during hot rolling in combination with a high coiling temperature resulted in the observed microstructural gradient. The anisotropic mechanical properties were amplified by the slight carbon segregation.     

硅钢绝缘涂层的研究进展

本文系统介绍了取向硅钢与无取向硅钢表面绝缘涂层，包括有机涂层、无机涂层和半无机涂层三大类。无机涂层具有良好的耐热和焊接性能，但其冲制性和粘结性不佳。半无机涂层具有良好的冲制性和粘结性，但其耐热性和焊接性不及无机涂层。另外，最新研究的取向硅钢表面物理气相沉积ＴｉＮ、ＣｒＮ和ＴｉＣ绝缘涂层可使硅钢获得极低的铁损，大大提高了硅钢的磁通量密度，并具有优异的耐热、焊接、冲制和粘结性。     

Si和Nb对高强热轧高扩孔钢组织和性能的影响

为了研究Si和Nb对高强热轧高扩孔钢板显微组织、力学性能和扩孔性能的影响,在CSP连轧线上进行了3种成分试验钢的热轧试制,并对试验钢在扩孔过程中裂纹的形成和扩展行为进行了分析.研究表明:3种成分热轧钢板的显微组织均由铁素体和贝氏体组成,钢板的抗拉强度均高于610 MPa,伸长率大于24.5%,扩孔率高于104%;Si含量的增加,提高了组织中铁素体的含量,钢板的强度、伸长率和扩孔率得到提高;Nb含量的增加,细化了钢板的组织,钢板的强度和扩孔率增加明显,伸长率变化不大;试验钢在扩孔过程中裂纹主要沿铁素体和贝氏体的晶界处扩展,部分裂纹穿过铁素体晶粒.     

A Study of Microstructures and Properties of High‐Carbon Si‐Cr Cast Steel Containing Rare Earth and Titanium

The microstructure, tensile and impact behaviour of high‐carbon Si‐Cr cast steel containing rare earth (RE) and titanium have been determined after austempering. The additions of RE and titanium refined the primary austenite grain size resulting in improving toughness. The addition of silicon handicapped the formation of carbide and carbide‐free bainitic ferrite and carbon enriched retained austenite could be obtained in the austempering structures of high‐carbon Si‐Cr cast steel, which had excellent mechanical properties and abrasion resistance. Moreover, the basic tendency of the mechanical properties of high‐carbon Si‐Cr cast steel influenced by the austempering temperature was that the hardness and tensile strength reduced and the impact toughness and fracture toughness increased with increasing temperature. The comprehensive properties were the best while austempering at 330^oC.     

Effect of a high gradient magnetic field on the distribution of the solute Si and the morphology of the primary Si phase

Effect of a high gradient magnetic field on the distribution of the solute Si and the primary Si phase in the Al-18 wt.% Si alloy has been investigated. It has been found that a high gradient magnetic field is capable of separating the solute Si and the primary Si phase from matrix. Moreover, the field also affects the shape of the primary Si phase; indeed, the field has refined the primary Si phase and caused the morphological transition from flake to grain.     

沉积扩散法制备高硅钢

高硅钢(6.5%(质量分数)Si)是一种具有高磁导率、低矫顽力和低铁损等优异软磁性能的合金.但高硅钢的室温脆性和低的热加工性能严重影响了其在工业领域的应用.综述了化学气相沉积、等离子体化学气相沉积、电泳沉积、熔盐电沉积、电子束物理气相沉积及激光熔覆等6种沉积扩散法制备高硅钢的工艺和参数,从工艺路线、反应机理分析和性能的改善等几方面,概述了各种方法的研究现状和主要的优缺点,并简要论述了其发展前景,指出了今后的主要研究方向.     

Development of P/M Fe–P soft magnetic materials

Phosphorous is treated as an impurity in conventional steels owing to segregation of phosphorous and formation of brittle phosphides along the grain boundaries. It is responsible for cold and hot shortness in wrought steels. In conventional powder metallurgy, involving compaction and sintering, high phosphorous content (up to 0·7%) in Fe-based alloys exhibit attractive set of mechanical and magnetic properties. These powder-processed alloys suffer from increasing volumetric shrinkage during sintering as phosphorous is increased beyond 0·6%. Thus both cast as well as conventional powder metallurgy routes have their own limitations in dealing with iron?Cphosphorous alloys. Hot-powder forging was used in the present investigation for the development of high-density soft magnetic materials containing 0·3?C0·8% phosphorous to overcome these difficulties. It was observed that phosphorous addition improves the final density of the resulting product. It was further observed that hot-forged iron?Cphosphorous alloys have excellent hot/cold workability and could be easily shaped to thin strips (0·5?C1·0?mm thick) and wires (0·5?C1·0?mm diameter). The powder hot-forged alloys were characterized in terms of microstructure, porosity content/densification, hardness, soft magnetic properties and electrical resistivity. Magnetic properties such as coercivity 0·35?C1·24?Oe, saturation magnetization 14145?C17490 G and retentivity 6402?C10836 G were observed. The obtained results were discussed based on the microstructures evolved.     

PCVD涂硅的动力学研究

采用等离子体化学气相沉积（PCVD）法,在0．1－0．3mm厚的普通硅钢片表面涂硅,再进行短时间高温扩散,使硅钢片的含Si量增加到6．5％,铁损P10／50比原来钢片降低50％,其他磁性能也大有改善。试验结果表明,在460－600℃涂硅,其他条件不变,涂硅速度随温度升高而降低,并对等离子体反应的动力学和热力学进行了研究。     

High damping properties of Mg–Si binary hypoeutectic alloys

The damping properties of as-cast Mg–Si hypoeutectic alloys with Si contents of 0.25, 0.5, 1 wt.% were investigated by Dynamic Mechanical Analysis (DMA), respectively. The results show that the Si content has an interesting influence on the damping properties due to the primary cyrstallized Mg₂Si. The damping capacities of high damping Mg–Si hypoeutectic alloys are strain amplitude strongly dependent while the strain amplitude weakly dependent part hardly appears due to very few Si dissolved in matrix. In addition, the damping measurement of Mg–0.5 wt.% Si alloy with increasing temperature was carried out and the grain boundary peak is detected.     

The control of grain boundary segregation and segregation-induced brittleness in iron by the application of a magnetic field

Recycling of iron and steel becomes an universally important issue from the viewpoint of energy and resource saving. Impurity elements like Sn and Cu tend to accumulate in steels by repeated recycling and remarkably degrade mechanical properties of recycled iron alloys due to segregation-induced intergranular embrittlement. The goal of this work is to study the potential of magnetic annealing for the control of grain boundary segregation and intergranular embrittlement in iron alloy. This paper reports several important findings regarding the effect of magnetic annealing on segregation-induced brittleness in iron-tin alloy. Of particular importance is the observations that the concentration of tin at grain boundaries in iron is decreased by magnetic annealing and fracture toughness of iron-tin alloy is drastically improved to the level as high as pure iron.     

Microstructure and mechanical properties of a hot pressing-dynamic partition treated steel

The microstructure and mechanical property of improved press-hardened steel with hot pressing combined dynamic partitioning (HP-DP) treatment are presented. Microstructure of the steel subjected to HP-DP treatment is featured by multi-martensite phases and the retained austenite (RA) phase with carbon content gradient. Compared with conventional hot-pressed samples, the HP-DP samples show better tensile property especially ductility. The effect of HP-DP parameters on the evolution of RA and mechanical property is then discussed. Finally, hot pressing of a double U-shaped part using both 22MnB5 steel sheet and the developed HP-DP steel sheet was carried out with exact control of part temperature at the end of hot pressing followed by air cooling.     

Mechanisms of inherent and impurity-induced brittle intercrystalline fracture in pure FCC-metal iridium

Low cohesive strength of grain boundaries and high sensitivity of this parameter to the presence of non-metallic impurities are considered as the causes of grain boundary brittleness and poor workability of refractory fcc-metal iridium. The mechanisms of grain boundary brittleness in both contaminated and non-metallic impurity-free iridium are discussed in the presented paper.     

润滑剂对Si3N4陶瓷摩擦磨损性能的影响

在销—盘试验机上考察了水、油和一种常用切削液GMY对Si3N4／钢摩擦副摩擦磨损性能的影响．试验选用的速度和载荷范围分别是0．8—3．2m／s和58．8～235．2N润滑剂对摩擦和磨损的影响与润滑剂种类有很大关系．水润滑膜的强度弱，边界润滑效果差，所以在水润滑条件下，仍不能防止钢转移到Si3N4摩擦面上．油膜的强度较高，但由于验用的油不含添加剂等极性化合物，其边界润滑性也随载荷增大而逐渐变坏．GMY溶液中含有多种极性化合物，这些物质能在摩擦面上形成强度较高的边界膜，并在滑动过程中与表面作用形成摩擦化学反应膜，能起到很好的边界润滑作用，是一种良好的切削润滑剂．试验还发现，随着GMY溶液浓度的增大，其边界润滑性能可进一步得到改善．     

Mechanisms of inherent and impurity-induced brittle intercrystalline fracture in pure FCC-metal iridium

Low cohesive strength of grain boundaries and high sensitivity of this parameter to the presence of non-metallic impurities are considered as the causes of grain boundary brittleness and poor workability of refractory fcc-metal iridium. The mechanisms of grain boundary brittleness in both contaminated and non-metallic impurity-free iridium are discussed in the presented paper.