原材料

首钢硬质合金组合式轧辊研发获重大进展 首钢型材轧钢厂与首钢烟台东星公司共同进行的“硬质合金组合式轧辊在小型轧机上应用技术”研发工作,经过4次试验,一对采用新型材质的轧槽使用了近24小时,使用寿命是普通铸铁辊的10倍。这项总公司级的重点科技攻关项自的试验成功,填补了国内一项轧辊应用技术的空白,为首钢用高新技术改造传统钢铁业添了彩。成功开发出硬质合金组合式轧辊后,型材轧钢厂三条轧制生产线每月的换辊、换槽和生产准备时间,以及因换辊换槽而产生的废品量将明显减少。同时,高强度钢筋、冷镦用圆钢等一批精品材可实     

GCr15钢旋压轧辊表面失效原因分析

通过宏观分析、化学成分分析、硬度测试、金相检验、断口分析以及能谱分析等方法对某批GCr15钢旋压轧辊的早期表面崩裂剥落失效原因进行了分析。结果表明:由于旋压轧辊钢材中的碳化物发生了偏聚,呈链状和长条状分布,增加了轧辊的脆性,降低了轧辊的疲劳寿命,从而导致轧辊在使用一轮后就在受力最大区域出现了表面崩裂剥落现象,发生接触疲劳失效。     

铝基碳化硅精密铣削刀具磨损实验研究

针对铝基碳化硅切削加工中刀具易磨损、寿命低、切削难度大和加工成本高等问题,选用不同材料的硬质合金铣刀及金刚石铣刀进行切削加工实验,并利用扫描电镜和工具显微镜对高体积分数铝基碳化硅铣削时刀具磨损形态进行了分析研究.研究表明:硬质合金刀具前刀面和刃口磨损主要形式为粘结磨损和微崩刃,后刀面磨损主要为刻划磨损,而金刚石铣刀加工时刀具磨损很小;YG6X铣刀材料微观组织致密,抗磨损能力较强,宜粗加工时选用;金刚石刀体的硬度远大于SiC颗粒,且金刚石与工件的摩擦系数小,金刚石铣刀寿命远大于硬质合金铣刀,宜精加工时选用.     

盾构刀具硬质合金激光表面处理研究现状

盾构刀具由硬质合金刀头与高强度钢基体钎焊连接而成.硬质合金刀头的过早脱落与过快磨损是影响盾构刀具工作寿命的主要原因.激光技术具有节能、快速、绿色、精确自动化的独特优势.应用激光技术对硬质合金进行表面处理,可提高盾构刀具的可靠性.综述了改善硬质合金性能的激光技术,论述了激光处理对盾构刀具性能的改善情况;详细评述了激光织构技术对硬质合金钎焊性能、表面摩擦性能以及涂层结合强度的改善研究;介绍了激光相变硬化技术对硬质合金表面进行处理,提高硬质合金刀具耐磨性的研究进展;最后对盾构刀具硬质合金表面激光处理的发展趋势进行了分析展望.     

一种特殊烧结技术对梯度结构硬质合金性能影响的研究

研究了分段烧结制备梯度结构硬质合金技术以及粘结剂含量对梯度硬质合金的力学性能、梯度结构的影响.测试了梯度硬质合金刀片的切削性能.结果表明,分段烧结技术能成功地制备梯度结构硬质合金,且随着钴含量增多,合金梯度层厚度增厚,梯度结构更明显;合金的强度与磁饱和提高.切削试验表明:具有梯度结构涂层硬质合金刀片的切削性能比无梯度结构涂层硬质合金刀片的切削性能更为优良.达到同一磨损高度VB=0.15mm时,前者的切削寿命较后者提高了近一倍.     

从专利技术角度分析轧辊内部冷却技术发展

轧辊是轧机的主要部件,轧机工作时会导致轧辊温度升高,不利于金属轧制,对轧辊进行良好的冷却可以减少轧辊的磨损,延长使用寿命,提高被轧制金属的质量。本文通过cnabs数据库、ven数据库、dwpi数据库和sipoabs数据库中检索到的文献对轧辊内部冷却领域的专利申请进行了分析,阐述了国内外轧辊内部冷却领域的专利申请趋势、专利申请国家分布,并根据冷却介质的不同,将轧辊内部冷却技术划分为轧辊内部液体冷却、轧辊内部气体冷却和轧辊内部其他冷却等3方面进行技术发展路线研究。     

加热炉内背景补偿测温系统

钢坯在轧制前必须在加热炉内被均匀地加热到规定的温度。过热会增加氧化铁皮的损失和能源损失,甚至局部熔化、烧毁炉内设备、缩短炉子寿命等,过冷将不能完成轧制,甚至毁坏轧辊,因此测量钢坯的温度十分重要。     

轧辊表面激光处理技术的研究进展

轧辊是轧机的主要变形部件.总结了轧辊材质、主要工作形式及失效方式和轧辊表面处理技术应用概况,具体从激光淬火与重熔技术、激光合金化和激光熔覆3个方面介绍了轧辊激光表面处理(修复)技术的研究和应用现状,并展望了激光表面处理技术修复表面失效轧辊的发展前景.     

超细WC-Co硬质合金粉末的制备及其致密化研究

以超细碳化钨(WC)、氯化钴(CoCl2.6H2O)和柠檬酸钠(C6H5O7Na3.2H2O)为原料,水合肼(N2H4.H2O)为还原剂,使用液相还原法制备超细WC-Co硬质合金粉末,并通过低压烧结使其致密化,制得力学性能良好的WC-Co硬质合金。考察了反应体系温度对硬质合金粉包覆率、反应时间对包覆效果的影响,采用SEM、TEM、XRD等手段对硬质合金粉进行了表征,确定了制备超细WC-Co硬质合金粉的优化工艺条件,并对比了不同规格的WC-Co硬质合金烧结体的力学性能。结果表明,此方法制得的WC-Co硬质合金粉纯度高,粒径均匀,无团聚,低压烧结后所得硬质合金烧结体力学性能良好。     

从专利技术角度分析变凸度轧辊技术发展

随着生产技术的不断发展,用户对带钢的质量和品种的要求越来越高,变凸度轧辊作为一种近年来发展较新的轧辊,在板带材生产领域得到了较好的应用。本文针对变凸度轧辊的专利申请进行了统计,对国内外专利申请量、申请人分布等多方面进行了分析,并阐述了变凸度轧辊领域的专利申请发展趋势,给出了其技术领域的发展脉络,了解到了VC轧辊和CVC轧辊的发展路线。     

Evolution of elastic modulus in roll forming

Roll forming is a continuous process in which a flat strip is incrementally bent to a desired profile. This process is increasingly used in automotive industry to form High Strength Steel (HSS) and Advanced High Strength Steel (AHSS) for structural components. Because of the large variety of applications of roll forming in the industry, Finite Element Analysis (FEA) is increasingly employed for roll forming process design. Formability and springback are two major concerns in the roll forming AHSS materials. Previous studies have shown that the elastic modulus (Young’s modulus) of AHSS materials can change when the material undergoes plastic deformation and the main goal of this study is to investigate the effect of a change in elastic modulus during forming on springback in roll forming. FEA has been applied for the roll forming simulation of a V-section using material data determined by experimental loading-unloading tests performed on mild, XF400, and DP780 steel. The results show that the reduction of the elastic modulus with pre-strain significantly influences springback in the roll forming of high strength steel while its effect is less when a softer steel is formed.     

Structure formation and properties of NbC-Hadfield steel cermets

The structure and properties of based on NbC cermets with a binder of Hadfield Steel has been studied. The cermets have been produced by the infiltration of NbC skeletons with steel at 1450°C in the argon atmosphere. The resultant materials have two-phase structure, namely, manganese austenite and NbC grains. The optimal complex of mechanical properties has been attained in cermets with the 55–60 vol % concentration of the carbide phase.     

Life of rolls in a cold rolling mill in a steel plant-operation versus manufacture

Failures of rolls occur due to improper manufacturing and operational parameters. Prematurely failed (spalled) roll samples collected from a reputed steel plant were examined for their chemistry, inclusion content, microstructures, carbide characteristics, hardness and retained austenite content. The residual stresses were also measured on the inner and outer surfaces of the spalled roll pieces. The higher content of retained austenite was primarily responsible for the spalling of indigenous rolls for which subzero treatment has been recommended. Several suggestions have also been made for smooth operation of the mill and consequently for the life extension of work rolls.     

Microstructure and Eutectic Carbide Morphology of the High Speed Steel Strips Produced by Twin Roll Strip Casting Process

The M2 high-speed steel strip was produced by using the laboratory scale twin roll strip caster. The microstructure and eutectic carbide morphology of thus produced products were observed and analyzed, and the comparison of those with conventional products was carried out. The effects of the processing parameters such as the melting temperature, the pouring temperature, rolling speed and separating force on the microstructure and eutectic carbide morphology and their distribution were analyzed. The spheroidizing process of the strips in the annealing process was investigated. The relations between the growth and spheroidizing of the eutectic carbide and the annealing technology were obtained, and the mechanism of the twin roll strip casting process improving the eutectic carbide spheroidizing was discussed. The theoretical instruction for determining the subsequent treatment process was provided.     

Development of new material and heat treatment for tools ensuring high performance in hot seamless tube rolling

Abstract

A new technology has been developed to improve the life of tools used for high temperature steel rolling in seamless tube manufacturing. It is a joint technology combining a new chemical composition and a special heat treatment. The new steel tool material has high Cr, C, and Ni contents compared with those of the conventional tools in order to increase the volume fraction of carbide which increases wear resistance. Through the new heat treatment, the macroscopic distribution pattern of eutectic carbide changes from meshlike to granular form increasing resistance against crack propagation. The validity of the results in the laboratory has been verified on the production line.     

Investigation into the cracking of inner cover of batch annealing furnace at bokaro steel plant

A detailed metallurgical investigation was undertaken to ascertain the cause of the premature cracking of inner covers used in the batch annealing furnaces of Bokaro Steel Plant of the Steel Authority of India Limited (SAIL). It was found that the cracking was a result of the profuse precipitation of chromium carbide. Precipitation of chromium carbide sensitizes the steel to corrosion attack because of denudation of chromium from the matrix. Use of a properly stabilized austenitic stainless steel was recommended for prolonged life of the inner covers.     

Influence of Ti on MC Carbide in M2 Steel

Influence of Ti on MC carbide of M2 high speed Steel was investigated by experimental observation, thermodynamic calculation and crystallographic calculation. With addition of Ti into M2 steel, large quantities of dispersed TiC particles formed in the steel melt at higher temperature than that of the formation of MC carbide. TiC can act as heterogeneous nuclei for the crystallization of MC carbide particles, and therefore promote the formation of blocky MC carbide.     

Effect of electromagnetic centrifugal casting on solidification microstructure of cast high speed steel roll

Using self‐made electromagnetic centrifugal casting machine, optical microscopy (OM) and D/max2200pc X‐ray diffraction, the solidification microstructure and phases of as‐cast high speed steel(HSS) roll made by sand casting, centrifugal casting and electromagnetic centrifugal casting were investigated. The experiment results show that the phases of as‐cast high speed steel (HSS) roll are alloy carbide (such as W₂C, VC, Cr₇C₃), martensite and austenite. The centrifugal casting and electromagnetic centrifugal casting can apparently improve the solidification structure of HSS roll. With the increase of electromagnetic field intensity (B), the volume fraction of austenite in the HSS solidification structure increased obviously and eutectic ledeburite decreased, the secondary carbide precipitated from the austenite is more fine and distribution of secondary carbide is more even.     

Fundamental investigation of interfaces in particle reinforced steel sheets processed by thin strip casting

Along the steel industry history, the production of flat‐steel products has technologically evolved towards reducing slab thickness at the output of the continuous casting machine. This development has been related to the incessant requirement of providing a certain steel quality at lower costs. As a result of this procedure, the thin strip casting technology emerged in a commercial scale at the end of the nineties, with all the advantages of a near‐net‐shape manufacturing process. In particularly, the higher energy efficiency and reduced environmental impact turned it as a very promising and attractive technology for the steel industry. With the purpose of obtaining new types of steel sheets, characterized by improved mechanical and tribological properties, reinforced steel strips have been produced by introducing slight modifications to a twin‐roll caster. In this regard, a considerable enhancement of the mechanical properties has been achieved.     

Technology of the fabrication and launching the production of large-size cemented carbide products for the metallurgy industry of Ukraine

Scientific research, on the basis of which a technology of manufacture large-size cemented carbide products has been developed, and special features of the fabrication of cemented carbide rolls to be used in the metallurgy industry have been considered.