认清形势转变观念迎接新的挑战实现钢管行业可持续发展--中国钢铁工业协会钢管分会理事长严泽生在钢管分会第四届三次理事(扩大)会议上的报告(有删节)

1 我国钢管行业运行状况 2005年我国钢铁工业发展出现了历史性的重要转折。在上级协会的大力支持和全体会员企业的共同努力下,中国钢管行业走过了不平凡的历程,取得了新的成就,已连续5年高速健康地发展,在从钢管大国向钢管强国转变的进程中迈出了坚实的步伐。     

The challenge to produce consistent mechanical properties in Nb-HSLA strip steels

High strength steels have provided a unique opportunity for the automotive industry to achieve weight reduction via reduced material thickness whilst maintaining performance requirements such as crash worthiness. However, the initial success of high strength low alloy (HSLA) steels was constrained by inconsistencies in the final mechanical properties. Although significant improvements in both mechanical and dimensional properties have been made, increasingly stringent customer specifications for high strength steels mean that the challenge to reduce variability in automotive HSLA steel products and enure their continued competitiveness has never been greater.

This paper addresses the issues concerning the controlled hot rolling of Nb-HSLA strip steels through a series of laboratory and commercial trials. Both sets of data established that: (i) the strength was decreased by reducing the soak temperature from 1250 to 1150 °C; (ii) the presence of furnace skid chills during soaking locally reduced the strength; (iii) lowering of the finishing temperature towards the Ar₃ reduced the overall strength, but improved the coil width property consistency; and (iv) the existence of an optimum coiling temperature developed higher strengths and improved property consistency.

The programme of work conducted also indicates that, by finishing near the Ar₃ temperature, very fine ferrite subsurface grains are created which limit the fall in strength. Additionally, the commercial trials highlight the need to compensate for the exposure-related cooling effects of the inner and outermost laps of the hot rolled coil, thereby reducing any potential for developing further inconsistencies.     

加快轧钢行业结构调整迎接21世纪挑战

分析了轧钢行业板,管,型材生产工艺及设备存在的诸多问题,进而指出轧钢企业调整结构,开拓市场不容缓。为此,提出了调整结构首先应优化区域结构,然后是产品结构的调整。并应积极开国民经济急需的铁路,建筑,石油,汽车,集装箱,造船业等用材。     

Flash welding Hadfield steel to rail steel

The results of investigation of the special features of the formation of the structural and phase composition of R6M5 steel – TiC composite coatings in relation to the content of titanium carbide are presented. It is shown that the amount of retained austenite in the hardened layer does not exceed 5% of the total volume of the matrix already after adding 5% titanium carbide. The mean size and the volume fraction of the titanium carbide particles decreased in analysis of the structure from top to the bottom of the deposit.     

An atomic emission spectroelectrochemical study of corrosion inhibition: The effect of hexamethylenetetramine on the reaction of mild steel in HCl

The dissolution of low carbon steel in hydrochloric acid has been investigated by atomic emission spectroelectrochemistry. The rate of Mn, Fe and P dissolution was measured as a function of time for steels of variable Mn and P composition and as a function of HMTA concentration. Regardless of the reactivity of the steel in uninhibited solutions, at high concentration of HMTA, all steel grades show a nearly identical dissolution rate. The effect is selective for Fe; the dissolution of segregated Mn is not affected by HMTA.     

我国废钢铁和用整体下滑,逆转艰难——2013年中国废钢铁市场展望及2012年市场回顾

2012年我国废钢铁市场低迷,供需两弱,废钢铁应用总量自2000年以来第一次出现负增长,废钢比大幅度下滑,跌人谷底,创历史新低.废钢铁回收利用市场进入了一个真正的寒冬期,形势严峻.我国废钢铁利用下滑的主要原因,除欧债危机持续发酵及美国经济疲软,全球大宗商品系统性风险全面爆发等世界经济危机的影响外,我国经济的不景气(2012年中国GDP增长率为7.8％、创2000年以来最低),钢材市场长期低价运行,需求市场疲软,钢铁原料配置不合理,环保违法成本过低,政策引导乏力等都是造成2012年废钢铁回收利用下滑的主要刺激因素.     

Effect of nitrogen on toughness and strain age embrittlement of ferritic steel weld metal

Abstract

Investigations were carried out to evaluate the influence of dissolved nitrogen in ferritic steel weld metal on its toughness and strain aging behaviour through fracture mechanics as well as conventional impact testing approaches. Manual metal arc C–Mn steel weld metals with nitrogen contents between 80 and 210 ppm (wt) were investigated under four different post-weld conditions, namely, (i) as welded, (ii) stress relieved, (iii) artificially strain aged, and (iv) artificially strain aged and stress relieved. Quantitative metallography and low load microhardness studies of microphases were an integral part of these investigations. The results demonstrate the highly detrimental effect of nitrogen on the toughness behaviour of C–Mn steel weld metal, particularly under strain aging conditions. This is substantiated by the decrease of acicular ferrite content with the accompanying increase in primary ferrite and ferrite with second phases in the microstructures. Also, there is a distinctive increase in acicular ferrite microhardness. Post-weld stress relieving heat treatment under these conditions results in only a marginal improvement in toughness and shifts the fracture behaviour from brittle to ductile or quasiductile only for low nitrogen weld metals. Comparing the results of the crack tip opening displacement and Charpy tests, it is observed that both methods show the influence of nitrogen on toughness behaviour to have the same form but the magnitudes of the effect measured are different, the results obtained using the fracture mechanics method appearing very conservative.     

纯铜与不锈钢扩散焊接头性能及原子扩散动态解析

采用微观组织观察、硬度测试、拉伸试验、EPMA(电子探针)等手段研究了焊接工艺条件对纯铜与铁素体410L以及奥氏体304不锈钢扩散焊接接头性能的影响,结合理论计算对两种接头的原子扩散机理进行了解析.结果表明,在焊接压力、时间一定的条件下,接头的抗拉强度随焊接温度的升高而增大.Cu原子与410L最适宜的焊接温度比Cu原子与304的大约小50K,这是由于Cu原子向体心立方晶体(bcc)铁素体系中的扩散速度比在面心立方晶体(fcc)奥氏体系中快的缘故.Cu原子向不锈钢一侧扩散的实测值比理论值小是由于理论的初期条件是假定试样100%完全密接,而实际的接合界面却是粗糙不平,要达到接合初期的完全密接是需要时间的.     

Mineral resources — A challenge to extractive metallurgy

The following article is a slightly revised version of a speech delivered during the Extractive Metallurgy Division Symposium on Electrometallurgy held in Cleveland, Ohio, in December, 1968.     

45钢/304不锈钢连续驱动摩擦焊接工艺

异种材料焊接结构以其在力学性能、耐腐蚀性等多方面的综合优势,而被广泛应用到装备制造中.针对电机行业中的应用需求,采用连续驱动摩擦焊接实现了45钢和304不锈钢异种钢棒材的优质高效连接,通过工艺优化试验获得了成形以及性能良好的焊接接头.结果表明,在焊接界面处有碳化物层的形成,45钢侧有很薄的铁素体层出现,304不锈钢侧奥氏体晶粒发生了细化,但热影响区内晶粒发生粗化.焊态试样抗拉强度达到870 MPa,拉伸断裂在焊缝界面,为脆性断裂,但微观上有韧窝断裂和准解理断裂两种断裂机制.     

Corrosion resistance of TiO2 films grown on stainless steel by atomic layer deposition

Titanium dioxide (TiO₂) films have been deposited onto stainless steel substrates using atomic layer deposition (ALD) technique. Composition analysis shows that the films shield the substrates entirely. The TiO₂ films are amorphous in structure as characterized by X-ray diffraction. The electrochemical measurements show that the equilibrium corrosion potential positively shifts from − 0.96 eV for bare stainless steel to − 0.63 eV for TiO₂ coated stainless steel, and the corrosion current density decreases from 7.0 × 10^− 7 A/cm² to 6.3 × 10^− 8 A/cm². The corrosion resistance obtained by fitting the impedance spectra also reveals that the TiO₂ films provide good protection for stainless steel against corrosion in sodium chloride solution. The above results indicate that TiO₂ films deposited by ALD are effective in protecting stainless steel from corrosion.