Hydrogen Degradation of High-Strength Weldable Steels in Seawater

Hydrogen degradation of high-strength weldable steels was evaluated under monotonic static tensile loading in seawater at room temperature. Two types of quenched and tempered steels and their submerged-arc welded and shielded-metal-arc welded joints were examined. The slow-strain-rate tests were carried out on cylindrical smooth specimens in air and in artificial seawater. The tests in seawater were performed under cathodic polarization for various current densities. The relative values of fracture energy, time to failure, elongation, reduction in area, and tensile strength were used as measures of hydrogen degradation. The permeation of hydrogen through the base metal, the heat-affected zone, and the weld metal were analyzed by using the conventional Devanathan-Stachurski method. The hydrogen diffusivity and the content of diffusible hydrogen were established. The observed decrease in the relative values of the degradation parameters with the increase in the current density exhibits a certain minimum. The loss of plasticity was as high as 70–90% for the base metals and welded joints. The subsequent increase in the current density does not cause higher degradation. Good correlation was obtained between the relative parameters of degradation (except tensile strength) and the concentration of diffusible hydrogen.__________Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 6, pp. 101–104, November–December, 2004.     

组合焊缝对中碳合金钢焊接裂纹的影响

采用Ｙ形坡口裂纹试验和显微分析方法，研究了三种不同的组织焊缝对中碳合金钢焊接裂纹的影响，结果表明，底层焊道熔俣区裂纹为氢致延迟裂纹；底层焊条的合金系统对该裂纹的生成有一定的影响，底层焊道熔合区的马氏体和氢的富集以及大的拘束应力，是裂纹生成的必要和充分条件；提出了防止裂纹产生的用工艺。     

高强钢低匹配焊接接头应用性能研究

本文采用低匹配焊条材料焊接了高强度钢材,对其焊接接头硬度、强度、抗弯性能、韧性和抗爆性能进行了综合试验研究,研究结果表明,对于屈服强度高达1,000 MPa的钢,其低匹配焊接接头如果采用常规焊缝余高控制工艺,将出现以下不利状况:(1)无余高焊缝金属承受横向拉应力,在母材及HAZ拘束下首先屈服时,发生低延性破坏;(2)有余高焊接接头在弯曲应力及弯曲、拉伸复合作用下,焊接接头易出现焊缝首先塑变破裂的低应力失效现象。其根本原因为焊接接头软质焊缝区塑性变形抗力的不足。此类破坏发生时,钢板尚未充分塑性变形,从承受应力水平和吸收能量能力来看,这将导致焊接接头系统的服役能力大为降低,因此提高低匹配焊接接头焊缝区塑性变形抗力变得极为重要。利用第三强度理论分析了低匹配焊接接头变形特点,并进行了此类接头焊缝余高的特殊设计,获得和传统等强匹配等效的焊接接头,即在服役状态下,确保焊缝金属不先于母材发生塑变集中而失效。     

铜在高强度合金钢及焊缝金属中的作用

评述了铜对高强度低合金钢及焊缝性能的影响 ,详细阐述了铜在钢中的溶解特性和沉淀强化机理。并对今后的研究工作提出了建议     

Physical Simulation-Based Characterization of HAZ Properties in Steels. Part 1. High-Strength Steels and Their Hardness Profiling

Strength of Materials - In the vehicle industry, there is an increasing demand for wider application of high-strength steels. New generations of high-strength steels, with higher strength and...     

Susceptibility to Hydrogen-Induced Cracking of Weld Beads on High-Strength Structural Steel

We study the hydrogen embrittlement and rupture of specimens of high-strength low-alloy steel with weld beads subjected to hydrogenation under the conditions of cathodic polarization. The specimens fail in the heat-affected zone on the boundary between the main metal and the weld bead in the zone of application of the latter and, especially, near its end. This explained by a higher hardness of the metal in this zone caused by the specific features of the temperature field formed in the process of welding. __________ Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 2, pp. 101–104, March–April, 2005.     

Cold Cracking Resistance of Butt Joints in High-Strength Steels with Different Welding Techniques

Strength of Materials - Investigation results are presented to improve the structural strength (cold crocking resistance) of weld joints in high-strength steels with the yield limit over 600 MPa....     

Strength Assessment of Welded Joints of High-Strength Alloy Steels by Indentation Method

Strength of Materials - The paper presents the indentation method for strength assessment of the welded joints in high-strength alloy steels, including base metal, heat-affected zone, and welded...     

Surface Hardening of High-Strength Low Alloy Steels (HSLA) Dual-Phase Steels by Ball Burnishing Using Factorial Design

Burnishing is used increasingly as a finishing operation which gives additional advantages such as increased hardness, fatigue strength, and wear resistance. Experimental work based on 3⁴ factorial design was carried out to establish the effects of ball burnishing parameters on the surface hardness of high-strength low alloy steels (HSLA) dual-phase (DP) steel specimens. Statistical analysis of the results shows that the speed, feed, lubricant and ball diameter have significant effect on surface hardness.     

Effect of Mechanical Cut-Edges on the Fatigue and Formability Performance of Advanced High-Strength Steels

Mechanical cut-edge properties influence the fatigue lives and formability capacity of advanced high-strength steels. This factor is critical as S355MC and DP600 exhibited an increased sensitivity to fatigue cracks initiating from defects on the cut-edge fracture zone. Mechanical cut-edges as a result displayed a decreased level of formability that was highly dependent on the cut-edge surface and internal microstructure of the cut-edge produced. It was determined that, by controlling the mechanical clearance, optimized mechanical cut-edges were produced. This was achieved through minimizing surface damage and by controlling the internal and topographical properties of the cut-edge zones.     

Strain-Induced Precipitation Kinetics of Vanadium Carbonitride Precipitates with the Cubic Structure in High-Strength Weathering Steels

Strength of Materials - The strain-induced precipitation kinetic model of vanadium carbonitride [V(C, N)] precipitates with the cubic structure in vanadium-nitrogen (V–N) microalloyed...     

The Use of Crack-Tip Opening Displacement for Testing of the Hydrogen Embrittlement of High-Strength Steels

Stress-corrosion cracks are, as a rule, brittle and often encountered under stresses much lower than the yield strength. For this reason, the methods of linear elastic fracture mechanics (LEFM) can be used for the investigation of stress-corrosion cracking (SCC). However, in some cases, these methods are inapplicable, and it is necessary to use the methods of so-called elastoplastic fracture mechanics (EPFM). In the EPFM approach, the J-integral is the most commonly used parameter for correlating crack initiation and propagation but the crack-tip opening displacement (CTOD) and crack-tip opening angle (CTOA) prove to be promising alternatives, especially for thin-sheet materials. Since both these parameters are connected with the crack geometry and, hence, reflect the level of strain at the crack tip, they appear to be useful correlation parameters for the cases of SCC, where the level of strain in the vicinity of the crack tip and, in particular, the strain rate, are the determining variables of the process. The hydrogen embrittlement of a higher-strength structural steel and welded joints of a C-Mn steel is assessed by using the CTOA and CTOD methodologies. In constant-extension-rate tests (CERT), fatigue precracked specimens were loaded with various low strain rates and electrolytically charged with hydrogen. It was discovered that hydrogen embrittlement significantly affects the crack-growth resistance curves (R-curves) thus generated and the opening angle for which the crack propagates into the material.__________Published in Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 6, pp. 35–40, November–December, 2004.     

Structural Transformations of the Metal of Heat-Affected Zone of Welded Joints of High-Strength Armor Steels

Materials Science - We construct the thermokinetic diagrams of austenite decomposition and analyze the influence of the rate of cooling of specimens simulating the metal of the heat-affected zone...     

钢铁晶粒超细化方法及其研究进展

综述了目前钢铁材料的各种晶粒细化方法、原理及其研究动态,展望了钢铁材料晶粒细化技术的研究前景,以期对新一代钢铁材料的研究和开发提供理论指导。分析认为今后钢铁晶粒超细化技术的研究方向主要有2个方面:一是继续深入讨论和探索晶粒超细化机理以及超细晶粒材料结构与性能的关系;二是开发适宜于工业化生产的钢铁晶粒超细化技术。     

Some Reasons for Fracture of Load-Bearing Elements of Landing Gears Made of High-Strength Steels in Antonov Airplanes

We give the results of tests of some reasons for the unpredicted fracture of force components of a landing gear made of high-strength steels.     

铁素体不锈钢的进展

近年来，不锈钢的开发者们已把大部分注意力集中于开发铁素体不锈钢。本文论述了铁素体不锈钢的合金化、优点（耐蚀性和经济性）、局限性（脆性倾向），以及该类型合金的研究、开发和应用状况。     

抗菌不锈钢材料及其发展现状

综述了各种抗菌不锈钢材料(包括加铜和加银的抗菌不锈钢、表面涂层抗菌不锈钢、抗菌复合不锈钢板)的抗菌机理、特点,应用和开发现状。在普通不锈钢内添加一定量的抗菌金属元素Cu,Ag,Zn等,控制铸造、锻压、轧制以及热处理过程,使抗菌金属元素在不锈钢基体内以一定的大小、形态,均匀弥散地析出,并保证析出相的体积百分比,在不降低普通不锈钢的力学性能和抗腐蚀性能的情况下,赋予其优异的抗菌性能。