高强度船板钢冲击性能偏低原因分析

针对E36船板钢冲击性能偏低做了分析,采用金相组织分析、SEM断口形貌分析等手段。分析结果表明,组织的不均匀以及珠光体的分布形态不良是导致冲击性能不合格的主要原因。     

800MPa级别钢熔敷金属热处理脆化机理研究

用于制造船体结构的10Ni5CrMoV钢,为了消除焊接残余应力,在焊后需对其焊接接头进行热处理。试验采用纯氩气体保护焊接10Ni5CrMoV钢,焊后热处理后发现其熔敷金属-50℃冲击韧性大幅下降。利用扫描电镜(SEM)、透射电镜(TEM)和俄歇电子能谱分析方法(AES)对熔敷金属热处理前后的组织和冲击断口进行分析,找出其冲击韧性下降的原因。试验结果表明:10Ni5CrMoV钢熔敷金属热处理后由于回复作用板条状组织变粗或消失,在晶界磷元素的偏聚和大量的碳化物在晶界析出导致其冲击韧性下降。     

10CrNi5Mo船体高强韧特厚钢板的研究

研究开发了120mm高强韧特厚钢板,通过力学性能分析和断口形貌、组织观察对工业试制钢板的综合性能进行了研究。结果表明,采用NiCrMo合金系成分设计,工业试制的10CrNi5Mo特厚钢板获得了良好的综合性能,显示出了高的上平台冲击功和良好的低温韧性。     

Microstructure of Al-Mg-Si Weld Joints Produced by Pulse TIG Welding

Al-Mg-Si alloys (6000 series) are heat-treatable aluminum alloys and are extensively used in various sectors such as aerospace, automobiles, and general construction. Fabrication of these alloys often requires welding. Pulse TIG offers many advantages over conventional TIG welding as far as control of microstructure is concerned. This research investigated the effect of pulsed TIG welding parameters such as pulse duration, peak current, pulse frequency on the microstructure of heat-affected zone, and fusion line and weld metal of Al-0.5%Mg-0.5%Si weld joints. It was observed that a significant change in microstructure takes place in moving from the base metal to weld centerline. Dissolution of phases present along the grain boundary occurs as the fusion line is approached. Grain structure of heat-affected zone, fusion line, and weld metal appears to have tangible relationship with pulse parameters.     

Influence of temperature on impact fracture behavior of an alloy steel

In this paper, the influence of temperature on impact toughness and fracture behavior of alloy steel (AISI Classification 8320) is presented and discussed. Impact toughness decreased with a decrease in test temperature. The extrinsic influence of temperature on impact toughness–fracture resistance relationships is rationalized in light of the conjoint and mutually interactive influences of intrinsic microstructural features, local stress states and macroscopic fracture behavior.     

An analysis of interface delamination mechanisms in orthotropic and hybrid fiber-metal composite laminates

The onset and propagation of interlaminar defects is one of the main damage mechanisms in composite materials. This is even more the case when considering layered materials comprising metallic laminae (typically Aluminium) and FRP laminae. Propagation of delamination mainly depends on the initial crack extension and its loading mode.This work presents some results of a combined analytical-numerical-experimental study on the onset and propagation mechanisms regarding interlaminar defects. Two cases have been analysed in particular, the first consisting of a glass-fibre reinforced epoxy resin laminate, and the second consisting of a hybrid laminate where a lamina of aluminium is layered between FRP laminae.     

Continuous Drive Friction Welding Studies on AISI 304 Austenitic Stainless Steel Welds

An attempt has been made to study the friction welding characteristics of an austenitic stainless steel AISI 304 employing a continuous drive friction welding machine. The central region in some of the welds exhibited abnormal grain growth. Optimization studies revealed that the optimum parameters depend on the property of interest. In general, friction welds exhibited lower notch tensile strength and impact toughness than the parent metal due to aligned microstructure features. An inverse relationship has been observed between notch tensile strength and impact toughness.     

Effect of Post-weld Heat Treatment on Microstructure and Fracture Toughness of 30CrMnSiNi2A Steel Welded Joints

The electron beam local post-weld heat treatment (EBLPWHT) is a rather new method that provides the advantages of high precision, flexibility and efficiency, energy saving and higher productivity. This paper studies the effect of two post-weld heat treatment processes on the microstructure, mechanical properties and fracture toughness of an electron beam welded joints in 30CrMnSiNi2A steel. EBLPWHT, in a vacuum chamber, immediately after welding and a traditional furnace whole post-weld heat treatment (FWPWHT) were compared. The experimental results show that, after EBLPWHT treatment, the main microstructure of weld was changed from coarse acicular martensite into lath rnartensite, HAZ was changed from lath martensite, bainite into lower bainite, and base metal was changed from ferrite and pearlite into upper bainite and residual austenite. The microstructures of different zones of joints in FWPWHT condition were tempered sorbite. The properties of welded joints can be improved by the EBLPWHT in some extent, and especially largely for the fracture toughness of welded joints. However the value of fracture toughness of base metal is comparatively low, so appropriate heat treatment parameters should be explored in the future.     

10MnNiCrMoV钢低温冲击韧性的研究

10MnNiCrMoV是新一代造船材料,本文通过对该钢种的低温冲击韧性进行系统研究发现,10MnNiCrMoV钢具有良好的抗脆性破坏能力,可作为无限海区的舰船船体材料。确定了冲击能VET与能量转变温度VTrE和试验温度的关系模型VET/VEo=9+95/{1+exp[-0.05×(T-VTrE-2.5)]},通过该模型可确定舰船在不同的最低使用温度下,10MnNiCrMoV钢的-40℃最低冲击功。     

一种适用于通讯器材的铝锰合金开发研究

测试了不同锰含量Al—Mn合金的硬度和冲击韧性,分析了锰含量对Al—Mn合金断口形貌特征及断裂形式的影响。结果表明：随着锰含量的增加Al—Mn化合物数量增加,Al—Mn合金铸态硬度提高,冲击韧性降低;随着锰含量的增加Al—Mn化合物形态由细变粗,由长变短,由头部圆形转变具有尖角形块状,材料的冲击韧性急剧下降。随着锰含量的增加Al—Mn合金断口形貌由塑性断裂向准解理断裂、脆性断裂特征变化。     

焊接热循环对一种低合金船体钢组织及性能的影响

通过焊接热循环模拟试验,对试样进行微观组织结构观察和低温韧性测试,研究了不同条件的热循环过程对一种低合金高强度船体钢组织及性能的影响。结果表明:在一定的焊接线能量范围内,t8/5对试验钢的组织及性能影响不大,模拟粗晶区组织主要为马氏体和贝氏体;峰值温度对试验钢热影响区组织及低温韧性影响较大,粗晶区为热影响区薄弱环节,二次热循环可提高试验钢粗晶区的低温韧性;试验钢经历两次粗晶区热循环后仍保持有细小的板条结构及条间奥氏体,冲击韧性较为稳定。     

管线钢在役焊接热影响区显微组织的热模拟研究

为探讨在役焊接这种严酷的焊接条件下管线钢焊接热影响区显微组织的变化,采用焊接热模拟技术、金相分析及透射电镜对比研究了X70管线钢在役焊接热影响区和常规焊接热影响区的金相组织和精细结构.结果表明,在役焊接的快速冷却只对粗晶区的金相组织产生了较大影响,而对过渡区、细晶区和类母材区的金相组织几乎没有影响.金相显微镜下两者粗晶区的组织均为贝氏体铁素体和粒状贝氏体,但各组织的形态和数量不同.在透射电镜下观察,两者粗晶区的精细结构有较大差异,在役焊接粗晶区生成了少量细小的横穿贝氏体铁素体板条的板条马氏体,常规焊接粗晶区生成了少量的块状铁素体组织.     

07Cr12NiMoVNb耐热钢回火脆性研究

通过冲击试验和断口形貌分析确定07Cr12NiMoVNb耐热钢有回火脆性,并存在二个回火脆性温度区间(450～525℃和575～625℃)。低温回火脆性到高温回火脆性区间的断口形貌从准解理+解理到解理+沿晶断裂,出现沿晶断裂时,冲击值最低。为方便工程上判断是否出现回火脆性,借用了韧/脆转变的(FATT50)概念。     

Fabricating Defect-Free API X65 Steel Welds under Underwater Wet Conditions using Friction Taper Plug Welding

The experiment on API X65 steel was carried out using friction taper plug welding (FTPW) under underwater wet conditions at room temperature. Sound weld formation can be achieved vastly at axial force ranging from 25 to 40 kN and a rotating speed of 7000 rpm. The microstructure of the weld zone consists of lath martensite, upper bainite, granular bainite, polygonal ferrite, and acicular ferrite. The microstructure of heat affected zone (HAZ) mainly consists of lath bainite as well as a bit of lath martensite and granular bainite. The tensile properties of defect-free welds are excellent. The maximum impact energy of the V-notch of bonding area can reach 110 J, which was conducted at 0°C with an error of ±12.5 J. The typical SEM impact fracture morphology presents areas of cleavage, quasi-cleavage, and dimples.     

On the Effect of Hydrogen on the Fracture Toughness of Steel

A model is developed to quantify the effect of hydrogen on the critical stress intensity factor or fracture toughness of steels. The stress-assisted hydrogen diffusion model proposed by Liu (1970) is assumed and combined with the elastic stress field around the crack tip for quantifying the hydrogen concentration at the crack tip. Introducing a fracture criterion as the critical hydrogen concentration at a critical distance ahead of the crack tip, this model is successfully applied to the interpretation of hydrogen embrittlement behavior in a piping material. Experimental data at constant temperature were used to validate the model. With further development, the model has the potential to predict fracture toughness values at temperatures other than the test temperature.     

脆性材料断裂韧性测定的山形缺口试件和方法

本文扼要地介绍了测定新型结构陶瓷、高强度金属、以及其他脆性材料断裂韧性的山形缺口试件与方法。概述了这个方法的发展史、优缺点、目前研究概况、主要理论分析与实验研究成果,以及存在的问题和发展动向。     

Effects of strength mis-matching on the fracture behavior of nuclear pressure steel A508-III welded joint

In this paper, according to the nuclear pressure steel A508-III, the effect of strength mis-matching on the fracture behavior was analyzed by fracture mechanics test and the crack tip stress field of three-point bend specimen was analyzed by using finite element analysis method (FEM). The fracture of heat-affected zone (HAZ) was emphasized especially. The results of FEM show that if the under-matching weld was used, the opening stress and stress triaxiality in the vicinity of crack tip would increase for weld-crack specimen, and would reduce for HAZ-crack specimen. This tendency was confirmed by the test results.     

D40M埋弧焊丝改进研究

适当增加D40M埋弧焊丝中C、Cu的含量,解决了该埋弧焊丝与705-ch焊剂配用时出现的熔敷金属低温韧性偏低和焊丝镀铜的问题,保证了D40M埋弧焊丝生产供货的合格率。     

10Ni5CrMoV钢低温冲击断裂行为研究

采用示波冲击试验方法，研究了１０Ｎｉ５ＣｒＭｏＶ钢在冲击断裂过程中各部分能量与温度的关系。在２０℃～－１００℃温度范围内，裂纹形成功（Ｅｉ）基本不变，裂纹扩展功（Ｅｐ）显示与总冲击功相一致的转变特征。在上平台，１０Ｎｉ５ＣｒＭｏＶ钢具有高的裂纹扩展功，Ｅｐ＞１００Ｊ；在转折区，钢的韧脆转变平缓。试验结果表明，Ｅｐ＝Ｅｉ对应的温度可作为韧脆转折温度。本试验钢的韧脆转折温度低达－８５℃，具有优良的低温韧性。     

低碳低合金钢SFHV23B的“意外”氢脆破坏

本文对某大化肥厂气化炉盖材料SFHV23B钢的脆性开裂事故,综合利用机械性能测试、化学成分分析、金相、SEM、电子探针和Auger等现代化手段,进行了深入地分析和讨论,揭示了在现场工况下产生了渗碳,使材料表面层成分由低碳变成高碳、在与环境中H_2的共同作用下,产生了“意外”的典型氢致开裂。