The weldability and properties of joints welded in new-generation creep resistant steels: HCM12A steel

HCM12A (ASME T122) steel, containing 10-12% chromium and 2% tungsten, is made by the Japanese companies Sumitomo Metal Industries and Mitsubishi Heavy Industries, and is intended for fresh steam superheaters. The aim is to increase the resistance to corrosion at elevated temperatures over that of steels containing 9% chromium, e.g. P91, P92, and E911. This steel, a modification of HCM12 alloy, has a di-phase structure of tempered martensite and some 30% delta ferrite. The resistance to creep of HCM12 steel is higher than that of HCM12 alloy and is close to that of P92 material (see Fig. 8 in Ref. 7). Basic characteristics of HCM12A steel are quoted in an article published earlier.     

Analysis of thermal cycles in resistance flash welding of steels

A comparative study of the clad electrode and tubular wire processes was carried out, looking at the mechanical and micro-structural properties of weld metals of high-resistance steel, in the ‘as-welded’ and ‘stress-relief heat treatment’ (PWHT) conditions. The results show that the procedures adopted for welding with tubular wire and clad electrodes allow satisfactory levels of mechanical resistance to be obtained, with the exception of the value of percentage lengthening of the tubular wire, in the as-welded condition. The impact tests show that both the weld metals showed satisfactory impact resistance, in both the as-welded and PWHT conditions, observing that, for the tubular wire, the impact resistance is lower for the clad electrode in both conditions, lying close to the limit applied for the acceptance criterion of 50 J at 0°C in the PWHT condition. It was confirmed that the productivity achieved by the tubular wire process was approximately twice as high as that for the clad electrode process. As a result, the inherent advantage of the tubular wire process must be complemented with a consideration of all the mechanical properties obtained, orienting suitable selection of the welding process, in particular, for application in equipment that operates in fatigue conditions.     

Investigation of the structure and mechanical properties of welded joints in steels of the K56 strength grade in different welding conditions

The results of investigations of the effect of the welding conditions of manual arc welding on the structure and mechanical properties of the welded joints in low-carbon, low-alloyed pipe steels of the K56 strength grade are presented. It is shown that in welding in different combinations of welding current and welding speed, the superheated zone of the heat-affected zone (HAZ) is characterized by the formation of ferrite and pearlite in the form of grains and Widmanstätten structure. The experiment planning method is used to determine the regression dependences of the hardness and impact toughness of the metal of the superheated zone on the controllable welding parameters.     

焊接热循环对含铜时效钢HAZ组织与力学性能的影响

研究了焊接热循环对含铜时效钢焊接热影响区组织与性能的影响.结果表明,经历单次热循环后,含铜时效钢焊接热影响区不同区域性能存在显著差异.粗晶区冲击韧度最差,这主要是奥氏体的晶粒长大及粒状贝氏体的增多所致;两相区是热影响区的"软化区",母材中析出相的粗化及重溶和铁素体量的增多是导致两相区硬度降低的主要原因.二次热循环对模拟HAZ组织和性能有显著影响,粗晶区 两相区是二次热循环中性能最差的区域.基体中部分析出物的粗化或回溶以及组织中铁素体量的增加是导致两相区硬度降低的主要原因;大尺寸粒状贝氏体的增多是导致该区域韧性下降的主要原因.     

微观组织对2A12铝合金熔焊接头力学性能的影响

采用TIG焊对2A12铝合金薄板进行焊接,并对接头的组织及力学性能相关性进行分析.金相观察发现焊缝及熔合区内晶粒粗大且不均匀,焊缝从边缘的柱状晶向中心的等轴晶过渡,熔合线附近出现粗细晶混杂分布.采用显微硬度及拉伸试验研究了焊接接头力学性能不均匀性.结果表明,硬度最小值处于焊缝的熔合区,拉伸试样亦断裂在该区,与组织分布相...     

Effect of the energy parameters of the welding process on the structure and properties of welded joints in low-alloy steels

The results of investigations of the effect of the pulsed welding process on the structure and mechanical properties of welded joints in low-alloy steels are presented. It is shown that the pulsed welding conditions improve the homogeneity of the structure and reduce the grain size of the metal of the welded joint and the heat-affected zone (HAZ). Changes in the structure increase the ductility of the welded joint.     

搅拌摩擦焊工艺参数对纯铜接头组织和力学性能的影响

研究了搅拌摩擦焊工艺参数对3 mm的纯铜板材焊接接头组织和力学性能的影响.结果表明,在搅拌头旋转频率固定为800 r/m in,焊接速度在60~300 mm/m in范围内均得到了外表面美观、内部无缺陷的接头.焊接接头由两边向中间依次由母材区、热影响区、热力影响区和搅拌区组成.搅拌区组织由于动态再结晶作用使得该部分区域...     

多层多道焊接DH40船用钢接头组织及力学性能

使用药芯焊丝CO2焊,在多层多道焊条件下对大厚板DH40船用钢进行了焊接试验,并较为系统研究了接头组织及力学行为,重点探讨了焊接接头冲击韧性尤其是焊缝根部热影响区熔合线外5 mm区域冲击韧性严重衰减的原因.结果表明,焊接接头抗拉强度均高于母材,(大子母材抗拉强度515 MPa).弯曲试验所有样品均合格,满足塑性要求;采用CO2气体保护焊多层多道焊接DH40船用钢,易在焊缝根部热影响区熔合线外5 mm左右的狭窄范围内出现脆性带.其中“组织遗传”作用,造成晶粒粗大,是其冲击韧性下降的次要因素,该区域产生大量粒状贝氏体,是其冲击韧性严重衰减的根本原因.     

铝锂合金的真空电子束焊接工艺及其接头组织与性能

采用真空电子束焊工艺焊接2090铝锂合金,并对获得接头进行拉伸强度、显微硬度等力学性能测试,时接头的金相组织、拉伸断口进行观察分析.结果表明,在电子柬流为8 mA,采用圆形扫描方式.焊接速度为1 000 mm/min的工艺条件下,获得的接头的力学性能最佳.接头微观分析显示,焊缝金属为细小等轴晶组织,在晶内均匀分布有数量...     

Effect of heat input on the mechanical properties of welded joints in high-strength steels

Experiments were carried out to determine the properties of the welded joints in 8 mm thick high-strength steels produced by quenching and tempering and thermomechanical rolling with accelerated cooling (tensile strength 821–835 MPa). The dependence of the strength, elongation, hardness, impact energy and crack opening displacement on the heat input in the range 1.0–0.7 kJ mm^? 1 was determined. The results show that the dependence of the strength of the welded joints decreases and that of the elongation increases. The heat input has only a slight effect on the impact energy and crack opening displacement in the heat-affected zone.     

Improving materials and welding technology for dissimilar welded joints in austenitic and pearlitic steels

The first layer of the deposit on the edges of low-alloy steels in producing welded joints with 08Cr18Ni10Ti steel is made using materials based on 02Cr24Ni13 composition (TsL-25L electrodes, welding wire SV-02Cr24Ni13) producing the deposited metal with a reduced carbon content and the required content of the ferritic phase (2–5%). Welding with these materials results in the required parameters of technological properties in welding and efficiency of the austenitic–ferritic deposited metal:

• resistance to solidification cracking;

• preventing the formation of a structure containing very hard brittle compounds;

• preventing the formation of the sigma phase and, correspondingly, embrittlement in tempering;

• the mechanical properties and fatigue strength satisfy the requirements of PNAE G-7-002–86.

Technical documents for the production of these welding materials have been compiled.     

Effect of welding technology on the mechanical properties of welded joints in pipes for deep water offshore gas pipelines

Results of investigations into the dependence of mechanical properties of welded joints of pipes for offshore pipelines on welding conditions are presented. In particular, the results show that the mechanical properties of pipes of the strength categories K60 (X70) and K56 (X65) are influenced mainly by the heat input, the fracture toughness of welded joints, and pipes of a high strength category are lower by 30–35% than in the case of the K56 (X65) pipes. The hardness of the weld metal in the upper layers is 15–17% higher for automatic submerged arc welding and in the lower layers for gas-shielded automatic arc welding. In inspecting the mechanical properties of the welded joints, special attention must be given to the longitudinal welded joints in the pipes.