线性摩擦焊IN718接头微观组织与织构演变

不同工艺参数下对IN718高温合金进行了线性摩擦焊接试验,采用OM,SEM,EBSD等对接头微观组织与织构进行了表征.结果表明,在摩擦压力169 MPa、振幅3 mm、频率35 Hz、摩擦时间6 s参数组合下获得的接头质量相对较好,但在焊缝端部仍能发现氧化物和碳化物.焊缝区δ相完全溶解,残留少量NbN;而热力影响区δ相部分溶解,部分晶界发生液化并伴有Laves相的产生.焊缝区发生了充分动态再结晶,呈现为等轴细晶组织,并在剪切力的作用下出现了明显剪切织构C（100）[011],而热力影响区发生部分动态再结晶,形成了（335）[186]织构.     

激光叠焊接头显微组织及力学性能分析

采用OM,SEM分析了TC4钛合金激光叠焊接头各部分显微组织特征,研究了接头力学性能.结果表明,TC4钛合金激光叠焊接头显微组织由焊缝及热影响区组成,焊缝为针状马氏体α'交织成的网篮状组织.0.8 mm厚TC4钛合金薄板激光叠焊最佳工艺参数为功率1 800～2 350 w,焊接速度为1.5～2.5 m/min,此时拉伸试样平均单位长度焊缝承载力为458 N/mm,连接焊缝最大抗剪强度达732 MPa.拉伸过程焊缝截面轴线偏转角θ与接头承载能力相关,θ角越大,接头承载能力越强.     

TZM钼合金钨极氩弧焊工艺及焊接接头组织

针对TZM钼合金,研究了钨极氩弧(TIG)焊工艺中不同焊接电流对焊接品质的影响,分析了焊接接头的显微组织及性能。结果表明,当TIG焊焊接电流为210 A,焊接速度4 mm/s,氩气流量8～12 L/min时,可获得品质优良的焊缝。焊接接头组织主要由焊缝中心粗大的柱状晶及热影响区的等轴晶组成,取代了母材的片层状纤维织构,削弱了材料的强度,改善了材料的塑性。     

Mechanical properties and microstructure of pure nickel PAW and PAW-TIG welded joints

A plasma arc welding( PAW)-tungsten inert gas( TIG) hybrid welding process is proposed. And this paper investigated the microstructure and properties of pure nickel N6 joints by PAW-TIG hybrid welding. Compared with the conventional PAW method,the characteristic of PAW-TIG welding process is that there is no interaction between the two arcs.The addition of TIG can enhance the intrinsic high-efficiency peculiarity and the stability of the keyhole status of PAW. The joints made using PAW and PAW-TIG,respectively,were subjected to microstructural evaluations and tensile testing so as to analyze the effect of TIG arc energy on the microstructure and mechanical properties of these joints. The results of this investigation indicate that significant grain coarsening was observed in the weld metal( WM) and heat affected zone( HAZ)and it is found that the extent of grain coarsening increased with the addition of TIG arc. And the microstructure in hybrid joint,with wider weld width and the smooth surface,is coarser than in PAW joint. Furthermore,the microhardness and ultimate tensile strength( UTS) of hybrid joint is slightly lower than that of PAW joint. The fractograph observation shows that the fracturing mechanism of PAW joints ductile,while the hybrid welding joints exists as brittle-ductile fracture mode. The outcome of this work shows that in the condition of same deposited rate,TIG arc post-weld heat treatment can improve the welding efficiency and welding speed. The proposed PAW-TIG hybrid welding process is demonstrated to be suitable for welding nickel and its alloys in industry application.     

ULCB钢电子束穿透焊组织与性能

为了进一步探索ULCB钢的焊接性能,采用真空电子束穿透焊不同束流强度对14 mm钢板对接接头进行了焊接,通过焊缝形貌比较,束流强度为100 mA时,接头焊缝成形最好,选取该接头做了拉伸、硬度、冲击试验及金相组织分析.结果表明,拉伸试样的断裂区域在母材区,抗拉强度为761 MPa、屈服强度为669 MPa,硬度范围在270~330 HV;冲击试样的断裂区域在热影响区,焊缝区平均冲击功为288 J,热影响区平均冲击功为273 J;接头显微组织中,焊缝区和热影响区产生了α'马氏体相,使焊缝区和热影响区产生相变强化,导致焊接接头的强度和硬度均高于母材.     

机械振动对WQ960钢焊接接头组织和性能的影响

采用机械振动辅助MAG焊焊接WQ960高强度钢,通过对不同振动参数下焊接接头的显微组织和力学性能分析,研究机械振动对焊接接头的显微组织、冲击韧性和抗拉强度的影响规律.结果表明,机械振动的施加提高焊缝和熔合区的冲击吸收功效果明显,可达15%,对热影响区的冲击吸收功影响不大,焊接接头的抗拉性能也有所提高,但幅度不大仅为2%.施加机械振动后改善了一次柱状晶的形态,得到以细小的针状铁素体为主的焊缝组织,这对提高焊接接头的强韧性十分有利.振动状态下焊缝冲击断口纤维区的韧窝较深,晶状区的解理台阶层次明显,存在较多的撕裂棱,且均匀细化.     

热处理对新型铸造模具钢焊接接头组织和性能的影响

对新型铸造模具钢进行焊接修复,研究焊后热处理对焊接接头组织和性能的影响。结果表明,焊后回火处理使模具钢完全淬火区组织由淬火马氏体转变成回火马氏体,不完全淬火区和回火区组织变化不明显。回火处理后淬火区和焊缝硬度明显降低,焊接接头抗拉强度增加。焊后回火处理对焊缝磨损率和平均摩擦系数影响不大。     

异质钛合金线性摩擦焊接头微观组织与显微硬度分析

选用优化的工艺参数对TC4/TC17异质钛合金进行线性摩擦焊及测温试验.焊后利用光学显微镜、扫描电镜及显微硬度仪等对接头微观组织及显微硬度进行分析.结果表明,线性摩擦焊接过程中界面温度超过1 200℃、超过β相变温度,在焊后冷却过程中发生再结晶,产生细小针状组织.界面混合区再结晶组织有等轴化甚至球化现象.TC4侧热力影响区由被拉长的α相及破碎的β相组成,TC17侧热力影响区的α相和β相被拉长细化.TC4侧热力影响区组织发生应变强化,TC17侧热力影响区靠近焊缝侧发生一定的软化现象,靠近母材侧强化现象明显.     

热处理工艺对系泊链焊接接头组织与性能的影响

分析了不同热处理工艺对22MnCrNiMo钢系泊链的焊接接头的组织和力学性能的影响.结果表明,22MnCrNiiMo系泊链钢焊接接头经过930℃×30 min+620℃×30 min一次淬火回火后,强度和塑性明显改善;经过930℃×30min+930℃×30 min+620℃×30min二次循环淬火回火后,晶粒更加细小均匀,消除了大小晶粒不均匀的情况,力学性能尤其是塑性和冲击韧性得到进一步提高.     

Effects of annealing on microstructure and properties of linear friction welded dissimilar titanium joints

Linear friction welds of Ti–6Al–4V (TC4, according to Chinese classification) to Ti–6·5Al–3·5Mo–1·5Zr–0·3Si (TC11, according to Chinese classification) were subject to post-weld heat treatment (PWHT) at 650°C×4 h (PWHT1) and at 950°C×1 h+530°C×4 h (PWHT2) under air cooling. In the as welded joint, TC4 had recrystallised sufficiently compared to TC11. After PWHT1, the α grains in the TC4 weld centre zone grew to some extent and many superfine equiaxed recrystallised α grains precipitated along β boundaries on the TC11 side. The grain growth along the weld line in the weld centre zone under PWHT2 was evident. PWHT2 reduced the joint tensile strength due to the coarsening of the microstructure. The joint microhardness decreased after PWHT.     

机械振动频率对高强度钢焊接接头低温韧性的影响

为了研究机械振动频率对低合金高强度钢焊接接头低温韧性影响,采用Ar+CO₂混合气体保护进行多层焊接,同时施加不同频率的机械振动.结果表明,机械振动可以改善高强度钢焊缝的低温韧性和显微组织,相比无振动焊接,施加振动后焊缝中针状铁素体以细小弥散形式分布,且焊缝中大夹杂物数量明显减少;在振幅一定的情况下,焊接接头冲击性能对振动频率不敏感;外加振动对焊接接头韧性的影响仅存在一定试验温度范围内,随着试验温度降低,振动对焊接接头韧性的提升效果逐渐减弱,试验温度降低至一定值,振动对焊接接头韧性的影响基本消失.     

Microstructure and mechanical properties of welded joints of NPP pipelines after long-term operation

The microstructure and mechanical properties of welded joints of cuts from Du 300 and Du 500 pipelines of the Leningradskaya and Novovoronezhskaya nuclear power plants are studied after 70 and 100 thousand hours of operation. The effects of thermal aging simulating operational impact on the microstructure and properties of welded joints of the cuts and of a model coil are determined. It is shown that long-term operation can be accompanied by embrittlement and decrease in the crack resistance of the metal of welds in Du 300 and Du 500 pipelines produced from steels 08Kh18N10T and 08Kh18N12T. The discovered changes in the microstructure can lead to deterioration of the mechanical properties of the metal of welded joints in operation of Du 300 and Du 500 pipelines. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 36–42, July, 2006.     

表面状态对铝合金激光焊接接头组织和性能的影响

采用激光焊焊接高强铝合金2524,研究三种表面状态——原始状态表面、去氧化膜表面、去包铝层表面对铝合金焊接接头组织和性能的影响。结果表明,三种表面状态下,去包铝层状态焊缝总裂纹长度最小,焊缝中心晶粒尺寸最大,接头抗拉强度368 MPa,达到母材强度的80.8%;原始状态接头抗拉强度最低331 MPa,比去包铝层状态低10.1%。     

2.25Cr-1Mo-0.25V钢焊缝冲击性能和显微组织分析

进行了2.25Cr-1Mo-0.25V钢的焊条电弧焊试验,测定其焊缝的成分和冲击吸收功,进行了金相及启裂源观察,对冲击吸收功较低的样品进行脱脆处理.结果表明,冲击吸收功较低的焊缝的Mn,Si,Mo及其杂质元素含量相对较高,Mn,Si,Mo等元素促进杂质元素在晶界上的偏聚,致使晶界性能变坏,断口以沿晶断裂为主,冲击吸收功降低,脱脆处理后,冲击韧性恢复说明焊缝存在高温回火脆性,导致高温回火脆性是由于杂质元素在晶界上的偏聚,因此研制焊条时要严格控制Mn,Si,Mo和杂质元素的含量.     

铝合金激光-MIG双面焊接接头组织和性能研究

针对16mm厚1561铝合金(俄罗斯牌号),采用不开坡口无间隙的双面激光-MIG复合焊接工艺,并研究焊接接头的拉伸性能、显微硬度和微观组织。结果表明,采用较大的激光功率使双面焊道交叉面积增大,有利于减少焊道根部缺陷,提高拉伸性能;接头中存在着基体相α-Al和第二相Fe(Mn Al)6,第二相经焊接热循环重熔后弥散分布,其中单独激光作用区弥散度最高;焊缝硬度在激光单独作用区相对于母材升高,而在激光-电弧复合作用区相对于母材降低,这与焊缝显微组织中的第二相数量和形态密切相关。     

Evaluation of the effect of strength mismatch in undermatched joints on the static tensile strength of welded joints by considering microstructure

High-tensile strength 950 MPa steel, HT950, which is steel used in penstocks, was developed to provide two vital properties: fracture arrest to stop brittle fracture and high weldability. This steel has been already used for penstocks in some hydropower plants in Japan. To widely apply high-tensile strength steels in penstocks in the future, fewer restrictions against their welding conditions such as pre-heat and post-heat temperature controls are required. One proposed solution is to undermatch the strength of the filler metal to that of the base material. This allows less pre-heating, or no pre-heating at all, and the use of conventional rod and process management is easier. Previous studies have shown that there are softening conditions under which the strength of the joint can be considered as that of the base material. However, the shape and distribution of the soft region are assumed to be ideal. In this study, the method for calculating the change of the strength in heat-affected zone (HAZ) during the welding process is discussed. Then, the influence of the strength distribution of HAZ and welded zone to the strength of the joint is investigated by a wide plate test in both experiment and elastic–plastic analysis. Applicability of undermatched joints to penstock fabrication is considered by these discussions. As a result, it is concluded that the Vickers hardness distribution in the HAZ can be estimated by the method which is proposed in this study and the strength of the under-matched joints is high enough in both experiment and analysis in which the Vickers hardness distribution is considered. From these conclusions, the applicability of undermatched joints, of which the weld metal is the HT570 class, to penstock fabrication is conformed.     

Prediction of microstructure and mechanical properties of line pipe welded joints based on hardness map

In this article, the variation of hardness in cross-section of X52 microalloyed steel joints before and after post-weld heat treatment and also the relationship of hardness with ultimate tensile strength, yield strength and microstructure have been investigated. For this purpose, the specimens were prepared in two conditions of as welded and post-weld heat treated, and the hardness maps of their cross-section were provided. Then, some equations were suggested to correlate the obtained hardness with the grain size and tensile and yield strengths. The equations made it possible to predict tensile and yield strengths with high accuracy. According to the results, the maximum hardness and strength belong to the weld junction. Normalisation of the joints at 950°C reduced significantly the hardness difference (and also the strength difference) in various joint areas and homogenised the microstructure considerably. The grain size distribution was also modelled acceptably for the post-weld heat treated joint, and the grain size map was obtained.