焊后热处理对输送H_2S介质压力管道维修焊接接头组织性能的影响

采用手工钨极氩弧焊(TIG焊)打底,焊条电弧焊(SMAW)填充、盖面的焊接工艺对输送H_2S介质压力管道(20钢)进行维修焊接,并对其焊接接头进行720～750℃下保温1h的焊后热处理.对热处理前、后焊接接头组织和性能进行分析研究,结果表明:720～750℃×1h热处理使焊缝区与热影响区成针状分布的魏氏组织铁索体晶粒得到细化,并使其呈退化形态;焊缝区、热影响区与母材的显微硬度整体呈下降趋势;焊接接头抗拉强度大幅度提高,断裂均处在远离焊缝的母材上.焊后热处理有效地降低了焊接接头的残余应力,改变了残余应力的分布特征,使其分布趋于"均匀",拉应力大幅度降低.     

焊后热处理对Al-Zn-Mg-Cu合金MIG焊接接头组织与性能的影响

采用ER5356焊丝对Al-4.6Zn-1.5Mg-0.15Cu合金板材进行熔化极钨极氩弧焊试验,并对焊接接头进行了不同的焊后热处理。借助光学显微镜(OM)、扫描电镜(SEM)研究不同焊后热处理试样的组织变化规律,并进行了显微硬度测试与拉伸试验。结果表明:经固溶加时效处理后,焊接接头抗拉强度与显微硬度得到明显提升,抗拉强度与焊缝硬度均值分别提高至304 MPa与85 HV,相比焊后未处理的263 MPa与66 HV,增幅分别达15.6%与28.8%。焊接接头经时效处理后,组织的不均匀性及强化相的分布得到改善;而经重新固溶后,第二相发生回溶,再经时效处理将使得一部分不稳定的过饱和固溶体重新析出且弥散分布。     

激光焊接热输入对Ti2AlNb合金组织性能的影响

研究激光焊接热输入对Ti-22Al-27Nb(at%)合金焊缝成形和力学性能的影响,利用OM、SEM、XRD和TEM等手段对焊接接头的显微组织特征进行了分析,并探讨了焊后热处理对焊接接头组织性能的影响。结果表明,连续激光焊接可以获得无缺陷、成形良好的焊接接头。焊缝区域组织主要为柱状的B2相,柱状晶的生长方向垂直于熔合线。焊缝和热影响区的显微硬度要高于母材,焊缝的平均显微硬度最高。随着热输入的增加,焊接接头的室温抗拉强度增加,但是焊接接头的延伸率较低。焊接接头650℃高温强度为母材的71%~75%,塑性则仅为母材塑性的40%左右。经过焊后热处理,焊缝由B2+O相组成。O相增多使得焊缝的室温强度略有提高,且提高了650℃高温拉伸性能,高温抗拉强度最高可达母材的87.5%。     

Effect of different pre- and post-weld heat treatments on microstructures and mechanical properties of variable polarity TIG welded AA2219 joints

The microstructures and mechanical properties of 2219 aluminium alloy joints welded by variable polarity TIG welding in four kinds of different heat treatment conditions, namely, with/without pre-/post-weld heat treatment, were analysed and compared. The post-weld artificial aging treatment rendered fine dispersed precipitates (metastable θ′ phase) separate out of weld metal, which made the hardness of weld metal increase by ～20%. Meanwhile, the fracture location of joints during tensile test changed from weld zone to heat affected zone (HAZ). The pre-weld solution treatment reduced the overaging degree of HAZ and a large number of θ′ phase reprecipitated in HAZ after post-weld artificial aging treatment. Intermediate state welding, with pre-weld solution treatment and post-weld artificial aging treatment together, could increase 20% of the hardness of weld zone, increase 11.5% of the hardness of HAZ and increase 20.3% of the tensile strength of joint.     

Ti-22Al-27Nb合金线性摩擦焊接头组织与显微硬度分析

对Ti-22Al-27Nb合金进行了线性摩擦焊及热处理试验,并对热处理前后焊接接头的微观组织和显微硬度进行测量分析. 结果表明,利用线性摩擦焊方法焊接Ti-22Al-27Nb合金得到的接头无焊接缺陷. 焊态下,焊缝区形成了B2单相区组织. 热力影响区为B2 + O + α₂相三相区,出现等轴α₂相,针状O相几乎消失. 热处理后在焊缝区析出板条状O相和针状O相,热力影响区为O相均匀分布的两相区. 母材处的显微硬度值最低约为300 HV,随着向焊缝靠近,显微硬度值逐渐增加,焊缝中心达到最大值354 HV. 热处理后,由于板条O相和针状O相的沉淀析出,使焊缝中心显微硬度急剧增加.     

Characterization of Dissimilar Linear Friction Welds of α-β Titanium Alloys

Characterization of dissimilar linear friction weld (LFW) of Ti-alloys has been carried out. The microstructure of a Ti-64 with Ti-6246 weld was analyzed using scanning and transmission electron microscopy. The microtexture of the weld was examined using electron back-scattered diffraction (EBSD) and the microhardness was measured. The dissimilar LFW weld shows an interface at the central weld zone (CWZ) with strong contrast. The element distribution measured using energy-dispersive X-ray spectrometer suggests that only limited atomic diffusion occurred during welding. In the weld region, the hardness of Ti-64 shows an increase while that of Ti-6246 shows a decrease, compared with the respective parent materials in as-welded condition. After post-weld heat treatment, a hardness increase was observed in Ti-6246, while Ti-64 shows no significant hardness increase. Although the EBSD pattern quality is poor in the CWZ at the as-welded condition, the pattern quality of the post-weld heat-treated sample shows that both the Ti-64 and Ti-6246 have similar texture.     

2195铝锂合金电子束焊接头的焊后热处理

采用光学显微镜、扫描电镜、能谱仪及X射线衍射仪等微观分析手段,研究不同热处理工艺条件下2195铝锂合金电子束焊接头焊缝区的显微组织演变,探讨接头的焊后热处理强化机制。结果表明,焊后热处理可显著改善接头区域的显微组织,促进强化相的析出,有利于提高接头的力学性能。经过焊后固溶+双级时效热处理,焊态下接头熔合线附近存在的等轴细晶区消失,β′、θ′和T₁等强化相在接头焊缝区析出,与单级时效处理工艺相比,双级时效处理的析出强化效果更为显著。力学性能测试表明,经过双级时效热处理后,接头的抗拉强度达到492.5 MPa,为母材强度的90.4%。接头拉伸断口表面存在许多小韧窝,并伴随出现解理面,接头呈韧-脆混合型断裂特征。     

Effect of post-weld heat treatment on microstructure and mechanical properties of welded joints of 6061-T6 aluminum alloy

6061 aluminum alloy T-joints were welded by double-pulsed MIG welding process. Then, the post-weld heat treatment was performed on the welded T-joints. The weld microstructure under different aging temperature and time was investigated by transmission electron microscopy and scanning electron microscopy. The mechanical properties were examined by hardness test and tensile test. The results showed that the micro-hardness was sensitive to heat treatment temperature and time. Increasing temperature was beneficial to the shortening of peak aging time. There were a large number of dislocations and few precipitates in the welded joints. With the increase of post-weld heat treatment temperature and time, the density of dislocation decreased. Meanwhile, the strengthening phase precipitated and grew up gradually. When the post-weld heat treatment temperature increased up to 200 °C, large Q' phases were observed. And they were responsible for the peak value of the micro-hardness in the welded joints.     

退火温度对50 mm厚316L电子束焊接头微观组织与力学性能的影响

中国聚变工程实验堆(China Fusion Engineering Test Reactor,CFETR)真空室窗口领圈的组焊采用电子束焊,由于板厚较大,焊后残余应力较大,且焊缝从顶部到底部存在组织不均匀性,需要采用焊后退火处理进一步优化组织性能. 为了探索合适的退火工艺,采用单温区管式炉对50 mm 316L不锈钢电子束焊试样在200 ~ 450 ℃的范围内进行了退火试验,并采用电子背散射衍射(electron backscattered diffraction,EBSD)手段分析了不同退火工艺下接头热影响区及焊缝的晶粒组织. 对不同退火工艺下接头的顶部、中部与底部区域进行了拉伸试验和显微硬度测试. 结果表明,随热处理温度的提高,焊缝及热影响区的位错密度出现下降,由此引起的第3类内应力得到释放;300 ℃热处理后接头不同区域的抗拉强度和断后伸长率都较为优异,且拉伸试样的断口中均未发现大量析出相颗粒; 接头各区域显微硬度在不同退火温度下的变化趋势与抗拉强度的变化趋势近似一致.     

Transient thermal stress analysis on rapid post-weld heat treatments applied to flash butt welded rails

Abstract

A finite element (FE) model has been established to estimate the transient thermal stresses developed during rapid post-weld heat treatments (RPWHT) and post-weld quenching (PWQ) of rail flash butt welds. Rapid post-weld heat treatment parameters, such as heat flux intensity, location and heating duration, were varied. Altering the PWQ initiation times was also studied. The sequentially coupled thermomechanical FE model incorporated rate independent plasticity with a constitutive linear kinematic hardening rule. This described the inelastic behaviour of the rail material caused by post-weld thermal cyclic loadings. Representative temperature dependent thermal and mechanical properties including the pearlitic transformation behaviour of rail steel were also used in the FE model. Significant reduction of local tensile residual stresses in the web region of the weld was obtained by RPWHT applied to the entire foot region. RPWHT applied to both the web and the foot regions of the weld resulted in further reductions in vertical tensile residual stresses but a lesser effect on the longitudinal tensile residual stresses. A series of PWQ conditions, which were initiated after completion of the austenite–pearlite phase transformation, had significantly affected residual stresses. Numerical predictions revealed that PWQ initiated after transformation induced higher tensile residual stresses in the web region of the weld with respect to normal cooled welds, without affecting the microstructure.     

异质TC17线性摩擦焊接头焊后时效处理组织与性能

线性摩擦焊是制造航空发动机整体叶盘的关键技术. 通过光学显微镜、扫描电镜、电子式万能试验机及显微硬度仪对比分析了TC17(α + β)/TC17(β)钛合金线性摩擦焊接头焊态及不同时效温度下接头的组织与性能. 结果表明,焊态下焊合区及附近区域的微观组织为过冷β细晶,硬度最低;经焊后时效处理,析出了细小针状α相,硬度升高. 焊后时效温度为400 ℃时,焊合区及附近区域的硬度值明显提高,焊接区脆化. 焊后时效温度为630 ℃时,接头弯曲角度最高,但强度降低. 综合焊接接头的硬度、弯曲与拉伸性能优化出的焊后时效温度为550 ℃. 接头弯曲角度和抗拉强度分别达到母材的36%和95%. TC17(α + β)侧热力影响区( thermal-mechanical affected zone,TMAZ)受力后微观塑性变形更均匀,其强塑性能均优于TC17(β)侧TMAZ. 接头的弱化区对应于TC17(β)侧TMAZ硬度变化梯度及组织梯度最大的区域. 相比母材,接头的塑性损失比强度损失要大得多.     

Strength and microstructure of 2091 Al-Li alloy TIG welded joint

　The microstructure and tensile properties of TIG welding joints of 2091 Al-Li alloy were investigated both in as-welded and different postweld heat treatment condition. The results show that solution strengthening played an important role in the as-welded condition, though the precipitation strengthening δ′ phase formed already in the as-welded weld metal, but its effect was not apparent due to the lower volume fraction of δ′ phase. So the strength coefficient (φ) of the welded joint/base metal was 64%. After artificially aging heat treatment, the precipitation strengthening effect increased much due to the formation of more δ′ phase and s′ phase. Its φ value was increased up to 89%. The highest strength of the welded joints was obtained after solid solution and then artificially aged heat treatment. Due to the proper size of precipitation strengthening phases and their well distribution, the φ value was increased up to 98%.     

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.     

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.     

焊后热处理对AA7075铝合金DP-MIG焊接接头组织及力学性能的影响

采用双脉冲熔化极精性气体保护焊（DP-MIG）工艺方法焊接AA7075-T651铝合金,焊接试板采用固溶处理（480℃×50 min）后水淬,再进行（80℃×24 h）+（120℃×24 h）两级人工时效热处理,通过金相观察、扫描电镜观察、X射线衍射分析、拉伸试验以及硬度测试,研究焊后热处理（PWHT）工艺对焊接接头显微组织及力学性能的影响.结果表明,焊缝区经热处理后,晶粒由枝晶向等轴晶转变,晶界处非平衡第二相溶解,晶界变细,焊缝显微组织特性改善明显;焊接接头经热处理后,抗拉强度由342.5 MPa提高到490 MPa,接头强度系数为0.872,焊缝软化区硬度得到较大改善,焊接接头力学性能有显著提升.     

热处理对TC21钛合金线性摩擦焊接头组织与性能的影响

基于先进飞机构件研制需求,针对TC21钛合金线性摩擦焊接头,设计了3种热处理制度,开展了焊态及不同热处理状态下接头显微组织及力学性能研究. 结果表明,焊态试样的焊缝区由细化的β晶粒组成,晶内析出含有大量位错的针状马氏体,起到了位错强化作用,显微硬度相比母材明显提高,热力影响区由于次生α相发生了溶解,显微硬度相比母材有所降低. 热处理后焊接接头内的α相发生了显著变化,在高温区退火时,长时间保温导致初生条状α相长大,在低温区退火则促进了次生针状α相的析出;所有热处理后的接头进行拉伸试验后均断裂于母材区,经过双重退火的接头其焊缝区及热力影响区组织均为β转变组织+初生长条状α相 + 次生针状α相,并且各区域显微硬度基本与母材一致,组织更加均匀.     

TC17钛合金线性摩擦焊接头组织及力学性能分析

针对固溶时效态TC17钛合金焊态及焊后热处理态线性摩擦焊接头，进行显微组织及力学性能对比分析. 结果表明，焊态时焊缝组织发生了回复与再结晶，由于焊后冷却速度较快，生成了亚稳定β相，焊缝区发生了软化；热力影响区组织沿受力变形方向拉长、细化、交替呈带状分布，加工硬化程度较高，显微硬度明显高于其它区域；热影响区由于二次次生α相基本溶解于亚稳定β相，导致显微硬度显著降低. 经过焊后热处理，亚稳定β相发生时效分解，析出了弥散程度更高的针状次生α相使得焊接区硬度大幅度提高. 由于亚稳定相的生成，焊态接头发生软化，拉伸均断裂在焊缝区，抗拉强度达到母材强度91.8%，断口呈脆性断裂形态；焊后热处理态接头由于二次次生α相的析出，起到弥散强化的作用，拉伸试验均断在母材，断口呈典型韧性断裂形态.     

2A12铝合金变极性等离子弧穿孔焊缝性能分析

采用具有辅助压缩孔喷嘴结构的焊枪,在大电流高焊速的焊接工艺下制备了2A12铝合金变极性等离子弧穿孔焊缝,并分析了焊缝的组织和力学性能.由于辅助压缩孔对焊接电弧的压缩,使正面焊缝宽度变窄,背面焊缝宽度增加,并提高了两侧焊缝的余高.焊缝内部以细小的等轴非枝晶结构为主,其强化相以Al₂Cu为主,还有少量的S相.Al₂Cu的形状及其分布状况决定了焊缝的力学性能,试验表明基体和焊缝的硬度差别不大,焊缝沿中轴线的显微硬度呈马鞍状分布,焊缝内部比较平缓,正反两侧焊缝的硬度分布波动较大.     

Effect of post-weld heat treatment on microstructure and property of linear friction welded Ti17 titanium alloy joint

Abstract

In this study, post-weld heat treatment of linear friction welded Ti17 (Ti–5Al–2Sn–2Zr–4Mo–4Cr) titanium alloy joints was performed at 530, 610 and 670°C for 4 h followed by air cooling. Results show that with increasing treatment temperature, the recrystallisation extent of the α and β phases in the weld and deformation zones increases significantly. The overall property of the joint is remarkably improved, and the fracture behaviour of the tensile and impact samples changes from brittle failure to a ductile one. After treatment at 670°C, the impact toughness of the joint is 93·3% of the parent metal, and the failure of the tensile samples occurs in the parent metal far away from the weld. According to these findings, a treatment temperature slightly lower than 670°C but higher than 610°C would be a good value for linear friction welding Ti17 joints.     

焊后热处理对6063铝合金激光填丝焊接头组织与性能的影响

采用激光填丝焊对6063铝合金进行焊接,并对焊接接头进行人工时效和固溶+人工时效的热处理。通过光学显微镜、扫描电镜观察及拉伸试验,对焊后经不同热处理的焊接接头组织和性能进行研究。结果表明:未热处理的焊接接头抗拉强度为196 MPa,焊缝内部为铸态组织,弥散分布着Mg₂Si强化相,熔合线附近存在向焊缝内部生长的粗大柱状晶,焊缝内部为细小的树枝晶,焊缝中心为等轴晶;经时效处理后,焊接接头组织不均匀性和强化相的分布得到改善,焊接接头抗拉强度提高27 MPa;经固溶+时效处理的焊接接头抗拉强度提高64 MPa,焊缝组织、熔合区及热影响区组织得到显著细化。焊接接头均为韧脆混合断裂;时效处理的断口韧窝大小差异较大,韧窝较深;固溶+时效处理后的断口韧窝大小均匀,韧窝尺寸较大较深,韧窝数量更多。