TC4/6061异种金属电阻点焊接头组织与性能研究

采用2mm厚的TC4钛合金和1.5 mm厚的6061铝合金进行电阻点焊,研究焊接热量与时间对接头拉剪力与熔核直径的影响,观察接头断裂特征并对接头进行了显微组织分析.试验结果表明:热影响区和熔核区的晶粒尺寸相对母材区变得粗大,靠近熔核的6061侧热影响区出现晶粒长大,TC4侧组织出现了细小的针状α'马氏体组织,并呈一定位向排列.随着焊接热量的增加,接头的拉剪力和焊核直径逐渐增加,随着焊接时间增加,接头的拉剪力和熔核直径先增加后减小;当Q=600 J时,接头的拉剪力最高,为1.17 kN.接头靠6061侧显微硬度无明显变化,靠TC4侧熔核区与热影响区硬度分布不均匀,当Q=550 J,t=10s时硬度分布较理想.试验数据为钛/铝异种金属点焊提供理论指导.     

SAPH440酸洗板电阻点焊工艺研究

以2.0 mm厚SAPH440酸洗板为研究对象,通过检测点焊接头的抗剪性能及十字拉伸性能,综合评价接头的力学性能,并使用Axio Obersver A1m型光学显微镜观察点焊接头显微组织,测量熔核直径,分析焊接电流对熔核直径的影响,创建点焊工艺窗口。结果表明:酸洗板点焊工艺窗口为8.5 kA至12 kA,宽度3.5 kA,接头熔核直径及力学性能与焊接电流呈正相关,当出现飞溅后,熔核直径与力学性能略微下降,熔核区与热影响区组织均为马氏体,受焊接热循环的影响,熔核区组织为粗大柱状,热影响区组织为细小针状。     

QP980淬火-配分钢MAG焊接头组织及力学性能

QP980淬火-配分钢属于第三代先进高强钢，具有强塑积高、成形性好等优点而成为汽车轻量化发展的重要材料。对国内某公司生产的1.5 mm厚的QP980淬火-配分钢采用机器人MAG焊(熔化极活性气体保护焊)进行焊接，分析焊接工艺参数对其焊接接头组织和力学性能的影响。考虑到焊接的淬火作用以及焊接接头的等强匹配原则，采用ER50-6焊丝作为填充材料。研究结果表明，在合适的焊接工艺窗口内，减小焊接热输入有利于提高焊接接头的强度，但对其塑性有不利影响。焊接接头横截面的组织和力学性能变化非常大，焊缝金属区主要由铁素体和珠光体组成，硬度较低，但能达到原始母材的硬度值；靠近焊缝的热影响区主要是完全相变区，该区是由原始母材组织发生奥氏体转变后冷却产生的以板条马氏体为主的组织，硬度较母材有较大提升，该区成为焊接接头的硬化区，而靠近母材的焊接热影响区主要包括两相区和回火区，两相区中部分组织发生了奥氏体转变，冷却后转变的组织较原始组织中的马氏体含量有所降低，硬度略有下降，而回火区是由原始组织中的铁素体、少量奥氏体以及发生了回火的马氏体组成，由于马氏体的回火作用，硬度也略有降低。在该钢的MAG焊中，焊接接头软化现...     

热输入对DP600激光焊组织和力学性能的影响

摘要：为了研究DP600钢的焊接性能,采用5种不同的激光焊接工艺进行焊接试验。结果表明,焊接接头表面成形质量良好,随着热输入的增加,上下熔宽逐渐增大;熔融区均为板条状马氏体组织,当热输入高于33J/mm时热影响区组织为马氏体、铁素体和少量的回火马氏体;当热输入低于33J/mm时,热影响区组织为马氏体和铁素体。在低热输入条件下,回火时间很短,马氏体未发生分解;在高的热输入条件下,回火时间较长,马氏体分解显著,热影响区中出现M3C型碳化物,碳化物形貌以球状和片状为主。从熔融区到母材,显微硬度值逐渐降低;焊接接头静态拉伸失效位置均在母材,拉伸断口为韧性断口,DP600钢激光焊接接头不存在软化现象。     

热输入对DP600激光焊组织和力学性能的影响

为了研究DP600钢的焊接性能,采用5种不同的激光焊接工艺进行焊接试验。结果表明,焊接接头表面成形质量良好,随着热输入的增加,上下熔宽逐渐增大;熔融区均为板条状马氏体组织,当热输入高于33 J/mm时热影响区组织为马氏体、铁素体和少量的回火马氏体;当热输入低于33 J/mm时,热影响区组织为马氏体和铁素体。在低热输入条件下,回火时间很短,马氏体未发生分解;在高的热输入条件下,回火时间较长,马氏体分解显著,热影响区中出现M_3C型碳化物,碳化物形貌以球状和片状为主。从熔融区到母材,显微硬度值逐渐降低;焊接接头静态拉伸失效位置均在母材,拉伸断口为韧性断口,DP600钢激光焊接接头不存在软化现象。     

DP780冷轧板电阻点焊工艺研究

通过测量点焊接头的熔核直径、熔透率,检测接头抗剪力、硬度,分析接头显微组织构成及形态,评价DP780冷轧板电阻点焊性能,并给出试验条件下的可焊工艺范围,以及最优工艺参数。结果表明:DP780冷轧板点焊性能良好,当电极压力为3 k N时,焊接电流可取8~10 k A,焊接时间可取200~400 ms,但焊接电流10 k A,焊接时间400 ms不可取;电极压力为4 k N时,焊接电流可取8~9 k A,焊接时间可取200~400 ms,但焊接电流9 k A,焊接时间400 ms不可取;最优工艺参数为焊接电流9 k A,焊接时间300 ms,电极压力4 k N;熔核区显微组织为粗大板条状马氏体+铁素体,马氏体呈现柱状晶形态,热影响区显微组织为块状马氏体+铁素体;母材硬度(HV)为240,熔核区硬度(HV)为420。     

1800 MPa热成形钢与CR340LA低合金高强钢激光焊接性能

采用光纤激光焊接设备对1800 MPa级热成形钢与CR340LA低合金高强钢进行对接激光拼焊,研究了不同激光焊接功率和焊接速度下焊接接头的组织演变规律及热冲压成形性能,并对焊接接头的力学性能和硬度进行了分析。结果表明,3种焊接工艺下激光拼焊原板综合力学性能相差较小,由焊接接头造成的伸长率和抗拉强度的损失均在母材的28.3%和9.1%以内。激光焊接后焊缝区均为粗大、高硬度的马氏体结构;两侧热影响区组织主要为铁素体和马氏体,接头未出现明显的软化区。激光拼焊原板拉伸试样均断裂于CR340LA母材区,距离焊缝12 mm左右,且存在焊缝隆起现象。选取焊接功率和焊接速率分别为4000 W和0.18 m·s?1的焊接试样在高温下进行热冲压成形检测,未出现焊缝开裂,热成形后拼焊板具有良好性能,满足汽车激光拼焊板使用要求,拉伸结果表明,试样断裂位置与未热冲压成形前一致,均位于CR340LA母材区,拉伸过程中,焊缝向高强度母材侧偏移,在弱强度母材侧产生应力集中并缩颈断裂。      

纯镍N6填丝等离子焊接工艺及接头组织性能的研究

试验采用等离子弧焊设备对工业纯镍N6板材进行填充焊丝等离子焊接工艺试验。借助光学显微镜(OM)、扫描电镜(SEM)、能谱分析(EDS)、X射线衍射仪(XRD)和显微硬度计等手段分析了焊接接头的微观组织和力学性能。结果表明:采用合理的焊接工艺参数可以得到成形良好的焊缝,填丝焊接接头抗拉强度为333 MPa,其抗拉强度达到母材强度的97.6%,不填丝焊接接头抗拉强度为240 MPa,达到母材强度的70.5%;母材为均匀细小的等轴晶,填丝接头焊缝处呈树枝状结晶且晶粒粗大,热影响区靠近熔池部分的晶粒过热长大,靠近母材部分为均匀细小的等轴晶;填丝接头基体为γ-Ni组织,同时存在γ'(Ni3(Al,Ti)C)强化相,填丝接头拉伸断口表现为韧-脆混合断裂,焊接接头硬度最低值出现在热影响区;与母材相比,不填丝接头焊缝区与热影响区晶粒粗大,其基体组织为单相奥氏体,不填丝接头拉伸断口表现为脆性断裂,硬度最低值出现在接头热影响区。     

热镀锌DP780电阻点焊工艺研究

研究了热镀锌DP780电阻点焊性能,并优化其点焊参数。通过测量焊接接头的熔核直径、熔透率、压痕深度,观察焊接接头显微组织,检测焊接接头硬度、抗剪力及正拉力等参数,综合评价热镀锌DP780点焊性能。结果表明:DP780热镀锌板因其合金含量高的特点,点焊性能良好,但焊接工艺窗口较窄。当电极压力为3.5 k N,焊接电流为9.5 k A时,最佳焊接时间为300~400 ms,当焊接电流为10.5~11.5 k A时,焊接时间在200~400 ms均可。DP780热镀锌板点焊接头显微组织为马氏体和铁素体,这种焊接接头的组织决定了其塑性比仅有8%~30%,接头硬度值稍高。焊点的失效形式均为熔核剥离失效。     

热输入对DP980激光焊组织和力学性能的影响

为了研究DP980钢的焊接性能,采用3种不同的激光焊接工艺进行焊接试验。结果表明,熔融区为板条马氏体,热影响区为马氏体、铁素体和回火马氏体,随着热输入增加,上下表面的熔宽逐渐增大,强塑积逐渐减小,热影响区的软化程度逐渐恶化。从熔融区到母材,显微硬度的变化趋势是先降低后升高。焊接接头静态拉伸失效位置均在亚临界热影响区,拉伸断口为韧性断口,随着热输入增加,杯状韧窝逐渐转变为较大的抛物线状韧窝,通过分析不同热输入条件下焊接接头的静态拉伸应变场云图,可知在塑性变形阶段,熔融区两侧呈双峰形貌,随着热输入的增加,软化区的面积逐渐增大,颈缩易出现在熔融区两侧的软化区部位。     

Characterization of a friction-stir-welded aluminum alloy 6013

The aluminum alloy 6013 was friction-stir welded in the T4 and the T6 temper, and the microstructure and mechanical properties were studied after welding and after applying a postweld heat treatment (PWHT) to the T4 condition. Optical microscopy (OM), transmission electron microscopy (TEM), and texture measurements revealed that the elongated pancake microstructure of the base material (BM) was transformed into a dynamically recrystallized microstructure of considerably smaller grain size in the weld nugget. Strengthening precipitates, present before welding in the T6 state, were dissolved during welding in the nugget, while an overaged state with much larger precipitate size was established in the heat-affected zone (HAZ). Microhardness measurements and tensile tests showed that the HAZ is the weakest region of the weld. The welded sheet exhibited reduced strength and ductility as compared to the BM. A PWHT restored some of the strength to the as-welded condition.     

Laser Welding of Ultra-Fine Grained Steel SS400

Steeliswidelyusedbecauseofitsgoodcompre hensive properties ,plentyofresourceandlowerprice .Thestrengthandtoughnessaretwoimpor tantpropertiesofsteels ,andpeoplemakeeffortstoincreasetheirvalues .Addingalloyingelementandcontrollingmicrostructurearetwobasicwaystoac complishtheaim .Therefinedmicrostructureob tainedbyprocessingtechniqueenablesthestrengthandtoughnessofsteeltobeincreasedwithoutaddingalloyingelementandtheratioofperformance costtobeincreased .Theultra finegrainedsteelshavefer ritegrains…     

Weldability Evaluation and Microstructure Analysis of Resistance‐Spot‐Welded High‐Mn Steel in Automotive Application

In this paper, resistance spot weldability of high‐Mn steels were investigated in order to get high reliability in welded joints of automotive components. Microstructural characterizations, cross‐tensile test (CTT), microhardness tests of spot welded parts were conducted. The effects of weld current on the microstructural characteristics, mechanical properties, and fracture modes were investigated using optical microscopy (OM) and scanning electron microscopy (SEM). The hardness in the weld nugget was observed to be lower than that in the base metal (BM). In CTT, the failure initiation was observed to occur at the boundary of the weld nugget. Also welding imperfections of welded parts were investigated. Liquation cracking in heat affected zone (HAZ), porosity, and shrinkage cavity were found most common welding defects in welded parts. Furthermore, the effects of welding imperfections on weld quality and failure criteria were identified and discussed.     

Evaluation of Microstructure and Mechanical Properties of Laser Beam Welded AISI 409M Grade Ferritic Stainless Steel

 The microstructure analysis and mechanical properties evaluation of laser beam welded AISI 409M ferritic stainless steel joints are investigated. Single pass autogeneous welds free of volumetric defects were produced at a welding speed of 3000 mm/min. The joints were subjected to optical microscope, scanning electron fractographe, microhardness, transverse and longitudinal tensile, bend and charpy impact toughness testing. The coarse ferrite grains in the base metal were changed into dendritic grains as a result of rapid solidification of laser beam welds. Tensile testing indicates overmatching of the weld metal is relative to the base metal. The joints also exhibited acceptable impact toughness and bend strength properties.     

Effect of Welding Processes on Tensile and Impact Properties, Hardness and Microstructure of AISI 409M Ferritic Stainless Joints Fabricated by Duplex Stainless Steel Filler Metal

The effect of welding processes such as shielded metal arc welding, gas metal arc welding and gas tungsten arc welding on tensile and impact properties of the ferritic stainless steel conforming to AISI 409M grade is studied. Rolled plates of 4 mm thickness were used as the base material for preparing single pass butt welded joints. Tensile and impact properties, microhardness, microstructure and fracture surface morphology of the welded joints have been evaluated and the results are compared. From this investigatio.n, it is found that gas tungsten arc welded joints of ferritic stainless steel have superior tensile and impact properties compared with shielded metal are and gas metal arc welded joints and this is mainly due to the presence of finer grains in fusion zone and heat affected zone.     

Study of welding ultra‐fine grained ferrite steel by CO2 laser

Ultra‐fine grained ferrite steels have higher strength and better toughness than the normal ferrite steels because of their micrometer or sub‐micrometer sized grains. In this paper the ultra‐fine grained steel SS400 is welded by CO₂ laser. The shape of weld, cooling rate of HAZ, width of HAZ, microstructures and mechanical properties of the joint are discussed. Experimental results indicate that laser beam welding can produce weld with a large ratio of depth to width. The cooling rate of HAZ of laser beam welding is fast, the growth of prior austenite grains of HAZ is limited, and the width of weld and HAZ is narrow. The microstructures of weld metal and coarse‐grained HAZ of laser beam welding mainly consist of B_L + M (small amount). With proper laser power and welding speed, good comprehensive mechanical properties can be acquired. The toughness of weld metal and coarse‐grained HAZ are higher than that of base metal. There is no softened zone after laser beam welding. The tensile strength of a welded joint is higher than that of base metal. The welded joint has good bending ductility.     

Comparison of microstructure and properties between joints of FSW and TIG 316L austenitic stainless steel

FSW and TIG were conducted on 316L stainless steel.Variation during microstructure and properties in joints obtained by different welding methods was studied.The results show that the effect of severe mechanical stirring and intense plastic deformation creat a fine recrystallized grain in the welding joint during FSW.As for TIG,the temperature of welding joint exceeds the melting point of welded material itself.The entire welding process belongs to the solidification of a small molten pool;and the microstructure of the joint takes on a typical casting structure.When the welding parameters were selected appropriately,the average ultimate tensile strength of FSW joints can reach 493 MPa,which is 83.6%of base metal;the average elongation is 52.1%of base metal.The average ultimate tensile strength of TIG joints is 475 MPa, which is 80.5%of base metal;the average elongation is 40.8%of base metal.The tensile test of FSW joints is superior to the TIG joints.The microhardness of FSW joint compared to base metal and TIG joint having a significant improvement,which arel95.5 HV,159.7 HV and 160.7 HV,respectively;grain refinement strengthening plays an important role in enhancing the microhardness.The electrochemical corrosion tests show that the joint of FSW 316L austenitic stainless steel has a good corrosion resistance.     

Characterization of Gas Metal Arc Welded Hot Rolled DP600 Steel

Dual‐phase (DP) steels are suitable candidates for automotive applications due to their high strength and ductility. These advanced mechanical properties result from the special microstructure of the DP steel with 5～20% martensite phase in a soft ferrite matrix. However, during welding, which is an important process in automotive industry, this special microstructure is destroyed. In this research the characterization of Gas Metal Arc (GMA) welded joining zones was performed by optical microscopy and hardness mapping. Tensile tests were also performed keeping the welded portion in the gauge length. Scanning Electron Microscopy (SEM) was used for the fracture investigation. From the characterization and tensile tests, the soften zones were found, which are caused by the tempered martensite and larger ferrite grain size than that in base metal. Furthermore, GMA welding make a large Heat Affected Zone (HAZ).     

DP590钢薄板单道次焊接区的组织和性能

在不同焊接参数下分别通过Φ3 mm E4303碳钢焊条（/%:≤0.12C、≤0.25Si、0.30～0.60Mn）和Φ1mm H10MnSi焊丝（/%:0.14C、0.65～0.95Si、0.80～1.10Mn）对3.8 mm DP590钢薄板（/%:0.07C、0.45Si、1.61 Mn）进行手工电弧焊接和CO₂气体保护焊接,并利用ZEISS光学显微镜、LEICA显微硬度计分别对焊接接头的组织和显微硬度进行了观察和分析。结果表明,在焊缝区手工电弧焊焊缝组织为沿柱状晶分布的先共析铁素体和珠光体,CO₂气体保护焊为针状铁素体和少量贝氏体,在粗晶区手工电弧焊为贝氏体和先共析铁素体,CO₂气体保护焊为板条马氏体和贝氏体,且其粗晶区晶粒尺寸大于手工电弧焊;采用CO₂气体保护焊,选择较大的热输入,焊缝和粗晶区的魏氏组织消失;显微硬度最大值均出现在粗晶区,手工电弧焊的热影响区宽度小于CO₂气体保护焊。