CO_2激光焊接600MPa DP钢接头组织与性能

采用CO2激光对抗拉强度为600MPa,厚度1.4mm的DP钢进行焊接.研究焊接速度对焊缝外观和截面成形的影响、接头的组织特点、硬度、强度和成形能力.结果表明,激光功率相同,焊接速度较低时焊缝易产生气孔,焊接速度较高时易发生飞溅;焊接速度对焊缝熔深及熔宽也有影响.焊缝区组织主要由马氏体构成,从焊缝、焊接热影响区到母材,组织中马氏体含量下降,接头的最高硬度出现在焊缝或热影响区.在平行于焊缝方向,焊接接头的抗拉强度高于母材,垂直于焊缝方向,接头的抗拉强度与母材相当.由于焊缝出现马氏体组织,接头的塑性和韧性降低,板材的冲压成形能力下降.     

DP590高强钢激光焊接接头组织与显微硬度分析

使用YAG型光纤激光器对DP590钢进行激光焊接试验,研究了焊接接头的微观组织和显微硬度。结果表明:激光输出功率为3 k W,焊接速度为3、4、5 m/min时,焊接接头外观形貌较好,没有出现裂纹、气孔。随着焊接速度的增大,焊接接头的焊缝区和热影响区的宽度逐渐减小。焊缝中心的组织为板条状的马氏体,靠近焊缝热影响区的组织为马氏体和少量的铁素体,靠近母材热影响区的组织为马氏体和大量的铁素体。接头焊缝区的显微硬度明显高于母材,焊缝中心的最高硬度为380 HV。焊接接头的硬度从焊缝到母材呈逐渐减小的趋势。     

超大离焦量对TRIP800高强钢激光焊接接头微观组织与力学性能的影响

传统激光焊接车用先进高强钢时，经常容易发生焊接接头热影响区软化、焊缝脆化以及塌陷等影响焊接接头成形性能和力学性能的问题。针对此问题，使用超大离焦量激光焊接工艺，对1.6 mm厚度的TRIP800高强钢进行激光焊接，获得一种大尺寸的新型焊接接头，并对新型焊接接头的微观组织、硬度和力学性能进行分析。结果表明，当采用激光功率3 500 W、焊接速度3 m/min、离焦量为50 mm时，能够获得形貌良好、无明显缺陷的激光焊接接头。接头热影响区的组织以残余奥氏体和马氏体组织为主，焊缝区域以马氏体组织为主。焊接接头硬度的分布曲线由焊缝区至母材区呈现逐步降低的趋势，超大离焦焊接接头的抗拉强度与母材的强度相当，断后延伸率约为无离焦接头的1.25倍，断口呈现大量的韧窝，以韧性断裂为主。对于TRIP800高强钢的新型焊接接头力学性能的提升，主要是由于较宽的焊缝区域组织，增强了抵抗裂纹的能力，分散了激光焊接时的能量集中，使焊接接头不易产生较大的内应力，成形性能较好。     

焊接速度对TRIP590钢激光焊接头组织性能的影响

利用金相、拉伸及硬度试验研究不同焊接速度对TRIP590钢激光焊接头组织结构及力学性能的影响。结果表明,接头热影响区(HAZ)组织主要由贝氏体、铁素体及残留奥氏体组成,焊缝区(WZ)主要由板条状马氏体组成,随焊接速度提高,马氏体板条更加细长,晶粒细化。接头宏观断裂发生在母材区,其抗拉强度与母材相当。接头焊缝区硬度达430 HV,约为母材2倍,随焊接速度提高,热影响区变窄,焊缝硬度增加。     

TC11高强钛合金激光焊接接头的显微组织与力学性能

采用光纤激光进行TC11钛合金对接焊接,分析焊接接头的显微组织和力学性能。结果表明,TC11钛合金焊缝为α′马氏体组织,从母材至熔合线组织由α+β逐渐向α′转变;随着热输入量的增加,焊缝柱状晶尺寸变大,马氏体分布更加密集交错,同时热影响区宽度增加,粗晶区晶粒尺寸变大;2 mm厚TC11钛合金在焊接速度2.0m/min、激光功率2.8~3.2 k W的工艺参数下得到的焊缝成形良好;焊缝硬度高于母材硬度,并随热输入量的增加而增大;焊接接头抗拉强度达到母材的97%以上,塑性明显下降,低于母材的50%,焊缝断口形貌为低塑性沿晶断裂特征。     

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.     

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%。     

焊接速度对高强钢激光焊热影响区软化的影响

以双相钢和马氏体钢为对象,进行了不同焊接速度下不同强度等级的先进高强钢光纤激光焊接热影响区硬度及软化行为的试验研究.结果表明:双相钢激光焊接焊缝区硬度远高于母材硬度,而马氏体钢焊缝区硬度与母材强度相近.而激光焊接热影响区中近母材区域产生的回火马氏体,造成该区域硬度显著降低,出现热影响区软化.在同一焊接速度下,先进高强钢的强度等级越高,热影响区硬度越低,软化现象越明显.焊接速度的减小,激光焊接过程热量增大,热影响区硬度减小,软化现象也越明显.     

1Cr12Ni3MoVN不锈钢TIG焊接工艺及接头性能北大核心

采用TIG焊焊接2.5 mm厚1Cr12Ni3MoVN马氏体不锈钢板材,研究焊接工艺参数对接头组织与力学性能的影响规律,并优化工艺参数。结果表明,焊接速度为0.95 mm/s时,随着焊接电流的增加,接头强度先增后减;焊接速度为2.33 mm/s时,随着电流持续增大,接头强度不断下降。当焊接电流为96 A、焊接速度为0.95mm/s、送丝速度为1 mm/s时,工艺参数所获接头力学性能最好,抗拉强度达988.8 MPa,与母材相当。硬度最高值位于焊缝处,约为611 HV;最低硬度处于热影响区的回火区,约为292 HV;母材硬度值约为321 HV。拉伸试样均在热影响区的回火区处断裂,试样断口形貌为浅韧窝形;焊缝组织为铸态板条马氏体,完全淬火区组织为粗大的板条马氏体组织,不完全淬火区组织为板条马氏体-铁素体组织,回火区组织为高温回火索氏体,其硬度比母材调质回火索氏体差。     

1Cr12Ni3MoVN不锈钢TIG焊接工艺及接头性能

采用TIG焊焊接2.5 mm厚1Cr12Ni3MoVN马氏体不锈钢板材,研究焊接工艺参数对接头组织与力学性能的影响规律,并优化工艺参数。结果表明,焊接速度为0.95 mm/s时,随着焊接电流的增加,接头强度先增后减;焊接速度为2.33 mm/s时,随着电流持续增大,接头强度不断下降。当焊接电流为96 A、焊接速度为0.95mm/s、送丝速度为1 mm/s时,工艺参数所获接头力学性能最好,抗拉强度达988.8 MPa,与母材相当。硬度最高值位于焊缝处,约为611 HV;最低硬度处于热影响区的回火区,约为292 HV;母材硬度值约为321 HV。拉伸试样均在热影响区的回火区处断裂,试样断口形貌为浅韧窝形;焊缝组织为铸态板条马氏体,完全淬火区组织为粗大的板条马氏体组织,不完全淬火区组织为板条马氏体-铁素体组织,回火区组织为高温回火索氏体,其硬度比母材调质回火索氏体差。     

Characteristics of Nd： YAG laser welded 600 MPa grade TRIP steel

Microstructures and mechanical properties of Nd: YAG laser welded transformation induced plasticity (TRIP) steel with tensile strength of 645 MPa were studied. Due to high cooling speed of laser welding, the weld metal mainly consists of martensite different from the base metal, which is composed of ferrite matrix with bainite and a little retained austenite. Therefore, the weld metal has maximum hardness at welded joint. The yield strength and tensile strength of welded specimens tested perpendicular to weld line were almost equal to those of the base metal. But the yield strength and tensile strength of welded specimens tested parallel with weld line were a little higher than those of the base metal. The formability of laser welded TRIP steel was decreased compared with that of the base metal.     

0Cr15Ni5Cu4Nb中厚板锁底结构大功率光纤激光焊接工艺特性

采用大功率光纤激光对7 mm厚度0Cr15Ni5Cu4Nb不锈钢锁底结构实施了焊接试验,通过对不同焊接工艺参数下的接头质量、力学性能、微观组织结构的分析,研究了其焊接工艺特性. 结果表明,焊缝中的主要缺陷是焊接气孔,采用负离焦、高速度的焊接参数能够有效抑制气孔的形成. 焊缝区域硬度有所增加,并且焊缝上部和下部的硬度要高于中部的硬度值,接头的力学性能稳定,焊缝平均抗拉强度为970 MPa,冲击韧性略有降低,为母材的89%. 焊缝组织主要由马氏体、残余奥氏体和δ-Fe组成,焊缝中部δ-Fe要多于上部,马氏体转变不充分,热影响区中主要由晶粒细小的淬火马氏体组成.     

高强钢CO2激光-MAG复合焊接性能

为了研究CO₂激光-熔化极活性气体保护焊（MAG）复合焊接性能,采用CO₂激光和CO₂激光-MAG复合焊接590MPa级高强度钢,对其焊接接头的显微组织和力学性能进行了研究.结果表明,激光-MAG复合焊接的焊缝金属中,MAG电弧作用区主要为珠光体和贝氏体,激光作用区主要为马氏体;激光-MAG复合焊接的焊缝金属中Mo和Mn合金元素的分布具有不均匀性;激光和激光-MAG复合焊接的试件焊接接头拉伸性能完全满足要求,焊缝强度高于基体强度;激光-电弧复合焊缝金属在-60℃～+15℃试验温度范围内的冲击韧性比激光焊缝金属高;激光-MAG复合焊接焊缝金属硬度在250～400 HV之间,高于基体金属的硬度.     

Macrostructural and microstructural features of 1 000 MPa grade TRIP steel joint by CO2 laser welding

Bead-on-plate CO2 laser welding of 1 000 MPa grade transformation induced plasticity (TRIP) steel was conducted under different welding powers, welding speeds and shield gases. The macrostructural and microstructural features of the welded joint were investigated. The increase of welding speed reduced the width of the weld bead and the porosities in the weld bead resulting from the different flow mode of melted metal in weld pool. The decrease of welding power or use of shield gas of helium also contributed to the reduction of porosity in the weld bead due to the alleviation of induced plasma formation, thus stabilizing the keyhole. The porosity formation intimately correlated with the evaporation of alloy element Mn in the base metal. The laser welded metal had same martensite microstructure as that of water-quenched base metal. The welding parameters which increased cooling rate all led to fine microstructures of the weld bead.     

10Ni3CrMoV钢CO2激光多层焊的接头组织与性能

与传统电弧焊相比,激光焊接厚板优势明显。采用纯激光焊和激光电弧复合焊等多道焊接技术实现了28 mm厚10Ni3CrMoV钢的高效焊接,采用光学显微镜分析焊缝、热影响区和焊缝重叠区的组织,激光复合焊缝组织主要为针状铁素体,纯激光焊缝、粗晶区和细晶区组织主要为板条马氏体,激光复合焊缝重叠区组织为粒状贝氏体+马氏体,纯激光焊缝和激光复合焊缝重叠区组织为马氏体+少量粒状贝氏体。测试了焊接接头的力学性能,结果表明,激光复合焊缝金属的冲击韧性较高,焊接接头的抗拉强度和屈服强度与母材相当,延伸率略小于母材,焊接接头的最大硬度小于360 HV,弯曲性能合格。     

Effect of Laser Welding Process Parameters on Microstructure and Mechanical Properties on Butt Joint of New Hot-Rolled Nano-scale Precipitation-Strengthened Steel

A 4 kW fiber laser was chosen to weld the new hot-rolled nano-scale precipitation-strengthened steel with a thickness of 4.5 mm. The effect of laser power, defocusing distance, and welding speed on the welded joint appearance was examined, and the microstructure and mechanical properties on the typical butt joints were investigated. Results showed that increasing laser welding power may cause faster downward flow of molten metal to produce greater root humping. With the welding speed increasing, the average welding seam （WS） width decreased, and the average WS and heat-affected zone （HAZ） hardness increased. The microstructures of WS, fusion line, and coarse grain heat-affected zone were lath martensite, but the growth direction of the original austenite grain boundaries was significantly different. The microstructures of fine grain heat-affected zone were ferrite and martensite, and the microstructure of mixed grain heat- affected zone contained ferrite, massive M/A island, and a small amount of martensite. The micro-hardness values of WS, HAZ, and base metal （BM） were 358, 302, and 265 HV, respectively. The butt joint fracture at the BM far from the WS and the welded joint tensile strength are observed to follow proportional relationship with hardness.     

新型9Cr-1Mo钢搅拌摩擦焊接头组织及性能

采用钨铼合金搅拌工具对新型9Cr-1Mo钢进行搅拌摩擦焊工艺试验,探讨焊缝成形、组织及性能变化规律. 结果表明,在300和400 r/min的转速,50 mm/min的焊接速度下可获得无缺陷接头;焊缝主要由搅拌区和热力影响区组成,具有明显的马氏体淬硬组织特征;高温热影响区为淬硬马氏体和回火马氏体混合组织,低温热影响区为过回火马氏体组织. 焊缝区具有晶粒细化特征,其晶粒尺寸约为母材69.2%. 焊缝区产生明显硬化,最高硬度约为母材硬度值的2.0倍. 焊接接头抗拉强度达到母材98%以上,搅拌区和热影响区冲击吸收能量分别达到母材的77.8%和87.4%,表明搅拌摩擦焊接头仍具有较好强韧匹配.     

Microstructure and Fatigue Properties of Laser Welded DP590 Dual-Phase Steel Joints

In this paper, cold-rolled DP590 dual-phase steel sheets with 1.5 mm thickness were butt-welded by a fiber laser, and the evolution and effect on microhardness, tensile property and fatigue property of the welded joint microstructure were studied. The results showed that the base metal is composed of ferrite and martensite, with the martensite dispersed in the ferrite matrix in an island manner. The microstructure of the weld zone was lath-shaped martensite that can be refined further by increasing the welding speed, while the heat-affected zone was composed of ferrite and tempered martensite. The microhardness increased with increasing welding speed, and the hardness reached its highest value—393.8 HV—when the welding speed was 5 m/min. Static tensile fracture of the welded joints always occurred in the base metal, and the elongation at break was more than 16%. The conditional fatigue limits of the base metal and the weld joints were 354.2 and 233.6 MPa, respectively, under tension–tension fatigue tests with a stress rate of 0.1. After observation of the fatigue fracture morphology, it was evident that the fatigue crack of the base metal had sprouted into the surface pits and that its expansion would be accelerated under the action of a secondary crack. The fatigue source of the welded joint was generated in the weld zone and expanded along the martensite, forming a large number of fatigue striations. Transient breaking, which occurred in the heat-affected zone of the joint as a result of the formation of a large number of dimples, reflected the obvious characteristics of ductile fracture.     

工业纯钛光纤激光-MIG复合焊接工艺及性能

采用光纤激光与熔化极惰性气体保护电弧焊(MIG焊)复合焊接工业纯钛,分别对激光焊、MIG焊和复合焊接头的焊缝表面成形、横断面进行了观察,并进行了激光焊和复合焊接头的拉伸试验及杯突试验.结果表明,复合焊的电弧稳定性比MIG焊显著提高,焊接速度可提高7倍;复合焊与激光焊接头的抗拉强度高于母材;复合焊接头的杯突值优于激光焊接头的杯突值,这是因为复合焊焊缝的微观组织有利于接头的塑性.因此,采用光纤激光-MIG电弧复合焊接方法很好地实现了工业纯钛的高速焊接,焊缝成形良好,接头的塑性优于单一激光焊的塑性.

Abstract：

Fiber laser-metal inert gas (MIG) arc hybrid welding was used to weld the commercial pure titanium (CP-Ti). The weld appearance, cross section, tensile strength, Erichsen value and microstructure of the CP-Ti welded joints were studied. The results show that the arc stability is substantially improved and the welding speed can be increased to 7 times by fiber laser-MIG hybrid welding. The welded joints by laser welding and the hybrid welding exhibit the higher ultimate tensile strength than those of the base metal. In addition, the welded joint by the fiber laser-MIG hybrid welding has higher Erichsen values than that by laser joints. The difference in plasticity is attributed to the microstructure changes in the welded joint of hybrid welding. Thus, the fiber laser-MIG hybrid welding of CP-Ti can be carried out suecessfully at higher welding speed with a good combination of weld bead appearance and plasticity.