Cold Cracking of Flux Cored Arc Welded Armour Grade High Strength Steel Weldments

In this investigation, an attempt has been made to study the influence of welding consumables on the factors that influence cold cracking of armour grade quenched and tempered （Q＆.T） steel welds. Flux cored arc welding （FCAW） process were used making welds using austenitic stainless steel （ASS） and low hydrogen ferritic steel （LHF） consumables. The diffusible hydrogen levels in the weld metal of the ASS and LHF consumables were determined by mercury method. Residual stresses were evaluated using X-ray stress analyzer and implant test was carried out to study the cold cracking of the welds. Results indicate that ASS welds offer a greater resistance to cold cracking of armour grade Q＆T steel welds.

Evaluation of diffusion and phase transformation at Ag/Al bimetal produced by cold roll welding

Aluminum and silver strips were cold welded by rolling and a bimetallic strip was produced. To create cold weld between A1 and Ag, mating surfaces were specially prepared and various rolling thickness reductions were applied. The minimum critical thickness reduction to begin cold weld was specified as 70% which equals 0.1630 critical rolling shape factors. The bimetallic strips were treated by diffusion annealing at 400 ~C and various annealing time. The A1/Ag interface of strips was observed by scanning electron microscope to investigate the formation of hard and brittle probable phases. The effect of anneal time on diffusion distance and phase transformation was also analysed by EDS analysis and line scan. A diffusion region along the interface in the Ag side was observed and its width increased with prolonging annealing time. Some 8 phases were detected close to the interface after anneal treating for 3 h and 8 phase was thicker and more continuous by increasing annealing time. The microhardness measurement showed that in spite of formation of 8 phase due to diffusion annealing, the interface hardness was reduced.

Experimental and Simulation Studies on Cold Welding Sealing Process of Heat Pipes

Sealing quality strongly affects heat pipe performance, but few studies focus on the process of heat pipe sealing. Cold welding sealing technology based on a stamping process is applied for heat pipe sealing. The bonding mechanism of the cold welding sealing process （CWSP） is investigated and compared with the experimental results obtained from the bonding interface analysis. An orthogonal experiment is conducted to observe the effects of various parameters, including the sealing gap, sealing length, sealing diameter, and sealing velocity on bonding strength. A method with the utilization of saturated vapor pressure inside a copper tube is proposed to evaluate bonding strength. A corresponding finite element model is developed to investigate the effects of sealing gap and sealing velocity on plastic deformation during the cold welding process. Effects of various parameters on the bonding strength are determined and it is found that the sealing gap is the most critical factor and that the sealing velocity contributes the least effect. The best parameter combination （AIB3CID3, with a 0.5 mm sealing gap, 6 mm sealing length, 3.8 mm sealing diameter, and 50 mm/s sealing velocity） is derived within the experimental parameters. Plastic deformation results derived from the finite element model are consistent with those from the experiment. The instruction for the CWSP of heat pipes and the design of sealing dies of heat pipes are provided.

Cold welding sealing of copper-water micro heat pipe ends

The quality of micro heat pipe(MHP) is strongly affected by sealing technology. Based on the analysis of requirements of sealing technology, a cold welding technology was presented to seal MHP. In the cold welding process, compression force was used to flatten micro groove copper(MGC) tube. Then the bonding of MGC tube was reached because of intensively plastic deformation of MGC tube under pressure. It is found that the plastic deformation area of the cold welding of MGC tube can be divided into three sections. The deformation of micro grooves in each section was investigated; the influence of the dimensions of cylindrical heads on the weld joint shape and strength was studied; and a comparison between smooth copper tube and MGC tube was done. The results show that a groove compression stage exists in the cold welding of MGC tube besides a flattened stage and a melting stage.

Interfacial energy and match of cold pressure welded Ag/Ni and Al/Cu

The technology of cold pressure welding was adopted to achieve the bonding of Al/Cu(limited soluble and forming compounds), Ag/Ni (hardly mutual soluble), and the relative state of interface was tested by HREM. The results indicate that stable interface is always corresponding to the low interfacial energy value; the stable interface is not coherent but partly-coherent because of the twisting of grain boundary caused by pressure, meanwhile existing dislocation. Namely, the interfacial match and other states under the condition of cold pressure welding are different from the situation that under the condition of thermal action. Moreover, theoretical analyses and calculation on the base of thermodynamics, crystallogeny, solid physics etc, were discussed.

Study on Interfacial Bonding State of Ag-Cu in Cold Pressure Welding

The interfacial bonding of Ag-Cu (they are limited soluble) formed by the technology of cold pressure welding was discussed from the point of metallurgic view in this paper. Meanwhile, tensile test and microscopic test were adopted for studying the state of interfacial bonding, suggesting that the joint of Ag-Cu has not only strong welding joint but also atomic diffusion on the interface. For Ag-Cu, the interaction of dislocation caused by plastic deformation will cause the strain and the vibration of microconstructer defects, accompanied by emitting energy. The energy increases the atomic action and the amplitude of atomic vibration, and the result is that the atom can diffuse to several lattice parameters deep from interface to inner metals. Therefore, under the condition of chemical potential gradient, the special technique, cold pressure welding rather than basic requirements of diffusion should be taken into account. During the cold pressure welding, plastic deformation plays an important role for it causes the metals′ displacement, crystal defects, further activates the surface atoms. Finally, the fracture of atomic bonding leads to the atomic exchange and diffusion between the new metals′ surfaces.In other words the metals Ag,Cu can achieve solidate bonding by cold pressure welding accompanied by the atomic diffusion. Moreover, theoretical analysis and calculation on the basis of thermodynamics, crystallogy, so- lid physics,etc, have been applied to calculate the amount of atomic diffusion, which has further proved the testing results that joint Ag-Cu has strong bonding strength through the mechanism of atomic diffusion.

Precipitating Mechanism of Carbide in Cold-Welding Surfacing Metals

Carbides in a series of cold-welding weld metals were studied by means of SEM, TEM and EPMA, and the forming mechanism of carbide was proposed according to their distribution and morphology. Due to their different carbide-forming tendency, Nb and Ti could combine with C to form particulate carbide in liquid weld metai and depleted the carbon content in matrix, while V induced the carbide precipitated along grain boundary. But too much Nb or Ti alone resulted in coarse carbide and poor strengthened matrix. When suitabie amount of Nb, Ti and V coexisted in weld metai, both uniformly distributed particulate carbide and well strengthened matrix could be achieved. It was proposed that the carbide nucleated on the oxlde which dispersed in liquid weld metai, and then grew into multi-layer complex carbide particies by epitaxial grovvth. At different sites, carbide particies may present as different morphologies.

Effect of heat treatment on microstructure and properties of single crystal copper cold-welded joints

With the means of electron backscattered diffraction(EBSD),mechanical properties test and digital eddy current metal conductivity,the single crystal copper cold-welded joint was tested and analyzed,the structure change of cold-welded joint and the effect of heat treating on the structure and property of cold-welded joint were discussed.The results show that:The deformation area of the single crystal copper cold welded joint is broken,the crystalline grain at the interface of the joint is refined,and the single crystal structure is still maintained in the base metal area.The hardness of the deformation area increases greatly,the conductivity of the joint does not change much,and the tensile strength of the joint reaches about 70%of that of the base metal.At the interface of the heat treating joint,the single crystal structure of the deformation area and the base metal area are destroyed,and the grains grow up at the interface and the orientation is different.The hardness of the joint interface is much lower than that of the non-heat treating joint,the electrical conductivity of the joint is good,and the tensile strength of the joint is higher than that of the base metal.

Research on the properties of laser welded joints of aluminum killed cold rolled steel

Aluminum killed cold rolled steel used for automobiles was welded in this paper by using CO 2 laser with wavelength 10.6μm.The experiment shows that high quality of welding can be realized at welding speed of 4 500mm/min by optimizing the parameters.The strength and hardness of laser welded joints for aluminum killed cold rolled steel increased compared to those of the base metal while the formability decreased.Forming limit diagram of joint material indicated that the laser weld seam should avoid the maximum deformation area of automobile parts during the designing period for the position of weld seam.

THE DEVELOPMENT OF COLD WELDING SURFACING ELECTRODE FOR BLAST FURNACE VALVE

The Authors of this Article have done research on the cracking resistance of cold welding surfacing electrodes for blast furnace valves by adjusting the basicity of slag component, decreasing the hydrogen content and improving microstructure. The DF 2 Cold Welding Surfacing Electrodes prove to possess the following characters: 1) Excellent cracking resistance for surfacing alloys at normal temperature. 2) Excellent cracking resistance for repair welding and rewelding. 3) Excellent machinability for surfacing alloying.

Cold Welding of Au Nanostructures at Room Temperature

The common Au nanostructures(nanospheres,nanorods and nanosheets)were prepared by the seed growth method to explore the cold welding phenomenon of these non-single crystal nanostructures at room temperature.Systematic studies show that the concentration of surfactant cetyltrimethylammonium bromide(CTAB)and drying conditions are important factors to determine the evolution and final configuration of nanostructures during welding.The key factor of cold welding is the concentration of surfactant as low as 0.3 mm/L,and the welding should be carried out under the condition of slow evaporation and sufficient relaxation time,rather than rapid drying process.At the same time,the structural evolution during the welding process of gold rod head and tail is simulated by combining the electronic microscope characterization and density functional theory,which reveals that the stability of the welding nanostructure is better than that of the dispersed nanostructure.In the slow evaporation process of Au nanostructures with the same crystal structure,the low surfactant attached to the surface of the nanoparticles increases the attraction between the nanoparticles,which makes the nanoparticles close to each other adhere due to the interaction,and improves the physical properties of the intersection due to the diffusion,epitaxy and surface relaxation of the metal surface atoms.The results provide a research basis for the physical property analysis of nanostructures and the construction of defect devices.

The study on interfacial bonding strength of Ag-Ni, Ag-Cu in cold pressure welding

The area of combination actually is a kind of interfacial phenomena that exist on the surface or thin film. The properties of interface have important effect on the whole welded joint, even decide directly the interfacial bonding strength. The bonding strength of metals in cold pressure welding such as Ag Ni (they are hardly mutual soluble) and Ag Cu(they are limited soluble) are discussed in this paper. The results of the tensile test suggest that two kinds of welded joints have enough strength to satisfy with the demand for being used. Moreover, thermodynamics, crystal logy, physics and metal electronic microscopic analysis etc are adopted to further calculate the bonding strength. The results of test and theoretical analyses prove that Ag Ni, Ag Cu, especially, for Ag Ni can form strong welded joint which is higher than that of the relative soft base metals in cold pressure welding.

Interfacial bonding state on different metals Ag, Ni in cold pressure welding

The interfacial bonding state for the different metals Ag, Ni without metallurgic are actions was studied. The tensile test of the joint concludes that the bonding strength of Ag,Ni in cold pressure welding is strong enough to satisfy the demand of application, while the value of bonding strength is larger than that of Ag base. The conclusions further signify that the metals(hardly being mutual soluble) can be welded, and supply extremely important references to the further study either on test or theory for the weldability of different metals. The theoretical analysis and calculations of the bonding strength were made on the base of thermodynamics, crystallography, solid physics etc. Moreover, by means of microscopic test and analysis, especially drawing support from the research of Al Pb, this strong bonding mainly depends on the mechanical bonding power and metal atomic linkage, but not on the atomic diffusion.

基于SYSWELD的铝钢薄板CMT焊接温度场数值模拟

使用冷金属过渡(cold metal transfer,CMT)焊对1 mm厚的6061-T6铝合金和Q235镀锌钢薄板进行了搭接焊试验,并使用SYSWELD有限元软件对铝钢薄板搭接焊的温度场进行了数值模拟,研究了焊接速度对铝钢异种金属CMT焊接温度场的影响。结果表明,焊接电流为68 A,焊接电压为10.9 V,送丝速度为3.9 m/min,焊接速度为0.56m/min时,焊缝成形较均匀。铝钢薄板搭接焊时,温度场偏向铝板一侧,呈非对称分布;在焊接电流、焊接电压和送丝速度相同时,焊接速度越高,热输入越小,焊缝越窄。

Microstructure characteristics and mechanical properties of steel stud to Al alloy by CMT welding-brazing process

Cold metal transfer （CMT） welding of nickel-coated Q235 steel studs with 606l Al alloy was carried out using ER4043 as filler metal. The welding process was stable, and appearance of weld formed well without surface defect under the parameters of welding current 121 A, welding voltage 15.4 V and welding speed 6 r/min. The microstructure of fiUer metal was analyzed by means of scanning electron microscopy. The filler metal and 6061 Al alloy were fused to form fusion welding interface, the fusion zone had a good bonding without any micro defect. The steel stud did not melt and brazing interface was formed between the filler metal and steel stud. Two different reaction layers existed in the brazing interface, the Fe2Al5 layer about 10 -12 p^m formed near the steel stud side, and the other layer was mainly composed of FeAl3. Nickel-rich zone was formed in the root toe area of the fillet weld, which was mainly composed of Al3Ni2. The tensile tests showed that the maximum shearing strength of the joints was 129 MPa. The joint was brittle fractured in the intermetallic compound layer where plenty of FeAl3 were distributed continuously.

Stud welding for fixation of cryogenic insulation of membrane tanks in LNG ship building

The support plates including all of the inner hulls such as E grade steel, weld seams and SUS304L were considered to establish the optimal stud welding condition in LNG ship building. The stainless steel plate was especially applied to the bracket on the liquid dome. The polished and etched surfaces of the welded stud and support plate were examined if the bead was properly formed. With the micrographic examination, the fusion boundary of metal weld zone formed by stud welding was analyzed to optimize the welding parameters. And also the analysis of the unacceptable welding faults such as cold and hot weld were performed. The mechanical tests such as tensile tests and bending tests were carried out to reveal any abnormal variation in the relationship of process parameters and the strength.

EWM coldArc“冷弧焊”——一种低能量的熔化极气体保护焊技术及其应用

介绍了EWM coldArc"冷弧焊"技术,该焊接电弧是在熔化极气体保护电弧焊中短路过渡电弧基础上的一种创新。通过对焊接过程中电弧电压和电流进行精确的控制和调节,使电弧稳定,同时又能显著地降低电弧能量。焊接中工件的受热少,变形小,在薄板焊接,电弧钎焊,异种材料焊接和厚板打底焊等应用中提高了MIG/MAG的焊接质量,扩展了MIG/MAG的应用范围。

Cold metal transfer(CMT) technology-An overview

Cold Metal Transfer technology has revolutionized the welding of dissimilar metals and thicker materials by producing improved weld bead aesthetics with controlled metal deposition and low heat-input. In this study, the process, weld combinations, laser-CMT hybrid welding and applications of CMT welding are critically reviewed. Microstructure and other weld characteristics have been discussed at length for various base metal combinations. Particularly, the welding of aluminium and steel with better results has been possible with CMT Welding. The results reviewed in this article indicate that the CMT-Laser hybrid welding is more preferable to Laser or Laser hybrid welding. CMT welding has found applications in automobile industries, defence sectors and power plants as a method of additive manufacturing.

Cold-rolling technologies of advanced high strength steels in Ansteel

Low - carbon becomes a high - frequency and fashionable word which gets the greatest concern in the world.Low - carbon refers to a minimal output of greenhouse gas emissions into the biosphere, specifically refers to the greenhouse gas carbon dioxide.To reduce energy consumption of automobile,more and more high strength steels are used by vehicle companies.To meet the request of vehicle companies, various high strength steels are developed in steel companies all over the world.Ansteel can provide,ultra-low carbon bake hardening(BH) steels,dual phase(DP) steels and transformation - induced plasticity (TRIP) steels with the grades of under 780 MPa,up to now.AHSS steels have much different composition, microstructure and strenght than conventional vehicle steels,so there are some trouble in producing in cold rolling mills,for example,difficult to join,poor thickness and flatness,accurate temperature and velocity control and so on.To reduce the opportunity of strip breakage,we have done many welding experiments and special research.Now,DP and TRIP steels can be continuously produced in Ansteel.To assure thickness and flatness of strips,we optimized the hot rolling parameter to get low deformation resistance,optimized rolling oil to get fit frictional coefficient and fix on the targat rolling curve.To get more accurate and repetitive results over the production shifts,the Mathematical Model(MM) is used in Ansteel.The MM analyses information transmitted by various sensors and transmitters,compares the collected data with the chosen parameters and adjusts the settings of the various pieces of equipment to hone on the parameter setpoints.At present,the key production technologies of AHSS were grasped by cold rolling mill Ansteel,and Ansteel is the first company to apply the TRIP with the grade of 780 MPa.

Effects of Severe Plastic Deformation and Heat Treatment on Transformation Behavior of Explosively Welded Duplex TiNi-TiNi

The effects of severe plastic deformation and heat treatment on the transformation behavior of explosively welded duplex TiNi-TiNi shape memory alloys （SMAs） were investigated by differential scanning calorimeter （DSC） measurements. The explosively welded duplex TiNi-TiNi plate of 0.7 mm thickness was cold-rolled at room temperature to a 60% reduction in thickness and then annealed at different temperatures for different durations. The results showed that low temperature （623-723K） heat-treatment led to the crystallization of the amorphous region, and re-crystallization occurred in the specimens annealed at higher temperatures （over 873 K）. Research indicated that the change of martensitic transformation temperature is due to the change of internal stresses with increasing heat treatment temperature. The change of annealing time also led to a change in martensitic transformation temperature, which was associated with the precipitation and decomposition of Ti3Ni4 in TiNi-1.