Shizuo Mukae

Effect of heat treatment on bond characteristics of aluminium clad steel: Production and characteristics of vacuum roll bonded clad materials (2nd Report)

Summary This paper describes production of aluminium clad steel by vacuum roll bonding. The clad steel was heated at 560–650 °C × 0–20 sec to study the formation of intermetallic phases and the shear strength in the bond interface subjected to welding thermal cycles. The results obtained may be summarised as follows: Even under rapid heating at a temperature just under the melting point of aluminium, no intermetallic phases are formed in the bond interface of aluminium clad steel unless there is holding at this temperature. The intermetallic phases formed in the bond interface are FeAl3 and Fe2Al5. The activation energy of their formation is 41 kcal/mol. Even under rapid heating at a temperature just under the melting point of aluminium, the bond shear strength is the same as that of the as‐welded material unless there is holding at this temperature. The bond shear strength depends on the heating temperature and holding time, sharply decreasing under short‐term holding with a rising heating temperature an...

Effect of Heat Treatment on Bond Characteristics of Aluminum Clad Steel. Development of Clad Materials by Vacuum Roll Bonding and its Characteristics. (Report 2).

An aluminum clad steel was produced using the vacuum roll bonding. The clad steel was heated at 560 to 650°C for 0 to 20 s to study formation of intermetallic phases and bond shear strength in the bond interface between the aluminum and the steel of the aluminum clad steel given weld thermal cycles. Main results obtained are as follows ; (1) Although the clad steel was heated at 650°C without holding, an intermetallic phase was not formed in the bond interface. (2) However, when the clad steel was heated for a certain time, intermetallic phases of FeAl3 and Fe2Al5 were formed in the bond interface and the activation energy for formation of the phases was 41 kcal/mot. (3) When the thickness of the phases was more than around 1.5μm, the bond shear strength of the clad metal was abruptly decreased in comparison with that of the clad steel in as-produced condition.

Effects of inserts in seam welds in stainless steel foils

Summary Bright‐annealed austenitic stainless steel foils with thicknesses of 100 μm and μ50 m were seam‐welded to produce seam bonds with an insert of Ni‐base amorphous foil, and the weldability was investigated in comparison with seam welds without the insert. The results obtained may be summarised as follows: Seam bonds in 100 μm thick stainless steel foils are obtained even if the insert metal is not used, whereas seam bonds in 50 μm thick stainless steel foils are obtained only when the insert is used.When amorphous foil is used as the insert, seam bonds are obtained within a wider welding current range than in seam welding without the insert.The microstructures of the seam bonds with the insert are divided into three types according to the solidification morphology of the melted zone of the insert and stainless steel foil.The maximum peel load of the seam bonds without the insert shows heavy scatter, whereas that of the seam bonds with the insert scarcely fluctuates at all.When the seam bonds are sub...

Diffusion bonding of tantalum and stainless steel

Summary This paper describes an investigation of diffusion bonding of commercially pure tantalum and austenitic stainless steel SUS304 in a vacuum of 8 mPa at temperatures ranging between 600–1200°C. Direct bonding of tantalum and stainless steel results in extremely low joint strength and formation of intermetallic compounds, such as e.g. FeTa, Fe7Ta3, NiTa2, NiTa, Ni2Ta, Ni3Ta, Ni8Ta, and Cr2Ta in the joint bond zone. To examine the effects of stainless steel alloying elements such as e.g. Cr, C, Fe and Ni on the joint strength, diffusion bonding was performed between tantalum and pure chromium, tantalum and carbon steel (0.42 mass%C), tantalum and pure iron, and tantalum and pure nickel. The effects of Fe, Ni and Cu foil inserts on the strength of tantalum and stainless steel joints were also studied. The results obtained may be summarised as follows: When tantalum and chromium are bonded, Cr2Ta is formed in the bond zone, and the bond strength then found is so low that the bonding materials cannot be ...

Diffusion Bonding between Tantalum and Stainless Steel.

Diffusion bonding between a commercial pure tantalum and an austenitic stainless steel SUS304 was performed in a vacuum of 8 mPa at temperatures ranged from 600 to 1200•Ž. The direct bonding of the tantalum to the stainless steel, resulted in extremely low joint strength and formed intermetallic compounds such as FeTa, Fe7Ta3, NiTa2, NiTa, Ni2Ta, Ni3Ta, Ni8 Ta and Cr2Ta in the bond zone of the joint. To examine the influence of Cr, C, Fe and Ni of alloying elements of the stainless steel to the joint strength, the diffusion bondings were carried out between the tantalum and a pure chromium, the tantalum and a carbon steel (C: 0.42 mass%), the tantalum and a pure iron and the tantalum and a pure nickel. The effect of the insert metals of Fe, Ni and Cu foil on the joint strength between the tantalum and the stainless steel has been also studied. Main results obtained are as follows :

Microcracks in aluminium alloys developed in the cleaning action region

Summary Microcracks developed in the cleaning action region during the GTA (TIG) process have been investigated using aluminium and aluminium alloys. Although no microcracks are found in pure aluminium and commercially pure aluminium, microcracks are mainly developed in Al‐Mg alloys where the oxide film is ruptured by the cleaning action. The microcracking trend found is analogous to the weld solidification crack susceptibility of Al‐Mg alloys, and the microcracks developed in the cleaning action region are predicted to be related to solidification cracks. The microcracks readily develop with an increasing EN ratio of the welding current. A pattern of solidified dendrites is clearly visible, suggesting that the microcracking has developed by the cathode spot formed leading to local melting. The microcracking is also intergranular. The cooling rate during solidification can be estimated from the dendrite size, being put at around 104 °C/sec. Microcrack development is considered to be due to the fact that t...

The Effect of an Insert Metal on Seam Welds of Stainless Steel Foils

Austenitic stainless steel foils having thicknesses of 100μm and 50μm were seam welded to make an seam bond with an insert metal of a Ni base amorphous foil. The weldability has been investigated in comparison with seam welds without the insert metal. Main results obtained are as follows:(1) The seam bonds of 100μm thick stainless steel foil were obtained even if the insert metal was not used, however, the seam bonds of 50μm thick stainless steel foil were obtained only when the weldings were performed with the insert metal.(2) When the amorphous foil was used as the insert metal, the welding current range that seam bonds were obtained was wide in comparison with the seam welding without the insert metal.(3) The microstructures of the seam bonds with the insert metal were divided into three types by the solidification morphology of melted zone of the insert metal and the stainless steel foil.(4) The maximum peel load of the seam bonds without the insert metal largely fluctuated, however, that of the seam bonds with the insert metal hardly fluctuated.(5) When the peel test and the tensile shear test were carried out for the seam bonds, the fractures occurred in the stainless steel foils near the seam bonds.

Study on strain distribution in Al and Al alloys subjected to several procedures and deformations by X-ray diffraction.

Strain distributions in the deformed layer of Al alloys strained by abrasion with emery papers were studied by X-ray diffraction. The strain in the tensile and tear tested specimens was also studied. The equivalent plastic strain is the strongest on the specimen surface and weakens with the depth from the specimen surface. The specimen surfaces abraded with emery papers of #120, #700 and #1000 have equivalent plastic strains 4.5, 6.4 and 1.8% respectively bearing an indistinct relation to the roughness of emery papers. The deformation layer thins down with the roughness of the papers. When machined by a shaper, the equivalent plastic strain amounts to 58%. When two regions differently deformed coexist, the equivalent plastic strain is greatly determined by a smaller strain. Measured and calculated strains in the necked region in the tensile tested bars have a good correlation up to the reduction of area about 40%. Tear test specimens have large values of equivalent plastic strain over a wide range from the tip of the crack.

Effects of Ti and Al on notch toughness of synthetic heat affected zone in steels with low nitrogen.

Effects of Ti and Al in steels on the notch toughness of the synthetic weld heat affected zone have been investigated using 41 kgf/mm2 grade steels containing various quantities of N. The results obtained are as follows: (1) Synthetic HAZ toughness of the steel containing 13 ppm of N is the most superior to the other all steels. Charpy transition temperature (vTrs) is droped about 15°C per the decreasing of 10 ppm of N. When N in steels is less than 20 ppm, additions of Ti and/or Al deteriorate the notch toughness. (2) Notch toughness is improved by Ti addition, especially, when Ti is added about 3.4 times of N content, the notch toughness becomes the best, because of the decreasing of free N content and the refining of microstructures on each N content of 20 to 60 ppm. (3) Even if the ratio of Ti and N contents, Ti/N, is 3.4, the notch toughness is improved with the decrease in N content of steels. However, when 0.06 wt% of Al is added in steels containing more than 0.015 wt% Ti and more than 50 ppm N the notch toughness is further improved. (4) Optimum Ti content neccesary to improve the notch toughness is 0 wt% in steels containing 10 ppm N, and about 3.4 times of N content in more than 20 ppm N. (5) vTrs of synthetic HAZ of steels containing optimum content of Ti is very low comparing to steel without Ti and this tendency becomes remarkably as N content increases. While the additions of Al are effective in steels with nitrogen above 35 ppm.

Change of Weld Solideification Structure of Commercially Pure Aluminum after Annealing at High Temperature

Inside of columnar crystals which are developed in the weld metal of commercially pure aluminum subgrains are generally observed. Besides, Al-Fe compound is developed along boundaries of the subgrains. These subgrains would affect the mechanical properties and corrosion resistivity of the weld metal. In this report the investigation was made on the change of weld solidification structure when the weld metal was annealed at high temperature which had been as-welded, tensile strained or cold rolled.Macrostructures after annealing were grouped into following three classes: (i) macrostructure similar to that as-welded, (ii) base metal recrystallises and in the weld metal recrystallisation occurs partially only near the fusion boundary, (iii) recrystallisation occurs all over the weld metal. On the other hand, no considerable change was observed in features of the subgrains in the weld metal. That is, it would be concluded that the subgrains are considerably stable thermally. In the columnar crystal zone of aluminum weld metal fiber texture is developed whose fiber axis is [100]. This fiber texture was also observed after the annealing in the area where the columnar crystals were observed in the weld metal, but disappeared in the area where recrystallization occurred.Then, the intensity distributions of FeKa radiation in the weld metal were measured with electron probe microanalyser. Each maximum in the intensity distribution curves corresponded to the part which was observed black in the microstructure. Electron micrographs showed that in the weld metal which was annealed at high temperature there existed both compounds and dislocations along the boundaries of the subgrains. This phenomenon is similar to that which was observed in the as-welded metal. When the weld metals which had been tensile strained or cold rolled were annealed the boundaries of the subgrains became discrete and rod- or granular-shaped compounds were also observed inside of the subgrains. These compounds found to be A13Fe by selected area diffraction.