Formability of zinc plated steel has been investigated by tensile, Erichsen, deep drawing and conical cup tests. Zinc was deposited onto the steel surface from a conventional zinc sulphate solution with the thickness ranging from 2 to 100μm, and the roughnesses from 5 to 25μm. From these examinations, it was found that the tensile and proof stresses of the zinc electroplated steel decreased with increasing thickness of zinc deposits. The strain hardening coefficient increased slightly, whereas the plastic strain ratio remaind practically unchanged. The Erichsen value and the limiting drawing ratio decreased with an increase in coating thickness of zinc, while the conical cup value increased. All of these properties degradated the formability of the zinc plated sheet steel. When the thickness of zinc was smaller than 10μm, no degradation of stretch formability of the steel was observed, and when the thickness was smaller than 20μm, the degradation was slightly detectable in deep drawability. By and large, the formability of the zinc plated steel tended to be favorable for smoothly deposited surface. It is concluded that formability of the steel with a small thickness of zinc is preferable than with a large thickness of zinc on the basis of the following reasons: (1) the tensile strength decreases with increasing thickness of zinc, and (2) the surface roughness increases, causes an increase in the frictional force on the subsequent plastic deformation.

抄録全体を表示

Aluminum specimens were anodized in Ematal bath at temperature of 50°C by applying constant current density or voltage. The anodic current and the voltage transient were measured as a function of anodizing time. The porous structure of the films was examined by electron microscopy using carbon replicas taken from the film section and cell base patterns at various electrical conditions. On anodizing at constant voltages, current density transient with time at the voltage less than 100V showed the well known shape observed in conventional anodizing. At the voltage more than 100V, considerable increase of current followed by gradual decrease was observed. On anodizing at constant current density, the voltage increased with time after stay on steady value. The higher the current density, the more the rise of the voltage was accelerated. Electron micrographs of the section of the opaque Ematal films showed irregular structure which contained branching, curving, cessation and distortion of pores and a number of curved pores in cell wall. These branched and curved pores produce the roughening of the metal-oxide interface and make the appearance of the film more opaque. The mechanisms of pore branching on anodic film growth was discussed.

抄録全体を表示

Anodized oxide coating obtained from phosphoric acid bath at the voltage lower than that employed in the usual method was successfully colored by varying the a. c. electrolytic duration in nickel sulfate bath alone. Addition of boric acid and well known complex, such as ammonium compounds, amines, and aqueous ammonia, was very effective for multicoloring. Boric acid was particularly the best additive. These additives seem to promote the deposition of nickel in the pores. Addition of tartaric acid, sulfulic acid, and aluminium sulfate delayed multi-coloring and resulted in single-coloring. These additives seem to restrain growth of the deposits in the pore of the coating. Color of the coatings can be controlled by varing the electrolytic duration, and kind and amount of the additives.

抄録全体を表示

The relation between plating conditions and some properties of films deposited from an electroless cobalt-nickel-phosphorous alloy plating bath with pyrophosphate as a complexing agent was investigated. 1) Preferable plating conditions were obtained in 0.1M of cobalt sulfate+nickel sulfate, 0.4M of sodium pyrophosphate, 0.5M of ammonium sulfate, and 0.2M of sodium hypophosphite at pH 10.5 (adjusted with ammonia) and at 70°C. Under the above conditions, relatively high deposition rate and bath stability were obtained. 2) A film of the composition desired in the ratio of nickel to cobalt was obtained by controlling the ratio of the concentration of nickel to cobalt in the bath. The content of phosphorus in this alloy films varied in the range of 3-4%. 3) Addition of nickel to the electroless cobalt plating film below 20% improved the magnetic property of the film. 4) The magnetic property of the film was affected by the change in its structure parameters such as grain size and anisotropy caused by the addition of nickel.

抄録全体を表示

The purpose of this study is to establish a method for heat-diffusion coating of aluminum with corrosion- and wear-resistant metals, especially with indium. Aluminum, coated with zinc of about 2μm thickness by using zincate process, is electroplated with copper prior to indium plating. In this paper, heat-diffusion of copper on the zinc film has been studied. The electroplated aluminum specimens were subjected to heat-treatment at two different temperatures, 160°C and 190°C, for 12, 24, and 36hrs, respectively. Intermetallic compounds produced as a result of interdiffusion were found to be CuZn and δ-Al₄Cu₉ for 160°C, and CuZn, δ-Al₄Cu₉, and θ-Al₂Cu for 190°C. Thus the hardness of aluminum surface increased from the original value (H_mv60) to H_mv 350-370 in maximum. Hardness and metal-concentration distributions were also measured. It was found that the surface hardness varies considerably with the conditions for the heat-treatment. The following formula has been obtained by using multiple regression analysis with a reasonability of 72.7%. Y=229.5-1.696X₁+0.748X₂+1.181X₃ where Y: surface hardness, X₁: thickness of Cu deposit, X₂: diffusion temperature, X₃: diffusion time.

抄録全体を表示