A method of reproduction of aluminum extrusion scraps has been investigated by using a laboratory extrusion equipment. Small pieces of aluminum alloys, JIS H4100 and A6063, were cut from extruded shapes and put into the container. The pressure in the container was decreased before extrusion was carried out. Metallographic observation and mechanical testing were made on the reproduced shapes. The following results were obtained.
(1) The strength of the reproduced shapes linearly increased with the decrease of the pressure in the container.
(2) The number of remained bubbles in the reproduced shapes could be decreased by decreasing the pressure in the container to about 50mmHg.
(3) The chemical composition of aluminum alloy shapes was scarcely changed by repeated extrusion.

抄録全体を表示

In this study, the following degassing treatments were compared for molten magnesium produced by the Pidgeon process; gas fluxing by chlorine or nitrogen, agitation treatment, flux treatment and vacuum degassing. The effectiveness of each treatment was determined by measuring the hydrogen content before and after degassing treatment. The specific gravity was also measured complementally. The obtained results are summarized as follows.
(1) Chlorine gas fluxing was the most effective degassing treatment for molten magnesium as for molten aluminum. Hydrogen content in magnesium could be decreased to 2ccH₂/100g Mg after 6% chlorine gas fluxing. Nitrogen gas fluxing was also one of the effective degassing methods. for molten magnesium.
(2) Agitation treatment of molten magnesium was effective for degassing.
(3) No significant degassing of molten magnesium was attained by the flux treatment employed.
(4) Hydrogen content in magnesium was decreased from 20 to 5-9cc in 100g of magnesium by vacuum degassing treatment under 10-100 Torr.

抄録全体を表示

Effects of casting temperatures, remelting temperatures and repeated melting-casting cycles on refinement of primary silicon in an Al-20%Si alloy treated with red phosphorus were studied by means of an optical microscope and an X-ray microanalyzer. When a melt was cast at 700°C after treated with phosphorus at 700-900°C, primary silicon crystals were not refined. In P-treated end remelted specimens, 5 melting-casting cycles did not influence the microstructural refinement, however remelting in the range of 750-700°C decreased the refinement of primary silicon. Coarse black-colored particles were present in some primary silicon and in the eutectic structure of P-treated specimens cast at 750-700°C or remelted at 750-700°C. These black particles were identified to contain Al and P components by X-ray microanalysis. These results could be explained on the basis that the dispersion of black particle was extremely sensitive to the casting temperature.

抄録全体を表示

Edge cracking in sheet rolling often causes a lower yield due to edge trimming, surface damage of the sheet by fragments and sheet breakage in the case of tension rolling. Several methods to prevent edge cracking have been proposed. In sheath rolling, the sheet is sheathed with other material. In edge adhering rolling, a ductile material is adhered to the edges of the sheet, and in edge restraint rolling, the rolling machine is reconstructed so as to give the edge restraint.
In this experiment, edge adhering rolling was applied to the relatively thick material like a slab. To prevent edge cracking, it is not necessary that the side plate adheres all over the edge, but it is enough that it adheres only at the sheet surface. It is considered that the lateral spread at the edge is restrained and tensile stress there is compensated by the adhered side plate.

抄録全体を表示

It is well known that the hot workability of an aluminum alloy strongly depends on its Mg content. In this paper, the changes of extrudability and mechanical properties of extrusions of commercial Al-Zn-Mg alloys with the increase of Mg content were investigated in a wide range of 0.41-2.00%Mg. Extrusion experiments were carried out by using a 1600 ton press. Extrudability was evaluated by the maximum extruding pressure and maximum extruding rate. The obtained results are summarized as follows.
(1) With the increase of Mg content, the extrudability of Al-Zn-Mg alloys declined, particularly a remarkable decrease in the maximum extruding rate which is directly related to the industrial productivity was observed. The maximum extruding rate increased in a low Mg range of 0.4-1.2% and still more at lower extruding temperature near 410°C. An approximate linear relationship was empirically obtained between the maximum extruding pressure and the logarithm of Mg content.
(2) Tensile strength and 0.2% proof stress of the extrusions were generally higher for higher Mg content. But for a higher Mg content between 1.2 and 2.0%, these stresses strongly depended on the extrusion temperature and rate, and in case of low extruding temperature and rate, strength decreased due to insufficient quenching and incomplete dissolution of precipitates during extrusion.
(3)Alloys containing 0.7-1.0%Mg showed both excellent extrudability and high strength; the maximum extruding rate higher than 20m/min and 0.2% proof stress higher than 25kg/mm². For these alloys, suitable extrusion temperature is between 410 and 450°C.

抄録全体を表示