Tungsten Alloy Blanks Preparation Process(a)

Qualified tungsten blanks is one of the key timber production, a good system to choose a qualified first blank tungsten powder. Feature powder (average particle size, particle size distribution, chemical composition), mixing, forming and sintering process on the blank composition, density and microstructure have a direct impact, and strongly influences the processing and performance. Does not sag tungsten added silicon, aluminum, potassium is tungsten trioxide or "Blue W" (for a variety of low-cost tungsten oxide mixture) in the form of oxides added, the mixture containing hydrofluoric acid solution used washed to remove impurities in the powder.

Production of silk and small blank sheet more in the press forming, may also isostatic press forming. Powder compact size is generally 12 × 12 × 400 mm, there is also a larger-sized round bar, square bar or rectangular bar. First obtaining 1200 ℃ powder compact in a hydrogen atmosphere for 1 hour so as to have prefired certain strength and electrical conductivity, and then perform a power on self resistance sintering. Self-powered resistance sintering commonly known as "vertical melt" is a method developed tungsten processing. The principle is the current directly through the sintered compact, due to the resistance of the blank itself, Joule heat is generated, with this heat the billet sintering, the sintering current is typically 90% of the fusion current. The resulting self-resistance sintered blank strips (also known as a sintered article).

Processed into a general standard vertical wire melting section shall control the number of grains per square millimeter of about 10,000 to 20,000, a density of 17.8 ~ 18.6 g / cm 3. For pipe, sheet, or other large-sized products, often using isostatic pressing (pressure at 2500 kg / mm 2 or more) formed and sintered at 2300 ~ 2700 ℃ high temperature in a vacuum or hydrogen protection.

Swaging the blank is produced and the fine tungsten wire rods commonly used plastic working method, different sizes of rods in a hydrogen atmosphere is heated to 1400 ~ 1600 ℃, be swaged on a different model of the swaging machine. Start track deformation of the times is not too large, then be appropriate to increase the amount of deformation. Swaging deformation between the workpiece and the die graphite lubrication process. Tungsten rod density after processing up to 18.8 ~ 19.2 g / cm 3. Because forging billet into a round billet, deformation of each part is different, so the organization is uneven, you should recrystallization annealing.




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