A die;
1, the compression ratio (or filling coefficient) : the mixture of fine, is the greater the apparent specific volume, to be compressed into a given density of briquette compression ratio is large. Generally between 2.5 4 times; Die elastic deformation occurred during pressing process often cause after demoulding pressure piece of the transverse crack.
2, line contraction coefficient: press block size and the ratio of the sintering products corresponding size. The smaller the briquette density, the greater the shrinkage coefficient.
Two, suppression techniques: molding including the said material, mold, pressing, demoulding and briquetting dry, trim (a check) and pressure processing; Suppress press operation is simple, is the key to adjust the single, size and processing due to some of the problems of equipment and material is not stable.
Three, suppression of waste:
1, layered: along the edge of briquetting, angled and compression, form a neat interface layer. The cause of briquetting stratification is internal stress or pressure block elastic tension. Low cobalt content such as mixture, carbide high hardness, the fine powder or granule material, forming agent, uneven distribution of too little or too wet or too dry mixture, pressing pressure, single is too big, press block shape is complex, bad mould finish, mesa, could cause stratification. Increase briquetting strength, reduce the pressure of internal stress and springback is one of the effective methods to solve the delamination.
2, crack: press block in irregular fracture phenomenon called local crack. Due to the pressure inside a tensile stress is greater than the tensile strength of pressure. Press block internal tensile stress from the elastic internal stress. Should be paid attention to: the influencing factors of stratification also affect the crack. In addition, prolong the holding time or multiple pressure, reduced pressure, single weight, improve the mold design and the appropriate increase mold thickness, speed up the mold release, increase the forming agent, improve apparent density material; Can reduce the crack.
Good particles (show) : 3, no pressure though briquetting porosity can reach 40%, but due to suppression materials or pressure drop, compact pore is uneven; If local gap size is too big, cannot eliminate in sintering, the name is not good. Fodder grain is too hard, too thick, loose material is too large; Loose loading grain of uneven distribution in the cavity, single weight on the low side. All may cause no good pressure (particles).
Section 3 other molding method
A, add plastic blank processing:
Use of plasticizer, improve the plasticity of the molding press, then do all kinds of mechanical processing, made of extruded method is called by plastic blank processing, the production principle:
1, the general blank contraction coefficient should be controlled between 1.23 to 1.30.
2, presintering: objective to improve the intensity of blank, at the same time, the removal of forming agent in form small space, to facilitate subsequent permeability wax, presintering should maintain a long time at 400 ℃, presintering temperature is between 700-800 ℃, pre burn time 1-1.5 hours. To prevent the briquetting peeling in the dewaxing process.
3, the permeability of wax: to improve the plasticity of the blank to facilitate processing, blank in the temperature of 60 ℃, put in paraffin wax slowly stop up to 180-200 ℃. Blank out is paraffin wax temperature of 60 ℃.
4, cutting: cutting is should be paid attention to, because of the low strength of blank, easy to clip to crack; Carbide high hardness, wear easily cutting tools, you should use low cobalt fine alloy cutting tools, use the larger rake Angle and back Angle, low speed, a knife into the quantity;
A, isostatic pressing
Using high pressure liquid static pressure direct effects on materials within the elastic mould, make the briquetting multidirectional balanced pressure a molding method at the same time, through the transfer medium of pressure is aqueous solution, thus also known as water static pressing; Isostatic pressing, briquetting strength and linear shrinkage and forming pressure doesn't matter much, be in commonly 2 tons/cm2.
1, mould (core and die set) used for molding plastic appearance, drill a hole in the thin sheet metal sleeve; (elastic mould) must be out of shape not easily, no adhesive pressure.
2, the molding process, the powder loading elastic mould, put in high pressure vessel, after sealing by high-pressure pump into the liquid medium, such as static pressure, make materials uniform compression, decompression release liquid medium in high pressure vessel, and then remove the pressure;
Use a thin material grain can improve the surface quality of the briquette. Die uniform, compact, good material of mold with plastic plug plug, tied tightly with wire. Vacuum exhaust treatment after sealing mode, lest appear big pores and surface defects. High pressure container loading isostatic pressing machine, molding, pressure is 600-1800 kg/cm2.
3, powder (dry bag) : this craft production mode is evolved by isostatic pressing, materials packed in plastic mould, compressed air driven liquid medium, static pressure, material compression molding; General pressure booster cylinder pressure in the 13 to 15 mpa. Take out after SongYa compact. Mainly used in bar or mold core production.
Second, extrusion:
Will be after plasticizing of mixture is put into the container, the container placed at the end of the mold, mold die of it needs extrusion products section, at the other end of the extrusion tube inserted into the extrusion rod, extrusion press pressure through the extrusion rod to mix, make it become a certain shape by die products.
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