Die casting process type of large diameter thick wall pipe and its application method

Large diameter stainless steel thick wall pipe die casting process has been used to produce various types of stainless steel thick wall pipe die casting pieces.In martensite stainless steel series, there are 12Cr12(403), 12Crl3 (410), 20Cr13 (420), 17Cr16N12(431) and 68Cr17(440).In the austenitic stainless steel series, there are 12Cr18N19 (302), 06Cr19N110(304),20Cr25 N120(310) and 06Cr17N12M02(316).The precipitated hardened steel series has 05Cr17N14Cu4Nb(17-4ph).The pouring temperature of stainless steel in commonly 1500 ~ 600 ℃, l the pouring temperature slightly higher temperature than copper and alloy.The metal melts in a coreless induction furnace with a capacity of 200 ~ 300kg.Due to the die casting machine every shot pressure casting only a small part of the metal, stainless steel shot pressure continues, in order to make the metal must be in a furnace, heat preservation, this requires using inert gas to protect, to run the melting.In order to prevent the loss of easily oxidized chemical components such as Cr, Mn, Si and C in thick-walled stainless steel tubes, nitrogen is used as a protective gas in stainless steel melting.

At present, large diameter thick wall pipe die casting method is adopted, a hand side near the ladle from out in the furnace of liquid metal, pouring of liquid metal die casting machine for the this and similar general aluminium alloy die casting production.The operator takes the metal liquid out of the furnace with the ladle, pours it into the injection system of the die-casting machine, and then presses the button to shoot the metal hydraulic into the mold.The normal range of injection pressure is 5000 to 15000psi.Metal injection type, under the action of the injection system, less than Is can be completed.For some fairly thin die-casting pieces (from 1 ~ 20mm), the solidification actually begins within 1s.The holding time of the casting in the mold is generally about 2 ~ 4s, that is, the time interval between the liquid injection of metal and the opening of the mold to take out the die casting.

In order to prevent "cold" and other casting defects, in order to obtain smooth surface castings, pressure type must be preheated, average operating temperature should keep a few hundred degrees Celsius, the suitable temperature depends on the characteristics of the cast metal.Before the metal injection molding, on the surface of molding need to besmear to brush a layer of parting agent, graphite is a good parting agent, its function is to improve the surface finish, make the radiation pressure of the faster, the higher roughness of casting.However, this condition is usually obtained at the expense of the compactness and non-porosity of the casting.Under good conditions, the surface finish of austenitic stainless steel die casting can reach 0.008 ~ 0.0013 mm.

A skilled operator working on a modern die-casting machine can produce 100 pieces or more per hour.Compared with other casting methods, the output of each operator in die casting process is much higher, especially when the pressure type of multi-cavity is adopted.For small pieces, each operation of die casting process, the pressure type can contain more than 10 different cavity at the same time, or all of the cavity are the same kind of parts or related to the same kind of different parts.

Generally, the mass of die casting pieces is from several grams to several kilograms, and the size of casting is from LCM to the maximum size of 20 ~ 30cm.The dimension tolerance of casting can reach several millimetres per centimetre.

The thermal expansion coefficient of high temperature resistant alloys used for large diameter stainless steel thick wall pipes is very different from that for pressure type.Therefore, in most cases, the outside surface of die casting parts does not require the drawing inclination, but the inner surface of casting requires the drawing inclination, that is, the surface of parts and cores must have at least 5.~ 10.The slope.A fairly simple choice of parts can be made directly from a two-half pressure type with a defined inner cavity.The more complex parts can be made from a compression type with a movable core or from a specific component with a cavity.These parts are removed from the casting by a die-casting machine or both before the two halves of the main die are opened.Generally, there are auxiliary rods (ejector rods) designed for the die casting. When a die casting cycle is over, the die casting machine opens the die casting mould.Stainless steel thick wall pipe thick wall stainless steel pipe, large diameter stainless steel pipe ,large diameter thick wall pipe.