CN1555947A

CN1555947A - Sand mould negative pressure gravity casting method

Info

Publication number: CN1555947A
Application number: CNA2004100235056A
Authority: CN
Inventors: 王一诚
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-01-06
Filing date: 2004-01-06
Publication date: 2004-12-22
Anticipated expiration: 2024-01-06
Also published as: CN1223420C

Abstract

A negative-pressure gravitational casting method with sand mould including such steps as making sand mould in metallic jacket with air exhausting hole, covering press plate with sprue, covering vacuum hood, installing pouring cup, sealing by sealant, vacuumizing, pouring molten metal while vacuumizing, and cooling.

Description

A kind of sand mold negative pressure gravity casting method

Technical field:

The invention belongs to the casting method of metal parts.

Background technology:

The process characteristic of metal casting moulding is the shape that production efficiency height, cost are low, can once form complexity, thereby become metal machine components blank make in one of most important method, especially the cast iron part of widely applying in the modern industry almost all comes moulding by casting.The most widely used casting method is an ordinary sand casting in casting industry at present, and its technical process is: the apperance, dead head and the running channel that 1, produce foundry goods with timber; 2, wooden model is put into the sandbox that separates from maximum die joint, filled on every side and go up damp sand and smash tight strickling, take out wooden model gently; 3, after the molding sand drying, surface brush skim coating, the sandbox that closes forms the die cavity of metal parts blank; 4, after metal material melts in smelting furnace, from the cast gate of sandbox, pour into die cavity and be full of.Just formed the metal parts blank after the molten metal cooled and solidified.Ordinary sand casting has flexibility, versatility and low cost, thereby becomes the main production method that present casting industry adopts, and in iron casting production, the ironcasting of ordinary sand casting has reached 90% of foundry goods gross weight.If form the material of die cavity and be not sand but the higher metal of fusing point then is called permanent mold casting.No matter the material of formation die cavity how,, thereby be commonly referred to as the casement casting again because molten metal all charges into cooled and solidified in the cavity.Because sand casting carries out in atmosphere, thus high-temperature liquid metal very easily air-breathing the and cooled and solidified of oxidation is inhomogeneous causes producing following defective: 1, pore, slag inclusion, shrinkage cavity, shrinkage porosite, cold shut etc.; 2, crackle and distortion; 3, rough surface and scab; 4, misrun; 5, size and weight are overproof; 6, tissue abnormalities.

Along with the development of chemical industry, expanded material costs such as polystyrene reduce in recent years, have developed with the expanded material replacing wood and have made casting form.Because the expanded material volatilization point is low, apperance can be taken out from molding sand, the expanded material apperance is heated volatilizees to disappear, thereby be referred to as lost foam casting, be referred to as cavityless casting again.In order to allow volatilization gas discharge as early as possible, generally adopt the moulding of negative pressure dry sand, the mould that promptly disappears is imbedded in the dry sand, with sandbox is airtight be pumped into negative pressure after, the dry sand in the sandbox can be tightened to one automatically, as long as keep negative pressure state, dry sand just can not be defeated and dispersed.After treating that molten metal solidifies, unpack again and take out foundry goods.The advantage of negative pressure dry sand lost foam casting is that molten metal is poured into a mould cooled and solidified under negative pressure, pore and oxide inclusion have been eliminated, improved the liquid metal filling ability, it is stable that subnormal ambient helps all even condensation rate of gas permeability, thereby in theory should be than ordinary sand casting quality and accepted product percentage height.But practice shows that lost foam casting all has very high requirement to technological parameters such as expanded material, surperficial fireproof coating, dry sand granularity and distribution thereof, casting alloy fusing point, smelting temperature, pouring temperature, poring rate, casting case vacuum and the speed of evacuations, otherwise casting flaws such as sand, burning into sand, leakage, carbon deposit, surface galling scab will occur collapsing, especially be higher than the speed of evacuation by the local gasification rate of disappearance mould and cause that local decompression destroys the local knockout burning into sand that causes moment; Not exclusively forming the carbon black that carbon deposit causes by foamed material gasification in foundry goods is mingled with; Destroy or excessive extremely difficult the most common, the foaming material shaped in addition costs of removing of three kinds of defectives such as cast(ing) surface wire plucking scab that cause of the speed of evacuation by dope layer, all hindered applying of negative-pressure los mould casting technology to a certain extent.

In sum, at present a kind of advantage that had both kept the sand casting that tradition uses do not arranged as yet industrial, again can be in conjunction with the simple and reliable method for casting production of negative pressure casting advantage.

Summary of the invention:

Purpose of the present invention is to provide a kind of advantage that promptly keeps ordinary sand casting and negative-pressure los mould casting, can overcome the low-cost sand mold negative pressure gravitational casting technology of the two shortcoming again.

Technical scheme of the present invention is:

1, on a metab, make sand mold according to common sand sell moulding method, and sand mold be produced in the protective metal shell that has steam vent, cover have water the road junction pressing plate form the foundry goods die cavity;

2, cover one on the base of sand mold and have the exhaust tube joint and have the vacuum (-tight) housing that waters the road junction making, cup is plugged at the road junction of watering by vacuum (-tight) housing and pressing plate, the running channel of cup is communicated with the sand mold running channel, water slit between the road junction and the slit between vacuum (-tight) housing and the base with clay sealing cup and vacuum (-tight) housing then;

3, vacuum (-tight) housing exhaust tube joint is connected on the vacuum equipment by pump-line, the sandbox in the vacuum (-tight) housing is vacuumized;

4, vacuumize after, the casting of molten metal while taking out waters and stops to bleed after full, takes out foundry goods after the condensation.

Advantage of the present invention is: 1, formative method is identical with traditional sand casting, and protective metal shell just is equivalent to the sandbox in the ordinary sand casting, is easy to apply; 2, the sand mold die cavity is a cavity, the influence of having eliminated disappearance mould foamed plastics gasification rate and having decomposed carbon black, and sand burning into sand and carbon black inclusion defect collapse in no part; 3, molten metal improves in the negative pressure current downflow, therefore can suitably reduce pouring temperature, improves the nucleation rate of solidification and crystallization, makes the foundry goods interior tissue obtain refinement, has improved the mechanical property of foundry goods; 4, cooling velocity is even under the negative pressure, has reduced the wall thickness effect of casting solidification, produces the medium casting quality in batches and controls easily; 5, under the acting in conjunction of gravity and negative pressure, the molten metal feeding is abundant, has improved the formability and the compactness of foundry goods, to small-sized foundry goods simple in structure, rising head can be set, can suitably reduce rising head to big-and-middle-sized foundry goods, make full use of the direct feeding of cast gate, improved the molten metal utilization rate; 6, be not subjected to the influence of weather temperature and humidity, reduced common casting flaws such as pore, shrinkage porosite to greatest extent; 7, casting dimension accuracy height, the technology applicability is strong, is not only applicable to cast iron, also is applicable to cast steel and non-ferrous metals casting, especially is easy to oxidation and loose Metal and Alloy; 8, equipment investment is little, and is easy and simple to handle, and percent defective is low.

Description of drawings:

Fig. 1 is embodiment master's pseudosection of casting hollow foundry goods (as cylinder jacket).

Fig. 2 is embodiment master's pseudosection of the real core foundry goods of casting.

Marginal data: 1-base, 2-location-plate, 3-sand mold, 4-protective metal shell, the 5-steam vent, 6-collection chamber, the hollow arbor of 7-, 8-core, the 9-foundry goods, 10-sand mold, 11-steam vent, 12-steam vent, the 13-cross gate, 14-cup, 15-sprue, 16-vacuum equipment, the 17-exhaust tube, 18-hand stop valve, 19-air extraction connector, 20-vacuum (-tight) housing, the 21-pressing plate, 22-lute in, 23-core.

The specific embodiment:

The casting method of 1 pair of hollow foundry goods further specifies in conjunction with the accompanying drawings.

Placement positioning plate 2 and the sheath 4 that has steam vent 5 on base 1, on base plate 2, the wooden model of core 23 and foundry goods 9 is located, make sand mold 3 according to common sand sell moulding method, take out wooden model, put into the prefabricated core that has hollow arbor 78, cover sand mold 10 that has cross gate 13 and the pressing plate 21 that has steam vent 11, the vacuum (-tight) housing 20 that has air extraction connector 19 on the cover, the cup 14 that has sprue 15 is put at the center, between cup 14 and pressing plate 21 and sand mold 10, leave steam vent 12, install the back and seal slit between cup 14 and the vacuum (-tight) housing 20 and the slit between vacuum (-tight) housing 20 and the base 1 respectively with clay 22.Seal the upper oral part (not drawing among the figure) of sprue 15 before the cast with bottle cap shape foamed plastics, vacuum equipment 16 is connected with hand stop valve 18 with air extraction connector 19 usefulness exhaust tubes 17.When beginning to pour into a mould, open hand stop valve 18, the air in sand mold and the collection chamber 6 is extracted out by exhaust tube 17, at this moment can inject molten metal fast, the limit cast, bleed in the limit, after watering full cup 14 and feeding condensation certain hour, close hand stop valve 18, open vacuum (-tight) housing 20, take out foundry goods 9.The quantity of hand stop valve 18 can cast production continuously according to the number configuration of vacuum pressing and casting case.

The casting method of 2 pairs of solid castings further specifies in conjunction with the accompanying drawings.

On base 1, place the sheath 4 that has steam vent 5, make sand mold 3, take out the wooden model of foundry goods 9, the sand mold 3 that closes, the die cavity of formation foundry goods 9 according to common sand sell moulding method; Cover and have the pressing plate 21 that waters road junction and steam vent, have the vacuum (-tight) housing 20 that waters road junction and air extraction connector 21 on the cover again, put the cup 14 that has running channel 15, install the back and seal slit between slit between cup 14 and the vacuum (-tight) housing 20 and vacuum (-tight) housing 20 and the base plate 1 respectively with clay 22.The top (not drawing among the figure) of sealing sprue 15 with bottle cap shape foamed plastics before the cast.Vacuum equipment 16 is connected with hand stop valve 18 with air extraction connector 19 usefulness exhaust tubes 17.When beginning to pour into a mould, open hand stop valve 18, by the air in vacuum equipment 16 and exhaust tube 17 extraction sand molds 3 and the air collecting chamber 6, inject molten metal fast, bleed while pouring into a mould, up to watering full cup 14, and close hand stop valve 18 behind the feeding condensation certain hour, open vacuum (-tight) housing 20, take out foundry goods 9.

In order to prove effect of the present invention, utilize technology of the present invention to cast 1 over thousands of of boron alloy cast iron cylinder jacket of large-scale diesel engine, accepted product percentage has reached more than 98%, and steady quality, and comprehensive mechanical performance is all than traditional ordinary sand casting method height.

Claims

1, a kind of sand mold negative pressure gravity casting method is characterized in that:

(1) on a metab, make sand mold according to common sand sell moulding method, and sand mold be produced in the protective metal shell that has steam vent, cover have water the road junction pressing plate form the foundry goods die cavity;

(2) cover one on the base of sand mold and have the exhaust tube joint and have a vacuum (-tight) housing that waters the road junction making, cup is plugged at the road junction of watering by vacuum (-tight) housing and pressing plate, the running channel of cup is communicated with the sand mold running channel, water slit between the road junction and the slit between vacuum (-tight) housing and the base with clay sealing cup and vacuum (-tight) housing then;

(3) vacuum (-tight) housing exhaust tube joint is connected on the vacuum equipment by pump-line, the sandbox in the vacuum (-tight) housing is vacuumized;

(4) vacuumize after, the casting of molten metal while taking out waters and stops to bleed after full, takes out foundry goods after the condensation.