CN1041300A

CN1041300A - The production method of sand core for investment casting

Info

Publication number: CN1041300A
Application number: CN 88109008
Authority: CN
Inventors: 陈晋公; 杨明宏; 解广泉
Original assignee: TAIYUAN MINE MACHINE PLANT
Current assignee: TAIYUAN MINE MACHINE PLANT
Priority date: 1988-09-30
Filing date: 1988-09-30
Publication date: 1990-04-18
Also published as: CN1014686B

Abstract

A kind of waterglass base-CO ₂The production method of the sand core for investment casting of sclerosis is furnished with Ludox and PVC paste resin, through CO in the core sand ₂Sclerosis back in the brushing of core outer surface with zircon sand refractory material coating.This core water-resistance and medium temperature intensity are higher, and stable molding is easy to deposit, and cast back core collapsibility is good, sand removal easily, and sand removal is clean.

Description

The production method of sand core for investment casting

The invention belongs to a kind of casting technique, specifically is the production method of sand core for investment casting.

The production method of known formation investment-casting wax-pattern inner chamber mainly is to be shaped by the core that is arranged on the die mould.But, then can adopt the molten core method that discharges water of in wax-pattern, giving, wax-pattern combined method and change the combination, extraction form etc. of die mould core for having the crooked or interior big outer little wax-pattern inner chamber of shape.Though these methods can solve complicated inner cavity shaping problem on the wax-pattern, can not solve the difficulty that its inner chamber shell is shaped, can not solve the sand removal difficulty of these complicated inner cavities.At present for solving the shaping difficulty of investment shell intracavity, can adopt the method for being put ceramic core or quartz glass core when the compacting wax-pattern, this core is the manufacturing process complexity not only, and cost is too high, do not fit into the requirement of common engineering foundry goods, this in addition core sand removal is difficult too.For this reason, the employing that has in wax-pattern, give the glass resin core technology that discharges water, but its waterglass of selecting for use is high mode, the core sand wet strength is low, demoulding difficulty, and be difficult to deposit must have the holder of supporting plate pad during depanning in addition, also can't be shaped to many special shapes, can not satisfy the needs that wax-pattern in enormous quantities is produced.

The purpose of this invention is to provide and a kind of all kinds of difform complicated investment shell intracavities are had good formability, and have better water-resistance and a higher medium temperature intensity, sand removal is easy to the production method of sand core for investment casting.

The object of the present invention is achieved like this: with SiO ₂Content is 98%(weight %) above quartz sand 95-99 part and granularity be that the dried even back that is mixed of 200 purpose one-level bauxite 1-4 parts adds 1-5%(and accounts for refractory material gross weight %) polyethylene sticks with paste and uses the property mixed with resin even, adding 1-5%(then and account for refractory material gross weight %) the dibutyl phthalate mixed grind is even, add again by low modulus water glass and Ludox by the modified water glass 6-8%(refractory material gross weight % that forms at 3: 1) mixed grind evenly forms waterglass base polyvinyl chloride resin sand in the back.With this sand coremaking, logical CO ₂After the sclerosis, get core finishing, through 180-200 ℃ of oven dry core to buff, core outer surface brushing fireproof coating after the model inspection again, its fireproof coating prescription is as follows:

320 order zirconium English powder, 1000 grams

Ludox 700-900 gram

Phenolic aldehyde hybrid resin 1-10 gram

Organic pottery clay 50-100 gram

Suspending agent CMC 5 grams

Surfactant JFC 0.05-0.1%(accounts for above-mentioned material weight %)

N-octyl alcohol 0.003-0.006%(accounts for above-mentioned material weight %)

Brushed with after coating, natural air drying again through 110-140 ℃ of oven dry, was deposited after the reconditioning 24 hours, can drop into wax-pattern production.

Advantage of the present invention and good effect are: model casting and sand casting, waterglass and the diverse technology of organic thermoplastic resin two classes are respectively got its length and are fused to one again, are used for smart casting and produce.Not only solve the casting accuracy of complicated inner cavity, and solved the coating extension sand of little revolution section and the sand removal difficulty after the cast.Casting yield can be reached more than 85%.

The present invention adopts low modulus water glass to add the binding agent of the modified water glass of Ludox as core.As waterglass CO ₂Generate SiO during sclerosis ₂Colloidal particles and Na ₂CO ₃, and be mixed with dehydration, make the SiO in the Ludox ₂Particle is easy to coagulation, forms the different SiO of two kinds of granularities in the core after sclerosis ₂Interparticle mutual iron chains embedding becomes fine and close three-dimensional space network, has improved the water-resistance and the medium temperature intensity of core.Because Na in the low modulus water glass ₂O content height has increased the stability of Ludox, has also improved the property deposited of core sand.

In the modified water glass core sand, add the polyvinyl chloride thermoplastic resin, can between sand grains, form the micelle network between the powder, not only improve sand core strength, increased core toughness, water-resistance, and in the intensification degradation process, decomposite a large amount of HCL, make the Na in the waterglass ₂O is neutralized in a large number, has quickened the sclerosis of core and has impelled the core sclerosis fully.For preventing that thermoplastic polyvinyl chloride's resin from causing core distortion in the thermoplasticity under the dewaxing temperature, added the wet strength that bauxite improves core.

Along with the pyrolysis of Corvic generates a large amount of HCL gas and various saturated and unsaturation hydrocarbon mixture gas, produce the pinhole that is evenly distributed after making core produce give vent to anger capillary channel and roasting, and along with the raising of sintering temperature with keep this pinhole rate to increase, burn the soaking and scattering quality of annotating the back core thereby improved, help sand removal.

Most preferred embodiment of the present invention is:

1, example foundry goods feature

Investment-casting title high pressure thermodynamic trap valve body (D _G15-D _G50)

Castings material stainless steel EG ₃Crl ₃

Casting weight 0.74-4kg

Casting structure characteristics profile is two skewed crossing cylindrical shells, its outer wall need cast out 0.8 mm wide and high font and mark, 360 ° of annular revolution steam passages of cross dimensions 8 * 8-10 * 20 millimeter are arranged at inner chamber top, and the inner chamber bottom is interior big outer little inclined hole.(as shown in drawings)

2, example implementation process:

Wax-pattern and investment shell intracavity are made up of annular core and oblique core respectively.Its core sand prescription is:

Quartz sand (50/100 order) 96-99 part

One-level bauxite (200 order) 1-3 part

Welvic accounts for refractory material weight % with property resin 1.5-3%()

Dibutyl phthalate 1-3%(accounts for refractory material weight %)

Modified water glass is (with Ludox: M=2.2-2.5 waterglass=be made at 1: 3)

6-8%(accounts for refractory material weight %)

Each component of core sand adds and mixed grind is in proper order:

The dress polybag is deposited (can deposit 24-48 hour).

The system of giving meets the metal-cored dish of core shape.Above-mentioned core sand put into hit reality, can straighten footpath 1-2 millimeter iron wire to the toroidal cores turning is arbor, logical CO ₂Core is taken out in the sclerosis back, and recontour.

Dry in the far infrared core oven, baking temperature is 180-200 ℃, is incubated 1-2 hour, and core dries by the fire to buff, takes out cooling after model is checked, and the brushing fireproof coating, and the fireproof coating prescription is:

Zirconium English powder 1000 grams

Ludox 800-850 gram

Phenolic aldehyde hybrid resin 5 grams

Organic pottery clay 70 grams

Suspending agent CMC 5 grams

Surfactant JFC 2 grams

N-octyl alcohol 0.5-1 gram

Behind the core natural air drying, through secondary drying, baking temperature is 110-140 ℃.Behind the reconditioning edge, deposited 24 hours, finish the core technical process, change system wax-pattern operation over to.

In the molding core is placed in the die mould, presses wax-pattern routinely, repair a die, assemble module.System shell, dewaxing, formation has the shell of core, and to carry out routinely after the roasting temperature be that 1580-1620 ℃ molten stainless steel implantation temperature is in 500-550 ℃ the shell, afterwards, foundry goods is through the sand removal of shake shell, core cavity core stain looses after 30 seconds, and cutting is watered then, annealing and soak cleaning, sandblast, finishing, check and become casting finished products.

Claims

1, a kind of waterglass base-CO ₂The production method of the sand core for investment casting of sclerosis is characterized in that: with SiO ₂Content is that above quartz sand 95-99 part of 98% (weight %) and granularity are that dried even back adding 1-5% (the refractory material gross weight %) Welvic that is mixed of 200 purpose one-level bauxite 1-4 parts is even with the property mixed with resin, it is even to add 1-5% (refractory material gross weight %) dibutyl phthalate mixed grind then, add again by low modulus water glass and Ludox and evenly form waterglass base polyvinyl chloride fat sand in the back by modified water glass 6-8% (the refractory material gross weight %) mixed grind of forming at 3: 1, with this sand coremaking, logical CO ₂After the sclerosis, get core finishing, through 180-200 ℃ of oven dry core to being coated with yellow, the core outer surface brushing fireproof coating after model is checked, its fireproof coating prescription is as follows:

320 order zirconium English powder, 100 grams

Ludox 700-900 gram

Phenolic aldehyde hybrid resin 1-10 gram

Organic pottery clay 50-100 gram

Suspending agent CMC 5 grams

Surfactant JFC 0.05-0.1% (accounting for above-mentioned material weight %)

N-octyl alcohol 0.003-0.006% (accounting for above-mentioned material weight %)

Core after the brushing again through 110-140 ℃ of oven dry, was deposited after the reconditioning 24 hours behind natural air drying.

2, by the described production method of claim 1, it is characterized in that: the core sand prescription can be: quartz sand (50/100 order) 96-99 part; One-level bauxite (200 order) 1-3 part; Welvic accounts for refractory material weight % with property resin 1.5-3%(); Dibutyl phthalate 1-3%(accounts for refractory material weight %); Modified water glass (with Ludox: M=2.2-2.5 waterglass=1: 3) 6-8%(accounts for refractory material weight %).

The fireproof coating prescription can be: zircon sand 1000 grams, Ludox 800-850 gram, phenolic aldehyde hybrid resin 5 grams, organic pottery clay 70 grams, suspending agent CMC5 gram, surfactant JFC2 gram, n-octyl alcohol 0.5-1 gram.