CN102962401A - SrZrO3 shell for titanium and titanium alloy precise casting and preparation method thereof - Google Patents

Abstract

The invention discloses a SrZrO3 shell for titanium and titanium alloy precise casting and a preparation method thereof. According to the preparation method, with strontium zirconate as a filler, zirconium acetate or yttrium sol, which does not react with titanium alloy, as an adhesive, the shell is prepared by the working procedures of pre-treatment, forming, hardening and sintering. The shell hardly reacts with titanium and titanium alloy, and a thin sticky dirty layer is formed on the surface of a casting; the strontium zirconate ceramic shell is high in strength, and the surface of the casting is high in smooth finish; and a coating containing strontium zirconate is stable, does not easily gelatinize, has good suspension property, and can be stored for a long time.

Description

A kind of SrZrO for the titanium or titanium alloy hot investment casting 3Shell and preparation method thereof

Technical field

The present invention relates to shell for the titanium or titanium alloy hot investment casting and preparation method thereof.Belong to the alloy precision casting technology field.

Background technology

Titanium or titanium alloy is widely used in the aspects such as aerospace industry, energy industry, marine transportation, chemical industry owing to have the characteristic of a series of excellences such as density is little, specific strength is high, corrosion-resistant.But titanium and titanium alloy at high temperature have very high chemism, with various refractory material generation chemical reactions commonly used.This just needs the very high chemical stability that has of refractory material that Ti alloy casting uses and binding agent.Use at present more titanium alloy precision casting shell, be broadly divided into: graphite shell, tungsten surface layer ceramic shell, New Oxide Ceramic Shell Mould etc.Wherein, the foundry goods that the graphite shell is poured into a mould out has the α brittle layer of one deck carburizing from the teeth outwards, and thickness is approximately 0.2～0.3 mm, and it might cause generation and the expansion of crackle under effect of stress.The heat endurance of graphite shell has certain limit, when graphite contacts with titanium liquid, is reaching under the condition of Activation energy, and rapid heat release chain reaction might occur, so the complicated titanium alloy casting of the unsuitable casting large of graphite shell.In addition, the shrinkage factor of graphite shell is high, is the twice of common fusible pattern ceramic shell, and this has affected the precision of fusible pattern graphite shell titanium alloy fine casting spare.When tungsten surface layer ceramic shell prepared, tungsten powder used as the filler in the coating, and the performance of tungsten powder has great impact to the quality of shell, tungsten powder is answered the higher purity of tool, impurity content can not surpass specified standard, and exceeding standard of oxygen, carbon content will affect the quality of titanium casting.Tungsten surface layer investment shell must adopt solvent dewaxing, thereby health is had very large injury, and the while is contaminated environment also.The roasting under reducing atmosphere of tungsten surface shell is deposited on the lip-deep mould material of shell ash content and is difficult to burn after the dewaxing, be easy to when cast and the reaction of liquid titanium, forms pore at cast(ing) surface.Mainly used the oxide less with the reaction of titanium liquid such as zirconia, yittrium oxide, calcium oxide in the surface layer of New Oxide Ceramic Shell Mould and the adjacent bed coating, wherein better as the investment precoat casting character of filler with yittrium oxide, but hydration occurs in yittrium oxide easily, its slurry changes very responsive to the pH value, easily gelling.New Oxide Ceramic Shell Mould can't be avoided forming α pickup layer at cast(ing) surface in addition, and the thickness of α pickup layer does not wait from 0.02 ~ 0.2mm.Strontium zirconate is the highly stable refractory material of a kind of chemical property, and strontium zirconate ceramics shell and the titanium or titanium alloy extent of reaction are little.Because the stable chemical property of strontium zirconate, chemical reaction does not occur in it in water, weak acid, highly basic in addition, and the coating of strontium zirconate is stable to be difficult for gelling so contain.

Summary of the invention

The object of the present invention is to provide a kind of SrZrO for the titanium or titanium alloy hot investment casting ₃Shell and preparation method thereof is characterized in that the surface layer of described shell is made of filler and binding agent, and described filler is strontium zirconate; Described binding agent be acetic acid zirconium or yttrium colloidal sol not with the binding agent of titanium alloy reaction; The weight proportion of filler and binding agent is 3:1～5:1; The backing layer of shell or inferior surface layer are made of as binding agent or silester with as the mullite powder of filler the silicon melten gel.

The present invention is a kind of SrZrO for the titanium or titanium alloy hot investment casting ₃The preparation method of shell is characterized in that described preparation method has following process and step:

The preliminary treatment of a strontium zirconate raw material: the strontium zirconate powder after the pickling is obtained less than 200 purpose strontium zirconate particles through methods such as airflow screen, ball millings;

The preparation of b surface layer and backing layer or inferior investment precoat: in binding agent, add through pretreated strontium zirconate, and constantly stir with agitator, add in right amount additive; Additive is that chemical composition is that stearic surfactant and chemical composition are the defoamer of dimethyl silicone polymer; The weight proportion of investment precoat is that 75 ~ 84.5wt% strontium zirconate, 15 ~ 25wt% binding agent and 0.1 ~ 0.5wt% surfactant and 0.1 ~ 0.5wt% defoamer form.Control is coated with the viscosity of slip greatly about 15 ~ 65s(No. 4 flow cups made in U.S.A); The weight proportion of backing layer or inferior investment precoat is: mullite powder: binding agent=4:1;

The preparation of c shell: after coating preparation is good, wax-pattern is immersed in the investment precoat, when unnecessary coating gutters down, and coating is coated with equably carry out stucco when hanging on the wax-pattern, 80 ~ 120 purpose strontium zirconate powder are sprinkling upon equably have been coated with on the coating wax-pattern; After the abundant drying of coating and the sclerosis, repeat again above-mentioned steps 1-2 time; The coating of backing layer or inferior surface layer then uses above-mentioned silester or silicon melten gel binding agent and filler mullite powder, and its viscosity of the coating of composition is controlled at 10 ~ 20s, and then with 20 order mullite powder stuccos; Repeat 2-3 time; Then dry;

The dewaxing of d shell: the shell that drying is good uses high steam still or microwave dewaxing;

The sintering of e shell: the shell that will dewax is put into roaster at the air sintering, 1150 ~ 1250 ℃ of sintering temperatures, and then sintering one hour 300 ℃ of lower insulations 2 ~ 3 hours, cools to room temperature with the furnace subsequently, namely gets the shell finished product.

Description of drawings

Shell before and after Fig. 1 pours into a mould (left is that cast is rear, right for before pouring into a mould)

The alloy that Fig. 2 knocks out behind the part shell is local

Fig. 3 removes the alloy of shell fully

Specific implementation

After now specific embodiments of the invention being described in

Embodiment

Preparation process and step in the present embodiment are as described below:

(1) preparation of coating: through adding binding agent two acetic acid zirconiums in levigate, as the to cross 200 mesh sieves strontium zirconate powder, constantly stir with agitator, the viscosity that control is coated with slip is greatly about 30s, the weight ratio 4:1 of strontium zirconate powder and binding agent;

(2) preparation of shell: wax-pattern is immersed in the above-mentioned coating that configures, stays a minute, allow coating be coated with equably when hanging on the wax-pattern, but stucco, strontium zirconate dry powder is dispersed in equably be coated with on the coating wax-pattern, the stucco process repeats 1 time; And then carry out backing layer coating; The used binding agent of backing layer coating is ethyl silicate or Ludox, and used filler is mullite powder, and both weight proportions are 1:4; This backing layer coating slurry coating in the skin of above-mentioned coating wax-pattern, is carried out stucco with thicker mullite powder subsequently again; Backing layer coating repeats 3 times by this operation; The final gross thickness that forms coating is 5mm.

(3) above-mentioned wax-pattern with laminated coating is carried out drying, after the sclerosis to be dried, remove wax-pattern, form shell.

(4) sintering of shell; The shell that has dewaxed is put into roaster roasting under nitrogen protection, 1150 ~ 1250 ℃ of sintering temperatures, sintering 1 hour in 300 ℃ of insulations 2 hours, cools to room temperature with the furnace subsequently, finally makes the strontium zirconate ceramics shell for the titanium or titanium alloy hot investment casting.

The shell cast Ti-Ni alloy that utilization is made through this operation, without the significant reaction layer, the metal surface is bright and clean after the melting, and alloy property is good.

Claims (2)

1. SrZrO who is used for the titanium or titanium alloy hot investment casting ₃Shell is characterized in that the surface layer of described shell is made of filler and binding agent, and described filler is strontium zirconate; Described binding agent be acetic acid zirconium or yttrium colloidal sol etc. not with the binding agent of titanium alloy reaction, the weight proportion of filler and binding agent is 3:1～5:1; The backing layer of shell or inferior surface layer are made of as binding agent with as the mullite powder of filler silicon melten gel or silester.

2. SrZrO who is used for the titanium or titanium alloy hot investment casting ₃The preparation method of shell is characterized in that described preparation method has following process and step:

The preliminary treatment of a strontium zirconate raw material: the strontium zirconate powder after the pickling is levigate and obtain less than 200 purpose strontium zirconate particles by airflow screen through ball milling;

The preparation of b surface layer and backing layer or inferior investment precoat: in binding agent, add through pretreated strontium zirconate, and constantly stir with agitator, add in right amount additive; Additive is that chemical composition is that stearic surfactant and chemical composition are the defoamer of dimethyl silicone polymer; The weight proportion of investment precoat is that 75 ~ 84.5wt% strontium zirconate, 15 ~ 25wt% binding agent and 0.1 ~ 0.5wt% surfactant and 0.1 ~ 0.5wt% defoamer form; Be coated with the viscosity of slip greatly about 15 ~ 65s with No. 4 flow cups control made in U.S.A; The weight proportion of backing layer or inferior investment precoat is: mullite powder: binding agent=4:1;

The preparation of c shell: after coating preparation is good, wax-pattern is immersed in the investment precoat, when unnecessary coating gutters down, and coating is coated with equably carry out stucco when hanging on the wax-pattern, 80 ~ 120 purpose strontium zirconate powder are sprinkling upon equably have been coated with on the coating wax-pattern; After the abundant drying of coating and the sclerosis, repeat again above-mentioned steps 1-2 time; The coating of backing layer or inferior surface layer then uses above-mentioned silester or silicon melten gel binding agent and filler mullite powder, and its viscosity of the coating of composition is controlled at 10 ~ 20s, and then with 20 order mullite powder stuccos; Repeat 2-3 time; Then dry;

The dewaxing of d shell: the shell that drying is good uses high steam still or microwave dewaxing;

The sintering of e shell: the shell that will dewax is put into roaster at the air sintering, 1150 ~ 1250 ℃ of sintering temperatures, and then sintering one hour 300 ℃ of lower insulations 2 ~ 3 hours, cools to room temperature with the furnace subsequently, namely gets the shell finished product.

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