Method for preparing titanium alloys based on aluminothermic self-propagating gradient reduction and slag-washing refining

Patent metadata

Field	Value
Publication number	US-11060166-B2
Application number	US-201816320000-A
Country	US
Kind code	B2
Filing date	May 21, 2018
Priority date	Jun 13, 2017
Publication date	Jul 13, 2021
Grant date	Jul 13, 2021

Abstract

The invention relates to a method for preparing titanium alloys based on aluminothermic self-propagating gradient reduction and slag-washing refining, and belongs to the technical field of titanium-aluminum alloys. The method comprises the following steps of pre-treating raw materials, weighing the raw materials in the mass ratio of rutile or high-titanium slags or titanium dioxide to aluminum powder to V2O5 powder to CaO to KClO3 being 1.0:(0.60-0.24):(0.042-0.048):(0.12-0.26):(0.22-0.30), performing an aluminothermic self-propagating reaction in a gradient feeding manner to obtain high-temperature melt, performing a gradient reduction melting, performing heat insulation and separating the melt after the feeding is completed, then adding CaF2—CaO—TiO2—V2O5 based refining slags into the high-temperature melt, performing slag washing refining, and finally removing slags to obtain titanium alloys. This method has the advantages including short flow, low energy consumption, easy operation, easy control on Al and V contained in alloys, and so on.

First claim

What is claimed is:

1. A method for preparing titanium alloys based on aluminothermic self-propagating gradient reduction and slag-washing refining, comprising the following steps:
Step 1: material pre-treatment
pre-treating aluminothermic reduction reaction materials separately to obtain pre-treated aluminothermic reduction reaction materials, wherein the aluminothermic reduction reaction materials include titanium-containing material, aluminum powder, V 2 O 5 powder, CaO and KClO 3 , the titanium-containing material is at least one selected from the group consisting of rutile, titanium slags and titanium dioxide;
weighing the pre-treated aluminothermic reduction reaction materials with a proportional ratio, wherein the proportional ratio is a mass ratio of titanium-containing material:aluminum powder:V 2 O 5 powder:CaO:KClO 3 being 1.0:(0.60-0.24):(0.042-0.048):(0.12-0.26):(0.22-0.30), respectively;
wherein a particle size of the pre-treated aluminothermic reduction reaction materials is as follow: rutile and titanium slags no larger than 3 mm, titanium dioxide no larger than 0.02 mm, and aluminum powder, V 2 O 5 powder, CaO and KClO 3 no larger than 2 mm, 0.2 mm, 0.2 mm and 2 mm, respectively;
Step 2: aluminothermic self-propagating reaction performing gradient aluminothermic reduction with one of the two following feeding manners:
feeding manner I:
mixing the weighed aluminothermic self-propagating reaction materials other than aluminum powder uniformly to obtain a material mixture, and dividing the material mixture into several parts;
then assigning aluminum powder to each part of the material mixture according to a sequence of each part of the material mixture being fed into a reaction furnace, and gradually reducing the amount of aluminium powder assigned from 1.15-1.35 times the stoichiometric ratio to 0.85-0.65 times the stoichiometric ratio;
wherein the mass of a part of the material mixture that is fed into the reaction furnace as a first batch accounts for 10-30% of the mass of the total material mixture, the first batch of the material mixture requires an addition of magnesium powder as an ignition substance to ignite the material mixture to induce a self-propagating reaction, so that a first-batch high-temperature melt, that is sufficient to initiate subsequent reactions, is obtained;
feeding other parts of the material mixture into the reaction furnace according to a sequence with reduced stoichiometric ratio of the amount of aluminium powder assigned until all materials are fully reacted to obtain a high-temperature melt; or
feeding manner II:
mixing the aluminothermic self-propagating reaction materials other than aluminum powder uniformly to obtain a material mixture, and then feeding the material mixture into a continuous material mixer at a constant flow rate;
at the same time, adding aluminum powder into the continuous material mixer at a flow rate with reduced gradient, so that the amount of aluminium powder assigned to the continuously fed material mixture is gradually reduced from 1.15-1.35 times the stoichiometric ratio to 0.85-0.65 times the stoichiometric ratio, wherein the times of gradient changes of the amount of aluminium powder assigned conforms the following formula:
m =( b−c )÷ a   (1);

wherein, m is the times of gradient changes of the amount of aluminum powder assigned, b is the maximum amount of aluminum powder assigned, c is the minimum amount of aluminum powder assigned, a represents a coefficient for gradient changes of the amount of aluminum powder assigned, and 0<a≤0.04;
mixing the aluminothermic self-propagating reaction materials uniformly in the continuous material mixer, and continuously feeding the material mixture into the reaction furnace for aluminothermic reduction until all material are fully reacted to obtain a high-temperature melt;
Step 3: melt separation under electromagnetic field
heating the high-temperature melt through electromagnetic induction to perform heat insulation and melt separation, and realize slag-metal separation to obtain a layered melt with an upper layer being aluminum oxide based melt slags and a lower layer being alloy melt, wherein the temperature is controlled within the range of 1700-1800° C. and the heat insulation time is 5-25 minutes in the melt separation process;
Step 4: slag washing refining
(1) removing 85-95% of the total volume of the aluminum oxide based melt slags at the upper layer, stirring the remaining aluminum oxide based melt slags and the alloy melt at the lower layer by an eccentrically mechanical stirring at a stirring speed of 50-150 rpm under a temperature range of 1700−1800° C.;
(2) after the melt being uniformly mixed, continuously stirring, meanwhile, spraying and blowing CaF 2 —CaO—TiO 2 —V 2 O 5 based refining slags into the uniformly-mixed melt with inert gas as carrier gas, wherein the mass ratio of the aluminothermic self-propagating reaction materials in the weighing step to the CaF 2 —CaO—TiO 2 —V 2 O 5 based refining slags is 1.0:(0.02-0.08);
the CaF 2 —CaO—TiO 2 —V 2 O 5 based refining slags comprise the following chemical ingredients and mass percentages: 5%-10% of CaF 2 , 40%-60% of CaO, 0-2% of Na 2 O, 30%-40% of TiO 2 , 5%-15% of V 2 O 5 and the balance being inevitable impurities, wherein each component of CaO, CaF 2 , Na 2 O, TiO 2 and V 2 O 5 powder contained in CaF 2 —CaO—TiO 2 —V 2 O 5 based refining slags has a particle size no larger than 0.2 mm; and
(3) after spraying and blowing the CaF 2 —CaO—TiO 2 —V 2 O 5 based refining slags, performing heat insulation at 1700-1800° C. and continuously stirring with the eccentrically mechanical stirring for 10-30 minutes, so as to obtain a titanium alloy melt; and
Step 5: cooling
cooling the titanium alloy melt to room temperature, and then removing the melting slags on a top to obtain titanium alloys.

2. The method according to claim 1 , wherein the prepared titanium alloys comprise the following chemical ingredients and mass percentages: 5.5%-6.5% of Al, 3.5%-4.5% of V, 0.2%-1.0% of Si, 0.2%-1.0% of Fe, O≤0.9%, and the balance being Ti.

3. The method according to claim 1 , wherein in the step 1, the aluminothermic reduction reaction materials are pre-treated separately by the following steps:
(1) roasting the titanium-containing material, V 2 O 5 powder and CaO individually at a temperature no less than 120° C. for 12-36 hours; and
(2) drying KClO 3 at 150-300° C. for 12-48 hours.

4. The method according to claim 1 , wherein in the step 2, the number of the several parts is n, wherein n is no less than 4.

5. The method according to claim 1 , wherein in the step 3, an equipment for electromagnetic induction is a medium-frequency induction furnace, and the frequency of the electromagnetic field is no less than 1000 Hz.

6. The method according to claim 1 , wherein in the step 4, an eccentricity of the eccentrically mechanical stirring is 0.2-0.4.

7. The method according to claim 1 , wherein in the step 4, the spraying and blowing are performed at a bottom of the medium-frequency induction furnace.

8. The method according to claim 1 , wherein in the step 4, the inert gas is argon, and the purity is no less than 99.95%.

9. The method according to claim 1 , wherein in the step 4(2), the CaF 2 —CaO—TiO 2 —V 2 O 5 based refining slags are pre-treated before being used, under a roasting temperature of 150-450° C. for a roasting time of 10-48 hours.

Assignees

• Univ Northeastern

Inventors

• Dou Zhi He
• Zhang Ting An
• Liu Yan
• Lv Guo Zhi
• Zhao Qiu Yue
• Niu Li Ping
• Fu Da Xue
• Zhang Wei Guang

Classifications

• C22B7/04 Primary

  Working-up slag · CPC title

• C22B34/1295

  Refining, melting, remelting, working up of titanium · CPC title

• C22B9/10

  with refining or fluxing agents; Use of materials therefor, {e.g. slagging or scorifying agents}(C22B9/18 takes precedence){(C22B9/006 takes precedence)} · CPC title

• C22C14/00 Primary

  Alloys based on titanium · CPC title

• C22C1/06

  with the use of special agents for refining or deoxidising · CPC title