Method for producing titanium or titanium aluminum alloys through two-stage aluminothermic reduction and obtaining titanium-free cryolite as byproducts

Patent metadata

Field	Value
Publication number	US-2018202024-A1
Application number	US-201515743919-A
Country	US
Kind code	A1
Filing date	Sep 9, 2015
Priority date	Jul 17, 2015
Publication date	Jul 19, 2018
Grant date	—

Abstract

A method for preparing titanium or titanium aluminum alloys through two-stage aluminothermic reduction and obtaining titanium-free cryolite as byproducts. The method has the following steps: (1) using sodium fluoride and sodium fluotitanate as raw materials, or using sodium fluotitanate as raw materials, and using titanium aluminum alloy powder as a reducing agent; (2) mixing and pressing into pellets, and carrying out first-stage aluminothermic reduction and vacuum distillation; (3) finely grinding after taking out titanium-containing cryolite, mixing with the reducing agent and briquetting, and carrying out second-stage aluminothermic reduction; and (4) separating low-titanium titanium aluminum alloys from high-titanium titanium aluminum alloys, making the low-titanium titanium aluminum alloys and the high-titanium titanium aluminum alloys into powder and returning to the two-stage aluminothermic reduction as the reducing agent; or after the alloys are molten, making the alloys into powder for the two-stage aluminothermic reduction.

First claim

1 . A method for producing titanium or titanium aluminum alloys through two-stage aluminothermic reduction and obtaining titanium-free cryolite as byproducts, comprising the following steps:
(1) using sodium fluoride and sodium fluotitanate as raw materials, and using aluminum titanium alloy powder obtained through a second-stage aluminothermic reduction as a reducing agent, wherein the reaction formulas of the production proportion of all the materials are shown as follows:
12Na 2 TiF 6 +(12 x+ 16)Al=12TiAl x +3Na 3 AlF 6 +3Na 5 Al 3 F 14 +4AlF 3   (1)

and, Ti+ x Al=TiAl x   (2);

wherein x=0-10; (2) uniformly mixing the raw materials with the reducing agent to obtain a mixture, pressing the mixture into lumps, placing the lumps into a vacuum reduction furnace, heating the placed lumps to 900-1300° C. under a vacuum condition or in an argon atmosphere, and performing a first-stage aluminothermic reduction and vacuum distillation; coagulating a titanium-containing cryolite distilled out on a crystallizer at a low-temperature end of the vacuum reduction furnace, wherein the product mainly comprises Na 3 AlF 6 , Na 5 Al 3 F 14 , AlF 3 and titanium-containing sub-fluoride, and the residual product in the vacuum reduction furnace is TiAl x ; (3) taking out the titanium-containing cryolite, grinding the titanium-containing cryolite until a particle size is lower than 1.0 mm, using the aluminum powder as the reducing agent, uniformly mixing the grinded titanium-containing cryolite with the aluminum powder to obtain a mixture, and pressing the mixture into lumps, wherein the feeding amount of the aluminum powder follows the rule that the melting point of the Al—Ti alloys produced by the second-stage aluminothermic reduction is lower than or equal to the temperature of the second-stage aluminothermic reduction temperature; placing the lumps into the reduction furnace, heating the placed lumps to 900-1300° C. in the argon atmosphere and preserving the temperature for 0.5-2 h for the second-stage aluminothermic reduction, wherein according to the products obtained after the reduction reaction is ended and the temperature in the furnace body is reduced to normal temperature, white titanium-free cryolite is formed at upper parts of the products and the aluminum titanium alloys are formed at bottoms of the products, wherein alloys with low content of titanium are formed at the upper parts of the aluminum titanium alloys, which are called as the low-titanium titanium aluminum alloys; the aluminum titanium alloys with comparatively high content of titanium is formed at the lower parts of the aluminum titanium alloys, which are called as the high-titanium aluminum titanium alloys; and (4) dividing or separating the low-titanium aluminum titanium alloys and the high-titanium aluminum titanium alloys with a mechanical division method or a remelting and dumping method of the induction furnace, making the low-titanium aluminum titanium alloys divided out or separated out into powder as the reducing agent of the first-stage aluminothermic reduction, or remelting the aluminum titanium alloy produced by the second-stage aluminothermic reduction to make powder, and returning the powder back to the first-stage aluminothermic reduction as the reducing agent for use.

2 . A method for producing titanium or titanium aluminum alloys through two-stage aluminothermic reduction and obtaining titanium-free cryolite as byproducts, comprising the following steps:
(1) using sodium fluotitanate as raw materials, and using aluminum titanium alloy powder obtained through a second-stage aluminothermic reduction as a reducing agent, wherein the reaction formulas of the production proportion of all the materials are shown as follows:
3Na 2 TiF 6 +2NaF+(3 x+ 4)Al=3TiAl x +Na 3 AlF 6 +Na 5 Al 3 F 14   (3)

and, Ti+ x Al=TiAl x   (4);

wherein x=0-10; (2) uniformly mixing the raw materials with the reducing agent to obtain a mixture, pressing the mixture into lumps, placing the lumps into a vacuum reduction furnace, heating the placed lumps to 900-1300° C. under a vacuum condition or in an argon atmosphere, and performing a first-stage aluminothermic reduction and vacuum distillation; coagulating titanium-containing cryolite distilled out on a crystallizer at a low-temperature end of the vacuum reduction furnace, wherein the product comprises the main components of a mixture of Na 3 AlF 6 , Na 5 Al 3 F 14 , AlF 3 and titanium-containing sub-fluoride, the residual product in the reduction furnace is TiAl x ; (3) taking out the titanium-containing cryolite, grinding the titanium-containing cryolite until the particle size is lower than 1.0 mm, using the aluminum powder as the reducing agent, uniformly mixing the grinded titanium-containing cryolite with the aluminum powder to obtain a mixture, and pressing the mixture into lumps, wherein the feeding amount of the aluminum powder follows the rule that a melting point of the Al—Ti alloys produced by the second-stage aluminothermic reduction is less than or equal to the temperature of the second-stage aluminothermic reduction; placing the lumps in the reduction furnace, heating the placed lumps to 900-1300° C. in the argon atmosphere and preserving the temperature for 0.5-2 h for the second-stage aluminothermic reduction, wherein according to the products obtained after the reduction reaction is ended and the temperature in the furnace body is reduced to normal temperature, white titanium-free cryolite is formed at upper parts of the products and the aluminum titanium alloys are formed at bottoms of the products, wherein the low-titanium aluminum titanium alloys are formed at the upper parts of the aluminum titanium alloys, which are called as the low-titanium aluminum titanium alloys; the aluminum titanium alloys with comparatively high content of titanium are formed at the lower parts of the aluminum titanium alloys, which are called as the high-titanium titanium aluminum alloys; and (4) dividing or separating the low-titanium aluminum titanium alloys and the high-titanium aluminum titanium alloys with a mechanical division method or a remelting and dumping method of the induction furnace, making the low-titanium aluminum titanium alloys divided out or separated out into powder as the reducing agent of the first-stage aluminothermic reduction, or remelting the aluminum titanium alloys produced by the second-stage aluminothermic reduction to make powder, and returning the powder back to the first-stage aluminothermic reduction as the reducing agent for use.

3 . The method for producing titanium or titanium aluminum alloys through two-stage aluminothermic reduction and obtaining titanium-free cryolite as byproducts according to claim 1 , wherein, when the first-stage aluminothermic reduction is performed for the first time, metal aluminum powder is used as a reducing agent, and the production proportion of the using dosage of the reducing agent is shown in the reaction formula in step (1).

4 . The method for producing titanium or titanium aluminum alloys through two-stage aluminothermic reduction and obtaining titanium-free cryolite as byproducts according to claim 1 , wherein, the vacuum distillation lies in that the reduction furnace is vacuumized to 10 Pa or below, and distillation is performed for 1 h or above under the condition that the temperature is 900-1300° C.

5 . The method for producing titanium or titanium aluminum alloys through two-stage aluminothermic reduction and obtaining titanium-free cryolite as byproducts according to claim 2 , wherein, when the first-stage aluminothermic reduction is performed for the first time, metal aluminum powder is used as a reducing agent, and the production proportion of the using dosage of the reducing agent is shown in the reaction formula in step (1).

Assignees

• Univ Northeastern
• Shenyang Beiye Metallurgigal Tech Co Ltd

Inventors

• Feng Naixiang
• Zhao Kun
• Wang Yaowu
• Peng Jianping
• Di Yuezhong

Classifications

• C22F1/04

  of aluminium or alloys based thereon · CPC title

• B01D3/10

  Vacuum distillation (B01D3/12 takes precedence) · CPC title

• C22C14/00

  Alloys based on titanium · CPC title

• C01P2002/72

  by d-values or two theta-values, e.g. as X-ray diagram · CPC title

• C22B5/04

  by aluminium, other metals or silicon · CPC title