CN1032962A - Technology of equiaxial miniaturization of crystal microstructure of alpha+beta titanium alloys - Google Patents

Abstract

The invention belongs to the titanium alloy technical field of hot working.

Adopt the present invention can eliminate strip or block α phase in the microstructure of original bar of alpha+beta titanium alloys or forging, and make axle α such as nascent refine to 1～2 μ m (mean diameter) mutually.

Alpha+beta titanium alloys adopts technical characterictic of the present invention to be: material is heated to the comparatively high temps of two-phase region, and during forging, deformation extent is greater than 50%, then carrying out β handles, under the temperature of two-phase region, use deformation extent to forge again greater than 50%, last, carry out recrystallization annealing again.With such technical process, can make the microstructure of former bar of alpha+beta titanium alloys or forging reach equiaxial miniaturization of crystal at last.

Description

Technology of equiaxial miniaturization of crystal microstructure of alpha+beta titanium alloys

The invention belongs to the titanium alloy technical field of hot working.

Used alpha+beta titanium alloys stamp work on aircraft and the engine thereof, for example compressor disc or compressor blade stamp work, its microstructure and mechanical property and its processing history have substantial connection, promptly be processed into bar or biscuit with ingot casting, be processed into stamp work from bar or biscuit again, heat-treat then and wait the processing parameter in each process segment that close ties are arranged.

Above-mentioned stamp work has strict demand to the original bar that provides or the microstructure of biscuit with mechanical property: microstructure should have even equiaxial primary mutually+β changes tissue, and is wherein nascent etc., and axle α phase content accounts for 30～50%; Mechanical property should reach the desired respective horizontal of stamp work.The reason that proposes this requirement is: during die forging, have the friction that is difficult to overcome fully on the surface in contact of mould and blank; Have temperature head between blank and the mould, when mould contacted with blank, chill zone appearred in the blank surface; Blank because of heat effect effect and titanium alloy poor thermal conductivity, makes blank local temperature rising etc. in deformation process.Owing to these reasons, blank uneven distribution of its internal modification in forging process is difficult to avoid, and is inhomogeneous just because of distortion, thereby caused the inhomogeneous of tissue behind the forging and mechanical property.If have residual cast structure, overheated structure (Widmannstatten structure) or bar (piece) shape α phase in former bar that die forging is used or the biscuit, distortion uneven distribution during then owing to die forging in the blank, these are organized just and may be retained in the stamp work, cause the uneven aggravation of tissue and mechanical property, even the decline of mechanical property.Therefore, for tissue and the mechanical property that guarantees stamp work, should avoid having residual cast structure, overheated structure or bar (piece) shape α phase constitution in used former bar or the biscuit, and make every effort to reach and have axle primary phase+β such as even and change tissue mutually, and the nascent crystal grain refinement as far as possible that waits axle α phase, so that the performance index such as intensity, plasticity and fatigue strength of raising stamp work.

For the cast structure of breaking pure titanium ingot also obtains the tiny forging rod of macroscopic view and micro-grain fineness number, rolls rod or pushes excellent, generally all adopt the ingot casting cogging to carry out at the β phase region, several subsequently procedures reduce initial forging temperature one by one, the initial forging temperature of final several procedures all is controlled at the alpha+beta district to carry out, final a few procedure must be lower than under the temperature of 10～30 ℃ of β transition points and forges, and could guarantee the best fit of intensity, plasticity, heat resistance, fatigue property and the tissue of alpha+beta titanium alloys like this.The content of the axle α phase such as nascent in the tissue is about 20～30% like this.The Soviet Union and China forge, squeeze, roll into that bar adopts all is above-mentioned technical process to the titanium ingot.Bar is forged, rolled, is extruded into to U.S.'s titanium ingot before the mid-1960s, and what also adopt is above-mentioned similar technical process.In the seventies, the U.S. had once developed the new technology that the titanium ingot is processed into forging, rolled parts or extrusion, it is said the recrystallize mechanism when utilizing titanium to be heated to above beta transus temperature, can further make after the press working product meet the strict demand of low, mirco structure subsequently (referring to the 365th page of the 9th edition the 3rd volume of U.S.'s metals handbook, American Society of Metals (ASM) 1980), but concrete technical process details all do not reveal.The main drawback that China produces the forging process that diphasic titanium alloy bar or biscuit adopted at present is: the bar of making or the microstructure of biscuit are thicker, the wherein nascent mean diameter that waits axle α phase and often has bar (piece) shape α phase generally all about 10～20 μ m in the microstructure.In the present homemade titanium material, because of there being bar (piece) shape α phase in the microstructure, disqualified upon inspection and, account for quite great proportion by the return of goods person of forging manufactory.

The purpose of this invention is to provide a kind of alpha+beta diphasic titanium alloy of eliminating and forge bar (piece) shape α phase in the excellent microstructure, and make it the method for equiaxial miniaturization of crystal.By retrieval, look into newly, find no the report identical with this problem.Only the Japanese Patent spy opens clear 61-177361 and the present invention has similar part.The technical process of this Japanese Patent is: alpha+beta titanium alloys applies 15～30% deformation extents in the alpha+beta humidity province, then 60 ℃ of heating more than beta transus temperature, water-cooled, and then below beta transus temperature 40～90 ℃ temperature range internal heating, at last 500～600 ℃ of temperature insulation back slow cooling.The present invention then belongs to complex heating treatment process.

Complex heating processing technological flow of the present invention is as follows:

Forging and thermal treatment process flow process comprise: forge at the two-phase region that is being lower than 20～30 ℃ of β transition points, deformation extent＞50%, water-cooled after forging+be higher than about 10～20 ℃ of short period of time β processing of β transition point, water-cooled+at the two-phase region that is lower than 70～100 ℃ of β transition points, with two fiery heats forged, each deformation extent＞50% is forged back air cooling+fully annealing of following short period of time of temperature of recrystallize, air cooling.

For example, the forging rod of using TC11 titanium alloy φ 90～120mm just can obtain to wait the thin brilliant α phase of axle after following complex heating processing technological flow, eliminates bar (piece) shape α phase.

φ 90～120 forges (960～980 ℃ of rods, 40～60min)/(＞50%) φ 60～85, water-cooled (1020～1040 ℃, 20～40min)/(foot of a hill or mountain  φ 60～85, (900～930 ℃ of water-cooleds, 25～30min)/(＞50%) φ 40～55, air cooling (900～930 ℃, 15～20min)/(＞50%) φ 28～35, (900～930 ℃ of air coolings, 25～30min)/(recrystallization annealing) φ 28～35, air cooling.

Revision test under working condition proves, the reproducibility of the microstructure of the forging rod made from above-mentioned technical process is good.The result who φ 28mm bar is carried out quantitative metallographic analysis shows, and is nascent grade for axle α phase average content is 32.83%, and the mean diameter of axle α phase such as come into being is 1.93 μ m.

By the repeated test under test and the working condition, reliable, the easy row of sufficient proof the method. Can be used for the production of alpha+beta titanium alloys bar or cake material, improve yield rate.

Claims (2)

1, the invention relates to the invention of titanium alloy heat working technology flow process, it is characterized in that: complex heating processing technological flow is: forge at the two-phase region that is lower than 20～30 ℃ of β transition points earlier, deformation extent is forged the back water-cooled greater than 50%; Then be higher than about 10～20 ℃ of temperature short period of time β processing of β transition point, water-cooled; Then at the two-phase region that is lower than 70～100 ℃ of β transition points with two fiery heats forged, the deformation extent of every fire is forged the back air cooling greater than 50%; At last make short period of time anneal, air cooling in the abundant recrystallization temperature of alloy.

2, as claim 1 said technical process, it is characterized in that the complex heating processing technological flow that is used for TC11 titanium alloy φ 28～35mm bar production is: φ 90～120 forges (960～980 ℃ of rods, 40～60min)/(＞50%) φ 60～85, (1020～1040 ℃ of water-cooleds, 20～40min)/(β processing) φ 60～85, (900～930 ℃ of water-cooleds, 25～30min)/(＞50%) φ 40～55, (900～930 ℃ of air coolings, 15～20min)/(＞50%) φ 28～35, air cooling (900～930 ℃, 25～30min)/(recrystallization annealing) φ 28～35, air cooling.Can obtain waiting the thin brilliant α phase of axle with this technical process, eliminate bar (piece) shape α phase.