CN102513479A - Production process for large-diameter fine isometric crystal tissue titanium alloy bar - Google Patents

Abstract

The invention provides a production process for a large-diameter fine isometric crystal tissue titanium alloy bar. The production process comprises the following steps of: repeatedly performing substituting forging on a titanium cast ingot which comprises the following raw materials in parts by weight: 6.0-6.2 parts of aluminum, 3.8-4.1 parts of vanadium, less than or equal to 0.10 part of iron, 0.18-0.15 part of oxygen, 0.01 part of carbon, 0.01 part of nitrogen, 0.005 part of hydrogen and the balance of titanium to obtain a bar blank, wherein the macrostructure of the bar blank meets the requirement of lower than grade 3; putting the bar blank into a rolling machine to be rolled into a bar; and annealing the bar.

Description

The tiny equiaxed grain structure titanium alloy rod bar of major diameter production technology

Technical field

The invention belongs to the metal material processing technical field, be specifically related to the tiny equiaxed grain structure titanium alloy rod bar of a kind of major diameter production technology.

Background technology

In the titanium alloy of the different trades mark and alloying component, Ti-6Al-4V is that production Technology is the most representative, and the scope of application is the widest, a kind of titanium alloy that consumption is maximum, and its combination property and cost cost performance in all titanium alloys is the highest.In recent years; Developmental research to various trade mark titanium alloy rod bar products trends towards gradually: in the production practices process; How to improve and stablize its internal performance and quality; Enlarge its scope of application and condition, to satisfy Aeronautics and Astronautics, naval vessel and military aspect higher level requirement and the ever-increasing needs of demand to this alloy.And wherein especially this demand to Ti-6Al-4V is the most outstanding.When the production of the Ti-6Al-4V in above field bar and buying, be reference standard all abroad with U.S. aerospace standard A MS4928 or U.S. army mark MIL-T-9047L; In these standards through to aspects such as performance and metallographic strict demand, the combination property of Ti-6Al-4V bar reached and satisfied these fields than higher instructions for use.Rod silk material for small dimension (Φ is below 50); Use Φ 470mm titanium ingot according to normal processing fire time and deflection forge, rolling; Basically can produce the small dimension titanium rod that satisfies standard-required; But for the titanium rod of major diameter specification (Φ 60～Φ 120mm) produce with process in difficulty appearred: one is to use 2 tons of substances to produce the titanium rod of this specification limit with interior titanium ingot, by traditional handicraft carry out cogging, some fire are inferior changes forging, forcing press or the moulding of electric liquid hammer finished product, though can satisfy standard-required; But production efficiency is too low, and output has satisfied not large batch of demand; The 2nd, directly rolling to get into large-scale roll mill after the interior titanium ingot cogging with 2 tons, though efficient has improved, the structural strain's rate is not enough, can not satisfy good microscopic structure requirement; Three are to use substance and the bigger titanium ingot of diameter; Carry out cogging, evolution and pull out the size of large-scale roll mill import; Rolling again; Though can improve final microscopic structure, the requirement to the large of equipment and middle operation in cogging and process is harsh more, and super large equipment that can machining large-sized titanium ingot is still fewer at home.How utilizing domestic existing conventional equipment high efficiency, low cost, the stay-in-grade high-quality titanium rod that satisfies the AMS4928 standard of producing, is the direction that we study.

Summary of the invention

The technical problem that the present invention solves: the tiny equiaxed grain structure titanium alloy rod bar of a kind of major diameter production technology is provided; Before the entering roll mill is rolling; Through the forging that changes more than five times; Make the macrostructure that is rolled excellent base before the operation satisfy 3 grades, guarantee the fine quality of final rolling bar, bar is carried out annealing in process after rolling with interior requirement.

The technical scheme that the present invention adopts: the tiny equiaxed grain structure titanium alloy rod bar of major diameter production technology, selecting parts by weight of raw materials is aluminium 6.0～6.2, vanadium 3.8～4.1, iron≤0.10; Oxygen 0.18～0.15, carbon 0.01, nitrogen 0.01; Hydrogen 0.005, surplus are the titanium ingot casting of titanium, and the titanium ingot casting is excellent base through repeatedly being forged into; The macrostructure of said excellent base satisfies 3 grades with interior requirement, then excellent base is put into roll mill and is rolled into bar, again bar is carried out annealing in process.

Above-mentioned repeatedly change to forge comprise the steps:

1) cogging is put into resistance furnace with the titanium ingot casting and is heated to 1150～1200 ℃, is incubated more than 180 minutes, is split into square billet after pulling out through three rammers three with forcing press, and titanium ingot casting deformation rate reaches 120%;

2) two fire change forging, with square billet put into resistance furnace be heated to alpha+beta/beta transformation point temperature more than 990 ℃ 50～100 ℃ change forging, insulation is more than 120 minutes, does three again with forcing press and upsets and three to pull out, the blank deformation rate reaches 110%;

3) three fire change forging, with two fire change blank after the forging put into resistance furnace be heated to alpha+beta/beta transformation point temperature below 990 ℃ 10～20 ℃ change forging, insulation is more than 120 minutes, does three with forcing press and upsets and three pull out, the blank deformation rate reaches 110%;

4) four fire change forging, with three fire change blank after the forging put into resistance furnace be heated to alpha+beta/beta transformation point temperature below 990 ℃ 20～30 ℃ change forging, insulation is more than 120 minutes, does three again with forcing press and upsets and three pull out, the blank deformation rate reaches 110%;

5) five fire change forging; With four fire change blank after the forging put into resistance furnace be heated to alpha+beta/beta transformation point temperature below 990 ℃ 30～40 ℃ change forging; Insulation is more than 120 minutes, and the electricity consumption liquid hammer tries again to change to forge and makes blank become excellent base, and the blank deformation rate reaches 70%;

6) will change the excellent base detail sanding polishing of forging through five fire, and wash down with clear water after corroding with the cyanogen fluoric acid again, macrostructure should satisfy in 3 grades.If macrostructure does not reach 3 grades with interior requirement, excellent base carried out upsetting like three of the described fire ofstep 5 time or several fire time again three pulls out, up to excellent base macrostructure satisfy 3 grades with interior requirement till.

When rolling, at first adjust roll mill pass size, excellent base is put into resistance furnace be heated to 930～940 ℃, insulation began rollingly more than 100 minutes, and excellent base is rolled into bar.

During annealing in process, bar is lower than in 500 ℃ of resistance furnaces of packing into, is heated to 750～785 ℃ of insulations 100 minutes, air cooling.

At last,, carry out local precision straightening then, cut cut lengths, polishing at last not removing surperficial oxygen-rich layer with being in the mood for lathe behind the bar cool to room temperature.

Above-mentioned forcing press is 2500 tons of forcing presses, and said electric liquid hammer is 4 tons of electric liquid hammers, and said resistance furnace is the 400KW electric furnace, and said roll mill is excellent base import Φ 180mm model rolling bar machine.

The present invention's advantage compared with prior art:

1, through of the comparison of several kinds of composition proportion to the material property influence, find the scope of only oxygen and iron content, both can satisfy the raising of intensity, can guarantee the needs of material plasticity simultaneously again;

2, through control heating-up temperature and the inferior deflection of every fire; Confirm reasonably to change forging process; The rod base advances before the roll mill; Through repeatedly changing forging, make the macrostructure of excellent base satisfy 3 grades with interior requirement, correct and only rely on next final other wrong-doing of microscopic structure level that changes and improve of last one rolling process;

3, utilize the common bar mill of gathering around usefulness of domestic enterprise, can roll out the tight bar that requires of high standard, reduced cost again, improved benefit.

Description of drawings

Fig. 1 organizes sketch map for titanium rod wire net;

Fig. 2 is each rank macrostructure sketch map of titanium rod;

Fig. 3 is each rank mirco structure sketch map of Ti-6Al-4V;

Fig. 4 is the tiny equiax crystal mirco structure sketch map of titanium rod.

The specific embodiment

One, the preparation of titanium ingot, the adjustment of Ti-6Al-4V chemical composition

Use the needs of actual conditions according to Aeronautics and Astronautics, naval vessel and military aspect; We need be with the performance of Ti-6Al-4V material on the basis of basic demand; Make every effort to the adjustment through other composition in the alloy, the mechanical property of lifting material that can be maximum makes material in use can farthest meet or exceed instructions for use; When tensile strength was improved, plasticity did not also reduce.This just need find an optimum range from the chemical composition proportioning aspect of material.

Through to alloying element aluminium and content of vanadium in fixed range to the change of Ti-6Al-4V material property and influence can be very not significantly after, impurity element oxygen in the titanium alloy and iron will be the emphasis that we study so.The purity of the low more material of oxygen and iron content is high more, and plasticity is just good more, but the tensile strength of material also can reduce simultaneously.Oxygen element belongs to interstitial element in titanium alloy, can improve the degree of stability of the α phase in the alloy, promotes the decomposition of metastable phase.The increase of oxygen element can improve the alpha+beta/β phase transition temperature in the titanium alloy, improves alloy at room temperature tensile strength simultaneously.Ferro element belongs to beta stable element in the titanium alloy, along with the increase of content can reduce the alpha+beta/β phase transition temperature of alloy, can significantly raise to alloy at room temperature tensile strength simultaneously, and reduce plasticity index such as percentage elongation.Therefore, for improving tensile strength of alloys, oxygen and iron content in the raising alloy that we can be suitable.Never reduce simultaneously the combination property aspect of transformation temperature, plasticity and the alloy of alloy and consider, only oxygen content is increased to certain content, do not advocate artificial increase iron content.

Several kinds of composition proportion below we pass through find the scope of only oxygen and iron content to the comparison that material property influences.Take the Φ 50mmTi-6Al-4V bar longitudinal test piece of the heterogeneity under the identical fabrication process condition and do detection.

Can find out that from the contrast of above data the increase of iron and oxygen element has all improved tensile strength of alloys, represent the percentage elongation of plasticity and the contraction percentage of area constantly to reduce simultaneously.And iron and oxygen element be all when higher, though tensile strength of alloys increases to some extent, plasticity obviously reduces.Therefore we are employed in the content (being the third proportioning) that improves the content of oxygen in the one-level titanium sponge and do not increase iron according to the special requirement that space flight is used, and so both can satisfy the raising of intensity, can guarantee the needs of material plasticity simultaneously again.

Two, production and processing technology process

Because that we adopt in production reality is substance 1500Kg; Three melting titanium ingots of external diameter Φ 470mm; Employed process equipment is 2500 tons of forcing presses; 4 tons of electric liquid hammers, excellent base import are Φ 180mm model rolling bar machine, so production and processing technology will carry out around the working ability of these equipment.If production technology according to common titanium rod; Φ 470mm titanium ingot is the requirement of satisfying deformation rate; Only need two fire just can advance the rolling bar machine to roll out finished product to changing to forge from cogging, but mostly the excellent microscopic structure of the titanium of producing like this is wire net shape tissue, does not reach requirement.We can't guarantee that suitable deflection is to reach purpose and the requirement that changes tissue, crystal grain thinning.The wire net tissue be since in the process deflection not enough, crystal grain is not exclusively broken and a kind of typical organization of forming is as shown in Figure 1.The wire net tissue is a kind of boundary tissue, and this tissue is an acceptable during as the product for civilian use, but is receptible anything but tissue for Aeronautics and Astronautics etc.Each rank metallographic structure of Ti-6Al-4V is as shown in Figure 3.

Through long-term experiment with grope, we are verified: can not only rely on last one rolling process and come the final rank that changes and improve microscopic structure.Before the machine that is rolled is rolling, must have favorable tissue through repeatedly reasonably changing forging, make the blank rod that is rolled before the operation, be the key that guarantees final rolling bar fine quality.Therefore reasonably change the critical process that forging process is a bar quality quality.We this interval bar by specification separated into two parts (60-100) mm and (100-120) mm.(60-100) blank of mm specification uses 4 tons of electric liquid hammer equipment to carry out upsetting pull in changing the forger preface; (100-120) blank of mm specification uses 2500 tons of press equipments to carry out upsetting pull in changing the forger preface; For guaranteeing the requirement of ultrasonic examination, every fire time final forging temperature can not be lower than 750 ℃ simultaneously.Can obtain to satisfy the titanium rod that each item requires in AMS 4928 standards like this.

Existing is that the finished product titanium rod of Φ 100 * 3000mm is an example to produce diameter, reaches each item requirement to titanium alloy rod bar through following technology mode.

1, cogging, changes confirming of forging process

Ti-6Al-4V is a kind of typical alpha+beta alloy.Through being processed to form in two districts of alpha+beta after the high power metallographic structure inspection; Ti-6Al-4V alloy with tiny, uniform α and β equiaxed grain structure; Just best combination property can be reached, the basic demand of the use in fields such as Aeronautics and Astronautics could be satisfied.Our target will be produced exactly has transverse and longitudinal intensity and plasticity is all good, and mechanical property requirements reaches the AMS4928 standard-required, and metallographic structure reaches the A5 level with interior high-quality bar.

Alpha+beta/beta transformation point temperature through detecting this Ti-6Al-4V ingot casting is 990 ℃.

(1), cogging

The titanium ingot casting has thick as-cast grain structure, at first requires it is broken into little β tissue, requires on crystal boundary, to produce the primary nucleus simultaneously.Because the effective travel of 2500 tons of forcing presses limits, and must will highly (highly be about 600～1000mm) for the titanium ingot casting of 2000mm is divided into 2～3 sections.Heat the titanium ingot casting at 1150 ℃ with resistance furnace, insulation is more than 180 minutes, to guarantee whole titanium ingot casting internal and external temperature consistent and uniform.This link firmly can not be used reverberatory furnace heating cogging, because the temperature of reverberatory furnace is uncontrollable, very easily the burning of titanium ingot casting is scrapped.Titanium ingot casting resistance of deformation is low under this temperature, and plasticity is high, is fit to the cogging requirement that the titanium ingot casting adopts big deflection, improves and forges passing through property, sufficient broken as-cast structure.2500 tons of hydraulic presses have good static pressure permeability, and production efficiency is high, are the excellent cogging equipment of forged titanium ingot casting.After the titanium ingot casting of Φ 470mm pulls out through three rammers three, be split into the square billet of 460mm.The inferior deformation rate of this fire reaches 120%.At this moment thick casting titanium is organized by preliminary fragmentation.

(2), two fire change forging

Square billet after cogging is accomplished; After polishing off blemish and oxygen-rich layer; Second fire will once change forging for 50～100 ℃ at alpha+beta/more than the beta transformation point temperature, and purpose is to make β phase crystal grain obtain sufficient fragmentation once more, makes α between β phase crystal boundary, generate nucleus simultaneously.We select 1050 ℃ in the 400KW resistance furnace, to heat, and insulation is more than 120 minutes, three pull out with three rammers that try again of 2500 tons of forcing presses.The inferior deformation rate of this fire reaches 110%.

(3), three fire change forging

Since the 3rd fire; The TC4 material will change over to below alpha+beta/beta transformation point temperature and forge; Purpose is in order to make original β crystal boundary energy access sufficient transformation, can to make α on the β crystal boundary, continue nucleation simultaneously, obtaining the bifurcation tissue of two district's processing of alpha+beta of excellent performance.This fire adopts the heating of 400KW resistance furnace, and heating-up temperature is that 970 ℃ of insulations are more than 120 minutes.Use 2500 tons of forcing presses try again three upset three pull out change forging.The inferior deformation rate of this fire reaches 110%.

(4), four fire change forging

This fire adopts the heating of 400KW resistance furnace, and heating-up temperature is that 960 ℃ of insulations are more than 120 minutes.Use 2500 tons of forcing presses try again one upset one pull out change forging, blank is pulled out the square billet of 290mm.The inferior deformation rate of this fire reaches 80%.

(5), five fire change forging

Blank is through polishing, after the band saw blanking, and the 5th fire uses 4 tons of electric liquid hammer equipment to change forging, and this fire still uses the heating of 400KW resistance furnace, and heating-up temperature is that 950 ℃ of insulations are more than 120 minutes.Use 4 tons of electric liquid hammers to try again and change forging, blank is pulled out the excellent base of 160mm.The inferior deformation rate of this fire reaches 70%.Purpose of this fire time is further refinement even grained tissue, makes the appearance and size of excellent base satisfy the requirement of roll mill import stomidium simultaneously.

After this fire finishes,,, observe macrostructure, should satisfy in 3 grades with washing down with clear water again after the corrosion of cyanogen fluoric acid with the detail sanding polishing of excellent base.Do not require just need the excellent base of 290mm to be used 4 tons of electric liquid hammers to carry out three rammers three inferior or that several fire are inferior of a fire again and pull out, till macrostructure meets the demands if reach.The macrograph that we change after this operation of forging completion is as shown in Figure 2.

Specification is less owing to single weight at the pole of (60-100) mm, can carry out following technique process:

(1), first fire, 1150 ℃ with resistance furnace heating titanium ingot casting, insulation is more than 180 minutes, uses 2500 tons of forcing presses that the square billet of 230mm is arrived in the direct cogging of titanium ingot casting, deformation rate is 70%.

(2), polishing, after the band saw blanking, second fire, 1050 ℃ are heated in the 400KW resistance furnace, insulation was used 4 tons of electric liquid hammers that blank is done three rammers and three is pulled out deformation rate 120% more than 120 minutes.

(3), the 3rd fire, 970 ℃ are heated in the 400KW resistance furnace, insulation is more than 120 minutes, continue to use 4 tons of electric liquid hammers that blank is done three and upsets and three pull out deformation rate 120%.

(4), the 4th fire, 960 ℃ in 400KW resistance furnace heating, insulation was used 4 tons of electric liquid hammers to try again and is changed forging more than 120 minutes, and blank is pulled out the excellent base of the following size of 150mm, the inferior deformation rate of this fire reaches more than 75%.

After this fire finishes, use etch to detect the blank macrostructure equally, require to reach in 3 grades.Do not pull out if reach three rammers three that require just need to use 4 tons of electric liquid hammers carry out a fire time or several fire time again, till macrostructure is met the demands in the 3rd fire time back.

Two, rolling mill practice.

This process is mainly the prepared billets, the last one fire after hot deformation times, eventually rolled into rods Yu.In this operation, rationally arrange technical process, still can further improve the even degree of refinement of microscopic structure.If but excellent base microscopic structure is not good, if want significantly to change and improve the microscopic structure rank, promote performance indications through this operation, effect can be very not remarkable or impossible.Realize several kinds of modes of this operation and the comparison of equipment:

(1) use 1 ton of direct draw out of flat-die hammer, with control diameter and the ovality of laing eggs, must double tempering during tune.Adopting this traditional production and processing mode advantage is that equipment tool is simple, with low cost, but shortcoming is quite a lot of; Production efficiency is low, and the ovality of whole bar is bad, and diameter is very big with rod difference deviation; Necessary tempering when tune is forged causes and forges a good end or contiguous position post bake, and the structural homogenity of whole bar is inconsistent; Reduced the metallographic rank, when this technology only is applicable to that bar quantity seldom.

(2) adopt precise forging machine to forge, domestic precise forging machine all is expensive import equipment at present, only uses in state-owned unit of indivedual a few family.Adopting this production and processing mode advantage is that efficient is higher, and blank can forge finished product by a fire, the rule of finishing simultaneously circle; Do not need double tempering; Guaranteed whole bar microstructure uniformity and uniformity, simultaneously ovality and dimensional tolerance can both better controlled, and shortcoming is that processing charges is too high; The equipment one-time investment is too big, and general enterprise holds and can't stand.

(3) adopt the rolling bar machine rolling.Present domestic rolling bar machine is very general, and equipment investment is few.Adopt this production and processing mode can the shortcoming of top dual mode be avoided; Combine simultaneously both advantages again; Be preferred plan, can guarantee the production high efficiency, can go out finished product by a fire again; Guarantee all even uniformity of bar microscopic structure, ovality and tolerance also can better controlled simultaneously.Concrete machining process:

Because roll mill is in the process of rolling blank, speed is very fast, and deflection is also very big, causes metal inside distortion heat shock to increase, and causes the bar hot-spot.Therefore we adopt heating-up temperature on the low side can not produce heat affecting to guarantee the temperature rise that distortion heat causes.930～940 ℃ of resistance furnace heating, insulation began rolling more than 100 minutes.Roll mill pass size is transferred to Φ 105+1mm, could guarantee the dimensional requirement that strips off the skin of finished product bar Φ 100 * 3000mm like this.

Three, annealing process.

Final mechanical property and metallographic structure plays crucial effects to the titanium rod in the annealing of Ti-6Al-4V titanium alloy.The purpose of alloy material annealing not only can be improved structure property through the crystallization again of crystal grain; And the dissolving that is attended by compound changes with α → β polymorphism mutually; Can the structural stress that metal inside in the hot and cold processing produces be released simultaneously, make the easy realization of machining in later stage and can not produce stress deformation.The crystallization again of α phase only takes place in the such annealing of alpha+beta alloy below transformation temperature for Ti-6Al-4V, so the material after the heat treatment still can keep the bifurcation institutional framework of two district's processing of alpha+beta.We adopt under alpha+beta/following 150-250 of beta transformation point temperature ℃ the temperature and do full annealing technology.The microscopic structure of certain combination property that purpose is stable in order to obtain, plasticity is good or corresponding.The crystallization again of α phase mainly takes place in this process.Too high meeting causes unnecessary oxidation and grain growth like temperature.A lot of tests and demonstration have been carried out in research for the Ti-6Al-4V anneal of material in the past, and we just do not do unnecessary trial here, just in this is produced, directly use the achievement of research and just can.The Technology for Heating Processing that we adopt is: in resistance-heated furnace, be lower than 500 ℃ of shove charges, 750-785 ℃ of insulation 100 minutes (thickness according to the pole diameter is selected holding temperature and temperature retention time), air cooling.

Four, bar surface processing technique.

Because the room temperature elasticity of Ti-6Al-4V bar is very big, so the aligning of bar must in time be taked thermal straightening after annealing.Small dimension can be aligned with multi-roll straightening machine, and big specification can adopt artificial aligning.Do not remove surperficial oxygen-rich layer with being in the mood for lathe (flaying machine) behind the cool to room temperature,, add tolerance is controlled in the critical field by different size diameter tolerance requirement in the standard.Carry out local precision straightening then, its objective is to guaranteeing the requirement of bar glacing flatness.Cut cut lengths, polishing at last.

Five, Metallographic Analysis, carrying out flaw detection:

We use supersonic detector that the finished product bar of surface smoothness Ra≤3.2 is detected by root; With reference to AMS 2631B standard, single reflected signal≤1.2mm, a plurality of reflected signal＜0.8mm; Clutter echo signal＜1.2mm meets the A1 level requirement in the standard.

We respectively get two groups of mechanical property samples along the vertical, horizontal of bar, and one group of lateral cross section circle is got one group of mirco structure appearance along bar lateral cross section 1/2 radius, send the physics and chemistry center to detect, and detecting content has room-temperature mechanical property, mirco structure.Testing result is following:

Φ 100mm Ti-6Al-4V bar room-temperature mechanical property

The metallographic structure photo is as shown in Figure 4.

In a word; According to the AMS4928 standard; Mechanical property has all reached requirement, and macrostructure does not have visual visible physics and metallurgical imperfection, and the high power metallographic structure is the bifurcation equiaxed structure structure of two district's processing of tiny and uniform alpha+beta; Rank judges that in the A3 level ultrasonic examination detects and meets the A1 level among the standard A MS2631B.The machining process that detects the Ti-6Al-4V titanium alloy rod that proves that we confirm through above each item is the operating position that can satisfy Aeronautics and Astronautics, naval vessel and military aspect fully; And can satisfy large batch of suitability for industrialized production processing; Production cost is low, and efficient is high, good stability.

The foregoing description is preferred embodiment of the present invention, is not to be used for limiting practical range of the present invention, so all equivalences of being done with the said content of claim of the present invention change, all should be included within the claim scope of the present invention.

Claims (7)

1. the tiny equiaxed grain structure titanium alloy rod bar of major diameter production technology is characterized in that: selecting parts by weight of raw materials is aluminium 6.0～6.2, vanadium 3.8～4.1, iron≤0.10; Oxygen 0.18～0.15, carbon 0.01, nitrogen 0.01; Hydrogen 0.005, surplus are the titanium ingot casting of titanium, and the titanium ingot casting is excellent base through repeatedly being forged into; The macrostructure of said excellent base satisfies 3 grades with interior requirement, then excellent base is put into roll mill and is rolled into bar, again bar is carried out annealing in process.

2. the tiny equiaxed grain structure titanium alloy rod bar of major diameter according to claim 1 production technology is characterized in that repeatedly changing forging and comprises the steps:

1) cogging is put into resistance furnace with the titanium ingot casting and is heated to 1150～1200 ℃, is incubated more than 180 minutes, is split into square billet after pulling out through three rammers three with forcing press, and titanium ingot casting deformation rate reaches 120%;

2) two fire change forging, with square billet put into resistance furnace be heated to alpha+beta/beta transformation point temperature more than 990 ℃ 50～100 ℃ change forging, insulation is more than 120 minutes, does three again with forcing press and upsets and three to pull out, the blank deformation rate reaches 110%;

3) three fire change forging, with two fire change blank after the forging put into resistance furnace be heated to alpha+beta/beta transformation point temperature below 990 ℃ 10～20 ℃ change forging, insulation is more than 120 minutes, does three with forcing press and upsets and three pull out, the blank deformation rate reaches 110%;

4) four fire change forging, with three fire change blank after the forging put into resistance furnace be heated to alpha+beta/beta transformation point temperature below 990 ℃ 20～30 ℃ change forging, insulation is more than 120 minutes, does three again with forcing press and upsets and three pull out, the blank deformation rate reaches 110%;

5) five fire change forging; With four fire change blank after the forging put into resistance furnace be heated to alpha+beta/beta transformation point temperature below 990 ℃ 30～40 ℃ change forging; Insulation is more than 120 minutes, and the electricity consumption liquid hammer tries again to change to forge and makes blank become excellent base, and the blank deformation rate reaches 70%;

6) will change the excellent base detail sanding polishing of forging through five fire, and wash down with clear water after corroding with the cyanogen fluoric acid again, macrostructure should satisfy 3 grades with interior requirement.

3. the tiny equiaxed grain structure titanium alloy rod bar of major diameter according to claim 2 production technology; It is characterized in that: if macrostructure does not reach 3 grades with interior requirement; Excellent base carried out upsetting like three of the described fire of step 5 time or several fire time again three pulls out, up to excellent base macrostructure satisfy 3 grades with interior requirement till.

4. the tiny equiaxed grain structure titanium alloy rod bar of major diameter according to claim 1 production technology; It is characterized in that: when rolling; At first adjust roll mill pass size, excellent base is put into resistance furnace be heated to 930～940 ℃, insulation is more than 100 minutes; Begin rollingly, excellent base is rolled into bar.

5. the tiny equiaxed grain structure titanium alloy rod bar of major diameter according to claim 1 production technology is characterized in that: bar is lower than in 500 ℃ of resistance furnaces of packing into, is heated to 750～785 ℃ of insulations 100 minutes, air cooling.

6. according to claim 1,2,3, the tiny equiaxed grain structure titanium alloy rod bar of 4 or 5 described major diameters production technology; It is characterized in that: with not removing surperficial oxygen-rich layer with being in the mood for lathe behind the bar cool to room temperature; Carry out local precision straightening then, cut cut lengths, polishing at last.

7. the tiny equiaxed grain structure titanium alloy rod bar of major diameter according to claim 6 production technology; It is characterized in that: said forcing press is 2500 tons of forcing presses; Said electric liquid hammer is 4 tons of electric liquid hammers; Said resistance furnace is the 400KW electric furnace, and said roll mill is excellent base import Φ 180mm model rolling bar machine.

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