CN108580547A - A kind of isometric helix milling method of large-scale titanium alloy ultra fine grained steel bar - Google Patents

Abstract

The invention relates to a method for equidistant spiral rolling of large-sized titanium alloy ultra-fine-grained rods, which relates to the technical field of mechanical processing, and in particular to a method for equidistant spiral rolling of large-sized titanium alloy ultra-fine-grained rods, comprising the following Steps: S1: Select a titanium alloy blank with a diameter D of 40-150mm and a length of 300-5000mm; S2: place the above-mentioned titanium alloy blank in a heating furnace and heat it to 840-1025°C; S3: heat the heated titanium alloy blank Transfer from the heating furnace to the guide trough of the skew rolling mill, the transfer time is 5-20s; S4: Feed in the guide trough of the skew rolling mill, and send the titanium alloy billet into the deformation zone between the entrance and exit of the skew rolling mill, titanium The alloy blank moves spirally in the deformation zone until the deformation ends; S5: repeat the above S2-S4 steps, and carry out 2-6 times of spiral rolling on the titanium alloy blank to obtain the TC18 titanium alloy overall ultra-fine-grained rod; the beneficial effect of the present invention is : The deformation zone has a large penetration depth and can be reciprocated for multi-pass rolling. Continuous and stable local deformation, combined with compression-torsion three-dimensional severe deformation, can obtain ideal grain refinement effect.

Description

A method for equidistant spiral rolling of large-size titanium alloy ultra-fine-grained rods

technical field

The invention relates to the technical field of mechanical processing, in particular to an equidistant spiral rolling method for large-scale titanium alloy ultra-fine-grained rods.

Background technique

Ultrafine crystal/nanocrystalline materials are one of the hot topics in current material science research. Compared with traditional coarse-grained metal materials, ultra-fine-grained/nanomaterials show more excellent or unique properties in some aspects, such as higher strength and hardness, better fatigue performance and superplasticity, better Corrosion resistance, wear resistance and biological characteristics, etc. These excellent properties make ultra-fine-grained materials have broad application prospects in engineering fields such as aviation, aerospace, automobiles, marine, and biology, and also make people pay more attention to the development of ultra-fine-grained/nano-prepared technologies. Compared with traditional coarse-grained metal materials, ultrafine-grained/nanomaterials show more excellent or unique properties in some aspects. From the perspective of mechanical properties, for pure titanium, the grain size is refined from 45um to 0.4um, the yield strength can be increased from 354Mpa to 582Mpa, and the tensile strength can be increased from 487Mpa to 645Mpa. For some titanium alloys, when the grain size reaches about 1.2um, its room temperature tensile strength can reach more than 1300Mpa, which is 60% higher than that of the original billet. The improvement of fatigue performance of ultra-fine-grained materials is very significant. Compared with 20um coarse-grained titanium, the fatigue limit of ultra-fine-grained titanium with an average grain size of 0.25um is increased from 252Mpa to 403Mpa, and the cyclic stress is increased from 4.211N to 34.504N. It can be seen from the above that large-sized titanium alloy ultra-fine-grained rods have great potential in industrial applications.

When using plastic deformation to prepare nano-scale materials, the equivalent strain should usually be greater than 6, which is difficult to achieve with traditional plastic processing methods, but can be achieved by applying Severe Plastic Deformation (SPD). Modern SPD started from the combined forming method of high pressure and shear deformation proposed by Bridgemen, and its rapid development began in the mid-1970s in the former Soviet Union and Western countries. Segal developed the Equal-Channel Angular Pressing technology (Equal-Channel Angular Pressing, ECAP), It marks the arrival of the microstructural era of SPD research. Over the past 10 years, thousands of research results have been published.

The definition of SPD generally recognized after 2006: a metal forming method that produces super large strains in the block but does not significantly change the geometric size of the block, and presents a grain refinement effect of large-angle grain boundaries, which can obtain grain sizes in the micron level ( 100-1000nm) and nanoscale (less than 100nm), both can be called nano-SPD (nanoSPD for short). Because the nanoSPD material has a large number of large-angle non-equilibrium grain boundary structures containing high-density dislocations and high internal stress, the material exhibits mechanical behavior and deformation mechanism different from traditional coarse-grained materials.

Currently available processing technology solutions: Typical SPD methods include High Pressure Torsion (HPT), equal channel angular press-ing (ECAP), and Accumulative Roll Bonding (ARB) ), twist extrusion (Twist Extrusion, TE) and multi-directional forging (Multi-Directional Forging, MDF).

Among them, (1) High-pressure torsional deformation: apply a pressure of several GPa to the original sample (block or powder) placed in the support tank, and relatively rotate the upper and lower anvils to cause strong shear deformation of the sample and refine the grains. The characteristic of high-pressure torsion is that the workpiece is disc-shaped and small in size, generally 10-20 mm in diameter and 0.2-0.5 mm in thickness.

(2) Equal-diameter angular extrusion deformation: Through two equal-section channels intersecting at a certain angle in the mold, the material is extruded from one end to the other end, and the bending angle changes the direction of material movement to produce pure shear deformation. The forming process can be repeated, and the amount of shear strain increases with the deformation pass.

(3) Cumulative stacking rolling method: stack the original plates in double layers after surface treatment, roll and weld them together after heating, then cut them from the middle and send them back to the surface treatment before the next rolling and welding cycle. The plates can be welded together, and the reduction in each pass must not be less than 50%, but the ARB process requires strong shear stress conditions, and lubricants cannot be used, which is detrimental to the service life of the rolls.

(4) Twisting extrusion: Beygelzime et al. proposed this process. This method is also a molding technique for refining grains through shear deformation. The columnar billet is extruded through a torsion die. Similar to HPT, there is a problem of uneven deformation, and the effect of grain refinement is lower than that of ECAP and HPT.

(5) Multi-directional forging: This process obtains large deformation by changing the free forging direction orthogonally several times. The grain refinement effect of this type of deformation is significantly lower than that of ECAP and HPT.

Another type of existing processing technology solution: derivative method, the basic forming principle is the same as the above method, and many new SPD forming technologies have been derived. These methods try to simplify tool design, reduce energy consumption, improve yield, increase workpiece size, and upgrade automation etc., including:

(1) ECAP derivative method: repeated bending and straightening (RCS), the blank is placed between the bending devices, and as the upper die moves down, the blank is bent and becomes wavy; then two flat plates are used for straightening, Bending is carried out again, and through continuous repetition, sufficient deformation is accumulated without significantly changing the size of the blank to refine the material structure.

(2) Cyclic Closed Die Forging (CCDF), the mold consists of a lower die with a cavity of a certain section and a punch of the same section that moves vertically in the cavity. Put the fully lubricated sample with graphite lubricant into the lower mold and heat it to a certain temperature. The workpiece is pressed into the lower mold by the punch, and after being taken out, it is rotated 90° around the Z axis in the same direction, and reinserted into the lower mold for deformation. In this way, the workpiece is rotated 90° around the Z axis between successive passes. In this way, 1, 3 and 5 compressions were subjected respectively.

(3) Reciprocating extrusion (CEC), the mold consists of two cavities, a compression belt and punches placed in the two cavities. The cross-sectional areas of the two cavities are equal, on the same axis, and connected by the middle compression belt. During the extrusion process, the sample reaches the compression zone under the action of the punch. At this time, the sample will be subjected to positive extrusion deformation, and the extruded workpiece will be upset under the action of the punch of another cavity. out of shape. Then, the punch on the other side presses the workpiece back in reverse according to the above process, completing an extrusion cycle. Repeat the above process until the desired strain is obtained.

(4) Continuous shear deformation of the plate. The device uses the upper mold, the lower mold and the lower roller to form two intersecting channels with a small difference in cross-sectional area. The sheet is fed into the cavity, and the sheet undergoes strong plastic deformation at the corner of the cavity, and then extrudes from the other side of the cavity. Grooves are machined on the surface of the feed roller for increased friction. Due to the fact that the cross-sectional area of the material remains unchanged before and after deformation, it is possible to repeatedly perform multiple passes of plastic deformation on the plate in the same mold.

(5) Elliptical spiral equal channel extrusion method (ECEA), under the action of extrusion force, the billet undergoes upsetting (circle-ellipse transformation), torsion (elliptical cross-section twisting) and reverse upsetting (elliptical —circle transformation) the process changes back to a round bar. Metals flow plastically primarily in cross-section, and accumulate strain. The shape of the mold utilizes the particularity of the round and elliptical shapes, and there are no sharp corners in the cavity, which makes the metal flow easily. The combination of multiple deformation modes in one process is realized.

(6) Continuous Friction Angular Extrusion (CFAE), the drive roller rotates and applies pressure P to the workpiece against its support. The first extrusion channel is formed between the drive roller and the workpiece support, and the second channel is a short slot in the stationary die assembly. After one to eight processings of the sheet-shaped workpiece, the maximum equivalent true strain can reach 5.3, and the orientation of the sheet remains constant.

An HPT derivative method for high-pressure torsion (HPTT) of tubes, with the tube inside a rigid disk and a mandrel placed in the tube, compressed in its elastic state with a compressor. Due to the axial compression of the mandrel, it expands in the radial direction, and the expansion is limited by the tube and the disk, forming a large hydrostatic stress in the tube and generating a large friction force on both sides of the tube. While keeping the mandrel fixed, deformation of the tube is achieved by rotating the disk with external torque. During the torsion process, the deformation mode is local shear, the normal direction of the shear plane is the radial direction of the tube, and the shear direction is parallel to the circumferential direction.

A TE-derived approach, Super High Torsion (STS), localizes the torsional strain (TS) region by localized heating and cooling to make this region less resistant to deformation than the other two parts. Simultaneously with the generation of the TS zone, the rod is moved along the longitudinal axis, thus continuously producing super large plastic strains throughout the rod. This new process, STS, involves a bar that creates a localized soft zone relative to the rest of the bar and the movement of the zone in the longitudinal direction. An important feature of STS is that the cross-sectional dimension of the rod remains constant under strain.

There are relatively few patent reports on titanium alloy ultrafine grain technology at home and abroad. In the patent [CN 103014574 A], Zhou Kechao et al. of Central South University mentioned a preparation method of TC18 ultra-fine-grained titanium alloy, which mentioned detailed heat treatment and ultra-fine-grain process parameters for multi-pass upsetting. This process adopts the method of multi-directional upsetting and drawing, which belongs to the traditional forging method. Due to the small range and penetration depth of single-pass deformation, in order to obtain ultra-fine grain structure, more than 8-10 times of repeated deformation are generally required. The cycle is long, the efficiency is low, and there is generally obvious uneven deformation.

In the patent [CN 103572186 A], Wang Liqiang of Shanghai Jiaotong University and others mentioned a method for preparing ultra-fine-grained titanium-based composite materials by deformation of equal-diameter curved channels. This method has been proposed in the background introduction of this patent, although severe plastic deformation can be repeated. , but the size after deformation is 10X10 X100mm, which is difficult to meet the needs of industrial grade. Du Suigeng of Northwestern Polytechnical University mentioned a method for preparing ultrafine-grained materials in the patent [CN 1446935 A]. This method mainly focuses on producing ultra-fine grains on the surface. Although the degree of deformation is high and can be deformed repeatedly, it is only limited to the preparation of surface nanocrystals, and the overall ultrafine crystals from the center to the surface cannot be achieved.

The patent [CN 107030111 A] by Liu Guohuai and others from Northeastern University mentioned a preparation method of an ultra-fine-grained TC4 titanium alloy sheet with equal thickness. This method is similar to the cumulative stack rolling in the patent background introduction. This process requires strong shear stress conditions, large loads, and large restrictions on its size conditions. Only plates can be prepared, but bars cannot be prepared. From the paper reports on titanium alloy ultra-fine grain technology, most of them use ECAP and HPT to deform titanium alloy, and the size of the products involved is small, so it is difficult to produce large-size bulk materials with industrial-grade overall ultra-fine grain.

A comprehensive analysis shows that the titanium alloy ultra-fine grain technology mentioned in existing patents or papers all use traditional HPT, ECAP and ARB methods to prepare small-sized uniform ultra-fine grain materials under extremely high loads, which are currently limited to Developed in the laboratory, it is difficult to prepare large-scale materials with industrial-grade overall ultra-fine crystals.

Contents of the invention

The purpose of the present invention is to provide a method for equidistant spiral rolling of large-sized titanium alloy ultra-fine-grained rods, so as to solve the problems of limited size, large load and low efficiency in the above-mentioned background technology.

The present invention is an equidistant spiral rolling method for large-scale titanium alloy ultra-fine-grained rods, which is characterized in that it comprises the following steps:

S1: Select a titanium alloy blank with a diameter D of 40-150mm and a length of 300-5000mm;

S2: Place the above titanium alloy billet in a heating furnace and heat it to 840-1025°C. The heating time is: diameter of titanium alloy billet D×(0.6-0.8) min;

S3: transfer the heated titanium alloy billet from the heating furnace to the guide groove of the skew rolling mill, and the transfer time is 5-20s;

S4: Feed in the guide groove of the skew rolling mill, and send the titanium alloy billet into the deformation zone between the entrance and the exit of the skew rolling mill. The titanium alloy billet moves spirally in the deformation zone until the deformation is completed, and the TC18 titanium with a diameter of Dm is obtained Alloy bar, where m is the number of times of rolling, the diameter of the TC18 titanium alloy bar obtained by rolling once is D1, the diameter of the TC18 titanium alloy bar obtained by rolling twice is D2, and so on;

S5: Repeating the above steps S2-S4, performing 2-6 times of spiral rolling on the titanium alloy billet to obtain TC18 titanium alloy overall ultra-fine grain bar;

The skew rolling mill is a two-roller skew rolling mill, the rolls are all single-tapered rolls, the cone angle γ1 is 17-19 degrees, and the arc radius r of the rolls biting into the titanium alloy billet is 50-380 mm, and the feed angle of the rolls is 50-380 mm. α is 15-17 degrees, the rolling angle β of the rolls is 17-19 degrees, the roll spacing Dg between the two rolls is 86%-94% of the diameter D of the titanium alloy billet, and the roll speed n is 28-50r/min ;

The titanium alloy blank is a large-size bar;

The heating time of the repeated rolling process in the step S5 is the diameter of the TC18 titanium alloy rod Dm×(0.3-0.4) min.

Preferably, the small end surface of the roll is set as an arc surface, and the radius of the arc surface is 50-380mm.

Preferably, the pass ellipticity coefficient is the ratio of the guide plate distance _Dd to the roll distance Dg, and in step S4, the titanium alloy billet is rolled in the deformation zone with a pass ellipticity coefficient of 1.2-1.4.

Preferably, during the rolling process of the titanium alloy billet, the roll distance Dg between the two rolls is constant, which is beneficial to realize multi-pass repeated rolling.

Preferably, during the repeated rolling process of step S5, the shape of the deformation zone remains unchanged.

The present invention compares with prior art, the beneficial effect of the present invention is:

(1) The penetration depth of the deformation zone is large, and a large-scale overall ultra-fine grain structure can be obtained. The plastic deformation inside the material during the cross rolling process consists of two parts, one is the compression deformation between the rolls, which is a periodic intermittent deformation, and the other is the continuous torsional deformation. The superimposition of compression and torsional deformation produces three-dimensional severe plastic deformation in the deformation zone during the cross rolling process, which is obviously different from conventional forging; (2) The diameter of the bar before and after cross rolling remains unchanged and can be reciprocated for multi-pass rolling. There is widening in the cross-rolling process, and the equivalent diameter in the cross-section of the titanium alloy billet remains unchanged; (3) Continuous and stable local deformation, rolling load is small, and the deformation process is stable. In the cross rolling process, the actual contact area between the workpiece and the titanium alloy billet is only a small part of the surface area of the titanium alloy billet, which is a local contact deformation, so the load is small; (4) The compression-torsion combined three-dimensional severe deformation can obtain ideal grains Refinement effect.

Description of drawings

Fig. 1 is a schematic diagram of a roll of the present invention.

Figure 2 is a schematic diagram of the original structure β grains.

Fig. 3 is a schematic diagram of embodiment 1 of the present invention that the number of rolling is 2 times.

Fig. 4 is a schematic diagram of embodiment 1 of the present invention that the number of rolling times is 6.

Fig. 5 is the relative position of each mold in the skew rolling process of the present invention

Fig. 6 is a top view of the relative positions of the molds in the skew rolling process of the present invention.

Fig. 7 is a left side view of the relative positions of the molds in the skew rolling process of the present invention.

Fig. 8 is a schematic diagram of the deformation zone in the cross rolling process of the present invention.

Reference signs: 1-roller, 2-titanium alloy blank, 3-guide plate.

Detailed ways

The present invention is an equidistant spiral rolling method for large-scale titanium alloy ultra-fine-grained rods, which is characterized in that it comprises the following steps:

S1: Select a titanium alloy blank 2 with a diameter D of 40-150 mm and a length of 300-5000 mm;

S2: Place the above-mentioned titanium alloy billet 2 in a heating furnace and heat it to 840-1025°C. The heating time is: diameter D of the titanium alloy billet 2×(0.6-0.8) min;

S3: transfer the heated titanium alloy billet 2 from the heating furnace to the guide groove of the skew rolling mill, and the transfer time is 5-20s;

S4: Feed in the guide groove of the skew rolling mill, and send the titanium alloy billet 2 into the deformation zone between the entrance and the exit of the skew rolling mill, and the titanium alloy billet 2 spirally moves in the deformation zone until the deformation is completed, and the diameter Dm is obtained. TC18 titanium alloy bar bar, where m is the number of rolling times, the diameter of the TC18 titanium alloy bar obtained by rolling once is D1, the diameter of the TC18 titanium alloy bar obtained by rolling twice is D2, and so on;

S5: repeating the above steps S2-S4, performing 2-6 times of spiral rolling on the titanium alloy blank 2 to obtain the TC18 titanium alloy overall ultra-fine-grained bar;

The skew rolling mill is a two-roll skew rolling mill, and the rolls 1 are all single-tapered rolls 1, the cone angle γ1 is 17-19 degrees, and the arc radius r of the roll 1 biting into the titanium alloy blank 2 is 50-380 mm, The feeding angle α of the roll 1 is 15-17 degrees, the rolling angle β of the roll 1 is 17-19 degrees, and the distance Dg between the two rolls 1 is 86%-94% of the diameter D of the titanium alloy billet 2, Roller 1 speed n is 28-50r/min;

The titanium alloy blank 2 is a large-size TC18 titanium alloy rod;

The heating time of the repeated rolling process in the step S5 is the diameter of the TC18 titanium alloy rod Dm×(0.3-0.4) min.

The small end surface of the roll 1 is set as an arc surface, and the radius of the arc surface is 50-380mm.

The pass ellipticity coefficient is the ratio of the guide plate 3 distance D _d to the roll distance Dg. In step S4, the titanium alloy billet 2 is rolled in the deformation zone with a pass ellipticity coefficient of 1.2-1.4.

During the rolling process of the titanium alloy billet 2, the roll distance Dg between the two rolls 1 is constant, which is beneficial to realize multi-pass repeated rolling.

During the repeated rolling process in step S5, the shape of the deformation zone remains unchanged.

In the present invention, the small end face of the roll 1 is a circular arc surface, which can quickly change the cylindrical titanium alloy blank 2 into an elliptical column, and provide sufficient deformation for constant roll gap spiral rolling; the main body shape of the roll 1 is a single taper , the cone angle is equal to the rolling angle, compared with the ordinary roll 1, the length of the compression deformation zone of the outer diameter is increased to twice the length, and after the rolled piece passes through a longer deformation zone than ordinary rolling, the accumulated large plastic deformation can occur; Rolling with a large ellipticity coefficient, after the titanium alloy billet 2 is pulled into the roll 1, the cross section becomes elliptical. The small deformation of 1 is compressed, and any point in the deformation zone rotates one circle, and is compressed twice by roll 1; the spiral rolling can be realized many times. Due to the large ellipticity, the diameter of the bar after spiral rolling is larger than the roll distance, and the deformation The final rolled piece can be repeatedly rolled under the same deformation parameter conditions, so that a larger deformation can be obtained; the use of a large feeding angle and a large rolling angle can obtain a more stable spiral forward power, and To meet the needs of large plastic deformation.

Generally, the type of material processing is distinguished by the recrystallization temperature. Above the recrystallization temperature is hot processing, and below the recrystallization temperature is cold processing. In the prior art, cold processing is used to prepare ultra-fine grains. Due to insufficient deformation, relatively small amounts can only be obtained by accumulating dislocations. Small grains, but such grains have poor thermal stability and cannot be heat treated. The purpose of this patent is to obtain grains that can be heat treated, that is, to obtain ultra-fine grains by accumulating large deformation and recrystallization, so as to distinguish them from traditional cold working.

Therefore, this patent provides a realistic choice for the industrial production of large-scale TC18 integral ultra-fine-grained rods.

Embodiment one:

Adopt above-mentioned technical parameter, design and process roll 1 as shown in Figure 1;

S1: The main deformation parameters are titanium alloy TC18, the diameter D is 100mm, and the length is 800mm; the radius r of the biting arc of the spiral roll shape is 100mm, the feeding angle α is 16°, the cone angle is 17°, and the rolling angle is 17°, the distance Dg between rolls 1 is 87.5% of the billet diameter D, the pass ellipticity coefficient is 1.23, and the speed n of roll 1 is 40r/min;

S2: Heating the cylindrical titanium alloy blank at 2 to 845°C in a heating furnace for 70 minutes;

S3: transfer the heated titanium alloy billet 2 from the heating furnace to the guide groove of the skew rolling mill, and the transfer time is 10s;

S4: The titanium alloy blank 2 moves helically in the deformation zone until the deformation ends.

S5: Repeated rolling 2 times and 6 times sampling analysis, its effect on titanium alloy grain refinement is significant, the grain size is small, and the heating time of repeated rolling process is: TC18 titanium alloy rod diameter Dm×(0.3 -0.4) min, where m is the number of rolling times, the diameter of the TC18 titanium alloy bar obtained by rolling once is D1, and rolling twice is to use the TC18 titanium alloy bar with a diameter of D1 as the blank for rolling again, The diameter of the obtained TC18 titanium alloy rod is D2, and so on, and the shape of the deformation zone remains unchanged.

Based on the above examples, the original structure is as shown in Figure 2. Among the figures, the β grains are the main, and the average size of the β grains is 80um; it adopts the method of the present invention, and Figure 3 is a typical titanium alloy grain diagram with 2 rolling times. , where the grain size is about 7.5um, and the degree of grain refinement is 90.63%; Figure 4 is the grain diagram of titanium alloy with rolling times of 6, where the grain size is about 1.2um, and the degree of grain refinement is 98.5% %.

The present invention is an equidistant spiral rolling method for large-sized titanium alloy ultra-fine-grained rods. The shape of the single-tapered roll 1 is adopted, and the roll distance in the deformation zone is kept constant, and the ellipticity coefficient of the super-large pass in the deformation zone is used. Repeated multi-pass rolling to gradually accumulate super large plastic deformation; moreover, since this method can perform multi-pass spiral rolling, for different types of titanium alloys, the number of rolling times is in the range of 2-6, and for titanium alloy grain refinement The effect is the best, and the obtained ultrafine crystal size is the smallest. The process is suitable for continuous severe plastic deformation of titanium alloy rods of various sizes and types under low load. It is used to prepare 1000-3000nm overall fine-grained or ultra-fine-grained rods, and can overcome the shortcomings of the existing severe plastic deformation process, which has a large load and can only process small-sized workpieces.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto, any person familiar with the technical field within the technical scope disclosed in the present invention, according to the technical solution of the present invention Any equivalent replacement or change of the inventive concepts thereof shall fall within the protection scope of the present invention.

Claims (5)

1. a kind of isometric helix milling method of large-scale titanium alloy ultra fine grained steel bar, which is characterized in that include the following steps：

S1：It is 40-150mm to choose diameter dimension D, and length is the titanium alloy blank of 300-5000mm（2）；

S2：By above-mentioned titanium alloy blank（2）It places in heating furnace and is heated to 840-1025 DEG C, heating time is：Titanium alloy blank （2）Diameter D ×（0.6-0.8）min；

S3：By the titanium alloy blank after heating（2）It is transported in skew rolling mill deflector chute from heating furnace, transhipment time 5-20s；

S4：Feeding is carried out in the deflector chute of skew rolling mill, by titanium alloy blank（2）The change being sent between skew rolling mill entrance and exit Shape area, titanium alloy blank（2）In deformed area, inside spin movement terminates until deforming, and obtains the TC18 titanium alloy bars of a diameter of Dm Material, wherein m are rolling number；

S5：Above-mentioned S2-S4 steps are repeated, to titanium alloy blank（2）2-6 screw rolling of progress obtains TC18 titanium alloys and integrally surpasses Fine grain bar；

The skew rolling mill is two-roller skew-rolling machine, the roll（1）It is single cone-shaped roll（1）, cone angle gamma 1 is 17-19 degree, and is rolled Roller（1）Bite titanium alloy blank（2）Arc radius r be 50-380mm, roll（1）Feed angle α is 15-17 degree, roll（1）'s Roll off angle beta is 17-19 degree, two rolls（1）Between roll（1）Space D g is titanium alloy blank（2）The 86%-94% of diameter D, Roll（1）Rotating speed n is 28-50r/min；

The titanium alloy blank（2）For large scale bar；

In the S5 steps repeat the operation of rolling heating time be TC18 titanium alloy rod bar diameters Dm ×（0.3-0.4）min.

2. a kind of isometric helix milling method of large-scale titanium alloy ultra fine grained steel bar as described in claim 1, which is characterized in that The roll（1）Small end face is set as arc surface, and circular arc radius surface is 50-380mm.

3. a kind of isometric helix milling method of large-scale titanium alloy ultra fine grained steel bar as described in claim 1, which is characterized in that Groove Ovality Factor is guide plate（3）Away from D_dThe ratio between with roll spacing Dg, titanium alloy blank in S4 steps（2）Hole is used in deformed area Type ellipse coefficient is that 1.2-1.4 is rolled.

4. a kind of isometric helix milling method of large-scale titanium alloy ultra fine grained steel bar as described in claim 1, which is characterized in that In titanium alloy blank（2）In the operation of rolling, two rolls（1）Between roll spacing Dg immobilize.

5. a kind of isometric helix milling method of large-scale titanium alloy ultra fine grained steel bar as described in claim 1, which is characterized in that In S5 steps repeat the operation of rolling, deformed area shape remains unchanged.