CN108580547B - Equidistant spiral rolling method for large-size titanium alloy ultrafine-grained bar - Google Patents
Equidistant spiral rolling method for large-size titanium alloy ultrafine-grained bar Download PDFInfo
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- 229910001069 Ti alloy Inorganic materials 0.000 title claims abstract description 100
- 238000005096 rolling process Methods 0.000 title claims abstract description 92
- 238000000034 method Methods 0.000 title claims abstract description 63
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- 239000013078 crystal Substances 0.000 claims abstract description 17
- 239000000463 material Substances 0.000 claims description 25
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- 230000009286 beneficial effect Effects 0.000 abstract description 4
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- 230000035515 penetration Effects 0.000 abstract description 3
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- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 3
- 230000009471 action Effects 0.000 description 3
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- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 238000010274 multidirectional forging Methods 0.000 description 3
- 239000002086 nanomaterial Substances 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 229910052719 titanium Inorganic materials 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 2
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- 230000009466 transformation Effects 0.000 description 2
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
- B21B1/16—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling wire rods, bars, merchant bars, rounds wire or material of like small cross-section
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B27/00—Rolls, roll alloys or roll fabrication; Lubricating, cooling or heating rolls while in use
- B21B27/02—Shape or construction of rolls
- B21B27/024—Rolls for bars, rods, rounds, tubes, wire or the like
- B21B27/025—Skew rolls
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B27/00—Rolls, roll alloys or roll fabrication; Lubricating, cooling or heating rolls while in use
- B21B27/02—Shape or construction of rolls
- B21B27/028—Variable-width rolls
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
Abstract
The invention discloses an equidistant spiral rolling method of a large-size titanium alloy ultrafine crystal bar, relates to the technical field of machining, and particularly relates to an equidistant spiral rolling method of a large-size titanium alloy ultrafine crystal bar, which comprises the following steps: s1: selecting a titanium alloy blank with the diameter dimension D of 40-150mm and the length of 300-5000 mm; s2: placing the titanium alloy blank in a heating furnace and heating to 840-1025 ℃; s3: transferring the heated titanium alloy blank from the heating furnace into a guide chute of a skew rolling mill for 5-20 s; s4: feeding in a guide chute of the skew rolling mill, feeding the titanium alloy blank into a deformation zone between an inlet and an outlet of the skew rolling mill, and performing spiral motion on the titanium alloy blank in the deformation zone until the deformation is finished; s5: repeating the steps S2-S4, and carrying out 2-6 times of spiral rolling on the titanium alloy blank to obtain a TC18 titanium alloy integral superfine crystal bar; the invention has the beneficial effects that: the deformation zone has large penetration depth and can carry out multi-pass rolling repeatedly. Continuous and stable local deformation and three-dimensional severe deformation of the composite pressing-twisting can obtain ideal grain refining effect.
Description
Technical Field
The invention relates to the technical field of machining, in particular to an equidistant spiral rolling method of a large-size titanium alloy ultrafine crystal bar.
Background
Ultra-fine grain/nano-grain materials are one of the hot topics for current material science research. Compared with the traditional coarse-grained metal material, the ultra-fine grained/nano material has more excellent or unique properties in certain aspects, such as higher strength and hardness, better fatigue performance and superplasticity, better corrosion resistance, wear resistance, biological characteristics and the like. The excellent characteristics lead the ultra-fine grain material to have wide application prospect in the engineering fields of aviation, aerospace, automobiles, oceans, biology and the like, and lead people to pay more attention to the development of the ultra-fine grain/nano preparation technology. The ultra-fine grained/nano-materials show in some aspects more excellent or unique properties compared to traditional coarse grained metal materials. From the mechanical property point of view, for pure titanium, the grain size is thinned 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 645 Mpa. For some titanium alloys, when the grain size reaches about 1.2um, the room temperature tensile strength can reach more than 1300Mpa, which is improved by 60% compared with the room temperature tensile strength of the original blank. The ultra-fine grain material is very remarkable in improvement of fatigue properties, wherein the fatigue limit of ultra-fine grain titanium having 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, as compared with 20um coarse grain titanium. From the above, the large-size titanium alloy ultrafine-grained bar has great potential in the field of industrial application.
When the nano-scale material is prepared by adopting a Plastic Deformation mode, the equivalent strain is usually more than 6, the traditional Plastic processing method is difficult to realize, and the method can be realized by applying a super Plastic Deformation method (SPD). Modern SPD starts from the combination of high pressure and shear deformation forming method proposed by Bridgemen, the rapid development starts from soviet union and western countries before the middle of the 70 th 20 th century, and Segal develops Equal-Channel angular Extrusion (ECAP), which marks the arrival of the microstructure era of SPD research. Over the last 10 years, thousands of research results have been published.
Definition of SPD generally accepted after 2006: the metal forming method can obtain the grain size of micron (100-1000 nm) and nanometer (less than 100 nm), which can be called nano SPD (nano SPD for short). The nano SPD material has a large amount of large-angle non-equilibrium grain boundary tissues containing high-density dislocation and high internal stress, so that the material shows mechanical behavior and a deformation mechanism different from those of the traditional coarse-grained material.
The current processing technical scheme is as follows: typical SPD methods include High Pressure Torsion (HPT), equal channel angular pressing-deforming (ECAP), cumulative rolling (ARB), Twist Extrusion (TE), and Multi-Directional Forging (MDF).
Wherein, (1) high-pressure torsional deformation: the original sample (block or powder) placed in the supporting groove is applied with a plurality of GPa pressures, and the upper anvil and the lower anvil are relatively rotated, so that the sample is subjected to strong shearing deformation to refine grains, and the high-pressure torsion is characterized in that the workpiece is in a disc shape, the size is small, the diameter is generally 10-20 mm, and the thickness is 0.2-0.5 mm.
(2) Equal channel angular extrusion deformation: the material is extruded from one end to the other end through two equal-section channels intersecting at a certain angle in the die, the material is subjected to pure shear deformation through the change of the motion direction of the material by the bending angle, the forming process can be repeated, and the shear strain amount is increased along with deformation passes.
(3) Cumulative pack rolling method: the method comprises the steps of carrying out double-layer stacking on an original plate after surface treatment, heating, carrying out roll welding together, then carrying out next roll welding circulation after cutting from the middle and returning to the surface treatment, wherein in order to ensure that the plate can be welded together after rolling, the reduction of each pass is not less than 50%, but strong shear stress conditions are required in the ARB processing process, a lubricant cannot be used, and the service life of a roller is not favorable.
(4) Torsion extrusion: beygelzime et al teach this process. The method also adopts a forming technology of thinning crystal grains through shearing deformation, and the columnar blank is extruded through a torsion die, so that the method has the similar problem of uneven deformation as HPT, and the effect of thinning the crystal grains is lower than that of ECAP and HPT.
(5) Multidirectional forging: the process changes the free forging direction through multiple orthogonal operations to obtain large deformation. The grain refining effect of such deformation is significantly lower than that of ECAP and HPT.
Another type of existing processing technical scheme is as follows: the derivation method, the basic forming principle is the same as the above method, many new SPD forming techniques are derived, these methods try to simplify the tool design, reduce the energy consumption, improve the yield, promote the workpiece size, upgrade the degree of automation, etc., wherein, include:
(1) ECAP derivatization method: repeated bending and straightening (RCS), wherein the blank is placed between the bending devices, moves downwards along with the upper die, is bent and becomes wavy; the material structure is then refined by straightening with 2 plates and bending again, with repeated iterations, accumulating sufficient deformation without significantly changing the dimensions of the blank.
(2) A Circular Closed Die Forging (CCDF) is composed of a lower die with a cavity with a certain cross section and a punch with the same cross section, which vertically moves in the cavity. And (3) putting the fully lubricated sample with the graphite lubricant into a lower die, and heating to a certain temperature. And pressing the workpiece into the lower die through the punch, taking out the workpiece, rotating the workpiece by 90 degrees around the Z axis in the same direction, and reinserting the lower die for deformation. Thus, the workpiece is rotated 90 about the Z-axis between successive passes. In this way, 1,3 and 5 compressions were respectively experienced.
(3) Reciprocating extrusion (CEC), a die is made up of two die cavities, a compression band and punches placed in the two die cavities. The two die cavities have equal sectional areas and are connected through a middle compression belt on the same axis. During the extrusion process, the sample reaches the compression belt under the action of the punch, at the moment, the sample is subjected to positive extrusion deformation, and the extruded workpiece is subjected to upsetting deformation under the action of the punch of the other die cavity. Then, the punch on the other side reversely presses the workpiece back according to the process to complete an extrusion cycle. The above process is repeated until the desired strain is obtained.
(4) The plate is continuously sheared and deformed, and the device utilizes an upper die, a lower die and a lower roller to form two mutually crossed channels with small difference in cross-sectional area. The plate is fed into the die cavity, and the plate is strongly shaped and deformed at the corner of the die cavity and then extruded from the other side of the die cavity. Grooves are machined on the surface of the feeding roller for increasing the friction force. Due to the characteristic that the cross-sectional area of the material is kept unchanged before and after deformation, the plate can be subjected to multi-pass plastic deformation repeatedly in the same die.
(5) The method is characterized in that a blank is converted into a round bar stock through upsetting-drawing (round-oval transformation), twisting (oval cross section twisting) and reverse upsetting-drawing (oval-round transformation) processes under the action of extrusion force. Metals produce plastic flow primarily in cross-section and accumulate strain. The shape of the die utilizes the particularity of a circular shape and an oval shape, and a sharp corner area does not exist in a cavity of the die, so that metal can flow easily. The combination of multiple deformation modes in one technological process is realized.
(6) Continuous Friction Angle Extrusion (CFAE), the drive roller rotates and applies pressure P to the workpiece against its support. A first extrusion channel is formed between the drive roller and the workpiece support member and a second channel is a short slot in the stationary die assembly. The sheet workpiece is processed for one to eight times, the maximum equivalent real strain can reach 5.3, and the orientation of the sheet material is always kept constant.
An HPT derivatization method is adapted for high pressure torsion (HPTT) of a pipe, the pipe being positioned within a rigid disk, a mandrel being placed within the pipe and compressed in its elastic state by a compressor. Due to the axial compression of the mandrel, which expands radially, the expansion is limited by the tube and the discs, creating large hydrostatic stresses in the tube, creating large friction forces on both sides of the tube. The deformation of the tube is achieved by an external torque rotating disc, with the mandrel held stationary. During the twisting process, the deformation mode is local shearing, the normal direction of the shearing surface is the radial direction of the tube, and the shearing direction is parallel to the circumferential direction.
One TE derivatization method, ultra-high torsion (STS), localizes the Torsional Strain (TS) region by locally heating and cooling to make the region less resistant to deformation than the other two portions. While the TS zone is created, the rod moves along the longitudinal axis, thereby continuously creating an ultra-large plastic strain throughout the rod. This new process STS includes a rod that creates localized soft zones and movement of the regions in the longitudinal direction relative to the rest of the rod. An important feature of STS is that the cross-sectional dimensions of the rod remain unchanged when strained.
Relatively few patent reports on the titanium alloy ultra-fine grain process at home and abroad are available. The patent [ CN 103014574 a ] of Zhongnan university department of science et al mentions a preparation method of TC18 ultra-fine grained titanium alloy, wherein detailed heat treatment and multi-pass upsetting ultra-fine grained process parameters are mentioned. The process adopts a multidirectional upsetting-drawing mode for deformation, and belongs to a traditional forging method. Because the range and penetration depth of the single-pass deformation zone are small, repeated deformation of more than 8-10 passes is generally required to obtain an ultra-fine grain structure. The cycle length is long, the efficiency is low, and the phenomenon of obvious deformation unevenness generally exists.
The patent of Wangliqiang et al (Shanghai university of transportation) in CN 103572186A mentions a method for preparing ultra-fine grained Ti-based composite material by equal-diameter curved channel deformation, and the introduction of this patent background suggests that although severe plastic deformation can be repeated, the size after deformation is 10X 10X 100mm, which is difficult to meet the industrial-grade requirement. The duinding more in the northwest university of industry [ CN 1446935 a ] mentions a method for preparing ultra-fine grained material. The method mainly focuses on the generation of ultra-fine grains on the surface. Although the deformation degree is high and the deformation can be repeated, the method is only limited to preparing surface nano-crystals and cannot prepare whole ultra-fine crystals from the core to the surface.
The patent [ CN 107030111A ] of the national Liu Huai of the northeast university mentions a preparation method of an equal-thickness ultrafine-grained TC4 titanium alloy plate. The method is similar to the accumulative pack rolling in the introduction of the patent background, the process needs strong shearing stress conditions, the load is large, the size condition of the process is greatly limited, only plates can be prepared, and bars cannot be prepared. From the report of the titanium alloy ultrafine crystal process, the titanium alloy is mostly deformed by ECAP and HPT, the related product has small size, and the large-size block material of industrial grade integral ultrafine crystal is difficult to generate.
The comprehensive analysis shows that: the titanium alloy ultrafine grain process mentioned in the existing patent or paper adopts the traditional methods of HPT, ECAP, ARB and the like to prepare small-sized uniform ultrafine grain materials under extremely high load, is only limited to be developed in laboratories at present, and is difficult to prepare industrial-grade large-sized materials with integral ultrafine grains.
Disclosure of Invention
The invention aims to provide an equidistant spiral rolling method for a large-size titanium alloy ultrafine crystal bar, which aims to solve the problems of size limitation, large load, low efficiency and the like in the background technology.
The invention discloses an equidistant spiral rolling method of a large-size titanium alloy ultrafine crystal bar, which is characterized by comprising the following steps of:
s1: selecting a titanium alloy blank with the diameter dimension D of 40-150mm and the length of 300-5000 mm;
s2: placing the titanium alloy blank in a heating furnace, heating to 840-1025 ℃ for the following time: the diameter of the titanium alloy blank is Dx (0.6-0.8) min;
s3: transferring the heated titanium alloy blank from the heating furnace into a guide chute of a skew rolling mill for 5-20 s;
s4: feeding materials in a guide chute of a skew rolling mill, feeding the titanium alloy blank into a deformation zone between an inlet and an outlet of the skew rolling mill, spirally moving the titanium alloy blank in the deformation zone until the deformation is finished to obtain a TC18 titanium alloy bar with the diameter Dm, wherein m is the rolling frequency, 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 steps S2-S4, and carrying out 2-6 times of spiral rolling on the titanium alloy blank to obtain a TC18 titanium alloy integral superfine crystal bar;
the skew rolling mill is a two-roller skew rolling mill, the rollers are single conical rollers, the cone angle gamma 1 is 17-19 degrees, the arc radius r of the titanium alloy blank gripped by the rollers is 50-380mm, the feeding angle β of the rollers is 15-17 degrees, the rolling angle beta of the rollers is 17-19 degrees, the roller distance Dg between the two rollers is 86-94% of the diameter D of the titanium alloy blank, and the rotating speed n of the rollers is 28-50 r/min;
the titanium alloy blank is a large-size bar;
the heating time of the repeated rolling process in the step S5 is TC18 titanium alloy bar diameter Dm x (0.3-0.4) min.
Preferably, the small end surface of the roller is provided with a circular arc surface, and the radius of the circular arc surface is 50-380 mm.
Preferably, the pass ovality factor is the guide plate distance DdAnd the ratio of the hole pattern ovality coefficient to the roll spacing Dg, the titanium alloy blank is rolled in the deformation zone by using a roll with the hole pattern ovality coefficient of 1.2-1.4 in the step S4.
Preferably, in the rolling process of the titanium alloy blank, the roll distance Dg between the two rolls is fixed, which is beneficial to realizing multi-pass repeated rolling.
Preferably, the shape of the deformed region is maintained during the repeated rolling at step S5.
Compared with the prior art, the invention has the beneficial effects that:
(1) the deformation zone has large penetration depth, and large-size integral ultrafine grain structure can be obtained. The plastic deformation in the material during the skew rolling process is composed of two parts, namely compression deformation between rollers, which is periodic discontinuous deformation, and continuous torsional deformation. The superposition of compression and torsional deformation enables three-dimensional severe plastic deformation which is obviously different from that of conventional forging to be generated in a deformation area in the skew rolling process; (2) the diameter of the bar material before and after the skew rolling is kept unchanged, and the bar material can be repeatedly rolled for multiple times. The width expansion exists in the skew rolling process, and the equivalent diameter in the cross section of the titanium alloy blank remains unchanged; (3) continuous and stable local deformation, small rolling load and stable deformation process. The actual contact area of the workpiece and the titanium alloy blank in the skew rolling process is only a small part of the surface area of the titanium alloy blank, and local contact deformation is realized, so that the load is small; (4) the pressing-twisting composite three-dimensional severe deformation can obtain ideal grain refinement effect.
Drawings
FIG. 1 is a schematic view of a roll of the present invention.
FIG. 2 is a schematic view of the original structure β grains.
FIG. 3 is a schematic view of 2 rolling passes according to an embodiment of the present invention.
FIG. 4 is a schematic diagram of 6 rolling passes according to an embodiment of the present invention.
FIG. 5 shows the relative positions of the dies in the skew rolling process of the present invention
FIG. 6 is a top view of the relative positions of the dies during skew rolling in accordance with the present invention.
FIG. 7 is a left side view of the relative positions of the dies during cross-piercing in accordance with the present invention.
FIG. 8 is a schematic view of the deformation zone of the skew rolling process of the present invention.
Reference numerals: 1-roller, 2-titanium alloy blank and 3-guide plate.
Detailed Description
The invention discloses an equidistant spiral rolling method of a large-size titanium alloy ultrafine crystal bar, which is characterized by comprising the following steps of:
s1: selecting a titanium alloy blank 2 with the diameter dimension D of 40-150mm and the length of 300-5000 mm;
s2: placing the titanium alloy blank 2 in a heating furnace, heating to 840-1025 ℃ for: 2 diameters Dx (0.6-0.8) min of the titanium alloy blank;
s3: transferring the heated titanium alloy blank 2 from the heating furnace into a guide chute of a skew rolling mill for 5-20 s;
s4: feeding materials in a guide chute of a skew rolling mill, feeding the titanium alloy blank 2 into a deformation zone between an inlet and an outlet of the skew rolling mill, spirally moving the titanium alloy blank 2 in the deformation zone until the deformation is finished, and obtaining a TC18 titanium alloy bar rod with the diameter Dm, wherein m is the rolling frequency, the diameter of the TC18 titanium alloy bar rod obtained by rolling once is D1, the diameter of the TC18 titanium alloy bar rod obtained by rolling twice is D2, and the like;
s5: repeating the steps S2-S4, and carrying out 2-6 times of spiral rolling on the titanium alloy blank 2 to obtain a TC18 titanium alloy integral ultrafine grain bar;
the skew rolling mill is a two-roller skew rolling mill, rollers 1 are single-cone rollers 1, the cone angle gamma 1 is 17-19 degrees, the arc radius r of the titanium alloy blank 2 which is bitten into the rollers 1 is 50-380mm, the feeding angle β of the rollers 1 is 15-17 degrees, the rolling angle beta of the rollers 1 is 17-19 degrees, the roller distance Dg between the two rollers 1 is 86-94 percent of the diameter D of the titanium alloy blank 2, and the rotating speed n of the rollers 1 is 28-50 r/min;
the titanium alloy blank 2 is a large-size TC18 titanium alloy bar;
the heating time of the repeated rolling process in the step S5 is TC18 titanium alloy bar diameter Dm x (0.3-0.4) min.
The small end surface of the roller 1 is arranged to be an arc surface, and the radius of the arc surface is 50-380 mm.
Pass ovality coefficient as guide plate distance DdRatio of roll gap Dg to titanium alloy in step S4The blank 2 is rolled in the deformation zone by a roller 1 with a pass ovality coefficient of 1.2-1.4.
In the rolling process of the titanium alloy blank 2, the roll distance Dg between the two rollers 1 is fixed, which is beneficial to realizing multi-pass repeated rolling.
During the repeated rolling in step S5, the deformed zone shape remains unchanged.
The small end surface of the roller 1 is a circular arc surface, so that the cylindrical titanium alloy blank 2 can be quickly changed into an elliptic cylinder shape, and sufficient deformation is provided for the spiral rolling of a constant roll gap; the main body of the roller 1 is in a single conical shape, the cone angle is equal to the rolling angle, compared with the common roller 1, the length of an outer diameter compression deformation area is increased to 2 times, and after a rolled piece passes through a deformation area which is longer than that of common rolling, large plastic deformation can be generated in an accumulated mode; the titanium alloy blank 2 is dragged into the roller 1 and the cross section is changed into an ellipse by adopting a larger ovality coefficient for rolling, and in the process of spiral advancing, because the radius of the major axis of the ellipse is larger than the distance between the rollers 1, the titanium alloy blank 2 always bears the small deformation compression of the roller 1, and any point in a deformation area rotates for one circle and is compressed by the roller 1 for two times; the spiral rolling can be repeatedly realized, because of large ovality, the diameter of the rod after the spiral rolling is larger than the roller distance, and the deformed rolled piece can be repeatedly rolled under the condition of the same deformation parameter for multiple times, so that larger deformation can be obtained; by adopting a large feeding angle and a large rolling angle, more stable spiral advancing power can be obtained so as to meet the requirement of large plastic deformation.
Generally, the type of material processing is distinguished by the recrystallization temperature, hot processing is carried out above the recrystallization temperature, cold processing is carried out below the recrystallization temperature, cold processing is adopted in the prior art for preparing ultra-fine crystals, small grains can be obtained only by accumulating dislocation due to insufficient deformation, but the grains have poor thermal stability and cannot be subjected to heat treatment. The object of this patent is to obtain grains that can be heat-treated, i.e. ultra-fine grains by means of recrystallization through accumulation of large deformations, thus being distinguished from conventional cold working.
Therefore, the method provides a practical choice for the industrial preparation of the large-size TC18 integral ultrafine crystal bar.
The first embodiment is as follows:
designing the processing roller 1 as shown in figure 1 by adopting the technical parameters;
s1, selecting titanium alloy TC18 as main deformation parameters, wherein the diameter D is 100mm, the length is 800mm, the radius r of a gripping arc of a spiral roller shape is 100mm, the feed angle α is 16 degrees, the cone angle is 17 degrees, the rolling angle is 17 degrees, the roll distance Dg is 87.5 percent of the blank diameter D, the pass ovality coefficient is 1.23, and the rotating speed n of a roller 1 is 40 r/min;
s2: heating the cylindrical titanium alloy blank 2 to 845 ℃ in a heating furnace for 70 minutes;
s3: transferring the titanium alloy blank 2 heated to the temperature from the heating furnace into a guide chute of a skew rolling mill for 10 s;
s4: the titanium alloy blank 2 spirally moves in the deformation zone until the deformation is finished.
S5: the sampling analysis of repeated rolling for 2 times and 6 times shows that the effect on the grain refinement of the titanium alloy is obvious, the grain size is small, and the heating time of the repeated rolling process is as follows: the diameter Dm x (0.3-0.4) min of the TC18 titanium alloy bar is obtained, wherein m is the rolling frequency, the diameter of the TC18 titanium alloy bar obtained by once rolling is D1, the TC18 titanium alloy bar obtained by twice rolling is rolled again by taking the TC18 titanium alloy bar with the diameter of D1 as a blank, the diameter of the TC18 titanium alloy bar obtained is D2, and the like, and the shape of a deformation zone is kept unchanged.
based on the above example, the original structure is shown in fig. 2, which shows beta grains as main grains, the average size of the beta grains is 80um, fig. 3 is a typical titanium alloy grain diagram with 2 rolling times, wherein the grain size is about 7.5um, and the grain refinement degree is 90.63%, and fig. 4 is a titanium alloy grain diagram with 6 rolling times, wherein the grain size is about 1.2um, and the grain refinement degree is 98.5%.
The invention relates to an equidistant spiral rolling method of a large-size titanium alloy ultrafine-grained bar, which comprises the steps of repeatedly carrying out multi-pass rolling by adopting a deformation region ultra-large hole ovality coefficient through the shape of a single conical roller 1 and keeping the roller distance in a deformation region unchanged, and gradually accumulating ultra-large plastic deformation; moreover, the method can carry out spiral rolling for multiple times, the rolling times are within the range of 2-6 for different types of titanium alloys, the effect on grain refinement of the titanium alloys is optimal, and the obtained ultrafine grain size is minimum. The process is suitable for low-load continuous severe plastic deformation of titanium alloy bars with various dimensions and types. The method is used for preparing 1000-3000nm integral fine-grained or ultra-fine-grained bars, and can overcome the defects that the load of the existing severe plastic deformation process is large and only small-sized workpieces can be processed.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (5)
1. An equidistant spiral rolling method of a large-size titanium alloy ultrafine crystal bar is characterized by comprising the following steps:
s1: selecting a titanium alloy blank (2) with the diameter dimension D of 40-150mm and the length of 300-5000 mm;
s2: placing the titanium alloy blank (2) in a heating furnace, heating to 840-1025 ℃ for the following time: the diameter Dx (0.6-0.8) of the titanium alloy blank (2) is min;
s3: transferring the heated titanium alloy blank (2) from the heating furnace to a guide chute of a skew rolling mill for 5-20 s;
s4: feeding materials in a guide chute of a skew rolling mill, feeding the titanium alloy blank (2) into a deformation zone between an inlet and an outlet of the skew rolling mill, and spirally moving the titanium alloy blank (2) in the deformation zone until the deformation is finished to obtain a TC18 titanium alloy bar with the diameter Dm, wherein m is the rolling frequency;
s5: repeating the steps S2-S4, and carrying out 2-6 times of spiral rolling on the titanium alloy blank (2) to obtain a TC18 titanium alloy whole ultrafine crystal bar;
the skew rolling mill is a two-roller skew rolling mill, the rollers (1) are single tapered rollers (1), the taper angle gamma 1 is 17-19 degrees, the arc radius r of the titanium alloy blank (2) which is bitten into the rollers (1) is 50-380mm, the feeding angle β of the rollers (1) is 15-17 degrees, the rolling angle beta of the rollers (1) is 17-19 degrees, the roller distance Dg between the two rollers (1) is 86-94 percent of the diameter D of the titanium alloy blank (2), and the rotating speed n of the rollers (1) is 28-50 r/min;
the titanium alloy blank (2) is a large-size bar;
the heating time of the repeated rolling process in the step S5 is TC18 titanium alloy bar diameter Dm x (0.3-0.4) min.
2. The method for equidistantly spirally rolling the large-sized ultrafine titanium alloy grain bar according to claim 1, wherein the small end surface of the roll (1) is provided with a circular arc surface having a radius of 50-380 mm.
3. The method of claim 1, wherein the pass ovality factor is the guide plate distance DdAnd the ratio of the roll spacing Dg to the roll spacing Dg, rolling the titanium alloy blank (2) in the step S4 by using a roll (1) with the pass ovality coefficient of 1.2-1.4 in a deformation zone.
4. The method for equidistantly spirally rolling the large-sized ultrafine titanium alloy grain bar according to claim 1, wherein the roll gap Dg between the two rolls (1) is constant during the rolling of the titanium alloy billet (2).
5. The equidistant helical rolling method of a large-sized titanium alloy ultrafine grained rod material according to claim 1, wherein the shape of the deformed zone is maintained during the repeated rolling at step S5.
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| CN109807176B (en) * | 2019-02-28 | 2020-05-15 | 西安东耘新金属材料有限公司 | Superfine crystal rolling method for large-size 45 steel bar |
| CN109807175B (en) * | 2019-02-28 | 2020-05-15 | 西安东耘新金属材料有限公司 | Superfine crystal rolling method for large-size titanium alloy bar |
| CN109807174B (en) * | 2019-02-28 | 2020-06-23 | 西安东耘新金属材料有限公司 | Reverse-cone spiral roller superfine crystal rolling method for large-size 45 steel bar |
| CN109909295B (en) * | 2019-02-28 | 2020-06-02 | 西安建筑科技大学 | Superfine crystal rolling method for large-size aluminum alloy bar |
| CN109772890B (en) * | 2019-02-28 | 2020-01-31 | 西北工业大学 | Superfine crystal rolling method for large-size high-temperature alloy bars |
| CN109909296B (en) * | 2019-02-28 | 2020-04-07 | 西安建筑科技大学 | Reverse-cone spiral roller superfine crystal rolling method for large-size titanium alloy bar |
| CN110076198B (en) * | 2019-04-30 | 2020-02-28 | 北京科技大学 | Two-roller skew rolling forming device and method for round bar |
| CN111441020B (en) * | 2020-04-30 | 2022-05-10 | 西安建筑科技大学 | Method for preparing TC4 titanium alloy sputtering target material at low cost |
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| CN104971940A (en) * | 2014-04-14 | 2015-10-14 | 西安中泰新材料科技有限公司 | Screw rolling method and screw rolling device for titanium rod |
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| DE102012007379B4 (en) * | 2012-04-12 | 2016-12-29 | Zhozef Rotenberg | Process for the cross rolling of cylindrical products |
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| JPS53131947A (en) * | 1977-03-14 | 1978-11-17 | Puroizubodosutobennoe Obiedein | Roll receiving stand for spiral rolling of rotational body |
| CN1429279A (en) * | 2000-05-19 | 2003-07-09 | 达尔米内公司 | Martensitic stainless steel and seamless steel pipes produced with it |
| CN104971940A (en) * | 2014-04-14 | 2015-10-14 | 西安中泰新材料科技有限公司 | Screw rolling method and screw rolling device for titanium rod |
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