Machining method for improving surface and internal structure properties of titanium and titanium alloy bars

Abstract

The invention discloses a processing method for improving the surface and internal structure performance of titanium and titanium alloy bars, which comprises the steps of smelting, reducing processing and rolling, and comprises the following steps: directly performing radial forging on a smelted cast ingot along the circumferential direction, and further performing multi-stage deformation on the cast ingot on the basis of reducing the deformation quantity of the cast ingot, so as to improve the surface and internal structure performance of the titanium and titanium alloy bars. The forging and pressing state with large deformation is formed on the whole, that is, the large deformation of the cast ingot is achieved within the preset forging and pressing period (each stage of forging and pressing has small deformation, and excessive damage to the internal structure (crystal grains) of the cast ingot caused by the large deformation at a time is avoided). In later application, the bar machined through the method has high surface precision, material waste caused by remachining of the surface can be effectively reduced, after the internal structure performance is improved, on the basis of guaranteeing the mechanical performance of the thin bar, the outer diameter of the thin bar is further reduced, material solving and using light weight are achieved, and the manufacturing cost is reduced. For example, the method is applied to the fields of in-vivo implantation and aerospace.

Description

Technical Field

[0001] The invention relates to the technical field of titanium and titanium alloy bar processing, and in particular to a processing method for improving the surface and internal structure performance of titanium and titanium alloy bars. Background Art

[0002] As a high-performance metal material, titanium and titanium alloys have been widely used in aerospace, medical equipment, chemical equipment, automobile manufacturing, sports and other fields due to their unique physical and chemical properties, such as low density, high specific strength, high temperature resistance and corrosion resistance. For example, high strength and low density enable titanium and titanium alloy bars to maintain sufficient structural strength while requiring lightweight materials; good corrosion resistance is used in chemical industry, marine engineering and other fields; good biocompatibility is widely used in the medical field, especially in dental and orthopedic implants; excellent weldability and machinability can be easily processed into parts of various shapes and sizes.

[0003] The processing technology and product structure of titanium and titanium alloys are similar to those of other metals. They can be made into plates, bars, pipes and other structural forms. Among them, bars are the most widely used structural form in processing and later applications. The currently processed titanium and titanium alloy bars (outer diameter less than 10mm) are as follows: Fig. 20 As shown in the bar on the left, its visible surface quality needs to be further improved. In the subsequent processing of this quality bar into filamentary material, the surface of the bar needs to be further processed, such as removing the oxide scale and surface defects (such as pits and cracks), which will cause material waste; and the internal structure such as Fig.21 As shown in the rod on the left, the lack of internal quality can be clearly observed. Therefore, in later applications, if its mechanical strength is to be guaranteed, the outer diameter of the rod will be larger. For example, when applied to the aerospace field, lightweighting cannot be effectively achieved. With the continuous advancement of science and technology and the continuous improvement of people's requirements for material performance, this application is intended to improve the surface and internal structure properties of titanium and titanium alloy rods. Summary of the invention

[0004] In response to the above-mentioned problems, the present invention aims to provide a processing method for improving the surface and internal structure properties of titanium and titanium alloy rods. Compared with the current processing method of squaring the ingots, the surface and internal structure quality of the thin rods can be significantly improved, thereby reducing material waste and achieving lightweight during further processing and use in the later stage.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A processing method for improving the surface and internal structure properties of titanium and titanium alloy bars, comprising the following steps:

[0006] S1. Melting

[0007] Melting the raw material into an ingot having a first outer diameter and a first length through a melting furnace;

[0008] S2, diameter reduction processing

[0009] Reducing the ingot in a circumferential direction into a rod, wherein the rod has a second outer diameter and a second length, wherein the second outer diameter is smaller than the first outer diameter, and the second length is larger than the first length;

[0010] S3, rolling

[0011] The bar is rolled into a bar of desired outer diameter in no less than one step.

[0012] Preferably, the deformation amount of the second outer diameter compared to the first outer diameter is 73-75%.

[0013] Preferably, the diameter reducing process in step S2 includes a radial forging machine having a diameter matching the first outer diameter, the radial forging machine having radial forging hammers arranged circumferentially and reciprocating radially synchronously, each of the radial forging hammers reducing the radial forging deformation of the ingot.

[0014] Preferably, the radial forging hammer is provided with a radial forging structure for increasing the deformation amount of the ingot in multiple steps.

[0015] Preferably, the radial forging structure is a multi-step structure in which the radial forging hammer and the ingot are arranged adjacent to each other along the radial forging axis.

[0016] Preferably, the multi-step structure has a plurality of radial forging surfaces with increasing radial heights.

[0017] The beneficial effects of the present invention are as follows: the present invention subjects the smelted ingot to direct radial forging along the circumferential direction, and further to multi-stage deformation, thereby reducing the deformation of the ingot and forming a forging state with a large deformation as a whole, that is, achieving a large deformation of the ingot within a predetermined forging cycle (each stage of forging has a small deformation, thereby avoiding excessive damage to the internal structure (grains) of the ingot caused by a large deformation at one time).

[0018] The thin rods obtained by the processing method disclosed in the present invention can improve the surface and internal structure quality of the thin rods compared to the current process of squaring ingots through forging, so as to facilitate the subsequent further processing and use of the thin rods (for example, the rods processed in this application have high surface accuracy, which can effectively reduce the waste of materials caused by re-processing of the surface during subsequent further processing, and after improving the internal structure performance, the outer diameter of the thin rods can be further reduced on the basis of ensuring the mechanical properties of the thin rods, so as to achieve material resolution and lightweight use, such as application in in vivo implants and aerospace fields). BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a diagram showing the current forging of an ingot by a forging hammer.

[0020] Figure 2 for Figure 1 Illustration of a square ingot after forging.

[0021] Figure 3 The figure shows the current process of forging an ingot into a square ingot by a forging hammer.

[0022] Figure 4 The diagram shows that the square ingot formed by forging is further rolled through a rolling roll group.

[0023] Figure 5 for Figure 4 Top view of the structure.

[0024] Figure 6 It is a diagrammatic representation of the forging and reducing diameter processing structure of the present invention.

[0025] Figure 7 This is a diagram illustrating the diameter reduction process of the ingot in Example 1 of the present invention.

[0026] Figure 8 This is a diagram illustrating the diameter reduction process of the ingot in Example 2 of the present invention.

[0027] Fig. 9 Schematic diagram of the structure of a 3-diameter forging hammer according to an embodiment of the present invention.

[0028] Fig.10 This is a diagram illustrating the diameter reduction process of the ingot in Example 3 of the present invention.

[0029] Fig.11 This is an example of the ingot deformation during the diameter reduction process according to Example 1 of the present invention.

[0030] Fig.12 This is an example of the ingot deformation during the diameter reduction process according to Example 2 of the present invention.

[0031] Fig.13 This is an example of the ingot deformation during the diameter reduction process according to Example 3 of the present invention.

[0032] Fig.14 This is a diagram of the internal forces of the ingot during the process of forging the ingot into a square ingot.

[0033] Fig.15 It is a schematic diagram of the internal forces of the ingot during the diameter reducing forging process of the present invention.

[0034] Fig.16 This is a diagram showing the current operation of forging an ingot into a square ingot.

[0035] Fig.17 for Fig.16Illustration of a square ingot formed by forging.

[0036] Fig.18 It is a diagram showing the operation of forging an ingot into a bar according to the present invention.

[0037] Fig.19 For the present invention Fig.18 Illustration of a forged bar.

[0038] Fig. 20 This is a diagram comparing the surface quality of the thin rods subsequently processed by the present invention and the thin rods currently processed (the left side is the thin rods currently processed, and the right side is the thin rods processed by the present application).

[0039] Fig.21 This is a comparative diagram of the internal structures of the thin rod to be subsequently processed in this application of the present invention and the thin rod currently being processed (the left side is the thin rod currently being processed, and the right side is the thin rod processed in this application).

[0040] Fig. 22 This is a performance test report for bars prepared by current conventional processing methods.

[0041] Fig.23 This is a performance test report of the rod prepared by the processing method of the present invention.

[0042] In the figure: 11-ingot; 12-rod; 13-square ingot; 2-forging hammer head; 3-rolling roller set; 4-diameter forging hammer; 41-diameter forging surface; 4a-first diameter forging surface; 4b-second diameter forging surface; t1-first forging step; t2-second forging step surface; t3-third forging step surface. DETAILED DESCRIPTION

[0043] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0044] First, the current forming process of titanium and titanium alloy bars 12 is described: Figure 1-5 As shown, the smelted ingot 11 is forged by a forging machine, and the deformation process of the ingot 11 is as shown in FIG. Figure 3 As shown, the forging hammer 2 symmetrically forges the upper and lower sides of the ingot 11, so that the circular ingot 11 (outer diameter of about 450-500mm) is gradually formed into a square ingot 1311 with a smaller side length (side length of about 130-180mm), which is commonly known as square opening. Figure 4-5The rolling roller set 3 shown in the figure (refer to the patent document with publication number CN217616813U) can form a titanium or titanium alloy bar 12 with an outer diameter less than 10 mm after multiple rolling. This forming process is currently widely used to form titanium or titanium alloy thin bars 12. The surface and internal structure visible to the naked eye after forming are as follows Figure 20-21 Shown in the left side bar 12.

[0045] As for the visible surface and internal structure quality of the titanium and titanium alloy rods 12 currently formed by the above process, this application intends to further improve the surface and internal structure of the titanium and titanium alloy rods 12 currently formed. The technical solution adopted is a processing method for improving the surface and internal structure performance of the titanium and titanium alloy rods 12. Figures 1 to 23 As shown, the following steps are included:

[0046] S1. Melting

[0047] The raw material (such as titanium sponge) is melted into an ingot 11 having a first outer diameter and a first length by a melting furnace (preferably a vacuum melting furnace or the like);

[0048] S2, diameter reduction processing

[0049] The ingot 11 is reduced in diameter along the circumferential direction to form a rod having a second outer diameter and a second length, wherein the second outer diameter is smaller than the first outer diameter and the second length is larger than the first length; the deformation of the second outer diameter compared to the first outer diameter is 73-75%.

[0050] S3, rolling

[0051] The bar material is rolled into a bar material 12 with a desired outer diameter in no less than one rolling operation.

[0052] Since the ingot 11 is forged at a high temperature (easy to plastically deform), and the ingot 11 is a metal, the forging deformation cycle is relatively long. During the relatively long forging cycle, the temperature of the ingot 11 body will be lost (temperature drop), and the forging time is too long, so that the ideal deformation amount cannot be achieved in the later stage of forging. Therefore, in order to solve this problem, in step S2, the diameter reduction processing includes a diameter forging machine that matches the first outer diameter, and the diameter forging machine has a diameter forging hammer 4 that is arranged along the circumferential direction and moves synchronously radially. Each of the diameter forging hammers 4 reduces the diameter forging deformation amount of the ingot 11. Since the diameter forging hammer 4 has a relatively small length along the axial direction of the ingot 11, the complete axial forging is completed in a step-by-step forging manner along the axial direction of the ingot 11. If the hammer head strikes too many times in the radial direction each time, so that the ingot 11 has a large deformation amount, the forging cycle along the axial direction is further extended, which is not conducive to the ingot 11 to complete the forging operation at the effective temperature. Therefore, after reducing the radial forging deformation, the radial forging hammer 4 can reduce the time spent on each radial forging, thereby shortening the cycle of complete axial forging, thereby achieving the overall forging operation of the ingot 11 within the effective forging temperature range.

[0053] Furthermore, the radial forging hammer 4 is provided with a radial forging structure that increases the deformation of the ingot 11 in multiple steps, and the radial forging structure is a multi-step structure that sets the radial forging hammer 4 and the ingot 11 in contact with each other along the radial forging axis. And further, the multi-step structure has multiple radial forging surfaces with increasing radial heights. Through multi-stage forging within a predetermined forging cycle, each stage in the multi-stage forging can reduce the deformation of the ingot 11, and the whole constitutes a forging state with a large deformation, that is, a large deformation of the ingot 11 is achieved within a predetermined forging cycle (each stage of forging has a small deformation, avoiding excessive damage to the internal structure (grains) of the ingot 11 caused by a large deformation at one time).

[0054] Example 1

[0055] S1. Melting

[0056] The raw material (such as titanium sponge) is melted into an ingot 11 having a first outer diameter and a first length by a melting furnace (preferably a vacuum melting furnace or the like). Usually, the first outer diameter (molding outer diameter) of the ingot 11 is determined by the inner diameter of the melting furnace, and the first length is determined by the height of the inner cavity of the melting furnace and the capacity of the added raw material. This application is described with the size of the ingot 11 having an outer diameter of 480 mm.

[0057] S2, diameter reduction processing

[0058] The ingot 11 is reduced in diameter along the circumferential direction to form a rod having a second outer diameter and a second length, wherein the second outer diameter is smaller than the first outer diameter and the second length is larger than the first length; the deformation amount of the second outer diameter compared with the first outer diameter is 73-75%, that is, the outer diameter of the rod after the reducing process is approximately 130-180 mm.

[0059] In the specific process of reducing the diameter, an axial diameter forging machine is used, such as Figure 6 As shown, the radial forging machine preferably has a plurality of radial forging hammers 4 distributed axially. Figure 7 As shown, the surface of the ingot 11 is repeatedly hammered back and forth in the radial direction with the axial width of the radial forging hammer 4 until the outer diameter of the hammered part reaches the outer diameter (130-180 mm) of the final desired bar 12. The ingot 11 is forged in this manner along the axial direction until the ingot 11 is integrally formed into an intermediate bar 12 blank of 130-180 mm that can be subjected to multi-roll rolling.

[0060] S3, rolling

[0061] The bar material is rolled into the required outer diameter bar material 12 at least once. That is, the multi-roll rolling mill with the publication number CN217616813U is used to roll the intermediate bar material 12 billet reduced to 130-180 mm for multiple times to form the titanium and titanium alloy thin bar material 12 with an outer diameter less than 10 mm.

[0062] Example 2

[0063] The embodiment 2 is the same as the embodiment 1 in step S1 of smelting and step S3 of rolling, except for the diameter reduction process in step S2. The specific diameter reduction process is as follows: Figure 8 As shown, the radial forging hammer 4 forges the ingot 11 once with its axial width, and completes the forging along the axial surface of the ingot 11 with this single forging operation, thereby achieving a primary diameter reduction of the ingot 11; and once again, a single continuous axial forging is performed on the end of the ingot 11 to achieve a secondary diameter reduction of the entire surface of the ingot 11. After multiple diameter reductions in this diameter reduction method, the ingot 11 can be forged into a rolled bar 12 of 130 to 180 mm.

[0064] Example 3

[0065] The difference between the embodiment 3 and the embodiments 1-2 is also the diameter reduction processing in step S2. The structure of the diameter forging hammer 4 used in the embodiment 3 is as follows: Fig. 9 As shown, the radial forging hammer 4 is provided with a radial forging structure for increasing the deformation amount of the ingot 11 in multiple steps, such as Fig. 9As shown, the radial forging structure is a multi-step structure in which the radial forging hammer 4 and the ingot 11 are arranged in contact with each other along the radial forging axis. Furthermore, the multi-step structure has a plurality of radial forging surfaces 41 with increasing radial heights. In this embodiment 3, the radial forging hammer 4 has a first radial forging surface 4a and a second radial forging surface 4b, and the first radial forging surface 4a and the second radial forging surface 4b have a radial height difference. The diameter reduction forging process is as follows Fig.10 As shown, the ingot 11 is first driven axially to move so that the peripheral surface of the ingot 11 near the end is radially corresponding to the second radial forging surface 4b, and then the radial forging hammer 4 moves toward the surface of the ingot 11, and the second radial forging surface 4b is brought into contact with the surface of the ingot 11 by impact, and the forging is formed. Fig.10 The first forging step t1 shown in FIG. 1 (the ingot 11 rotates circumferentially during the forging process to complete the radial forging of the entire circumference. Similarly, in Example 1-2, the ingot 11 moves axially and rotates circumferentially during the diameter reduction forging); then the ingot 11 moves axially so that the first radial forging surface 4a corresponds to the first forging step t1, and the second radial forging surface 4b corresponds to the circumferential surface of the unforged ingot 11, and the forging is continued, thereby forming Fig.10 As shown in the second forging step t2 surface and the third forging step t3 surface, the original first forging step t1 surface is formed into the second forging step t2 surface by forging the first diameter forging surface 4a, and the surface of the ingot 11 is again formed into the third forging step t3 surface. The second forging step t2 surface and the third forging step t3 surface have a two-stage forging forming structure, which forms a larger radial deformation as a whole. The two-stage forging process reduces the forging deformation of the adjacent forging parts of the ingot 11 in the axial direction, avoiding the problem that the deformation of the adjacent forging parts of the ingot 11 is too large due to a large single forging forming, thereby affecting the internal organization (grain) structure. On the basis of ensuring a larger overall deformation, the ingot 11 can reach the final bar 12 size of 130-180mm in a shorter time to ensure that the diameter reduction forging operation is completed before a large range of temperature drop.

[0066] Comparison of forging deformation of Examples 1-3 Figure 11-13 As shown, Fig.11 The deformation of Example 1 shown in the figure is obviously larger than that of Example 2-3, as shown by the radial difference d1 between the ingot 11a and b, which leads to the decrease of its internal organization (grain) structure due to the large deformation compared with Example 2-3; while Example 2-3 has the same overall deformation, the deformation of Example 2 is one-time forming ( Fig.12 As shown), that is, the radial deformation d2 of the ingot 11a and b is formed in one step; while the overall deformation of the ingot 11 in Example 3 is composed of d31 and d32 ( Fig.13As shown), there is a smaller deformation between d31 and d32, that is, there is a smaller deformation between parts a, b, and c of the ingot 11. Therefore, in Example 3, while ensuring the overall deformation (d31+d32), the deformation is graded, and the deformation between adjacent deformation levels is significantly smaller than the deformation d2 of Example 2. Therefore, Example 3 reduces the influence of larger deformation on the internal structure of the ingot 11 while ensuring a large overall deformation. That is, Example 3 ensures that the forging operation is completed within the effective temperature range, while also avoiding the influence of excessive deformation on the internal structure of the ingot 11.

[0067] The forging deformation of Examples 1-3 of the present application is compared with the current rapid forging forming method. Fig.14 As shown in the figure, the current square cutting method causes the ingot 11 to form a deformation structure with compression up and down and expansion left and right, which makes the internal grain displacement direction inconsistent, thus leading to the problem of uneven internal structure of the final formed rod 12. The internal structure visible to the naked eye is as follows Figure 20-21 The forging of Examples 1-3 is shown in FIG. Fig.15 As shown, the grains inside the ingot 11 move toward the middle position along the circumferential direction as a whole, which has a moving consistency compared to the current square opening method, thereby improving the uniformity of the internal structure of the rod 12, such as Figure 20-21 As shown in the thin rod on the right side of the figure. Through the implementation of the above embodiments 1-3, although the forging method of embodiment 3 is better than that of embodiment 2, and the forging method of embodiment 2 is better than that of embodiment 1, the consistency and uniformity of the internal structure of the rod 12 can be significantly improved as a whole compared with the current square opening method.

[0068] The principle of the present invention is: the processing method disclosed in the present invention processes the smelted ingot 11 by direct radial forging along the circumferential direction, and further preferably by multi-stage deformation. The obtained thin rod 12 can improve the surface and internal structure quality of the thin rod 12 compared to the current forging and squaring process of the ingot 11, so as to facilitate the subsequent further processing and use of the performance quality of the thin rod 12 (for example, the rod 12 processed in this application has a higher surface accuracy, and in the subsequent further processing, it can effectively reduce the waste of materials caused by re-processing of the surface, and after improving the internal structure performance, on the basis of ensuring the mechanical properties of the thin rod 12, further reduce the outer diameter of the thin rod 12, so as to achieve the material solution and lightweight use, such as application in in vivo implantation and aerospace fields).

[0069] The above shows and describes the basic principle, main features and advantages of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention claimed.

Claims

1. A processing method for improving the surface and internal structure properties of titanium and titanium alloy bars, characterized in that: The following steps are involved: S1. Melting Melting the raw material into an ingot having a first outer diameter and a first length through a melting furnace; S2, diameter reduction processing Reducing the ingot in a circumferential direction into a rod, wherein the rod has a second outer diameter and a second length, wherein the second outer diameter is smaller than the first outer diameter, and the second length is larger than the first length; S3, rolling The bar is rolled into a bar of desired outer diameter in no less than one step.

2. The processing method according to claim 1, characterized in that: The deformation amount of the second outer diameter compared with the first outer diameter is 73-75%.

3. The processing method according to claim 2, characterized in that: The diameter reduction process in step S2 includes a radial forging machine having a diameter matching the first outer diameter, wherein the radial forging machine has radial forging hammers which are arranged circumferentially and move radially and reciprocatingly synchronously, and each of the radial forging hammers reduces the radial forging deformation of the ingot.

4. The processing method according to claim 3, characterized in that: The radial forging hammer is provided with a radial forging structure for increasing the deformation amount of the ingot in multiple steps.

5. The processing method according to claim 4, characterized in that: The radial forging structure is a multi-step structure in which the radial forging hammer and the ingot are arranged adjacent to each other along the radial forging axis.

6. The processing method according to claim 5, characterized in that: The multi-step structure has a plurality of radial forging surfaces with increasing radial heights.

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