Thermal torsion protection die for titanium alloy ribbed tube

Abstract

The utility model relates to a thermal torsion protection die for a titanium alloy ribbed tube. The thermal torsion protection die comprises a hard aluminum alloy die body, the mold body is a hollow cylinder body; four axial notch grooves are uniformly formed in the circumference of the inner wall of the mold body; wherein the die body is made of a hard aluminum alloy material. According to the utility model, by adjusting the thermal torsion mold, periodic defects of the rib top of the titanium alloy pipe after thermal torsion can be effectively avoided, operators are prevented from being in contact with toxic and harmful substances in the production process, the investment of saponification and phosphorization equipment is reduced, the time cost for subsequently removing MoS2 is reduced, and the thermal torsion mold has a huge input-output ratio and is suitable for batch use.

Description

Technical Field

[0001] The utility model relates to the technical field of pipe thermal torsion, in particular to a titanium alloy ribbed pipe thermal torsion protection die. Background Art

[0002] After rolling, the titanium alloy ribbed tube is a straight ribbed tube with four mutually perpendicular ribs. The outer diameter D of the half base circle ranges from Φ8 to Φ15, the rib height ranges from 0.40mm to 0.75mm, the rib width ranges from 1.0mm to 1.4mm, and the wall thickness S ranges from 1.50mm to 2.00mm. Its cross section is as follows Figure 2 As shown, its side view is Figure 3 shown.

[0003] Since titanium alloy ribbed tubes are primarily used in heat exchangers, in order to enhance heat transfer efficiency, straight ribbed tubes often need to be processed into spiral ribs with a certain tilt angle to meet the requirements. To achieve this, the straight ribs obtained by rolling are thermally twisted into spiral ribs using a twisting die.

[0004] Typically, the torsion die is made of Cr12MoV die steel with a hardness of HB590, while the hardness of TA16 titanium alloy is HB195. The die is approximately 50mm long. Within this 50mm length, the rib on one side of the titanium alloy tube experiences both longitudinal friction from the torsion die's grooves and rotational pressure from the grooves during the die's rotation. Furthermore, the angle between the groove's sidewalls and the rib's sidewalls doesn't completely match, resulting in linear contact between the rib and the torsion die's grooves, rather than surface contact. Since the hardness of the torsion die is much greater than that of the titanium alloy, the top of the rib on the titanium alloy tube is subjected to continuous and complex alternating friction during the hot torsion process. When the accumulated friction exceeds the strength of the TA16 titanium alloy, the junction between the rib top and the rib side wall will be damaged, causing the titanium alloy metal at that point to be torn off. The continuous accumulation of friction causes the rib top metal to be torn off periodically, resulting in periodic defects. The morphology of normal ribs is as follows: Figure 4 As shown in the figure, the rib top has a defective morphology as shown in the figure. Figure 5 shown.

[0005] In order to eliminate this defect after the hot twisting process, the surface of the titanium alloy ribbed tube is generally saponified and phosphated before hot twisting, and then liquid MoS2 is applied. After the liquid MoS2 is dried in the shade, hot twisting is performed. During hot twisting, the powdered MoS2 attached to the side wall of the rib actually acts as an isolation layer and reduces the friction coefficient, which can greatly reduce the occurrence of rib top defects, but it cannot be completely avoided. Because MoS2 will be heated and turned into a hard shell after passing through the electromagnetic induction coil, subsequent removal requires the titanium alloy tube to be soaked in clean water for one day and then manually cleaned. MoS2 is a toxic and harmful substance that has an adverse effect on the health of operators and is not conducive to batch use and promotion. At the same time, saponification, phosphating, and the coating and removal of MoS2 also require large equipment and labor costs.

[0006] Therefore, it is urgent to develop a solution that can effectively perform thermal twisting while preventing operators from being exposed to toxic and harmful substances during the production process. Summary of the Invention

[0007] In view of the above problems, the purpose of the present invention is to provide a titanium alloy ribbed tube thermal torsion protection die, which can not only achieve effective thermal torsion, but also prevent operators from being exposed to toxic and harmful substances during the production process.

[0008] The technical solutions adopted in this utility model are as follows:

[0009] The utility model provides a titanium alloy ribbed tube thermal torsion protection die, which comprises a hard aluminum alloy die body; the die body is a cylindrical body with a hollow interior; and the inner wall of the die body is uniformly provided with four axial grooves.

[0010] Compared with the prior art, the present invention has the following beneficial effects:

[0011] This new method protects the metal integrity at the transition between the rib top and the sidewall during the hot twisting process for all 9 to 15 mm TA16 titanium alloy ribbed tubes. This method eliminates the need for pre-treatment processes such as phosphating, saponification, and coating the tubes with a MoS2 solution before air drying in preparation for hot twisting, as well as the manual removal of the hard MoS2 shell after hot twisting. This significantly reduces investment costs and avoids the need for manual removal of toxic MoS2. By replacing the hot twisting mold material, additional equipment investment is eliminated, production steps are reduced, time and costs are saved, and production organization is highly beneficial, effectively ensuring smooth production. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of the application effect of the utility model;

[0013] Figure 2 It is a cross-sectional schematic diagram of an existing titanium alloy tube with straight ribs;

[0014] Figure 3 for Figure 2 Side view of

[0015] Figure 4 Schematic diagram of the cross-sectional morphology of a normal rib;

[0016] Figure 5 Schematic diagram of the morphology of the rib top defect.

[0017] Wherein, the accompanying drawings are numerals: 1-mold body; 2-titanium alloy tube with straight ribs; 3-electromagnetic induction coil. DETAILED DESCRIPTION

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] It should be noted that, in the description of the present invention, the terms "upper", "lower", "top", "bottom", "one side", "the other side", "left", "right", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not mean that the device or element must have a specific orientation, be constructed and operated in a specific orientation.

[0020] See attached Figure 1 The utility model proposes a titanium alloy ribbed tube thermal torsion protection mold, including a mold body 1; the mold body 1 is a cylindrical body with a hollow interior; four axial grooves are evenly distributed on the inner wall of the mold body 1; in the utility model, the mold body 1 is made of hard aluminum alloy (grade 2a12).

[0021] Because the hardness of the mold steel Cr12MoV is significantly greater than that of TA16 titanium alloy, the inventors considered using a material with a lower hardness than TA16. To this end, they initially selected 20# steel as the mold material, which has a hardness of HB170. The mold design dimensions remained unchanged. After mold testing, they found that the periodic defects at the top of the titanium alloy tube ribs were reduced, but not completely eliminated.

[0022] To this end, copper was reselected as the mold material, with a brass hardness of HB100. The mold design dimensions remained unchanged. After mold testing, the periodic defects on the top of the titanium alloy tube ribs were completely eliminated. However, due to the extremely low hardness of brass, mold wear was significant. A single mold could only rotate about three titanium alloy tubes before being scrapped, making the mold economically uneconomical. Furthermore, copper shavings from friction adhered to the sidewalls of the ribs, making them difficult to remove. Therefore, a new material was considered.

[0023] The material chosen was a bronze SnCu alloy. SnCu alloy has a hardness of HB120 and is often used for wear-resistant parts. The mold design dimensions remained unchanged. After successful mold testing, the periodic defects on the top of the titanium alloy tube ribs were completely eliminated. One mold can rotate approximately 30 titanium alloy tubes. However, a significant amount of Cu chips were removed by friction, making removal difficult.

[0024] For this reason, the choice of a mold body made of hard aluminum is considered again. The hardness of hard aluminum (grade 2a12) is HB150, and it is also used as the raw material for wear-resistant parts. The mold design and processing dimensions remain unchanged. Using the processed mold test, the periodic defects of the top of the titanium alloy tube rib can also be completely avoided. One mold can twist about 30 titanium alloy tubes, and the width of the wear of the groove of each ribbed tube is about 0.2mm. The manufacturing cost of a mold is about 300 yuan, and the amortized cost of twisting a titanium alloy tube is about 10 yuan, which is more economical. At the same time, for each twisted titanium alloy tube, the Al attached to the side wall of the rib is reduced by about 60% compared to the copper cutting of the bronze mold. This small amount of Al cutting attached to the twisted part can be completely removed by sandblasting on the outer surface sandblasting equipment according to the normal process, and it will not affect the dimensional accuracy of the titanium alloy tube.

[0025] During hot twisting, the ribbed titanium alloy tube 2 is placed within the die body 1, with the ribs aligned with the axial grooves. An electromagnetic induction coil 3 is positioned at the front end of the die body 1, through which the ribbed titanium alloy tube 2 passes. The electromagnetic induction coil 3 instantaneously heats the 12mm length of the ribbed titanium alloy tube 2 within the coil to a temperature of 680°C to 750°C, enabling this heated portion of the tube to deform plastically. The leading end of the ribbed titanium alloy tube 2 is clamped in a four-jaw fixture that can advance or retreat along its length. The die body 1 can rotate counterclockwise or counterclockwise at a constant angular velocity, matching the fixture's longitudinal forward speed. This rotates the ribbed titanium alloy tube 2, which is simultaneously driven forward by the fixture. The ribbed tube within the electromagnetic induction coil 3 undergoes plastic torsional deformation. Upon exiting the electromagnetic induction coil 3, the temperature of the ribbed titanium alloy tube 2 immediately drops below 600°C, preserving the torsional deformation. The resulting ribbed titanium alloy tube is twisted with a fixed pitch of either counterclockwise or counterclockwise rotation.

[0026] Matters not described in detail in this utility model are known technologies.

[0027] The embodiments described above are merely descriptions of preferred implementation methods of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present invention.

Claims

1. A titanium alloy ribbed tube thermal torsion protection die, characterized by: The invention comprises a hard aluminum alloy mold body; the mold body is a cylindrical body with a hollow interior; and the inner wall of the mold body is provided with four axial grooves evenly distributed around the circumference.

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