Forming method of precise thin-wall high-temperature alloy special-shaped seamless tube for aviation

Abstract

The invention discloses a forming method of a precise thin-wall high-temperature alloy special-shaped seamless tube for aviation, which comprises the following steps: step 1, carrying out multi-pass cold rolling on a seamless tube blank to obtain a finish-rolled round tube; wherein the perimeter C0 of the finish rolling round pipe is 1.04-1.06 times of the perimeter C < different > of the finished special-shaped pipe, and the wall thickness of the finish rolling round pipe is 0.98 times of the wall thickness of the finished special-shaped pipe; 2, degreasing, heat treatment, straightening, UT flaw detection and tip making are conducted on the finish-rolled round pipe obtained in the step 1; and (3) the round pipe obtained through treatment in the step (2) is subjected to three-pass continuous air drawing process forming, and the finished special-shaped pipe is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of seamless pipe processing, and in particular to a forming method of a precision thin-wall high-temperature alloy special-shaped seamless pipe for aviation. Background Art

[0002] A special-shaped seamless tube made of high-temperature alloy for aviation is mainly used for ventilation and cooling of aircraft combustion chambers. The product has thin walls (wall thickness ≤ 0.7mm), is flat (ratio of major axis to minor axis ≥ 2), has a small R angle (≤ 3mm), and has high precision (wall thickness tolerance is ±0.04mm, major axis tolerance is ±0.08mm). Similar imported materials are special-shaped welded tubes of high-temperature alloy (about 10 million yuan / ton), which cannot meet the research and development needs of new aircraft. The difficulty in its production lies in the forming technology. Domestically, methods such as "rolling forming technology", "extrusion forming technology", and "pull-out forming technology" have been used for development, but there have been no reports of successful trial production. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to provide a method for forming precision thin-walled high-temperature alloy special-shaped seamless tubes for aviation, so as to solve the problem that the prior art cannot successfully produce precision thin-walled high-temperature alloy special-shaped seamless tubes for aviation in China.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A method for forming a precision thin-walled high-temperature alloy special-shaped seamless tube for aviation, comprising the following steps:

[0006] Step 1: cold rolling the seamless tube billet for multiple passes to obtain a final rolled round tube; wherein the circumference C0 of the final rolled round tube is the circumference C0 of the finished special-shaped tube. 异 The wall thickness of the final rolled round tube is 1.04 to 1.06 times of that of the finished special-shaped tube; and the wall thickness of the final rolled round tube is 0.98 times of that of the finished special-shaped tube;

[0007] Step 2: Degreasing, heat treatment, straightening, UT flaw detection, and sharpening the final rolled round tube obtained in step 1;

[0008] Step 3: The round tube obtained in step 2 is subjected to three-pass continuous air drawing process to obtain a finished special-shaped tube;

[0009] In step 3, the continuous air drawing process is as follows: the round tube is subjected to the first air drawing process to obtain the elliptical A tube; the elliptical A tube is subjected to the second air drawing process to obtain the elliptical B tube; the elliptical B tube is subjected to the third air drawing process to obtain the finished special-shaped tube.

[0010] Preferably, in step 1, the wall thickness deviation of the final rolled round tube is controlled within ±0.03 mm.

[0011] Preferably, in step 2, the degreasing is the following steps:

[0012] The method comprises the following steps: pickling with acid for 3 minutes, then boiling with alkali solution at 85-95°C for 60 minutes, washing with clean water, and finally flushing with steam; wherein, calculated by mass percentage, the HF content in the acid is 0.75wt%, and the HNO3 content is 4wt%; the pH value of the alkali solution is 9-11; the alkali solution contains a degreasing agent, which is KR-L400, and the mass ratio of the degreasing agent to water in the alkali solution is 1:20.

[0013] Preferably, in step 2, the heat treatment is: heating the degreased final rolled round tube to 1135° C. in a hydrogen protective gas atmosphere, maintaining the temperature for 8 minutes, and then rapidly cooling the tube.

[0014] Preferably, in step 2, the UT flaw detection refers to flaw detection performed in accordance with the L2 level regulations in GB5777-2008.

[0015] Preferably, in step 2, the tipping is performed by welding to ensure stable clamping and smooth air drawing.

[0016] Preferably, in step 3, C0 / C A =1, C A / C B =1.02~1.03, C B / C 异 =1.02~1.03, C0 is the circumference of the final rolled tube, C A is the circumference of the elliptical tube A, C B is the circumference of the elliptical tube B, C 异 It is the circumference of the finished special-shaped tube.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention improves the forming process. In order to control the wall thickness of the final rolled round tube, the present invention first adjusts the outer diameter and wall thickness of the final rolled round tube through multiple cold rolling, and then obtains the finished special-shaped tube through air drawing. The final rolled round tube is a plastic drawing after the air drawing of the present invention, and the longitudinal flow trend of the metal is weak. After the air drawing treatment, the wall thickness increases slightly, and the change rule is basically 0.04-0.05mm at the R corner and 0.02-0.03mm at the other parts. At the same time, the air drawing process is different from the top drawing process. The inner surface of the steel pipe does not contact the mold, and no new defects will be added to the inner wall.

[0019] 2. In the forming method of the present invention, the size of the transition steel pipe is detected to ensure the quality of the steel pipe during the processing, and the final rolled round pipe is pointed, which reduces the consumption of the main material and ensures the stable forming of the thin-walled finished special-shaped pipe.

[0020] 3. The finished special-shaped tube obtained by the molding method of the present invention has excellent quality, with a total deformation of about 15% (the deformation is the cross-sectional shrinkage rate of the steel tube), ensuring the crushing of the grains and ensuring that the grain size of the finished special-shaped tube is not less than grade 7 after solid solution. DETAILED DESCRIPTION

[0021] The present invention will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by ordinary technicians in this field based on the present invention belong to the scope of protection of the present invention.

[0022] Unless otherwise indicated in specific cases in the present invention, the numerical ranges listed herein include the upper and lower limits, and all integers and fractions within the range, and are not limited to the specific values ​​listed when defining the range.

[0023] 1. A forming method for precision thin-walled high-temperature alloy special-shaped seamless tube for aviation

[0024] Step 1: Perform multiple cold rolling on the seamless tube blank to obtain a final rolled round tube. The circumference C0 of the final rolled round tube is the circumference C0 of the finished special-shaped tube. 异 The wall thickness of the final rolled round tube is 1.04 to 1.06 times of that of the finished special-shaped tube.

[0025] Step 2: Degreasing, heat treatment, straightening, UT flaw detection, and sharpening are performed on the final rolled round tube obtained in step 1.

[0026] Step 3: The round tube obtained in step 2 is subjected to three-pass continuous air drawing process to obtain a finished special-shaped tube.

[0027] In step 3, the continuous air drawing process is as follows: the round tube is subjected to the first air drawing process to obtain the elliptical A tube; the elliptical A tube is subjected to the second air drawing process to obtain the elliptical B tube; the elliptical B tube is subjected to the third air drawing process to obtain the finished special-shaped tube.

[0028] After in-depth research on a variety of forming technologies, the present invention found that a certain aviation high-temperature alloy special-shaped seamless pipe is mainly used for ventilation and cooling of aircraft combustion chambers. The product has thin walls (wall thickness ≤ 0.7mm), flat (ratio of major and minor axes ≥ 2), small R angle (≤ 3mm), and high precision (wall thickness tolerance is ± 0.04mm, major and minor axis tolerance is ± 0.08mm). Similar imported materials are high-temperature alloy special-shaped welded pipes (about 10 million yuan / ton), which cannot meet the domestic research and development needs of new machines. The existing technology has adopted methods such as "rolling forming technology", "extrusion forming technology", and "top drawing forming technology" to prepare such seamless pipes, but none of them can successfully prepare products that meet the requirements. Therefore, the present invention conceives to improve the forming technology, first adjusting the size of the final rolled round pipe through multiple cold pressings to facilitate the smooth progress of the subsequent continuous air drawing process. Secondly, the finished rolled round tube is subjected to a series of treatments such as degreasing, heat treatment, straightening, UT flaw detection, and sharpening. On the one hand, the size and quality of the finished rolled round tube are timely controlled, and on the other hand, it also provides a guarantee for the smooth progress of the continuous air drawing process. In the present invention, the finished special-shaped tube is a finished tube with a rectangular cross-section perpendicular to the length direction of the steel tube. The rectangular cross-section has a major axis and a minor axis. The major axis is the long side of the rectangular cross-section, and the minor axis is the short side of the rectangular cross-section. According to the ratio of the major axis to the minor axis, C0 and C 异 When the ratio of the major axis to the minor axis is ≤2, C0 is C 异 When the ratio of the major axis to the minor axis is ≥2, C0 is C 异 1.04-1.05 times; the coefficient is determined based on the need for stable forming of special-shaped thin-walled tubes; if the ratio is too large, the plane part will be concave, and if the ratio is too small, the corners will not be fully filled and the shape will not meet the standard. At the same time, the wall thickness of the final rolled round tube is 0.98 times the wall thickness of the finished special-shaped tube, and the wall thickness deviation of the final rolled round tube is controlled within ±0.03mm. Because the forming process in the present invention is an empty drawing shaping process, the metal has a strong tendency to flow horizontally during the drawing process, and is in a state of increasing the wall. The basic rule is that the R corner increases the wall by 0.04-0.05mm, and the other parts increase the wall by 0.02-0.03mm.

[0029] In some embodiments of the present application, in step 1, the wall thickness deviation of the finished rolled round tube is controlled within ±0.03 mm. The inspection process of the steel tube size is as follows: a micrometer with an accuracy of 0.01 mm is used to detect the wall thickness and outer diameter of the head and tail of the steel tube.

[0030] In some embodiments of the present application, in step 2, the degreasing is the following steps:

[0031] A mixed acid solution is prepared by using HF acid with a concentration of 36wt%, HNO3 acid with a concentration of 98wt% and water. According to the mass percentage, the HF content in the acid solution is 0.75wt% and the HNO3 content is 4wt%. The acid solution is used for pickling for 3 minutes, followed by boiling with alkali solution at 85-95°C for 60 minutes, then washed with clean water, and finally rinsed with steam. The alkali solution contains a degreasing agent, which is KR-L400 (purchased from a certain enterprise in Nanjing), and the mass ratio of the degreasing agent to the water in the alkali solution is 1:20. The pH value of the alkali solution is 9-11.

[0032] In some embodiments of the present application, in step 2, the heat treatment is: heating the degreased final rolled round tube to 1135° C. in a hydrogen protective gas continuous mesh belt furnace, maintaining it for 8 minutes, and then rapidly cooling it.

[0033] In some embodiments of the present application, in step 2, the UT flaw detection refers to flaw detection according to the L2 level regulations in GB5777-2008, and qualified products after flaw detection are selected for subsequent air-drawing processing.

[0034] In some embodiments of the present application, in step 2, the tip is made by welding, the welding tip should be rolled into a rectangular flat mouth, the taper should be smooth and clean, and the welding point should be sanded and polished to ensure stable clamping and smooth pulling.

[0035] In some embodiments of the present application, in step 3, air drawing is used. Air drawing is to draw the steel tube through an external mold. The inner surface of the steel tube does not contact the mold, and no new defects will be added to the inner wall. At the same time, air drawing has a wall-leveling effect to ensure the quality of thick-walled tubes. Among them, the oval A tube obtained after the first air drawing process of the round tube is the round tube passing through the external mold to change it from a round tube to an oval tube, and the circumference is basically unchanged, so C0 / C A =1. C0 is the circumference of the final rolled tube, C A The circumference of the oval tube A is calculated according to the circumference of the cross-sectional shape of the steel tube. The oval tube A is subjected to the second air drawing process to obtain the oval tube B. The steel tube passes through the B die and becomes flatter, and the shape tends to the finished product shape. A / C B The value of is controlled at 1.02-1.03, which can avoid sharp deformation and surface collapse. The oval B tube is subjected to the third air drawing process to obtain a finished special-shaped tube. The steel tube passes through the finished mold and C B / C 异 The value is controlled at 1.02-1.03, the filling is full, the deformation is stable, the edges and corners meet the standards, and there is no collapse on the four sides, thus ensuring the quality of the finished special-shaped tube.

[0036] 2. Embodiment

[0037] Example 1

[0038] The steps for manufacturing a finished steel pipe of 33×12×0.7×4R3 and a length of 3m are as follows:

[0039] S1: Use LG-30, LD-30S and other cold rolling mills to perform multiple cold rolling on qualified seamless tubes to reduce the outer diameter and wall thickness to form final rolled round tubes. The size of the final rolled round tube is φ28×0.68, and the deviation of the specification size (outer diameter and wall thickness) is controlled within 0.03mm;

[0040] S2: The finished rolled round tube after S1 treatment is first degreased, then heat treated in a hydrogen-protected continuous furnace according to the process system "1135℃×8 minutes+fast cooling"; then straightened; and then flaw detection is carried out according to the L2 level regulations in GB5777-2008;

[0041] S3: Finally, the qualified products are sharpened and then continuously air-drawn three times to form; wherein, the process of continuous air-drawing three times is as follows:

[0042] Round tube: φ28×0.68 (outer diameter×wall thickness) → The first cold drawing is ellipse A: 34×16×0.68 (major axis×minor axis×wall thickness) → The second cold drawing is ellipse B: 35×14×0.69 (major axis×minor axis×wall thickness) → The third cold drawing is the finished rectangular tube: 33×12×0.7×4R3 (major axis×minor axis×wall thickness×R angle).

[0043] Example 2

[0044] The steps for manufacturing a finished steel pipe of 33×17.5×0.7×4R2 and a length of 1.8m are as follows:

[0045] S1: Use LG-30, LD-30S and other cold rolling mills to perform multiple cold rolling on qualified seamless tubes to reduce the outer diameter and wall thickness to form final rolled round tubes. The size of the final rolled round tube is φ32.2×0.68, and the deviation of the specification size (outer diameter and wall thickness) is controlled within 0.03mm;

[0046] S2: The finished rolled round tube after S1 treatment is first degreased, then heat treated in a hydrogen-protected continuous furnace according to the process system "1135℃×8 minutes+fast cooling"; then straightened; and then flaw detection is carried out according to the L2 level regulations in GB5777-2008;

[0047] S3: After the qualified products are sharpened, they are continuously drawn three times; the process of continuous drawing three times is as follows:

[0048] Round tube: φ32.2×0.68 (outer diameter×wall thickness) → The first cold drawing is ellipse A: 37.3×26.5×0.68 (major axis×minor axis×wall thickness) → The second cold drawing is ellipse B: 38.5×23.5×0.69 (major axis×minor axis×wall thickness) → The third cold drawing is the finished rectangular tube: 33×17.5×0.7×4R2 (major axis×minor axis×wall thickness×R angle).

[0049] Example 3

[0050] The steps for manufacturing a finished steel pipe of 22.7×11.3×0.7×4R2.5 and a length of 2m are as follows:

[0051] S1: Use LG-30, LD-30S and other cold rolling mills to perform multiple cold rolling on qualified seamless tubes to reduce the outer diameter and wall thickness into final rolled round tubes. The size of the round tube is φ21.3×0.68×2200, and the deviation of the specification size (outer diameter and wall thickness) is controlled within 0.03mm;

[0052] S2: The finished rolled round tube after S1 treatment is first degreased, then heat treated in a hydrogen-protected continuous furnace according to the process system "1135℃×8 minutes+fast cooling"; then straightened; and then flaw detection is carried out according to the L2 level regulations in GB5777-2008;

[0053] S3: After the qualified products are sharpened, they are continuously drawn three times; the process of continuous drawing three times is as follows:

[0054] Round tube: φ21.3×0.68 (outer diameter×wall thickness) → The first cold drawing is oval A: 24×17×0.68 (major axis×minor axis×wall thickness) → The second cold drawing is oval B: 25.7×14.5×0.69 (major axis×minor axis×wall thickness) → The third cold drawing is the finished rectangular tube: 33×11.3×0.7×4R2.5 (major axis×minor axis×wall thickness×R angle).

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the technical solution. Those skilled in the art should understand that those modifications or equivalent substitutions of the technical solution of the present invention that do not depart from the purpose and scope of the technical solution should be included in the scope of the claims of the present invention.

Claims

1. A method for forming a precision thin-walled high-temperature alloy special-shaped seamless tube for aviation, characterized in that: The steps include: Step 1: cold rolling the seamless tube billet for multiple passes to obtain a final rolled round tube; wherein the circumference C0 of the final rolled round tube is the circumference C0 of the finished special-shaped tube. 异 The wall thickness of the final rolled round tube is 1.04 to 1.06 times of that of the finished special-shaped tube; and the wall thickness of the final rolled round tube is 0.98 times of that of the finished special-shaped tube; Step 2: Degreasing, heat treatment, straightening, UT flaw detection, and sharpening the final rolled round tube obtained in step 1; Step 3: The round tube obtained in step 2 is subjected to three-pass continuous air drawing process to obtain a finished special-shaped tube; In step 3, the continuous air drawing process is as follows: the round tube is air drawn for the first time to obtain an elliptical A tube; the elliptical A tube is air drawn for the second time to obtain an elliptical B tube; and the elliptical B tube is air drawn for the third time to obtain a finished special-shaped tube.

2. The molding method according to claim 1, characterized in that: In step 1, the wall thickness deviation of the final rolled round tube is controlled within ±0.03 mm.

3. The molding method according to claim 1, characterized in that: In step 2, the degreasing is as follows: The method comprises the following steps: pickling with acid for 3 minutes, then boiling with alkali solution at 85-95°C for 60 minutes, washing with clean water, and finally flushing with steam; wherein, calculated by mass percentage, the HF content in the acid is 0.75wt%, and the HNO3 content is 4wt%; the pH value of the alkali solution is 9-11; the alkali solution contains a degreasing agent, which is KR-L400, and the mass ratio of the degreasing agent to water in the alkali solution is 1:

20.

4. The molding method according to claim 1, characterized in that: In step 2, the heat treatment is as follows: heating the degreased final rolled round tube to 1135° C. in a hydrogen protective gas atmosphere, maintaining the temperature for 8 minutes, and then rapidly cooling the tube.

5. The molding method according to claim 1, characterized in that: In step 2, the UT flaw detection refers to flaw detection according to the L2 level regulations in GB5777-2008, and the qualified products are screened for subsequent processing.

6. The molding method according to claim 1, characterized in that: In step 2, the tipping is performed by welding to ensure stable clamping and smooth air pulling.

7. The molding method according to claim 1, characterized in that: In step 3, C0 / C A =1, C A / C B =1.02~1.03, C B / C 异 =1.02~1.03, C0 is the circumference of the final rolled tube, C A is the circumference of the elliptical tube A, C B is the circumference of the elliptical tube B, C 异 It is the circumference of the finished special-shaped tube.