A method for producing a square aluminum alloy seamless pipe with unequal wall thickness

Abstract

The present application relates to the technical field of industrial aluminum profile production, and particularly relates to a production method of aluminum alloy square seamless pipe with unequal wall thickness. The steps include: (1) mold design and production; (2) heating treatment; (3) extrusion treatment; (4) quenching treatment; (5) seamless pipe straightening; and (6) post-treatment. The extrusion mold of the present application adopts eccentric design of extrusion needle head, the center of gravity of the cross section of the seamless pipe coincides with the axis of the mold outer frame, the flow rates of discharges in all directions are relatively balanced, and measures such as installation of special guide, centering and horizontal detection, and pipe blank wall thickness monitoring are taken in the production process, so that the quality of the seamless pipe product is improved and the rate of defective products is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial aluminum profile production, in particular to a production method of aluminum alloy square seamless pipe with unequal wall thickness. BACKGROUND

[0002] The square aluminum alloy seamless pipe has the advantages of high specific strength, low density, small bending stress and excellent fatigue resistance, and has broad prospects in the field of rail transit, and is a key structural material for high-speed trains, urban rail transit and other products. The square aluminum alloy seamless pipe with unequal wall thickness is a square aluminum alloy seamless pipe with four wall thicknesses that are not completely the same, and some types have protruding cantilevers outside the pipe wall. With the development of rail transit products towards high speed, super high speed, low noise and low cost, it is inevitable to study structural products suitable for complex operating environments, and the demand for square aluminum alloy seamless pipes with unequal wall thickness is also gradually increasing.

[0003] The production method of the square aluminum alloy seamless pipe is extrusion, the cast blank is placed in the extrusion cylinder, and the cast blank is extruded through the corresponding shape of the extrusion die under the action of the extrusion rod. The extrusion die includes a die outer frame and an extrusion needle, the die outer frame is installed on the extrusion cylinder, and the outer contour of the extrusion needle corresponds to the rectangular inner wall of the seamless pipe. According to the different force direction of the extrusion rod, it is divided into forward extrusion and reverse extrusion, and the square aluminum alloy seamless pipe with unequal wall thickness is mainly produced by the method of forward extrusion.

[0004] At present, in the production of square aluminum alloy seamless pipes with unequal wall thickness, the design of the extrusion die is the same as the design principle of the conventional square aluminum alloy seamless pipe with equal wall thickness, and the center of the extrusion needle is coincided with the axis of the die outer frame. Since the wall thickness of the seamless pipe is not equal, using the existing die design for production will easily cause the problem of different flow rates in each direction during extrusion, which further leads to the problem of easy distortion of the produced seamless pipe blank, high scrap rate, and difficulty in producing square aluminum alloy seamless pipes with unequal wall thickness that meet the use conditions. In addition, the relative position of the die outer frame and the extrusion needle is extremely high when extruding the square aluminum alloy seamless pipe with unequal wall thickness, and the wall thickness deviation problem easily occurs during continuous production, resulting in product scrap. SUMMARY

[0005] In view of the technical problems in the prior art that the extrusion production of the unequal wall thickness square aluminum alloy seamless pipe is prone to different flow rates in each direction, which causes the seamless pipe blank to be prone to distortion; and the continuous production is prone to wall thickness deviation, which causes the product to be scrapped and the high rate of defective products, the present application provides a production method of an unequal wall thickness square aluminum alloy seamless pipe, an extrusion die adopts eccentric design of an extrusion needle, the center of gravity of the cross section of the seamless pipe coincides with the axis of the die outer frame, the flow rates in each direction are relatively balanced, and special guide installation, centering and horizontal detection, pipe blank wall thickness monitoring and other measures are taken during the production process, so as to improve the quality of the seamless pipe product and reduce the rate of defective products.

[0006] The technical scheme of the present application is as follows:

[0007] A production method of an unequal wall thickness square aluminum alloy seamless pipe, steps comprising:

[0008] (1) die design and manufacturing, the extrusion die is designed according to the needs, the extrusion die includes an extrusion needle and a die outer frame, the die outer frame is installed on the extrusion cylinder; the eccentric design of the extrusion needle is adopted, the center of gravity of the cross section of the seamless pipe coincides with the axis of the die outer frame, and the cross section of the seamless pipe is a hollow shape surrounded by the cross section of the die outer frame and the extrusion needle at the outlet of the pipe blank;

[0009] (2) heating treatment, the cast blank and the extrusion die are heated respectively, and the cast blank is a solid aluminum alloy rod or a hollow aluminum alloy pipe;

[0010] (3) extrusion treatment, the heated cast blank is placed in the extrusion cylinder, and the cast blank is extruded to one end of the extrusion die by using an extrusion rod, so that the cast blank is extruded into a specified shape under the action of the die outer frame and the extrusion needle to obtain a pipe blank;

[0011] (4) quenching treatment, the pipe blank is subjected to quenching treatment;

[0012] (5) seamless pipe straightening, the quenched pipe blank is straightened;

[0013] (6) post-treatment, the straightened pipe blank is sequentially subjected to sawing and aging treatment to obtain a seamless pipe product.

[0014] Further, in step (1), when calculating the position of the center of gravity of the cross section of the seamless pipe, a plane rectangular coordinate system is first established, the cross section of the seamless pipe is divided into a plurality of simple geometric figures (such as rectangles), the horizontal coordinate of the center of gravity of the cross section of the seamless pipe is (the sum of the products of the areas of the simple geometric figures and their horizontal coordinates of the center of gravity / the sum of the areas of the simple geometric figures), and the vertical coordinate of the center of gravity of the cross section of the seamless pipe is (the sum of the products of the areas of the simple geometric figures and their vertical coordinates of the center of gravity / the sum of the areas of the simple geometric figures).

[0015] Further, in step (1), the die outer frame and the extrusion cylinder are each provided with a centering limiting ring.

[0016] Further, the heating temperature of the casting blank in step (2) is 540-600 DEG C, and the heating temperature of the extrusion die is 450-550 DEG C.

[0017] Further, in step (3), the centering and horizontal detection are performed before the extrusion, and the specific operation includes centering the extrusion cylinder, the extrusion rod and the die, and the centering deviation is less than or equal to 5 mm; the direction of the needle head is matched with the die; the levelness of the needle head is detected by the level meter; and the extrusion is performed after the centering and the detection are qualified.

[0018] Further, in the seamless extrusion process of the casting blank in step (3), a special guide is installed at the outlet of the pipe blank, the special guide is a long straight groove, and the inner wall is equal to the cross-sectional width of the seamless pipe.

[0019] Further, the extrusion speed in step (3) is 0.5-2.0 mm / s.

[0020] Further, the wall thickness of the pipe blank is detected after the extrusion in step (3) is completed, the extrusion is stopped when the wall thickness deviation occurs, and the extrusion is continued after the position of the extrusion needle head is adjusted according to the wall thickness deviation.

[0021] Further, the cross-section circumscribed circle diameter of the seamless pipe product is less than or equal to 400 mm, the length is less than or equal to 20 m, and the wall thickness is 5-30 mm.

[0022] Further, the wall thickness deviation of the seamless pipe product is less than or equal to 10%*h, the perpendicularity is less than or equal to 1 DEG, the plane gap is less than or equal to 4%*w, the straightness is less than or equal to 1 mm / m, and the full-length straightness is less than or equal to 2 mm / L; wherein h is the design wall thickness of the seamless pipe, w is the width of the seamless pipe product, and L is the full length of the seamless pipe product.

[0023] The beneficial effects of the present application are as follows:

[0024] 1. The extrusion die of the present application adopts the eccentric design of the extrusion needle head, the center of gravity of the cross section of the seamless pipe coincides with the axis of the die frame, the flow rates in all directions are relatively balanced during the extrusion production of the seamless pipe, the pipe blank of the seamless pipe is not easy to be twisted and deformed due to the different lengths of the discharges in all directions, the unequal wall thickness requirement of the seamless pipe can be realized, and the quality of the seamless pipe product is improved and the scrap rate is reduced.

[0025] 2. The special guide is installed at the outlet of the pipe blank in the present application, the produced pipe blank is transported along the special guide, the twisting and deformation of the pipe blank are further avoided, the smooth handover of the pipe blank to the next process is ensured, and the pipe blank is not scrapped due to hard bending.

[0026] 3. The application carries out centering and horizontal detection before extrusion, avoids the wall thickness deviation of the product caused by the relative position deviation of the extrusion needle and the outer frame of the die, and carries out wall thickness monitoring of the pipe blank after the pipe blank is produced by extrusion, so as to adjust the relative position deviation of the extrusion die caused by continuous production in time, control the wall thickness deviation of the product within the allowable range, and further improve the quality of the seamless pipe product and reduce the rate of defective products. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0028] Figure 1 is a schematic view of the cross section of the seamless pipe in Example 1.

[0029] Figure 2 is a schematic view of the cross section of the extrusion die in Example 1. DETAILED DESCRIPTION

[0030] In order to make the person skilled in the art better understand the technical solutions in the present application, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the protection scope of the present application.

[0031] Example 1

[0032] A production method of a square aluminum alloy seamless pipe with unequal wall thickness, each seamless pipe has a length of 5 m, the cross section shape of the seamless pipe is as shown in Figure 1 , the diameter of the circumscribed circle of the cross section is 280 mm, two broken cantilevers for welding are circumscribed on the right wall, the lengths of the broken cantilevers are both 6 mm, the thickness of the upper broken cantilever is 5 mm, the thickness of the lower broken cantilever is 13 mm, the thickness of the right wall is 6 mm, the thickness of the left wall is 7 mm, the thickness of the upper wall is 10 mm, and the thickness of the lower wall is 15 mm.

[0033] The steps include:

[0034] (1) Die design and manufacturing, the design of the extrusion die is as shown in Figure 2 , the centering limiting ring is arranged on the die outer frame and the extrusion cylinder; the shape surrounded by the cross section of the die outer frame and the extrusion needle at the outlet of the pipe blank is the cross section of the seamless pipe, the center of gravity of the cross section of the seamless pipe coincides with the axis of the die outer frame;

[0035] (2) heating treatment, respectively heating the cast blank and the extrusion die, the cast blank is a hollow aluminum alloy pipe, the heating temperature of the cast blank is 550℃, and the heating temperature of the extrusion die is 500℃;

[0036] (3) extrusion treatment, centering the extrusion cylinder, the extrusion rod and the die, the deviation of centering is less than or equal to 5mm; determining the matching of the needle head and the die direction; detecting the levelness of the needle head by using a level meter; after the centering and the detection are qualified, extruding, placing the heated cast blank in the extrusion cylinder, using the extrusion rod to extrude the cast blank to one end of the die outer frame, and the extrusion speed is 1.0mm / s; the cast blank is extruded into a specified shape under the action of the die outer frame and the extrusion needle head, a pipe blank is obtained, a special guide is installed at the outlet of the pipe blank, the special guide is a long straight groove, and the inner wall is equal to the cross-sectional width of the seamless pipe; after the extrusion is completed, the wall thickness of the pipe blank is detected, the extrusion is stopped when the wall thickness deviation occurs, and the extrusion needle head position is adjusted according to the wall thickness deviation, and then the extrusion is continued

[0037] (4) quenching treatment, quenching the pipe blank;

[0038] (5) seamless pipe straightening, straightening the pipe blank after quenching;

[0039] (6) post-treatment, the straightened pipe blank is sequentially sawed and aged, and a seamless pipe product is obtained.

[0040] The weight of the obtained seamless pipe product is 22kg, and the comprehensive indexes of the seamless pipe product are detected, and the results are as follows:

[0041] The wall thickness deviation is less than or equal to 0.6mm, the perpendicularity is less than or equal to 0.85°, the plane gap is less than or equal to 0.45mm, the straightness is less than or equal to 0.7mm / m, and the full-length straightness is less than or equal to 1.6mm / 5m.

[0042] Example 2

[0043] A production method of a square aluminum alloy seamless pipe with unequal wall thicknesses, each seamless pipe has a length of 10m, the cross-sectional circumscribed circle diameter of the seamless pipe is 338mm, two broken cantilevers for welding are circumscribed on the right wall, the lengths of the broken cantilevers are both 40mm, the thicknesses of the broken cantilevers are both 10mm, the right wall thickness is 13mm, the left wall thickness is 12mm, and the upper wall thickness and the lower wall thickness are both 10mm.

[0044] The steps include:

[0045] (1) mold design and manufacturing, the mold outer frame and the extrusion cylinder are both provided with a centering limiting ring; the cross-sectional shape of the mold outer frame and the extrusion needle head at the pipe blank outlet is a seamless pipe cross section, and the center of gravity of the seamless pipe cross section coincides with the axis of the mold outer frame;

[0046] (2) heating treatment, respectively heating the cast blank and the extrusion die, the cast blank is a solid aluminum alloy rod, the heating temperature of the cast blank is 600℃, the heating temperature of the extrusion die is 550℃;

[0047] (3) extrusion treatment, centering the extrusion cylinder, the extrusion rod and the die, the deviation of centering is less than or equal to 5mm; determining the matching of the needle and the die direction; detecting the levelness of the needle by using a level meter; after the centering and the detection are qualified, extruding, placing the heated cast blank in the extrusion cylinder, using the extrusion rod to extrude the cast blank to one end of the die outer frame, the extrusion speed is 0.5mm / s; the cast blank is extruded into a specified shape under the action of the die outer frame and the extrusion needle, a special guide is installed at the outlet of the tube blank, the special guide is a long straight groove, the inner wall is equal to the cross-sectional width of the seamless pipe; after the extrusion is completed, detecting the wall thickness of the tube blank, stopping the extrusion when the wall thickness deviation occurs, continuing the extrusion after adjusting the position of the extrusion needle according to the wall thickness deviation

[0048] (4) quenching treatment, quenching the tube blank;

[0049] (5) seamless pipe straightening, straightening the quenched tube blank;

[0050] (6) post-treatment, sawing and aging treatment are sequentially performed on the straightened tube blank to obtain a seamless pipe product.

[0051] The obtained seamless pipe product weighs 29kg, the comprehensive indexes of the seamless pipe product are detected, and the results are as follows:

[0052] The wall thickness deviation is less than or equal to 0.7mm, the perpendicularity is less than or equal to 0.90°, the plane gap is less than or equal to 0.50mm, the straightness is less than or equal to 0.8mm / m, and the full-length straightness is less than or equal to 1.8mm / 10m.

[0053] Example 3

[0054] A production method of a square aluminum alloy seamless pipe with unequal wall thicknesses, each seamless pipe has a length of 20m, the cross-sectional circumscribed circle diameter of the seamless pipe is 288mm, the right wall thickness is 8mm, the left wall thickness is 7mm, the upper wall thickness is 10mm, and the lower wall thickness is 12mm.

[0055] The steps include:

[0056] (1) die design and manufacturing, the die outer frame and the extrusion cylinder are both provided with a centering limiting ring; the die outer frame and the extrusion needle form a seamless pipe cross section at the cross-sectional center of the tube blank outlet, and the center of gravity of the seamless pipe cross section coincides with the axis of the die outer frame;

[0057] (2) heating treatment, respectively heating the cast blank and the extrusion die, the cast blank is a hollow aluminum alloy pipe, the heating temperature of the cast blank is 540℃, and the heating temperature of the extrusion die is 450℃;

[0058] (3) extrusion treatment, centering the extrusion cylinder, extrusion rod and die, the centering deviation being ≤5mm; determining the needle head and die direction matching; detecting the levelness of the needle head by using a level meter; after the centering and detection are qualified, extruding, placing the heated casting blank in the extrusion cylinder, using the extrusion rod to extrude the casting blank to one end of the die outer frame, the extrusion speed being 2.0mm / s; the casting blank is extruded into a specified shape under the action of the die outer frame and the extrusion needle head, obtaining a pipe blank, a special guide is installed at the outlet of the pipe blank, the special guide is a long straight groove, the inner wall of which is equal to the cross-sectional width of the seamless pipe; after the extrusion is finished, the wall thickness of the pipe blank is detected, the extrusion is stopped when the wall thickness deviation occurs, the position of the extrusion needle head is adjusted according to the wall thickness deviation, and then the extrusion is continued

[0059] (4) quenching treatment, quenching the pipe blank;

[0060] (5) seamless pipe straightening, straightening the quenched pipe blank;

[0061] (6) post-treatment, sawing and aging treatment are sequentially performed on the straightened pipe blank, obtaining a seamless pipe product.

[0062] The obtained seamless pipe product weighs 24kg, the comprehensive indexes of the seamless pipe product are detected, and the results are as follows:

[0063] The wall thickness deviation is ≤0.50mm, the perpendicularity is ≤0.60°, the plane gap is ≤0.30mm, the straightness is ≤0.6mm / m, and the full-length straightness is ≤1.2mm / 20m.

[0064] Although the present application has been described in detail by referring to the preferred embodiments thereof, it is to be understood that the present application is not limited to them. It is to be appreciated that those skilled in the art, on the basis of the technologies disclosed in the present application, can make various modifications or replacements to the embodiments of the present application without departing from the spirit and scope of the present application. Any modifications or replacements made by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application.

Claims

1. A method for producing a square seamless aluminum alloy tube with unequal wall thickness, characterized in that the steps include: include: (1) Design the extrusion die as needed. The extrusion die includes an extrusion needle and a die frame. The die frame is installed on the extrusion cylinder. The extrusion needle is designed with an eccentricity. The center of gravity of the seamless tube cross-section coincides with the axis of the die frame. The cross-section of the seamless tube is a hollow shape formed by the die frame and the extrusion needle at the tube outlet. Both the outer frame of the mold and the extrusion cylinder are equipped with centering limit rings; (2) Heat the billet and the extrusion die respectively. The billet is a solid aluminum alloy bar or a hollow aluminum alloy tube. (3) Place the heated billet in the extrusion cylinder and use the extrusion rod to extrude the billet to one end of the extrusion die. The billet is extruded into the specified shape under the action of the die frame and the extrusion needle to obtain the tube blank. Before extrusion begins, alignment and leveling checks are performed. Specific procedures include aligning the extrusion cylinder, extrusion rod, and die, with an alignment deviation of ≤5mm; ensuring the needle and die directions match; checking the needle's levelness using a level; and extrusion only proceeding after both alignment and checks are passed. In step (3), during the seamless extrusion process of the billet, a special guide is installed at the billet outlet. The special guide is a long straight groove with an inner wall width equal to that of the seamless tube cross-section. After extrusion, the wall thickness of the tube blank is checked. If the wall thickness deviates, extrusion is stopped. The position of the extrusion needle is adjusted according to the wall thickness deviation before extrusion is continued. (4) Quenching the tube blank; (5) Straighten the quenched tube blank; (6) The straightened tube blank is sawed and aged sequentially to obtain seamless tube products; The wall thickness deviation of seamless tube products is ≤10%×h, the perpendicularity is ≤1°, the plane gap is ≤4%×w, the straightness is ≤1mm / m, and the overall straightness is ≤2mm / L; where h is the design wall thickness of the seamless tube, w is the width of the seamless tube product, and L is the overall length of the seamless tube product.

2. The production method as described in claim 1, characterized in that, In step (2), the heating temperature of the billet is 540-600℃, and the heating temperature of the extrusion die is 450-550℃.

3. The production method as described in claim 1, characterized in that, The extrusion speed in step (3) is 0.5-2.0 mm / s.

4. The production method as described in claim 1, characterized in that, Seamless tube products have an outer circumscribed circle diameter ≤ 400mm, a length ≤ 20m, and a wall thickness of 5-30mm.

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