Preparation method of non-uniform-section ultra-long special-shaped pipe

Abstract

The invention provides a preparation method of a non-uniform-section super-long special-shaped pipe, belongs to the technical field of non-ferrous metal processing, and solves the problem that the quality of the super-long special-shaped pipe produced by a disc drawing process is poor, the preparation method comprises the following steps: extruding an oxygen-free copper cast ingot into a pipe blank meeting the weight of a finished product, and carrying out finishing treatment of straightening, saw cutting and coping on the pipe blank; carrying out first-pass rolling on the pipe blank subjected to finishing treatment, and carrying out second-pass rolling on a finished product subjected to the first-pass rolling to obtain a square-outside round-inside pipe; and rolling and annealing the square-outside and round-inside pipe to obtain a final finished product. According to the preparation method of the non-uniform-section super-long special-shaped pipe, the preparation efficiency and the preparation precision of the pipe are improved, the related problems of pass-by-pass annealing, unstable pipe quality and the like are solved, and the production efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of nonferrous metal processing, and in particular relates to a method for preparing an ultra-long special-shaped pipe with a non-uniform cross-section. Background Art

[0002] Ultra-long special-shaped tubes with non-uniform cross-sections, such as ultra-pure oxygen-free copper tubes with square outer edges and round inner edges, are widely used in superconductor materials, medical heavy ion accelerators and other fields due to their excellent thermal conductivity, electrical conductivity and processability. In addition, the special-shaped surface fits more closely than the round surface during winding, the filling gap is smaller and the precision is higher. The ultra-long tube formed in one step provides smoother acceleration channels for electronics, fluids, etc. than welded tubes.

[0003] At present, non-uniform cross-section extra-long special-shaped pipes are often produced by coiling process. This production method has high requirements on mold precision. If you are not careful, pipe breakage, high breakage rate of finished products, mold breakage, inner surface wrinkles, pipe twisting, etc. may occur. In addition, work hardening requires annealing of the pipe after each pass, resulting in poor quality of the finished product, high processing cost, poor timeliness, etc., which is not conducive to market promotion. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing super-long special-shaped pipes with non-uniform cross-sections, so as to solve the problem that the super-long special-shaped pipes produced by the coil-drawing process are prone to poor quality.

[0005] The technical solution of the present invention is: a method for preparing an ultra-long special-shaped pipe with a non-uniform cross-section, comprising the following steps: Step 1: Extruding the oxygen-free copper ingot into a tube blank that meets the weight of the finished product, and finishing the tube blank by straightening, sawing and grinding; Step 2: The finished tube blank is subjected to a first rolling process, and the finished product after the first rolling process is subjected to a second rolling process to be an outer square inner round tube; Step 3: Roll and anneal the outer square inner round tube to obtain the final product.

[0006] As a further improvement of the present invention, in step 1, the oxygen content in the oxygen-free copper ingot is ≤5ppm, and the extrusion ratio is ≥21.

[0007] As a further improvement of the present invention, in step 2, the elongation coefficient of the first rolling pass is 2.0-2.5, and the tube wall thickness of the first rolling pass is 9.5±5%.

[0008] As a further improvement of the present invention, in step 2, the cross-sectional reduction rate of the second rolling pass is 61.7±1%.

[0009] As a further improvement of the present invention, in step 2, the rotation angle of the mold in the second rolling pass is 89.5-90.5°, the outer mold tolerance is 22±0.1×22±0.1mm, and the core rod sizing band size is 10±0.1mm.

[0010] As a further improvement of the present invention, in step three, the annealing temperature is 500-580° C., and the holding time is 60-90 min.

[0011] The beneficial effects of the present invention are as follows: the present invention extrude oxygen-free copper ingots into larger-sized tube blanks, achieve uniform wall thickness through the first rolling process, and reach the outer diameter condition for entering the second rolling process, and then roll them into non-uniform cross-section special-shaped tubes through a special-shaped tube mill, and then rewind them, and finally produce finished products through heat treatment of finished products. Compared with the existing method, the present invention realizes the production of non-uniform cross-section ultra-long special-shaped tubes with high efficiency, high precision and low cost.

[0012] The present invention extrude larger-specification pipes through an extruder, which can meet the weight conditions for preparing non-uniform cross-section ultra-long special-shaped pipe blanks; the first rolling process allows the pipe to have the outer diameter wall thickness conditions for entering the secondary rolling, and the pipe can be finished during the rolling process to have uniform wall thickness conditions; the production parameters can be reasonably controlled to ensure that the accuracy fully meets the requirements of the finished product, greatly improve the yield rate of the finished product, greatly reduce the breakage rate of the finished product, and at the same time ensure that the inner and outer surfaces of the rolled pipe are smooth; the finished product produced by two rolling processes has a higher pass processing rate, finer and more uniform grain size, and thus better electrical conductivity and mechanical properties than the original multi-pass stretching production method; the finished product is produced by two rolling processes, which eliminates the requirement for the original method of annealing the semi-finished product during stretching, thereby greatly improving production efficiency.

[0013] The present invention provides a method for preparing an ultra-long special-shaped pipe with non-uniform cross-section, which improves the preparation efficiency and preparation accuracy of the pipe, solves the problems related to successive annealing and unstable pipe quality, and improves production efficiency. DETAILED DESCRIPTION

[0014] The present invention is further described in detail below in conjunction with specific implementation modes.

[0015] A method for preparing an ultra-long special-shaped pipe with a non-uniform cross-section comprises the following steps: Step 1: Extruding the oxygen-free copper ingot into a tube blank that meets the weight of the finished product, and finishing the tube blank by straightening, sawing and grinding; Step 2: The finished tube blank is subjected to a first rolling process, and the finished product after the first rolling process is subjected to a second rolling process to be an outer square inner round tube; Step 3: Roll and anneal the outer square inner round tube to obtain the final product.

[0016] In step 1, the oxygen content in the oxygen-free copper ingot is ≤5ppm, and the extrusion ratio is ≥21.

[0017] In step 2, the elongation coefficient of the first rolling is 2.0-2.5, and the tube wall thickness of the first rolling is 9.5±5%. In step 2, the cross-sectional shrinkage of the second rolling is 61.7±1%. In step 2, the rotation angle of the mold in the second rolling is 89.5-90.5°, the outer mold tolerance is 22±0.1×22±0.1mm, and the mandrel sizing band size is 10±0.1mm.

[0018] In step three, the annealing temperature is 500-580° C. and the holding time is 60-90 min.

[0019] The loading rack is designed with a loading length of 30m and the discharging rack is designed with a discharging length of 150m (removable and extendable). The longer loading and discharging racks can meet the storage of the finished products after the first rolling and the finished products after the second rolling. The special-shaped rollers are designed with the same precision as the finished products, which are formed by cold rolling. The coiler is designed at the rear for coiling of the pipes.

[0020] Embodiment 1, The oxygen-free copper ingot with a specification of 310 mm and an oxygen content of 5 ppm was produced by vertical semi-continuous casting. The ingot was extruded into a φ86*15 mm tube billet with a finished product weight by a 55MN extruder, and the extrusion ratio was 21. The tube billet was straightened, sawed and ground for finishing. The finished tube billet is rolled in the first pass by LG75 rolling mill, with an elongation coefficient of 2.0, a tube wall thickness of 4.5% in the first pass, and a rolled product of φ45*9.5mm; the finished product after the first pass is rolled by 30 special-shaped tube rolling mill, with a cross-sectional shrinkage of 60.7%, a mold rotation angle of 89.5°, an outer mold tolerance of 21.9×21.9mm, and a mandrel sizing band size of 9.9mm. According to the round-to-square process requirements, the finished tube after the first pass is rolled in the second pass, and the diameter is precisely determined to meet the standard outer square inner round tube, and the rolled product is L22*L22*Ф10 and L20*L20*Ф10; The outer square inner round tube is rolled and annealed at a temperature of 500°C and a holding time of 60 minutes to obtain the final product.

[0021] Embodiment 2, The oxygen-free copper ingot with a specification of 310 mm and an oxygen content of 4.5 ppm was produced by vertical semi-continuous casting. The ingot was extruded into a φ86*15 mm tube billet with a finished product weight by a 55MN extruder. The extrusion ratio was 21.5. The tube billet was straightened, sawn and ground. The finished tube billet is rolled in the first pass by LG75 rolling mill, with an elongation coefficient of 2.3, a tube wall thickness of 9.5% in the first pass, and a rolled product of φ45*9.5mm; the finished product after the first pass is rolled by 30 special-shaped tube rolling mill, with a cross-sectional shrinkage of 61.7%, a mold rotation angle of 90°, an outer mold tolerance of 22×22mm, and a mandrel sizing band size of 10mm. According to the round-to-square process requirements, the finished tube after the first pass is rolled in the second pass, and the diameter is precisely determined to meet the standard outer square inner round tube, and the rolled product is L22*L22*Ф10 and L20*L20*Ф10; The outer square inner round tube is rolled and annealed at a temperature of 540°C and a holding time of 75 minutes to obtain the final product.

[0022] Embodiment 3, The oxygen-free copper ingot with a specification of 310 mm and an oxygen content of 4 ppm was produced by vertical semi-continuous casting. The ingot was extruded into a φ86*15 mm tube billet with a finished product weight by a 55MN extruder, and the extrusion ratio was 22. The tube billet was straightened, sawed and ground for finishing. The finished tube billet is rolled in the first pass by LG75 rolling mill, with an elongation coefficient of 2.5, a tube wall thickness of 14.5% in the first pass, and a rolled product of φ45*9.5mm; the finished product after the first pass is rolled by 30 special-shaped tube rolling mill, with a cross-sectional shrinkage of 62.7%, a mold rotation angle of 90.5°, an outer mold tolerance of 22.1×22.1mm, and a mandrel sizing band size of 10.1mm. According to the round-to-square process requirements, the finished tube after the first pass is rolled in the second pass, and the diameter is precisely determined to meet the standard outer square inner round tube, and the rolled product is L22*L22*Ф10 and L20*L20*Ф10; The outer square inner round tube is rolled and annealed at a temperature of 580°C and a holding time of 90 minutes to obtain the final product.

[0023] Under the condition of producing the same number of finished products, the fracture rates of the finished products obtained by the method of Examples 1-3 are shown in Table 1. The present invention can first meet the weight conditions of preparing non-uniform cross-section ultra-long special-shaped pipe blanks through extrusion; the first rolling process allows the pipe to have the outer diameter wall thickness conditions for entering the secondary rolling, and the pipe can be finished during the rolling process to have uniform wall thickness conditions; the accuracy can be guaranteed to fully meet the requirements of the finished product by reasonably controlling the production parameters, greatly improving the yield rate of the finished product, and greatly reducing the fracture rate of the finished product. The finished product produced by two rolling processes has a higher pass processing rate, finer and more uniform grain size, and thus better electrical conductivity and mechanical properties than the original multi-pass stretching production method; the finished product produced by two rolling processes has no requirements for annealing of semi-finished products, which greatly improves production efficiency.

Claims

1. A method for preparing ultra-long special-shaped pipes with non-uniform cross-sections, characterized in that: The following steps are involved: Step 1: Extruding the oxygen-free copper ingot into a tube blank that meets the weight of the finished product, and finishing the tube blank by straightening, sawing and grinding; Step 2: The finished tube blank is subjected to a first rolling process, and the finished product after the first rolling process is subjected to a second rolling process to be an outer square inner round tube; Step 3: Roll and anneal the outer square inner round tube to obtain the final product.

2. The method for preparing a non-uniform cross-section ultra-long special-shaped pipe according to claim 1, characterized in that: In step 1, the oxygen content in the oxygen-free copper ingot is ≤5ppm, and the extrusion ratio is ≥21.

3. The method for preparing a non-uniform cross-section ultra-long special-shaped pipe according to claim 1, characterized in that: In step 2, the elongation coefficient of the first rolling pass is 2.0-2.5, and the tube wall thickness of the first rolling pass is 9.5±5%.

4. The method for preparing a non-uniform cross-section ultra-long special-shaped pipe according to claim 1, characterized in that: In step 2, the cross-sectional reduction rate of the second rolling pass is 61.7±1%.

5. The method for preparing a non-uniform cross-section ultra-long special-shaped pipe according to claim 1, characterized in that: In step 2, the rotation angle of the mold in the second rolling pass is 89.5-90.5°, the outer mold tolerance is 22±0.1×22±0.1mm, and the core rod sizing band size is 10±0.1mm.

6. The method for preparing a non-uniform cross-section ultra-long special-shaped pipe according to claim 1, characterized in that: In step three, the annealing temperature is 500-580° C. and the holding time is 60-90 min.

Images