Short-process preparation method of large-diameter cupronickel seamless tube

Abstract

The invention provides a short-process preparation method for a large-diameter cupronickel seamless tube, belongs to the technical field of non-ferrous metal processing, and solves the problem that the yield of a finished product prepared by an existing large-diameter copper tube production process is relatively low. Reheating the cast ingot subjected to primary perforation, and then carrying out secondary perforation extrusion to obtain a tube blank; carrying out acid pickling, straightening, saw cutting, coping and finishing treatment on the pipe blank subjected to secondary perforation and extrusion, and rolling the finished pipe blank; and the rolled pipe blank is subjected to softening annealing treatment, stretching is conducted after annealing treatment, and annealing treatment is conducted after stretching, so that a finished product is obtained. According to the method, the problems of timeliness, grain size, eccentricity and the like existing in multi-pass diameter expansion (reduction) stretching production of the existing BFe10-1. 6-1 large-piece-weight extruded pipe blank are solved, and short-process production of the BFe10-1. 6-1 cupronickel large-diameter cupronickel seamless pipe is achieved. And the production efficiency, the grain size refinement degree and the size precision of the large-diameter cupronickel seamless tube are greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of nonferrous metal processing, and in particular relates to a short-process preparation method for a large-diameter seamless copper-nickel tube. Background Art

[0002] At present, due to the continuous development of maritime defense, shipping and offshore oil exploration, copper-nickel alloy seamless pipes are widely used due to their corrosion resistance and excellent machinability. Copper-nickel alloy seamless pipes have better pressure resistance and fluid impact resistance than copper-nickel alloy welded pipes.

[0003] At present, for pipes larger than φ133mm, there are no large-scale rolling mills suitable for copper pipe products in the copper processing industry at home and abroad, so large-diameter white copper seamless pipe products can only be produced by multi-pass expansion / reduction and stretching. This leads to low pipe production efficiency and high cost, which is not conducive to enterprise production and market demand.

[0004] In addition, the grain size required for copper-nickel alloy pipes for deepwater equipment is 0.01-0.045μm. Relying solely on the traditional stretching method, due to the tension limitation of the stretching machine itself and the small pass processing rate, the grain size of the extruded tube billet is not completely broken, and the grain size of the final product exceeds the requirement, resulting in an extremely low yield rate. Summary of the invention

[0005] The purpose of the present invention is to provide a short-process preparation method for large-diameter seamless copper-nickel tubes, so as to solve the problem of low yield of finished products obtained by existing large-diameter copper tube production processes.

[0006] The technical solution of the present invention is: a short-process preparation method for a large-diameter seamless copper-nickel tube, comprising the following steps: Step 1: After heating the ingot, perform a punching operation, and after heating the ingot after the punching operation again, perform a second punching operation and extrude the ingot to obtain a tube blank; Step 2: pickling, straightening, sawing, grinding and finishing the tube billet after secondary piercing and extrusion, and rolling the finished tube billet; Step 3: Softening and annealing the rolled tube, stretching it after annealing, and annealing it after stretching to obtain the finished product.

[0007] As a further improvement of the present invention, in step 1, the ingot diameter is not less than 440 mm, and the ingot material is BFe10-1.6-1.

[0008] As a further improvement of the present invention, in step 1, the heating temperature before the first piercing is 880-920°C, and the heating temperature before the second piercing and extruding is 920-930°C.

[0009] As a further improvement of the present invention, in step 2, the elongation during rolling is ≥1.55.

[0010] As a further improvement of the present invention, in step 2, different hole types are changed during rolling, and the hole type used is φ273 or φ194.

[0011] As a further improvement of the present invention, in step three, the softening annealing treatment temperature is 800-850° C., and the holding time is 60-80 min.

[0012] As a further improvement of the present invention, in step three, the finished product size is φ159-340 mm and the wall thickness is 2.5-16 mm.

[0013] The beneficial effects of the present invention are as follows: The present invention provides a preparation method of vertical semi-continuous casting ingots, which includes one-time perforation → secondary perforation extrusion → hollow ingot extrusion → hot extrusion tube billet rolling → intermediate annealing → diameter expansion and wall reduction stretching → finished product annealing. The traditional extrusion method only relies on the traditional stretching method to produce ingots with larger unit weight. Due to the small pass processing rate, the grain size of the extruded tube billet is not completely broken, and the grain size of the final finished product exceeds the demand, resulting in an extremely low yield rate. This method cooperates with the existing equipment capacity, and can realize the extrusion of large unit weight extruded tube billets through one-time perforation and then secondary perforation extrusion.

[0014] The purpose of primary piercing is to reduce the piercing force required for secondary extrusion. The secondary piercing extrusion method can be used to produce heavy-weight thick-walled extruded tubes, providing suitable billets for cold rolling tube mills. In addition, this extrusion method can reduce the load on the extruder and avoid situations such as extrusion needle breakage and inability to extrude.

[0015] The rolling design has a high processing rate (elongation ≥ 1.55) which can completely break the original grains of the extruded tube billet, so that the subsequent finished product can obtain more uniform and finer grains; the rolling design can achieve uniform wall thickness, and by improving the eccentricity of the drawn tube billet, the eccentricity of the finished tube can be reduced, thereby improving the inspection pass rate of the tube billet; the rolling design can reduce the subsequent stretching passes through the high processing rate and large deformation, thereby improving the stretching efficiency.

[0016] During rolling, multiple sets of hole profiles are used to replace different hole profiles. Multiple sets of hole profiles means that one rolling mill is equipped with two sets of hole profiles. The hole profile is the mold of the rolling mill. The purpose is to produce rolled tubes with different outer diameters and wall thicknesses. The matching hole profiles can provide corresponding tube billets for different tube billets, so that the drawing process has fewer passes and higher efficiency. The intermediate pass annealing provides power guarantee for the recovery and recrystallization of the grains.

[0017] The invention solves the problems of timeliness, grain size and eccentricity existing in the existing BFe10-1.6-1 large single-weight extruded tube billet multi-pass expansion (reduction) diameter stretching production, realizes the short-process production of BFe10-1.6-1 white copper large-diameter white copper seamless tubes, and compared with the existing production method, greatly improves the production efficiency, grain size refinement and dimensional accuracy of large-diameter white copper seamless tubes. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below in conjunction with specific implementation modes.

[0019] A short-process preparation method for a large-diameter seamless copper-nickel tube comprises the following steps: Step 1: After heating the ingot, perform a punching operation, and after heating the ingot after the punching operation again, perform a second punching operation and extrude the ingot to obtain a tube blank; Step 2: pickling, straightening, sawing, grinding and finishing the tube billet after secondary piercing and extrusion, and rolling the finished tube billet; Step 3: Softening and annealing the rolled tube, stretching it after annealing, and annealing it after stretching to obtain the finished product.

[0020] In step 1, the ingot diameter is not less than 440 mm, and the ingot material is BFe10-1.6-1. In step 1, the heating temperature before the first piercing is 880-920°C, and the heating temperature before the second piercing and extrusion is 920-930°C.

[0021] In step 2, the elongation during rolling is ≥1.55. In step 2, different hole types are changed during rolling, and the hole type is φ273 or φ194.

[0022] In step 3, the softening annealing treatment temperature is 800-850°C, and the holding time is 60-80 minutes. In step 3, the finished product size is φ159-340mm and the wall thickness is 2.5-16mm.

[0023] Embodiment 1, Step 1: Place an ingot with a diameter of 440 mm and a material of BFe10-1.6-1 in a medium frequency induction furnace for heating at a temperature of 880°C, then perform a perforation on a 55MN extruder, and lubricate the perforating needle with pure asphalt. Place the ingot after the first perforation in a medium frequency induction furnace for heating at a temperature of 920°C, and then perform a second perforation extrusion on a 55MN extruder to obtain a tube blank. The extrusion die material is GH4169, and the extruded blank is φ234*12; Step 2: The tube billet after secondary piercing and extrusion is pickled for 60 minutes, straightened, sawed, and ground and finished. The finished tube billet is rolled using a cold rolling mill. The elongation during rolling is 1.55. Different hole types are changed during rolling. The hole type is φ194, and the rolled product is φ194*5.5mm; Step 3: The rolled tube is subjected to softening annealing treatment at a temperature of 800°C and a holding time of 60 minutes. After annealing, it is stretched by a stretching machine. After stretching, it is annealed by bright annealing. During the annealing process, nitrogen-hydrogen mixed gas is used as a protective gas for anti-oxidation and reduction measures. Finally, the tube is stretched again to obtain a finished product with a size of φ159mm and a wall thickness of 2.5mm.

[0024] Embodiment 2, Step 1: Place an ingot with a diameter of 450mm and a material of BFe10-1.6-1 in a medium frequency induction furnace for heating at a temperature of 900°C, then perform a perforation on a 55MN extruder, and lubricate the perforating needle with pure asphalt. Place the ingot after the first perforation in a medium frequency induction furnace for heating at a temperature of 925°C, and then perform a second perforation extrusion on a 55MN extruder to obtain a tube blank. The extrusion die material is GH4169, and the extruded blank is φ234*12; Step 2: The tube billet after secondary piercing and extrusion is pickled for 90 minutes, straightened, sawed, and ground and finished. The finished tube billet is rolled using a cold rolling mill. The elongation during rolling is 1.60. Different hole types are changed during rolling. The hole type is φ273, and the rolled product is φ273*5.5mm; Step 3: The rolled tube is subjected to softening annealing treatment at a temperature of 825°C and a holding time of 70 minutes. After annealing, it is stretched by a stretching machine. After stretching, it is annealed by bright annealing. During the annealing process, nitrogen-hydrogen mixed gas is used as a protective gas for anti-oxidation and reduction measures. Finally, the tube is stretched again to obtain a finished product with a size of φ240mm and a wall thickness of 9.5mm.

[0025] Embodiment 3, Step 1: Place an ingot with a diameter of 460 mm and a material of BFe10-1.6-1 in a medium frequency induction furnace for heating at a temperature of 920°C, then perform a perforation on a 55MN extruder, and lubricate the perforating needle with pure asphalt. Place the ingot after the first perforation in a medium frequency induction furnace for heating at a temperature of 930°C, and then perform a second perforation extrusion on a 55MN extruder to obtain a tube blank. The extrusion die material is GH4169, and the extruded blank is φ234*12; Step 2: The tube billet after secondary piercing and extrusion is pickled for 120 minutes, straightened, sawed, and ground and finished. The finished tube billet is rolled using a cold rolling mill. The elongation during rolling is 1.65. Different hole types are changed during rolling. The hole type is φ194, and the rolled product is φ194*5.5mm; Step 3: The rolled tube is subjected to softening annealing treatment at a temperature of 850°C and a holding time of 80 minutes. After annealing, it is stretched by a stretching machine. After stretching, it is annealed by bright annealing. During the annealing process, nitrogen-hydrogen mixed gas is used as a protective gas for anti-oxidation and reduction measures. Finally, it is stretched again to obtain a finished product with a size of φ340mm and a wall thickness of 16mm.

[0026] The finished products obtained by the method of Example 1-3 are shown in Table 1. The finished products obtained by the method are superior to the existing methods in terms of timeliness, grain size and uniformity. The present invention adopts a one-time perforation plus a secondary perforation extrusion method to extrude the rolling mill billet tube, and then uses a cold rolling tube machine to roll the extruded billet, and finally uses a stretching machine to perform multiple cold processing to the required size of BFe10-1.6-1 large-diameter white copper seamless tube, which solves the problems of timeliness, large grain size and poor uniformity of BFe10-1.6-1 large-unit-weight extruded tube billets and stretched large-diameter white copper seamless tubes, and realizes the short-process production of BFe10-1.6-1 large-diameter white copper seamless tubes. Compared with the existing production method, the production efficiency of large-diameter copper-nickel alloy tubes is greatly improved.

Claims

1. A short-process preparation method for large-diameter seamless copper-nickel tube, characterized in that: The following steps are involved: Step 1: After heating the ingot, perform a punching operation, and after heating the ingot after the punching operation again, perform a second punching operation and extrude the ingot to obtain a tube blank; Step 2: pickling, straightening, sawing, grinding and finishing the tube billet after secondary piercing and extrusion, and rolling the finished tube billet; Step 3: Softening and annealing the rolled tube, stretching it after annealing, and annealing it after stretching to obtain the finished product.

2. The short-process preparation method for a large-diameter seamless copper-nickel tube according to claim 1, characterized in that: In step 1, the ingot diameter is not less than 440 mm, and the ingot material is BFe10-1.6-1.

3. A short-process preparation method for a large-diameter seamless copper-nickel tube according to claim 1, characterized in that: In step 1, the heating temperature before the first piercing is 880-920°C, and the heating temperature before the second piercing extrusion is 920-930°C.

4. A short-process preparation method for large-diameter seamless copper-nickel tube according to claim 1, characterized in that: In step 2, the elongation during rolling is ≥1.

55.

5. The short-process preparation method of a large-diameter seamless copper-nickel tube according to claim 1, characterized in that: In step 2, different hole types are changed during rolling, and the hole type used is φ273 or φ194.

6. A short-process preparation method for large-diameter seamless copper-nickel tube according to claim 1, characterized in that: In step three, the softening annealing treatment temperature is 800-850°C, and the holding time is 60-80 minutes.

7. The short-process preparation method of a large-diameter seamless copper-nickel tube according to claim 1, characterized in that: In step three, the finished product size is φ159-340mm and the wall thickness is 2.5-16mm.

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