Specificat ion

Method for manufacturing a Tube of Copper or Copper Alloy

Technical Field

[ I J The piesent invention ielates to a method for manufacturing a tube made of copper or copper alloy Particularly, it relates to a method for manufacturing a tube made of coppei or copper alloy with high accuracy

Background

[2J In prior art, extrusion and rolling, skew rolling with a hoiizontal casting io PSW (planetenschragwalzwerk (German)), as well as skew rolling with a preheating casting blank through a PSW, are usually adopted for manufacturing tubes of copper or copper alloy As shown m Figure 1 and 2, a PSW comprises a case 94, a rotor 93 arranged in the case 94, and rollers 91, wherein the rollers 91 revolute in a direction denoted by the arrow M with a 15 simultaneous rotation in a direction denoted by the arrow N The operating principle of above PSW is that thiee rollers 91 are disposed around the workpiece 92 (tube blank) and spaced by 120 degrees each other, and a core iod 95 is centially arranged Three rollers 91 revolute with a simultaneous rotation, while the axis of the roller is skewed by an angle α with respect to in the i oiling axis The angle α is piopoitional to the offsetting of i olleis of the PSW If the offsetting becomes too large, mtei feience will appear among said thiee i olleis. iesulting in a requnement of a smaller offsetting, that is to say, a smaller α Due to the existence of this angle σ. these rollers 91 will apply an axial foice to the tubular blank dui mg the i oiling piocess. which uiges the ^ i olling tube moving forward Howevei. since the angle between the rollei 91 and the rolling axis cannot be too laige. the i oiling speed is inevitably low. less than 20m/mm At the same time, the tubular blank, to which the above

CONFIREWATION COPY

method can apply, has a small outer diameter, around 80mm. and the outer diameter of the rolled tube is less than 50mm. Thus, the production efficiency is quite low.

[3] Chinese Patent Application No. 02138022.8 discloses a method for manufacturing a tube of copper or copper alloy. Said method includes steps of: preheating the tubular blank, rolling the tubular blank and cooling the rolled piece, and is characterized in that the tubular blank is preheated to a temperature between the ambient temperature and the recrystallization temperature before the rolling process, the blank is then rolled by the PSW, so as to eliminate the nonuniformity of the rolling deformation. However, in the practical performance, this object cannot be achieved by preheating the tubular blank. The reason is that during the rolling process of the tubular blank, heat is produced from deformation processing. As a result, the recrystallization temperature of the tubular blank can be achieved without difficulty. Hence, the preheating process has no effect on the recrystallization of the tubular blank. On the contrary, preheating equipment is further needed due to this additional preheating process, the manufacturing cost is increased in view of suitable preheating methods, and waste of energy is inevitable. The preheating temperature of the tubular blank cannot be easily controlled, and heat will dissipate in the period from preheating to deformation processing, thus resulting in a drop of temperature. Thus, the increased temperature due to preheating cannot be superposed with the increased temperature due to the heat produced by tubular blank deformation during processing. Furthermore, since a tubular blank is transcalent, in practice, it is extremely difficult to maintain the temperature of a processing area much higher than that of the remaining part. Moreover, the oxidation surface layer of the tubular blank has already been removed before preheating. Since the temperature of said tubular

blank will rise during preheating, a protective gas must be supply to said tubular blank during the preheating process, to prevent the tubular blank from surface oxidation. Thus, additional equipments, materials and processing is required, resulting in a further reduce of the manufacturing efficiency and increase of the manufacturing cost of the tubular blank.

[4] Chinese Patent Application No. 03149757.8 discloses another method for manufacturing a tube of copper or copper alloy through a planet rolling mill. In this method, a PSW is adopted to roll the tubular blank so that the temperature of the tubular blank is between 701-850 ^" C ₅ the reduction of cross sectional area is between 85-95%, and the rolling speed is 12-30m/min. However, said method is disadvantageous in that: the rolling piece is greatly distorted, the rolling speed is relatively low, and the diameter of the rolling tube is small.

[5] Referring to Figure 2, three rollers 91 force a workpiece 92 to form an section which is close to a triangle. Just because this irregular section formed in a special space, the workpiece is largely deformed during the rotation thereof. Quality defect is easily formed in the rolled tube, and the resistance force is relatively large. The wall thickness at engage line 91 1 is great different from that at disengage line 912 and presents a poor uniformity. Even after the section of the workpiece becomes a complete round, the difference in the wall thickness (T) is still large, T _πiaN - T _1111n =50.35mm. This has an adverse effect on the subsequent procedures, and results in a relatively low accuracy.

[ 6] As a conclusion, conventional extruding rolling methods are complicated and include a heating procedure. With regards to discussed conventional rolling methods, the manufacturing cost is high, the rate of finished products is low, the accuracy of the finished products is poor, and a

long tubular material is difficult to produce At the same time, skewing rolling with a PSW and skewing rolling with preheating through a PSW are disadvantageous in that the i oiling speed is low, the rolled tube is small, a copper tube with a large diameter is difficult to produce, and energy more than necessary is consumed, etc

Summary of the Invention

[ 7] The object of the present invention is to provide a method for manufacturing a tubular material made of copper of copper alloy, the manufacturing process thereof being simple, and the accuracy of the finished product being high.

[8] Said object is attained by a method for manufacturing a tube made of copper or copper alloy according to the present invention, which including a) removing a surface oxidation layer from a tubular blank; b) rapidly rolling said tubular blank which has been free of surface oxidation with a four-planet rolling mill, c) rapidly cooling down said tubular blank which has been rapidly rolled, d) linearly drawing the cooled-down tubular blank with a linear drawing equipment

[9] Preferably, during the step b), the rolling speed of the tubular blank is 20-60m/mm

[ io] Prefeiably, said rolling speed is 45in/min

[ H ] Prefeiably. during the step b). the defoi mation of the tubulai blank during the rolling process is no less than 90%

[ 12 ] Preferably, during the step b), the temperature of the tubular matei uu rises up to 700 ⁰ C oi highei instantaneously

[ 13 ] Preferably, a two-stage cooling equipment is adopted during the step c). and the cooling iate of said tubular blank is 160-200 ^° C/s

[ 14] Preferably, after cooling down in the step c), the gram size of said tubular blank is maintained between 0 01 -0 04mm

[ 15 ] Preferably, during said step a), said removing of the surface oxidation layer is realized by scraping [ 16] Preferably, during said step a), said removing of the surface oxidation layer is realized by double face rotary milling with two milling cutters arranged at the top and the bottom

[ 17] Preferably, the outer diameter of said tubular blank is between 80-240mm [ 18] The present invention is superior over the prior art. In the method for manufacturing a tube made of copper or copper alloy according to the present invention, a four-planet rolling mill without an intermediate gear is adopted, and the sun gear directly engages with the planet gear fixed on the roller shaft As a result, the four-planet rolling mill is robust, and the four-planet rolling mill is provided with one more bearing point than a three-planet rolling mill. The four-planet rolling mill utilizes spacers to axially adjust the roller shaft, so that the strength thereof is greatly improved The rolling mill according to the present invention can be used to perform a rolling operation on both casted tubular blank and extruded tubular blank, so that it can be widely used Due to the high strength, the finished workpiece possesses a high accuracy The Linifoimity of the wall thickness of a rolled tubular blank is unproved by 25% with respect to the uniformity of the wall thickness of a iolled tubular blank by a three-planet tolling mill, which is advantageous for subsequent processing Furthermore, in the manufacruiing method according to the present invention, the step for preheating the tubulai blank is omitted Since the adopted four-planet rolling mill is high in stiength, a fast rolling speed is realized during processing, which can be three times of that in the prior art

processing. Consequently, huge deformation heat is produced and the recrystallization temperature of the tubular blank is achieved so that the recrystallizeation process of the coarse casting structures may be accelerated. The grains after recrystallization are small and uniform, with sizes of 0.010-0.040mm. Furthermore, equipments and procedures required by the preheating, as well as equipments and procedures required in the preheating process to prevent the tubular blank from oxydation are omitted. As a result, with regard to the method according to the present invention, the process flow is simple, the efficiency is high, and the cost is low. [ 19] Furthermore, compared with an prior art rolling mill, more rollers are adopted in the present manufacturing method. Thus, distortion of a workpiece during the rolling process is reduced, surface quality of the rolled tubular blank is improved, and the surface fineness improves by 50%. Furthermore, since more rollers are provided in a four-planet rolling mill, the area reduction rate after rolling treatment is improved, which can be more than 90%. A linear drawing processing is applied to a soft tubular blank after the rolling process, such that an abrasion of the tubular surface is avoided. Meanwhile, the present invention may provide a high efficiency, reduce energy consumption as well as manpower consumption, and greatly reduces the cost.

Description of Drawings

[20] Hereinafter, the embodiments of the present invention λvill be explained in detail with reference to accompany drawings. [ 21 ] Figure 1 is a plan view showing a prior ait PSW. [22 ] Figure 2 shows the working principle of a PSW in Figure 1 .

[23 ] Figure 3 is a plan view showing a four-planet rolling mill according to the present invention.

[24] Figure 4 is a cross-sectional view of Figure 3.

[ 25 ] Figure 5 shows the working principle of the rolling mill in Figure 4.

Embodiments [ 26] Referring to Figure 3 and 4, a four-planet rolling mill 100 used in the present invention comprises a case 7, a rotor 6 arranged in the case 7, four planet rollers 2 fixed on the rotor 6 and distributed evenly along the circumference thereof, wherein the rollers 2 revolute with the rotor 6 in a direction denoted by the arrow B with a simultaneous rotation in a direction denoted by the arrow A. During the rolling process, the workpiece 1 is provided among these four rollers 2, and an offset E exists between the roller axis 11 of each roller 2 and the rolling axis 12 of the workpiece 1 . Said offset E is determined by an angle. According to the formula N=F X E (in which N is a torque, F is a force, and E is the offset), with a given rolling force, a larger offset E will result in a higher torque.

[27] For a clarity purpose, among those four rollers 2, only two are shown in Figure 4. A motor (not shown) drives the drive gear 8. Gear 8 engages with another gear fixed on the rotor 6 and brings the rotors to rotate. Meanwhile, since the planet rollers 2 are fixed on the rotor 6, rollers 2 revolute together with the rotor 6. A motor (not shown) drives the drive gear 10. Gear 10 engages with the sun gear 9, while planet gear 5 engages with the sun gear 9. Thus, a rotation of the gear 10 drives the planet gear 5 so the gear 5 rotates too. The planet gear 5 fixed on the roller shaft 3 drives the roller shaft 3 to rotate, so that the roller 2 fixed on the roller shaft 3 is made to rotate, thereby forming a rotation.

[ 28 ] There is a certain inclination between said roller shaft 3 and the axis of the workpiece 1 . And this inclination is fixed, non-adjustable. A spacer 13 is

provided between the roller shaft 3 and the roller 2. Said spacer is may adjust, along the axial direction of the roller shaft 3, the distance between the roller 2 and the workpiece 1 . Since there may exist clearances between screws engaged with each other, e.g., a T85 X 8 screw with a tolerance grade 7 i s 5 formed with tolerance 0.2mm, the teeth of the screws, in use, will subject to a force and then may be easily broken. On the contrary, the manufacturing accuracy of a spacer can be as high as 0.01 mm, and spacers are not easily broken or distorted. Thus, both of the uniformity and the strength of a spacer are superiors over those of a screw, in other words, a spacer is more accurate K) and robust. Consequently, both of the strength and the accuracy of a four planet rolling mill is much higher than those of a three planet rolling mill. A rolling piece with higher dimensional accuracy may be achieved through above-mentioned four planet rolling mill.

[29] Figure 5 shows the rolling principle. A workpiece 1 rolled by said four 15 planet rolling mill 100 have a shape more like a circle, a smaller difference between the wall thickness of the engage line C and that of the disengage line D, a smaller curvature, and a good uniformity of the wall thickness are achieved. Moreover, it can be rolled with a smaller rolling resistance. Consequently, a higher rolling speed as well as better product accuracy is 0 realized.

[30] The method for manufacturing a tubular material made of copper or copper alloy with said four planet rolling mill 100 according to the present invention may include the following steps.

[31 ] 1 ) Firstly, removing the oxidation layer from the surface of the cast or ? extruded tube (rod) blank (workpiece 1 ).

[ 32 ] In this step, the oxidation layer on the outer surface of the workpiece 1 may be removed by means of machining, such as by means of shaving or by

means of milling face with a rotating milling machine. Take the later as example, during milling face with a rotating milling machine, two milling cutters are preferably provided at the top and the bottom, wherein each milling cutter mills a 60-90 degree area of the copper or alloy copper surface each time. Thus, a workpiece may be finished with 2-3 milling cycles. In the above method, a hydro-servo system is preferably utilized to control the milling depth.

[33] Since the clearance between four rollers 2 are relatively large, above-mentioned spacers 13 may be utilized to adjust this clearance. To facilitate a horizontal traction of the workpiece 1 to improve the manufacturing efficiency as well as to meet the requirement of mass production, the outer diameter of the blank workpiece 1 is preferably between φ 80 and φ 240mm.

[34] 2) Rolling the workpiece 1 by the above four-planet rolling mill 100, in high speed.

[35 ] The milled workpiece 1 is introduced into the four-planet rolling mill ] 00, and the workpiece 1 is rapidly rolled with a speed of 20-6Om/min. The primary deformation of the workpiece is over 90%. Said four rotating rollers 2 of the rolling mill 100 revolute about the workpiece 1 . The core rod 4 inside of the workpiece L under the action of the friction force, is forced to rotate with the woikpiece. Heat of deformation is produced in the material due to rapid and large deformation. Due to the rapid rolling, the temperature of the workpiece 1 may rise up to 700 ^° C or higher instantaneously. Preferably, said rolling speed may be 45m/min. [36] The roller axis 11 and the rolling axis 12 preferably form a space angle. Said space angle cannot be a plane angle, and cannot cause the workpiece 1 move forwardly along the axial direction. However, said space angle may

cooperatively work together with said offset E to form an axial force component. This axial force component may cause the workpiece 1 to move forward. Meanwhile, since four rollers 2 revolute with a simultaneous rotation, said rolling mill 100 may perform a rapid rolling on the workpiece 1 . After said step, the cross-sectional area of the workpiece 1 may be reduced more than 90%.

[37] For illustrative purpose, a φ 100 X 25 workpiece 1 is discussed, the outer diameter thereof being rolled to φ 60 X 3. According to the formula [ 38] S=1OO%X (D1 -D2)/D1, [39] wherein S is the deformation percentage, ώl is the outer diameter before the rolling process and ϊ)2 is the outer cjiameter after the rolling process _> the deformation, percentage is 90,9%,

[40] Said rolling speed is defined on the base of the shape of the rollers 2, the size of the offset E, the magnitude of the propelling force, the speed of the rotor 6, as well as the temperature and the flow rate of the cooling liquid which will be discussed later. A tubular material is rolled in above detailed description. If a rod material is rolled, no core rod 4 will be used. [41 ] 3) Rapidly cooling down the rolled workpiece 1. [42] Usually, a two-stage water-cooling device (not illustrated) is utilized to rapidly cool down the workpiece 1 . Said water cooling device is arranged behind said rolling mill 100. in which the first cooling down process is to directly spray cooling liquid on the rollers 2 and the yvorkpiece 1. The cooling liquid may be water or water with additives such as heat-conductive agent or lubricant. Thus, heat outflow s from the workpiece 1 during the rolling process. During the Second cooling down process, the workpiece 1 , which has already been cooled-down in the first stage, is immersed directly into the cooling-down liquid, and cools down at a rate of 160-200 ⁰ C /s to the ambient

temperature in the cooling liquid as so to achieve a finer, more uniform crystal structure. The grain size of the workpiece 1 which was rapidly cooled down may be kept between 0.01 -0.04mm.

[43 ] To ensure a grain size between 0 01 -0 04mm, the rolling temperature of the workpiece 1 must be higher than the recrystallization temperature of the corresponding copper or copper alloy, and the cooling of the workpiece 1 must be accurately carried out on time, so that the grains will not grow too much. Testing methods for said grains and testing apparatus thereof are all well known. [44] Consequently, the rapid rolling process and the rapid cooling down process eliminate the nonuniformity of the material deformation, reduce the frictional coefficient between the workpiece 1 and the rollers 2, improves the quality of the workpiece 1, and increase the service life of the roller 2 by 50% to 100%. [45] Preferably, said method to process a workpiece 1 may further includes a step of drawing the workpiece 2 with a linear drawing equipment (not shown). Said linear drawing equipment is arranged behind the four-planet rolling mill 100, in order to avoid the relative slip and scraping between different workpiece, as well as between workpiece and equipments. Thus, the surface defects in thin-wall tubular copper pieces caused by abrading or scraping during processing procedures are avoided. Consequently, after said procedure, the surface quality of the cooled-down workpiece 1 in soft state may be greatly improved with a linear diawmg equipment

[46 ] Several examples manufactured with the method according to the present invention are discussed hereinafter.

[47] Example 1 : A TP2 (a kind of phosphorus deoxidized copper) tubυlai blank is rolled by said four-planet rolling mill 100 The size of the tubular

blank to be rolled is φ 60 X 3 + 0.15, the rolling speed is around 45m/min, and the grain size is between 0.01 -0.04mm. After being continuously drawn by four linear drawing machines, the uniformity of the wall thickness of the rolled tube is high. The size of the finished product is φ 25 X 1 ± 0.08mm. ? [48] Example 2 : A TP2 tubular blank is rolled by said four-planet rolling mill 100. The size of said rolling tubular blank is φ 108 X 4.8 + 0.2, the rolling speed is around 45m/min, and the grain size is between 0.010-0.04mm. After four continuous drawings, the size of the finished product is φ 42 X 2.0 + 0. 10mm. [49] Example 3 : A Bfel O-1 -1 (BfelO- 1-1 copper-nickel alloy) tubular blank is rolled by said four-planet rolling mill 100. The size of the tubular blank to be rolled is φ 108 X 5 +0.15, the rolling speed is around 45m/min, and the grain size is between 0.010-0.04mm. After four continuous drawings, The size of the finished product is φ 42 X 2.0 + 0.10mm. [50] Preferred embodiments of the present invention has been described above. It should be noted that many improvements and variations may be accomplished by an ordinary person skilled in the art, without departing from the scope of the present invention. These improvements and variations also fall into the protective scope of the claims of the present invention.