A kind of magnesium-alloy tube hot-bending method and equipment thereof
Technical field
The present invention relates to a kind of bending method and equipment thereof that is applicable to magnesium-alloy tube, can be applicable to the bending forming processing of magnesium alloy pipe, belong to the tubing processing technique field.
Background technology
Magnesium alloy forming property at normal temperatures is relatively poor, and its Plastic Forming processing is generally all finished under hot condition.The bending forming of magnesium alloy pipe is typical Plastic Forming, so the bending forming of magnesium alloy pipe adopts hot bending process more.At present, Chang Yong tubing hot-bending method has heating bend in fire-heating elbow, Medium frequency induction local heat bend pipe and the stove.The flame heat thermal efficiency is not high, is only applicable to bend the large diameter thin wall pipe fitting, and magnesium alloy character is active, inflammable, can not use flame heat.The Medium frequency induction local heat is used for the hot bending of above large diameter carbon steel of external diameter 85mm and stainless steel pipe more, it be with the Medium frequency induction snare on pipe, rely on the Medium frequency induction electric current, with the local instantaneous required high temperature (800~1200 ℃) that is heated to of pipe, immediately heating part is carried out bending (stretch bending or push away curved), magnesium and alloy thereof are weak magnetic materials, and the Medium frequency induction local heat thermal efficiency is low, so be unaccommodated.Tubing is placed on pre-warmed method in the stove because be subjected to that the efficiency of heating surface is low, the restriction of many factors such as wayward, the bool size restrictions of temperature during bending forming, be not suitable for the hot bending of magnesium alloy pipe yet.The report of the crooked research of up-to-date magnesium alloy pipe is that the researcher in General Motors Overseas Corporation research center utilizes the mold hot conduction to carry out hot bending shaping (the Alan A.Luo of magnesium alloy pipe on CNC tube bending machine, Anil K.Sachdev: " Development of a ModerateTemperature Bending Process for Magnesium Alloy Extrusions ", Material Science ForumVols.488-489 (June 2005): the 477-482 page or leaf), it is to temperature required with mold heated, tubing is heating in advance not, heat is conducted to pipe reach temperature required thereby contact with mould, after insulation, carry out bending again by tube wall.The mould structure complexity of this method, the numerical control device investment is big, cost is high, and parts quality requires to have sufficient early-stage preparations and development work to the technological parameter sensitivity.Especially for the situation that bends the light-wall pipe product, improper if technological parameter is selected, be easy to occur the tube wall wrinkling and cause scrapping of part or even mould.
Summary of the invention
In order to overcome the deficiency of existing magnesium alloy pipe bending method, the invention provides a kind of hot bending manufacturing process of resistance heated bending, a cover tubing resistance heated bending apparatus is provided simultaneously.The requirement that the part was rapidly heated when this hot-bending method can satisfy the magnesium alloy pipe hot bending, at short notice can be with magnesium alloy pipe local heat to required bending forming temperature, efficiency of heating surface height, bending forming temperature are easy to control, are applicable to the hot bending shaping processing of magnesium alloy pipe.
A kind of magnesium-alloy tube hot-bending method, this hot-bending method may further comprise the steps:
(1) to fill the low-melting-point metal plug of dry sand or corresponding specification in filling filler magnesium alloy pipe is managed in pipe before bending forming;
(2) length and the position of heating of pipe blank determined in line;
(3) treating that bending section pipe surface smears lubricant, lubricant can be used animal oil resin acid sodium;
(4) pipe is installed and cooperates pressurization energising mechanism and bending mould, and pipe to be curved is installed to be fixed on the bending pipes fixed rack;
(5) bending mould is carried out preheating, 120~150 ℃ of preheat temperatures;
(6) by the footstep mechanism pressurization electrode is closely contacted with pipe, energising is heated to the pipe bending section then;
(7) adopt post bake technology with heating of pipe blank to temperature required (225 ℃);
(8) heating of pipe blank is after temperature required, and cutting off the electricity supply stops heating, cancels electrode pressure, and once property is finished the bending forming processing of pipe on the bending forming mould.
Magnesium alloy pipe resistance heated bending apparatus among the present invention is made up of following components:
(1) resistance heated power supply, the conductive arm up and down in its both positive and negative polarity output and the pressurization energising mechanism links;
(2) pressurization energising mechanism, it is by conductive arm up and down, conducting rod, upper/lower electrode and the utmost point that insulate are up and down formed up and down, design has cooling water path in conductive arm and conducting rod, and on conductive arm and conducting rod respectively the design intake-outlet is arranged, with cooling water pipe these intake-outlets and cooling water circulating device are linked;
(3) circulating cooling system, it is made up of cooling water path, cooling water pipe and cooling water circulating device in the pressurization energising mechanism, and cooling water circulating device can adopt ripe commercially available special product.
(4) bending mould, it is fixed on the bending pipes fixed rack, by roll wheel, roll wheel shaft, pivoted arm, roller and roller shaft form, heated pipe is at roller and roll between the wheel, rolling wheel maintains static moving, pivoted arm drives roller and rotates along rolling wheel shaft clockwise when crooked under the bending moment effect, thereby the bending forming of finishing pipe is processed.
The present invention adopts two electrodes to pass through bigger electric current in the short time in the section of the being bent pipe of magnesium alloy pipe, the resistance heat that utilizes this section body itself to produce heats, reach temperature required back deenergization, carry out single use deflectable immediately, finish the bending forming of tubing.In the resistance heated process of magnesium alloy pipe, need to adopt post bake technology, that is: at first heat certain hour, suspend heating in short-term after reaching uniform temperature, be heated to once more and stop after temperature required.Post bake technology can reduce the cooling velocity of magnesium alloy pipe in the bending forming temperature range effectively, for tube bending forming provides good bending forming performance and abundant bending machining time.
Beneficial effect of the present invention: can be in 2 minutes the magnesium alloy pipe be heated to required bending forming temperature, efficiency of heating surface height; The resistance heated bending apparatus is easy and simple to handle, adaptability good, working stability is reliable; The magnesium alloy pipe bending quality is good, and bending pipes section outer arc side crack-free, that the inner arc side does not have unstability is wrinkling, the maximum ellipticity of cross section<8%, thickest reduction<12.5%; The average per bending forming processing that can finish a magnesium-alloy tube in 5 minutes.There is huge applications to be worth in the tubing processing technique field.
Description of drawings
Fig. 1 is the front view of magnesium alloy pipe resistance heated bending apparatus; Wherein, 1. cooling water circulating device, 2. cooling water pipe, 3. resistance heated power supply, 4. pipe pressurization energising mechanism, 5. bending mould, pipe 6. to be curved, the 7. crooked fixed rack of pipe, 8. electrode pressurization pedal;
Fig. 2 is the front view of the pressurization energising of pipe shown in Fig. 1 mechanism, wherein, and 5. bending mould, 6. pipe to be curved, 9. top electrode, 10. water inlet, 11. last conducting rod, conductive arm on 12., 13. delivery ports, 14. the last insulation utmost point, 15. clam members, 16. fastening gripper shoes, 17. bottom electrode, 18. water inlets, 19. times conductive arms, 20. following conducting rod, 21. delivery ports, 22. times insulation utmost points;
Fig. 3 is the side view of the bending apparatus of resistance heated shown in Fig. 1; Wherein, 3. resistance heated power supply, 5. bending mould, pipe 6. to be curved, 9. top electrode, conducting rod on 11., conductive arm on 12., 19. times conductive arms, 20. times conducting rods, 22. times insulation utmost points, 23. delivery ports, 24. water inlets, 25. water inlets, 26. delivery ports;
Fig. 4 is the vertical view of bending mould shown in Fig. 1; Wherein, pipe 6. to be curved, 9. top electrode, 15. clam members, 17. bottom electrodes, 27. roll wheel, and 28. roll wheel shaft, 29. pivoted arms, 30. rollers, 31. roller shafts.
The specific embodiment
Below in conjunction with accompanying drawing magnesium-alloy tube hot-bending method among the present invention and equipment thereof are described further.
Fig. 1 is the front view of magnesium alloy pipe resistance heated bending apparatus, wherein, and 1. cooling water circulating device, 2. cooling water pipe, 3. resistance heated power supply, 4. pipe pressurization energising mechanism, 5. bending mould, 6. pipe to be curved, the 7. crooked fixed rack of pipe, 8. electrode pressurization pedal; In Fig. 1, pipe to be curved (6) is fixed on the crooked stand, and places the rolling between wheel and the roller of bending mould (5), by trampling pressurization pedal (8), drives mechanical precompressed mechanism electrode is closely contacted with the pipe maintenance.
Fig. 2 is the front view of the pressurization energising of pipe shown in Fig. 1 mechanism, wherein, and 5. bending mould, 6. pipe to be curved, 9. top electrode, 10. water inlet, 11. last conducting rod, conductive arm on 12., 13. delivery ports, 14. the last insulation utmost point, 15. clam members, 16. fastening gripper shoes, 17. bottom electrode, 18. water inlets, 19. times conductive arms, 20. following conducting rod, 21. delivery ports, 22. times insulation utmost points; In Fig. 2, connect closely between conductive arm (12,19) and conducting rod (11,20), conducting rod (11,20) and the upper/lower electrode (9,17), make that the contact resistance at these two positions is low as far as possible; The clamping contact-making surface of upper/lower electrode and pipe (6) is processed into circular arc according to the external diameter of pipe, keep good face to contact between exert pressure the arc-shaped inner surface that makes electrode and outer surface of tube blank by foot-operated mechanical precompressed mechanism in when heating, guarantee that conduction is good, in order to avoid contact resistance increases, cause the power loss in the heating process.The utmost point (14,22) that insulate up and down adopts insulation and heat-resisting materials processing to form, and the clamping contact-making surface of itself and pipe is processed into circular arc according to the external diameter of pipe equally, and is firm to guarantee clamping.Upper/lower electrode (9,17) can move along conducting rod (11,20), and electrode size can be processed according to the outside dimension of pipe, so just can satisfy the hot-bending forming that adds of various outer diameter and differently curved radius pipe fitting within the specific limits.
Fig. 3 is the side view of the bending apparatus of resistance heated shown in Fig. 1; Wherein, 3. resistance heated power supply, 5. bending mould, pipe 6. to be curved, 9. top electrode, conducting rod on 11., conductive arm on 12., 19. times conductive arms, 20. times conducting rods, 22. times insulation utmost points, 23. delivery ports, 24. water inlets, 25. water inlets, 26. delivery ports; In Fig. 3, resistance heated power supply (3) adopts the power transformer with decline external characteristics, can obtain different secondary floating voltages by the method for regulating the primary umber of turn, thereby realize the adjusting of heating power, cooling is forced in the transformer secondary output water flowing, and conductive arm (12,19) links to each other with the secondary of heating power supply transformer by the galvanic circle.
Fig. 4 is the vertical view of bending mould shown in Fig. 1; Wherein, pipe 6. to be curved, 9. top electrode, 15. clam members, 17. bottom electrodes, 27. roll wheel, and 28. roll wheel shaft, 29. pivoted arms, 30. rollers, 31. roller shafts; In Fig. 4, heated pipe (6) is positioned at roller (27) and rolls between the wheel (30), roll wheel and maintain static movingly, pivoted arm (29) drives roller and rotates along rolling wheel shaft (28) clockwise when crooked under the bending moment effect, thereby the bending forming of finishing pipe is processed.
Because electric current can reach thousands of amperes in the heating process, so the galvanic circle all adopts Forced water cooling to guarantee the reliable heating and the efficiency of heating surface of pipe.In Fig. 3, the cooling of power unit return conductors that comprises conductive arm is by four intake-outlets (23,24,25, the 26) water flowing on two conductive arms up and down, and design has cooling water path in the conductive arm; In Fig. 2, the design of conducting rod (11,20) center has through hole, cooling water path is provided, and has designed intake-outlet at two ends (10,13,18,21), can guarantee the cooling of conducting rod and electrode.Connect with cooling water circulating device (among Fig. 1 1) again after with cooling water pipe each intake-outlet being connected in proper order.
By following steps, the hot bending of finishing magnesium alloy pipe is shaped and processes:
(1) fills the low-melting-point metal plug of dry sand or corresponding specification in filling filler magnesium alloy pipe is managed in pipe before bending forming;
(2) length and the position of heating of pipe blank determined in line;
(3) treating that bending section pipe surface smears lubricant, lubricant is an animal oil resin acid sodium;
(4) pipe is installed and cooperates pressurization energising mechanism and bending mould, and pipe to be curved is installed to be fixed on the bending pipes fixed rack;
(5) bending mould is carried out preheating, 140 ℃ of preheat temperatures.
(6) pressurization makes electrode closely contact with pipe, and energising is heated to the pipe bending section.Adopt post bake technology with heating of pipe blank to 225 ℃;
(7) heating of pipe blank is after temperature required, and cutting off the electricity supply stops heating, cancels electrode pressure, and once property is finished the bending forming processing of pipe on the bending forming mould.
Utilize that this method and apparatus heating bending operation is easy, adaptability good, working stability is reliable; The magnesium alloy pipe bending quality is good, and bending pipes section outer arc side crack-free, that the inner arc side does not have unstability is wrinkling, and the average per bending forming that just can finish a magnesium-alloy tube in 5 minutes is processed.