CN115193920A

CN115193920A - Core rod manufacturing method, core rod repairing method and equipment for machining core rod

Info

Publication number: CN115193920A
Application number: CN202210930037.9A
Authority: CN
Inventors: 王旭午
Original assignee: Individual
Current assignee: Individual
Priority date: 2022-08-03
Filing date: 2022-08-03
Publication date: 2022-10-18

Abstract

The invention discloses a core rod manufacturing method, a defective core rod repairing method and equipment for processing a core rod, which are characterized in that the surface strengthening treatment of the core rod can be realized by simply modifying the existing production equipment, replacing a surface chromium plating and/or surface induction quenching process in the original process by a rolling or extruding process at a proper position in the original process, and through simpler design and improvement, the performance of the core rod is greatly improved, particularly when the surfacing technology is used for repairing the core rod in an equal diameter manner, a good nano-scale surface structure can be obtained by rolling or extruding a surfacing layer, the performance of the core rod is greatly improved, the service life of the core rod is prolonged, and the cost is very low.

Description

Core rod manufacturing method, core rod repairing method and equipment for machining core rod

Technical Field

The invention relates to the field of tools and dies used in the deformation process of hot-rolled seamless steel pipes, in particular to a core rod manufacturing method, a core rod repairing method and equipment for machining a core rod.

Background

The mandrel is a tool and a die used in the deformation process of the hot-rolled seamless steel pipe, and is a rod-shaped tool and a die which are inserted into the inner cavity of the steel pipe when the deformation of the steel pipe is realized in the working procedure of a pipe rolling mill (also called a steel pipe stretcher).

The relative movement speed of the mandrel and the steel pipe is high in the working process of the pipe mill, the mandrel can be short, the relative movement speed is low, and the mandrel needs to be long, so that the mandrel can penetrate through the deformation of the whole steel pipe. According to the condition that the Mandrel is used in a mainstream unit for producing the hot-rolled seamless steel tube, the Mandrel is roughly divided into a long Mandrel, a longer Mandrel and a short Mandrel, a floating Mandrel continuous rolling tube unit (Mandrel Mill, MM for short) uses the long Mandrel, and the length of a working rod is about 30-33 meters generally; the long mandrel is used on a retained mandrel continuous rolling Mill unit (such as Multi-Stand Pipe Mill, MPM for short; premium Quality Finishing, PQF for short and the like), and the length of the working rod is about 12.5 meters; short core rods are used on an inclined tube Rolling Mill (such as Accurate Rolling Mill, ACCU-ROLL for short), and the length of the working rods is about 4 meters generally; there are also groups using shorter mandrels.

The diameter of the mandrel is selected according to the diameter of the rolled steel pipe, the deformation and the like, and a factory needs to prepare the mandrel corresponding to each steel pipe product with different diameters. The core rod moves relative to the steel pipe in work, but relative friction is not beneficial to deformation, so that the smaller the friction force is, the better the surface smoothness of the core rod is, in addition, the surface quality of the core rod directly participates in the deformation of the steel pipe, the surface quality of the core rod is related to the quality of a finished product, for example, a defect of a few millimeters exists on a core rod with the length of tens of meters, the whole produced seamless steel pipe is judged to be a defective product or an unqualified product, meanwhile, the core rod directly participates in metal deformation, bears a large rolling load, and has larger consumption ratios such as abrasion, fatigue loss and the like, therefore, the performance quality requirement of the core rod is higher, frequent maintenance can also be involved, a seamless steel pipe factory with 50 ten thousand tons of a year can produce at least one core rod per day, and the core rod needs offline maintenance, and therefore, the core rod is a tool and die with the largest quantity and the highest manufacturing cost in the seamless steel pipe factory.

The existing core rod processing technology is slightly different according to different types of core rods:

the mandrel speed is limited when the retained mandrel continuous rolling mill rolls, namely, the movement speed of the mandrel is very slow relative to the movement speed of the steel pipe, the deformation and the movement speed of the steel pipe are relatively high, the metal deformation is very large, the relative sliding friction force between the surface of the mandrel and the steel pipe is very large, and stick-sticking accidents are easy to occur, namely, the mandrel cannot be extracted from the inner cavity of the (rolled) steel pipe, so that the surface of the mandrel is required to be smooth and hard, and the purpose is to reduce the surface friction coefficient of the mandrel and increase the wear resistance, and the stick-sticking accidents are avoided. Therefore, the requirement on the surface smoothness of the retained mandrel is very high, and a treatment process for plating hard chrome on the surface of the mandrel is generally selected. The manufacturing process of the longer mandrel for the retained mandrel continuous rolling unit comprises the following steps:

1) Manufacturing a new core rod: (1) rolling or forging a long billet; (2) Quenching and tempering are carried out through heat treatment, so that the metallographic structure of the blank has enough strength and toughness, and the comments of the same type are omitted; (3) Machining the round core rod, namely machining the round core rod into a round core rod with a specific diameter according to the required size precision, and omitting comments on the same type at the back; (4) Chromium plating is an essential ring on the surface of the core rod, and in order to improve the smoothness and comprehensive hardness of the surface of the round core rod, the same types of comments are omitted in the following; and (5) obtaining a finished core rod which can be used on a machine.

2) One of the defective core rod repairing (or re-turning) manufacturing processes is as follows: (1) Machining the defective core rod, namely turning off the defects such as fatigue cracks, abrasion/defect layers and the like on the surface of the defective core rod by machining the used defective core rod, and omitting comments on the same type; (2) Surfacing, generally submerged arc welding, because the diameter of the core rod after turning becomes small, when equal-diameter repair is carried out, the diameter lost due to turning must be compensated by means of surfacing technology, and comments are omitted in the same type of follow; (3) annealing treatment, and eliminating the internal stress of the surfacing structure; (4) machining the core rod material; (5) carrying out chrome plating on the surface of the machined core rod; and (6) finishing the core rod.

3) And a second defective core rod re-turning manufacturing process: (1) Machining the defective core rod into a non-defective core rod, namely directly turning the defective core rod to a new diameter on the basis of the defective core rod to obtain the non-defective core rod; (2) plating chromium on the surface of the flawless core bar; and (3) finishing the core rod. The mode is not equal diameter repair, and is diameter reducing modification of the core rod, namely turning off the flaws on the surface of a thick core rod with flaws, and continuing turning until the diameter of the core rod meets a certain smaller diameter specification, so that the core rod is used as a core rod of another specification.

The length of the floating mandrel is substantially equal to the maximum length of the steel tube to be produced, even longer than that of the steel tube to be produced, and the relative movement between the mandrel and the steel tube during rolling is small, so that the requirements on the surface quality of the floating mandrel are less strict, i.e. more so that sufficient hardness is required and the requirements on the finish are not as high as that of the retained mandrel.

The manufacturing process of the long core rod for the floating core rod continuous rolling mill set and the pipe jacking machine set comprises the following steps:

1) The manufacturing process of the new core rod comprises the following steps: (1) a rolled billet; (2) quenching and tempering by heat treatment; (3) machining the round core bar; (4) The surface of the core rod is quenched by high-frequency induction, and the core rod is long in length and large in volume, so that the step is generally realized by adopting a high-frequency induction surface quenching process; and (5) obtaining a finished core rod.

2) One of the repairing (or re-turning) manufacturing processes of the defective core rod is as follows: (1) machining a defective mandrel; (2) surfacing; (3) annealing treatment; (4) machining the round core bar; (5) carrying out high-frequency induction quenching on the surface of the core rod; and (6) finishing the core rod. This procedure is typically used for isodiametric repairs.

3) And a second defective core rod re-turning manufacturing process: (1) machining the defective core rod into a non-defective core rod; (2) carrying out high-frequency induction quenching on the surface of the core rod material; and (3) finishing the core rod. This step is generally used for diameter reduction and modification of the mandrel.

In the floating core rod manufacturing process, the core rod surface high-frequency induction quenching is unique: the object is to increase the surface hardness of the core rod to increase its wear resistance, which has no particular requirement on the surface friction coefficient.

Theoretically, the requirements of the skew rolling mill group on the mandrel bar are lower, and the surface of the mandrel bar has no special treatment requirements, but in actual production, due to the requirement of rolling special products, a factory occasionally carries out laser quenching on the surface of the mandrel bar used by the skew rolling mill group so as to improve the surface hardness of the mandrel bar and increase the wear resistance of the mandrel bar.

The inclined tube rolling unit uses the manufacturing process of the short core rod:

1) Manufacturing a new core rod: (1) rolling/forging a billet; (2) quenching and tempering by heat treatment; (3) machining the round core bar; and (4) finishing the core rod.

2) One of the repairing (or re-turning) manufacturing processes of the defective core rod is as follows: (1) machining a defective mandrel; (2) surfacing; (3) annealing treatment; (4) machining the core rod material; and (5) finishing the core rod.

3) And a second defective core rod re-turning manufacturing process: (1) machining a defective core rod into a non-defective core rod; and (2) finishing the core rod.

The industry is commonly known: the hard and smooth surface of the core rod is necessary, the higher the hardness is, the more ideal the smoothness is, but under the existing core rod manufacturing process technology, the high cost is needed for realizing the ideal core rod, the chromium plating and quenching need to consume a large amount of energy, special equipment is needed, the environment can be polluted, and some manufacturers have to relax the high requirement on the surface quality of the core rod so as to reduce the cost of the core rod.

In summary, the mandrel is one of the important steel pipe deformation tools, which directly involves in metal deformation, directly affects the quality of the rolled steel pipe, bears a large rolling load, and has large consumption of abrasion, fatigue loss and the like, so the performance and quality requirements of the mandrel are high, and naturally, the manufacturing cost of the mandrel is correspondingly increased, and the cost proportion of the mandrel is large. Therefore, it is very meaningful to research and improve a new process for improving the performance of the core rod and reducing the production cost.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: the manufacturing method of the core rod is provided, so that the production cost is reduced, and the working efficiency is improved.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

a method for manufacturing a mandrel comprises the following steps: s1, preparing a blank; s2, carrying out thermal treatment tempering on the blank to obtain a tempered blank; s3, machining the quality-adjusted blank to obtain a round core bar; s7, obtaining a finished core rod; and step S5 of performing one of cold rolling, warm rolling, cold extrusion and warm extrusion on the surface of the round core bar is further arranged after the step S3 and before the step S7.

Compared with the prior art, the invention has the following technical effects:

the cold rolling, the warm rolling, the cold extrusion and the warm extrusion are pure mechanical processing, the process is simple, the realization is easy, the environment is not polluted, the working hours are short, the surface hardness and the finish degree of the core rod processed by the working procedure can meet the requirements required by the current core rod, and the production cost is reduced. The principle is analyzed as follows:

principle of cold/warm rolling: at room temperature, carrying out mechanical rolling deformation on the surface of the finish-machined core rod, namely cold rolling; heating the finish-machined mandrel to hundreds of degrees centigrade (note, the temperature is required to be below the phase transition temperature of the metal material of the mandrel, specifically, the temperature is selected according to the material of the mandrel, generally 300-400 degrees centigrade), and mechanically rolling and deforming the surface of the finish-machined mandrel, namely, warm rolling;

principle of cold/warm extrusion: at room temperature, inserting the finish-machined mandrel into a closed annular or columnar inner cavity, extruding the mandrel through an inner cavity hole, forcibly drawing out or pushing out the mandrel and the like to perform surface deformation of the mandrel, and calling cold extrusion: or heating the core rod by hundreds of degrees (note that the temperature is below the phase transition temperature of the metal material of the core rod), inserting the finish-machined core rod into a closed annular or columnar inner cavity, and performing surface deformation on the core rod in a mode of forcibly pulling out or pushing out after the core rod is extruded through the inner cavity hole, and calling warm extrusion.

In the processes of cold rolling, warm rolling, cold extrusion and warm extrusion, the metal on the surface of the core rod can generate cold processing deformation, and the deformation zone comprises a pressing-in zone, a plastic deformation zone and an elastic deformation zone.

The cold rolling, the warm rolling, the cold extrusion and the warm extrusion have the following effects:

(1) Work hardening or cold work hardening occurs on the metal surface and is characterized by a surface hardness increase of at least 15-20%.

The Rockwell hardness of a core material of a common core rod is 37-39, the Rockwell hardness of metal chromium is 62-65, the traditional chromium plating process on the surface of the core rod is equivalent to that a layer of metal chromium with the Rockwell hardness of 62-65 is added on a base material with the Rockwell hardness of 37-39, the surface hardness of the metal chromium is higher than the original hardness of the base material, so the hardness value punched on the surface of the chromium plated core rod is the comprehensive hardness of the chromium layer and the base material, the comprehensive hardness is generally improved by about 10-15% on the hardness of the base material, and when the Rogowski hardness of the base material is 37-39, the comprehensive hardness is 40-44 Rockwell hardness.

After cold rolling or warm rolling, the hardness of the metal surface is improved by 15-20% relative to the original hardness, and when the original base material hardness is 37-39 Rogowski hardness, the hardness of the surface of the core rod after cold rolling or warm rolling reaches 42-46 Rogowski hardness, which is equivalent to the comprehensive hardness (Rogowski hardness 40-44) of the traditional chromium plating process, and meets the use requirement.

(2) Flattening the unevenness (0.45-0.70 micrometers) and microcracks of the microscopic surface of the metal, and performing the following characteristics: the surface smoothness is improved (the microscopic surface reaches 0.04-0.06 micron), and is equivalent to the surface smoothness of the core rod after chrome plating;

(3) The metal crystal grains on the surface and the surface layer (a certain depth below the surface) of the core rod are crushed and dislocated and deformed to generate nano-scale fine crystal grains, so that the high temperature resistance, corrosion resistance and wear resistance of the metal are greatly improved;

(4) The rolling mandrel surface introduces a 'compressive stress' state, has a great inhibiting effect on the generation of fatigue cracks, and greatly improves the fatigue resistance of the mandrel surface, thereby greatly prolonging the service life of the mandrel.

The method fully utilizes the characteristic of metal cold-work hardening, can realize the surface strengthening treatment of the mandrel through simpler design and improvement, greatly improves the performance of the mandrel, has low cost, and has great benefit to related steel pipe production enterprises.

The process technology of the invention can save the procedures of high-frequency quenching on the surface of the core rod and chromium plating on the surface of the core rod, thereby reducing the pollution of the production link of the core rod to the environment and reducing the requirement on energy.

On the basis of the technical scheme, the invention can be further improved as follows.

Preferably, after step S5 and before step S7, step S6 is further provided to perform surface chrome plating on the rolled or extruded round bar.

The beneficial effect of adopting the further scheme is that the comprehensive hardness of the surface of the core rod can be further improved.

The invention provides a method for repairing a defective core rod, which comprises the following steps: SF1, machining the core rod with the defects, removing the surface defect layer, machining to a new set size, and obtaining the core rod without the defects after machining; SF5, obtaining the repaired core rod, and arranging a step SF3 after SF1 and before SF5, and carrying out one treatment of cold rolling, warm rolling, cold extrusion and warm extrusion on the machined flawless core rod material.

Compared with the prior art, the invention has the following technical effects:

the technical effects of the cold rolling, the warm rolling, the cold extrusion and the warm extrusion technologies on the restoration of the core rod are represented by the improvement of the surface quality of the core rod, and the effects of the cold rolling, the warm rolling, the cold extrusion and the warm extrusion technologies are similar to the effects of the core rod manufacturing method and are not repeated herein.

Preferably, the machining to the new set size in the SF1 means direct turning or turning after overlaying;

the direct turning comprises the following steps: directly turning the defective core rod to a new set diameter, wherein the new set diameter is smaller than the original diameter of the defective core rod;

the turning process after overlaying comprises the following steps: removing the surface defect layer of the core rod with the defects to obtain a non-defective rod, overlaying the non-defective rod to obtain an overlaying rod, annealing the overlaying rod, and machining the overlaying layer of the overlaying rod to a new set diameter.

The adoption of the further scheme has the advantages that according to the production condition, the diameter-reducing modification or equal-diameter repair can be carried out on the defective core rod, the repair scheme is various, and the recycling direction of the defective core rod is expanded.

Particularly, for a repair process comprising a surfacing process, in the traditional repair process, after annealing treatment is carried out on a surfacing layer and machining is finished, the whole machining repair work is finished, but a core material of a core rod is subjected to quenching and tempering treatment, the surfacing layer is a solid state formed by directly cooling a welding material from a molten state, the core material is not subjected to quenching and tempering, the internal metallographic structure of the core rod is an as-cast dendritic structure, the difference between the metallographic structure of the core material of the core rod and the metallographic structure of the core rod after quenching and tempering is large, the surfacing layer in the state has poor high temperature resistance, wear resistance, corrosion resistance and fatigue resistance, and during the process of participating in rolling of a steel pipe, large fatigue cracks are easy to appear on the surface of the core rod subjected to surfacing repair, and the service life of the core rod reaches 80-90% of a pure modulation core rod at most; after this scheme of adoption, utilize cold rolling, warm rolling, cold extrusion or warm extrusion to carry out the cold work hardening processing to the surfacing layer, make the metal crystalline grain of the surface of surfacing layer and top layer (certain degree of depth under the surface) crushed, dislocation warp, appear "nanometer" tiny crystalline grain, and the plug surface introduces "compressive stress" state, this is just improving the high temperature resistant, corrosion-resistant, wearability, the fatigue resistance's of surfacing layer performance by a wide margin to improve the life of restoration back plug by a wide margin.

After the scheme is adopted, the welding material does not need to select high-end welding materials (containing various rare elements such as cobalt, nickel, molybdenum and the like), and the common 1Cr13 welding material (or the welding material with lower alloy) can also be used for obtaining the repair core rod meeting the production requirement, so that the surfacing cost can be effectively reduced by over 50 percent.

Preferably, after the step SF3 and before the step SF5, a step SF4 is arranged, and the surface of the flawless core rod material after cold rolling, warm rolling, cold extrusion or warm extrusion is subjected to chromium plating treatment.

The beneficial effect of adopting the above-mentioned further scheme is that the comprehensive hardness of core rod surface is further promoted.

The invention provides equipment for processing a core rod, which is used for realizing the core rod manufacturing method or the repair method of the core rod with defects, and comprises a rolling device or an extrusion device for performing rolling treatment or extrusion treatment on the core rod, wherein the rolling device or the extrusion device is arranged on a tool post or a sliding seat of a machine tool;

the rolling device is a rolling wheel or a rolling knife, and the rolling surface of the rolling knife can be a cambered surface or a plane; the extrusion device is an extrusion die, the independently arranged rolling device or extrusion device is arranged on a machine tool for the simplest design, the rolling wheel device or extrusion device is directly arranged on a tool post or a sliding seat of the lathe for machining the core rod, and after the finish machining of the core rod is finished, the rolling or extrusion work can be started.

The roller and the hole pattern on steel cold rolling, calendering and hot rolling equipment can also be directly used as a rolling device or an extrusion device of the core rod; the steel cold rolling, rolling and hot rolling equipment comprises a transverse rolling mill, a wedge transverse rolling mill, a longitudinal rolling mill, an inclined rolling mill, a rotary straightening machine, a cold drawing machine, a cold rolling mill, a push reducing machine, a spinning machine and the like, and can be used as a rolling device only by adjusting the rollers and the hole patterns of the lower transverse rolling mill, the wedge transverse rolling mill, the longitudinal rolling mill, the inclined rolling mill, the rotary straightening machine, the cold rolling mill and the spinning machine, or can be used as an extruding device only by adjusting the parameters of the circular hole outer dies of the cold drawing machine and the push reducing machine, so that the rolling or the extruding of the core rod is realized, the adjustment only relates to the adjustment of the parameters, and the existing equipment does not need to be improved in mechanical structure.

Preferably, an ultrasonic vibration device or an electromagnetic vibration device is additionally arranged on the rolling device or the extrusion device.

The ultrasonic vibration device or the electromagnetic vibration device can perform high-frequency micro-amplitude impact on the surface of the core rod in the rolling or extruding process, so that the surface quality of the core rod after rolling or extruding processing is better, and the surface finish quality of the core rod is further improved.

Drawings

FIG. 1 is a schematic view of a layout of a rolling cutter without a mandrel supporter according to embodiment 1 of the present invention;

FIG. 2 is a schematic view showing the positional structure of the rolling cutter and the mandrel holder in the first case in embodiment 1 of the present invention;

FIG. 3 is a schematic view showing the positional structure of the rolling cutter and the mandrel holder in the second case of embodiment 1 of the present invention;

FIG. 4 is a schematic view showing the structure of the position of a rolling wheel in embodiment 2 of the present invention;

FIG. 5 is a schematic view of the layout of an extrusion apparatus in example 3 of the present invention.

FIG. 6 is a schematic flow chart in example 4.

In the drawings, the parts names represented by the respective reference numerals are listed as follows:

1. a core rod; 21. a first rolling wheel; 22. a second rolling wheel; 23. a third rolling wheel; 4. rolling a cutter; 5. a mandrel support; 6. a circular hole outer die; F. and (4) pushing force.

Detailed Description

The principles and features of this invention are described below in conjunction with the following drawings, which are set forth to illustrate, but are not to be construed to limit the scope of the invention.

Example 1:

the utility model provides a cold rolling equipment of processing plug, includes the rolling press device, the rolling press device includes rolling press sword 4, as shown in figure 1, rolling press sword 4 is 1, is the circular arc type, sets up on the knife rest of lathe, if treat that processing plug 1 is shorter (non-slender pole), for example only 0.5 meters is long, then need not the assistance of other structures, the rigidity of plug 1 self is enough to bear the pressure of rolling press sword 4, guarantees that plug 1 self is whole can not be crooked.

If the mandrel 1 to be machined is in a slender rod shape, a mandrel support 5 should be provided opposite to the rolling cutter 4 to balance the pressure of the rolling cutter 4 on the mandrel 1, so as to avoid the bending of the mandrel 1 caused by the pressure, as shown in fig. 2, a mandrel support roller is provided opposite to the rolling cutter 4, the mandrel support roller can balance the pressure of the rolling cutter 4, and it is ensured that only the surface of the mandrel 1 is rolled and deformed, and the whole mandrel 1 itself cannot be bent integrally due to the pressure of the rolling cutter 4. Of course, a plurality of support rollers may be provided, as shown in fig. 3, two support rollers are provided opposite to the rolling cutter 4, and the whole mandrel bar 1 is ensured not to be bent and deformed by the pressure of the rolling cutter 4 as a whole as long as the pressure of the rolling cutter 4 is balanced.

Example 2:

the cold rolling equipment for machining the core rod comprises a 3-wheel rolling device, wherein the 3-wheel rolling device is distributed as shown in figure 4 and comprises 3 rolling wheels, the diameter of each rolling wheel is about 20mm, the rolling wheels are uniformly distributed along the circumferential direction of the core rod 1 to be machined, and the whole device is fixed on a tool post of a machine tool. Considering that the mandrel 1 is relatively long, 3 rolling wheels hold the mandrel 1 for rolling, so that the rolling pressure is balanced among the 3 rolling wheels, wherein the balance refers to internal force balance, and the resultant force of the forces applied to the mandrel 1 by the 3 rolling wheels in the radial direction is zero, that is, the rolling force only enables the surface of the mandrel 1 to be subjected to rolling deformation, and the integral bending of the mandrel 1 is not caused, so that the machining precision is not affected.

As described in example 1, the number of rolling wheels is not necessarily 3, but only 1 rolling wheel may be used, and when 1 rolling wheel is used, if the core rod 1 to be processed is relatively short (non-elongated rod), for example, about 0.5 m, no additional core rod support 5 is needed, and the core rod 1 has enough rigidity to bear the pressure of the rolling wheel, so as to ensure that the core rod 1 itself is not bent; if the slender rod mandrel 1 is processed, a mandrel support part 5 needs to be arranged at a position matched with the opposite side of the rolling wheel, so that the pressure of the rolling wheel is balanced by the mandrel support part 5, and the mandrel 1 is ensured not to be bent and deformed integrally. More rolling wheels may be used, so long as the resultant force applied to the core rod 1 by all the rolling wheels during the rolling process of the core rod 1 is balanced, so as to ensure that the core rod 1 is not bent and deformed as a whole.

The rolling process can also directly select the roll and the pass on the frames of a transverse rolling mill, an oblique transverse rolling mill, a longitudinal rolling mill, an oblique rolling mill, a rotary straightening machine, a cold rolling mill, a spinning machine and the like on site as the rolling device, at the moment, no new equipment is needed, and only the pass parameter of the roll is needed to be adjusted, so the modification cost of the new process on site is very low.

Example 3

The utility model provides an equipment of processing plug, includes the extrusion device, the extrusion device is the outer mould 6 of round hole of ring type, and its internal diameter equals the finished product diameter of waiting to process the plug, is less than to wait to process plug external diameter 0.1-0.3mm (specifically confirm according to the extrusion volume), will the outer mould 6 of round hole is installed on the knife rest or the slip table of lathe to provide drive power F through hydraulic system, drive the outer mould 6 of round hole along 1 axis direction removal of plug, the realization is treated the extrusion of processing plug 1.

Existing equipment on site, such as a cold drawing machine or a push reducing machine, can also be directly used as an extrusion device to realize the extrusion of the mandrel bar 1 to be processed.

Example 4:

a manufacturing method of a retained mandrel, as shown in fig. 6, includes the following steps:

s1, preparing a blank;

s2, carrying out thermal treatment tempering on the blank to obtain a tempered blank;

s3, machining the quality-adjusted blank to obtain a round core bar;

s5, performing cold rolling treatment on the surface of the round core bar by using cold rolling equipment;

and S7, obtaining the finished core rod.

The method has the advantages that the improvement on the existing production equipment is very small, the core rod with the surface comprehensive hardness and the surface smoothness basically equivalent to or even exceeding those of the traditional processing technology can be obtained after the 'core rod surface high-frequency quenching process' and the 'core rod surface chromium plating process' are cancelled, the energy is saved, the cost is reduced, and the method is more environment-friendly. Of course, if the chromium plating treatment is performed on the surface of the round bar subjected to cold rolling after step S5, the comprehensive hardness of the surface of the mandrel is further improved, and the use effect of the mandrel is better.

Example 5: the equal-diameter repairing method of the retained mandrel comprises the following steps:

the diameter of the repaired and manufactured mandrel is 192-460 mm, and the original mandrel repairing and manufacturing process comprises the following steps: used defective core rod → machining: turning a fatigue layer of a defective core rod → surfacing, generally adopting a submerged arc welding process → annealing, eliminating internal stress generated in a surfacing structure → machining, and finely turning to required size and precision to obtain a round core rod → plating chromium on the surface of the round core rod → obtaining a finished core rod which is used on a machine. Each time of chromium plating takes more than 14 hours, and environmental pollution is generated.

The process of the invention is changed to the following steps: used defective core rod → machining: turning a fatigue layer with a defective core rod → surfacing, submerged arc welding → annealing, stress relief → machining, and finish turning to the required size and precision to obtain a round core rod → rolling the surface of the round core rod → finishing the core rod, and using on a machine.

The three-wheel rolling device in the embodiment 2 is assembled according to the mandrel specification, wherein the first rolling wheel 21 and the second rolling wheel 22 are not moved, and the third rolling wheel 23 can adjust the radial pressing amount to meet different rolling amount requirements. Rolling for 2 times: the first pass is as follows: the rolling reduction of the single edge is 0.15mm; the second time: the rolling reduction of the single side is 0.05mm. The 12.5 meter long core rod only needs 2 hours for rolling once, and only needs 4 hours for 2 times of rolling. Compared with the chromium plating process, the time is saved considerably.

Compared with the original repair process: the surface hardness of the rolled core rod is improved by 18 percent, which is equivalent to the comprehensive hardness of the surface of the core rod of the traditional chromium plating process, and the smoothness reaches the level equivalent to the chromium plating surface. Because the chromium plating process is omitted, the requirement on the welding material is reduced, the common welding material is used for replacing the original welding material containing rare metal, the cost of the welding material is reduced by 50 percent, the processing working hour is also saved, the cost for manufacturing a single mandrel is reduced by about 40 to 50 percent compared with the prior art, and the method is environment-friendly;

example 5 after the repaired core rod is used on a machine, the number of rolled steel pipes is improved by 20-50%, the cost performance is greatly improved, and the cost performance is very high.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims

1. A core rod manufacturing method comprises the following steps: s1, preparing a blank; s2, carrying out thermal treatment tempering on the blank to obtain a tempered blank; s3, machining the quality-adjusted blank to obtain a round core bar; s7, obtaining a finished core rod; the method is characterized in that step S5 is further provided after step S3 and before step S7, and one of cold rolling, warm rolling, cold extrusion and warm extrusion is carried out on the surface of the round core rod.

2. The method of claim 1, further comprising a step S6 of performing surface chrome plating on the rolled or extruded round bar after step S5 and before step S7.

3. The core rod manufacturing method according to claim 1 or 2, wherein the cold rolling, warm rolling, cold extrusion or warm extrusion process is implemented by using rolls and pass thereof on steel cold rolling and cold drawing, rolling and hot rolling equipment; the steel cold rolling, cold drawing, calendering and hot rolling equipment comprises a transverse rolling mill, a wedge transverse rolling mill, a longitudinal rolling mill, an inclined rolling mill, a rotary straightening machine, a cold drawing machine, a cold rolling mill, a reducing pushing machine and a spinning machine.

4. A method for repairing a defective core rod comprises the following steps: SF1, machining the core rod with the defects, removing a surface defect layer, and machining to a new set size to obtain a non-defective core rod; SF5, obtaining the repaired core rod, and is characterized in that a step SF3 of performing one of cold rolling, warm rolling, cold extrusion and warm extrusion on the flawless core rod material is arranged after SF1 and before SF 5.

5. The method for repairing the defective core rod according to claim 4, wherein the machining to the new set size in SF1 is turning directly or after overlaying;

the direct turning process comprises the following steps: directly turning the defective core rod to a new set diameter, wherein the new set diameter is smaller than the original diameter of the defective core rod;

the turning process after overlaying comprises the following steps: and removing the defect layer on the surface of the core rod with the defects to obtain a non-defective rod, overlaying the non-defective rod to obtain a surfacing rod, annealing the surfacing rod, and machining the surfacing layer of the surfacing rod to a new set diameter.

6. The method for repairing a defective core rod according to claim 4 or 5, wherein after the step SF3 and before the step SF5, a step SF4 of performing chrome plating treatment on the surface of the non-defective core rod material after cold rolling, warm rolling, cold extrusion or warm extrusion treatment is provided.

7. The method for manufacturing a mandrel according to claim 4 or 5, wherein the cold rolling, warm rolling, cold extrusion or warm extrusion process is realized by using rollers and pass thereof on steel cold rolling and cold drawing, calendaring and hot rolling equipment; the steel cold rolling, cold drawing, rolling and hot rolling equipment comprises a transverse rolling mill, a wedge transverse rolling mill, a longitudinal rolling mill, an inclined rolling mill, a rotary straightening machine, a cold drawing machine, a cold rolling mill, a reducing pushing machine and a spinning machine.

8. An apparatus for processing a core rod for realizing the method for manufacturing a core rod according to claims 1 to 2 or the method for repairing a defective core rod according to claims 4 to 6, comprising a rolling device for performing a rolling process on the surface of the core rod or an extrusion device for performing an extrusion process on the surface of the core rod, wherein the rolling device or the extrusion device is provided on a tool post or a slide of a machine tool.

9. The apparatus according to claim 8, wherein the rolling device is a rolling wheel or a rolling knife.

10. The apparatus according to claim 8 or 9, further comprising an ultrasonic vibration device or an electromagnetic vibration device, wherein the ultrasonic vibration device or the electromagnetic vibration device is disposed above the rolling device or the extrusion device, and is configured to perform high-frequency micro-impact on the surface of the core rod during the process of rolling or extruding the surface of the core rod.