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

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

A kind of mandrel making method, mandrel repairing method and equipment for processing mandrel

technical field

The invention relates to the field of tools and moulds used in the deformation process of hot-rolled seamless steel pipes, in particular to a method for manufacturing a mandrel, a method for repairing a mandrel and a device for processing the mandrel.

Background technique

Mandrel is a tool used in the deformation process of hot-rolled seamless steel pipe.

During the working process of the pipe rolling mill, the relative movement speed of the mandrel and the steel pipe is large, the mandrel can be shorter, and the relative movement speed is small, the mandrel must be longer to ensure that the mandrel can penetrate the deformation of the entire steel pipe. According to the current situation of using mandrels in the mainstream units of hot-rolled seamless steel pipe production, it is roughly divided into three types: long mandrels, long mandrels and short mandrels. Floating mandrel mills (Mandrel Mill, referred to as MM) Long mandrels are used, and the working rods are generally about 30-33 meters long; long mandrels are used on the limit mandrel continuous rolling mills (such as Multi-Stand Pipe Mill, referred to as MPM; Premium Quality Finishing, referred to as PQF, etc.). The length of the working rod is about 12.5 meters; the short mandrel is used on the skew rolling mill (such as Accurate Rolling Mill, ACCU-ROLL for short), and the working rod is generally about 4 meters long; there are also units that use shorter mandrels.

The diameter of the mandrel bar is selected according to the diameter of the rolled steel pipe and the amount of deformation. The factory needs to equip the corresponding mandrel bar for each steel pipe product with different diameters. The mandrel moves relative to the steel pipe during work, but relative friction is useless for deformation, so the smaller the friction, the better. This requires the surface of the mandrel to be as smooth as possible. In addition, since the surface of the mandrel directly participates in the deformation of the steel pipe, the mandrel The surface quality is related to the quality of the finished product. For example, if there are several millimeters of defects on the mandrel with a length of tens of meters, the whole seamless steel pipe produced will be judged as a defective or unqualified product. The rod directly participates in metal deformation, it bears a large rolling load, and its wear, fatigue loss and other consumption are relatively large. Therefore, the performance and quality requirements of the mandrel rod are relatively high, and frequent maintenance will also be involved. An annual output of 500,000 yuan For a ton of seamless steel pipe factory, at least one mandrel needs to be repaired offline on average every day, so the mandrel is the tool with the largest number and the highest cost in the seamless steel pipe factory.

The existing mandrel processing technology is slightly different according to the different types of mandrels:

The speed of the mandrel bar is limited when the mandrel is rolled by the continuous rolling mill, that is, the movement speed of the mandrel bar is very slow relative to the movement speed of the steel tube, while the deformation and movement speed of the steel tube are relatively high, and the amount of metal deformation is large. The relative sliding friction of the steel pipe will be very large, and the sticking accident is prone to occur, that is, the mandrel cannot be pulled out from the inner cavity of the (rolled) steel pipe, so the surface of the mandrel is required to be smooth and hard, and the purpose is to reduce the surface friction of the mandrel coefficient and increase wear resistance to avoid sticking accidents. Therefore, the surface finish requirements of the limiting mandrel are very high, and the surface of the mandrel is generally plated with hard chrome. The manufacturing process of the longer mandrel bar used in the limit mandrel continuous rolling mill is as follows:

1) New mandrel production: (1) Rolling or forging long billets; (2) Heat treatment and tempering, so that the metallographic structure of the billet has sufficient strength and toughness, and the following similar comments are omitted; (3) Machined round core rods , that is, it is processed into a round core bar with a specific diameter according to the required dimensional accuracy, and the following similar comments are omitted; (4) The surface of the core bar is chrome-plated, and chrome-plating is an essential part, in order to improve the surface finish and comprehensiveness of the round core bar. Hardness, the following similar comments are omitted; (5) The finished mandrel is obtained, which can be used on the machine.

2) One of the manufacturing processes for repairing (or heavy turning) defective mandrels: (1) Machining of defective mandrels, for the defective mandrels that are about to be used, the fatigue cracks on the surface of the defective mandrels are removed by machining (2) Surfacing welding, generally submerged arc welding, because the diameter of the mandrel becomes smaller after turning, and surfacing welding technology must be used for equal diameter repairs, because The diameter lost by turning is made up, and the comments of the same kind are omitted later; (3) annealing treatment to eliminate the inherent stress of the surfacing structure; (4) machining of the mandrel bar; (5) chrome plating on the surface of the mandrel bar after machining; (6) Finished mandrel.

3) The second manufacturing process of heavy turning of defective mandrels: (1) Machining defective mandrels into flawless mandrels, that is, turning directly on the basis of defective mandrels to new diameters to obtain flawless cores bar; (2) chrome plating on the surface of flawless mandrel; (3) finished mandrel. This method is not equal-diameter repair, but is to reduce the diameter of the mandrel. After the defects on the surface of the defective thicker mandrel are turned off, the turning process is continued until the diameter of the mandrel meets a certain smaller diameter specification, as another One size mandrel is used.

The length of the floating mandrel is basically the same as the maximum length of the steel pipe to be produced, even longer than the steel pipe to be produced. During the rolling process, the relative movement between the mandrel and the steel pipe is small, so for the floating mandrel The surface quality requirements are not too strict, that is, they are more required to have sufficient hardness, and the requirements for their smoothness are not as high as those of the limiting mandrel.

Manufacturing process of long mandrel for floating mandrel rolling mill and pipe jacking mill:

1) New mandrel production process: (1) rolled billet; (2) heat treatment and tempering; (3) machined round mandrel bar; (4) high frequency induction hardening of the mandrel surface, due to the long length of the mandrel, The volume is large, and this step is generally realized by the high-frequency induction surface quenching process; (5) the finished mandrel is obtained.

2) One of the manufacturing processes of defective mandrel repair (or heavy car): (1) machining of defective mandrels; (2) surfacing; (3) annealing treatment; (4) machining of round core bars; ( 5) High frequency induction hardening on the surface of the mandrel; (6) Finished mandrel. This process is generally used for equal diameter repairs.

3) The second manufacturing process of the defective mandrel bar: (1) The defective mandrel bar is machined into a flawless mandrel bar; (2) The surface of the mandrel bar is high-frequency induction hardening; (3) The finished mandrel bar. This process is generally used to reduce the diameter of the mandrel.

In the manufacturing process of the floating mandrel, the unique "high-frequency induction hardening of the mandrel surface": the purpose is to increase the surface hardness of the mandrel to increase its wear resistance, and there is no special requirement for the surface friction coefficient.

Theoretically speaking, the requirements for the mandrel bar of the cross-rolling unit are lower, and the surface of the mandrel bar does not require special treatment. However, in actual production, due to the needs of special product rolling, the factory will occasionally use the cross-rolling unit for the mandrel bar. The surface of the mandrel rod is laser quenched to improve the surface hardness of the mandrel rod and increase its wear resistance.

The production process of the short mandrel bar for the skew rolling mill:

1) New mandrel production: (1) Rolling/forging billets; (2) Heat treatment and tempering; (3) Machining round mandrels; (4) Finished mandrels.

2) One of the manufacturing processes for repairing (or heavy vehicle) defective mandrels: (1) Machining of defective mandrels; (2) Overlay welding; (3) Annealing treatment; (4) Machining of mandrels; (5) ) finished mandrel.

3) The second manufacturing process of the defective mandrel heavy car: (1) the defective mandrel is machined into a flawless mandrel; (2) the finished mandrel.

Industry consensus: It is necessary for the surface of the mandrel to be hard and smooth. The higher the hardness and the higher the finish, the more ideal. However, under the existing mandrel manufacturing technology, it requires a high cost to achieve this ideal mandrel. It needs a lot of energy, special equipment and may pollute the environment. Some manufacturers have to relax the high requirements on the surface quality of the mandrel to reduce the cost of the mandrel.

In summary, the mandrel is one of the important steel pipe deformation tools. It directly participates in metal deformation and directly affects the quality of the rolled steel pipe. It bears a large rolling load, and its wear and fatigue losses are relatively large. Therefore, , The performance and quality requirements of the mandrel are relatively high. Naturally, the production cost of the mandrel will increase accordingly, and the proportion of the mandrel cost is relatively large. Therefore, it is very meaningful to study and improve the new process of improving the performance of the mandrel and reducing the production cost.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a mandrel manufacturing method, which can reduce the production cost and improve the work efficiency.

For solving the above-mentioned technical problems, the technical scheme adopted in the present invention is:

A method for manufacturing a mandrel bar, comprising the following steps: S1, preparing a blank; S2, heat-treating and tempering the blank to obtain a quenched and tempered blank; S3, machining the quenched and tempered blank to obtain a round core bar; S7, obtaining a finished core bar; after step S3 and before step S7, there is also step S5, one of cold rolling, warm rolling, cold extrusion, and warm extrusion is performed on the surface of the round core bar.

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

Cold rolling, warm rolling, cold extrusion, and warm extrusion are purely mechanical processing, the process is simple, easy to implement, does not pollute the environment, and has short working hours. The surface hardness and smoothness of the mandrel processed by this process can meet the current core rod required requirements, reducing production costs. The principle analysis is as follows:

The principle of cold/warm rolling: at room temperature, the surface of the finished mandrel is subjected to mechanical rolling deformation, that is, cold rolling; the finished mandrel is heated to several hundred degrees Celsius (note, this temperature must be Below the phase transition temperature of the rod metal material, the temperature is selected according to the material of the mandrel, generally 300--400 degrees Celsius), and the surface of the finished mandrel is subjected to mechanical rolling deformation, that is, warm rolling;

The principle of cold/warm extrusion: at room temperature, the finished mandrel is inserted into a closed annular or cylindrical cavity, the mandrel is extruded through the cavity hole, and the surface of the mandrel is forcibly pulled out or pushed out. Deformation, called cold extrusion: or heat the mandrel by several hundred degrees (note, this temperature must be below the phase transition temperature of the metal material of the mandrel), insert the finished mandrel into a closed annular or cylindrical cavity, etc., After the mandrel is extruded through the inner cavity hole, the surface of the mandrel is deformed by forcibly pulling out or pushing out, which is called warm extrusion.

During the process of cold rolling, warm rolling, cold extrusion and warm extrusion, the metal on the surface of the mandrel will be deformed by cold working, and the deformation zone includes the pressing zone, the plastic deformation zone and the elastic deformation zone.

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

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

Generally, the Rockwell hardness of the core material of the mandrel is 37-39, and the Rockwell hardness of the metal chromium is 62-65. The traditional chrome plating process on the surface of the mandrel is equivalent to adding a hardness of 37-39 to the base material of Rockwell hardness. The surface hardness of metal chromium with a Rockwell hardness of 62-65 is higher than the original hardness of the base material, so the hardness value printed on the surface of the chrome-plated mandrel is the comprehensive hardness of the chromium layer and the base material. The comprehensive hardness is generally in the base material. If the hardness of the material is increased by about 10--15%, then when the Rockwell 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 also increased by 15%-20% relative to the original hardness, then, when the original substrate hardness is 37-39 Roche hardness, after cold rolling or warm rolling The surface hardness of the mandrel rod reaches 42-46 Roche hardness, which is comparable to the comprehensive hardness (Roche hardness 40-44) obtained by the traditional chrome plating process, and meets the requirements of use.

(2) Flatten the unevenness (0.45--0.70 microns) and micro-cracks of the metal microscopic surface, and the performance characteristics: the surface finish increases (the microscopic surface reaches 0.04--0.06 microns), which is consistent with the surface of the mandrel after chrome plating. The finish is equivalent;

(3) The metal grains on the surface of the mandrel rod and the surface layer (a certain depth below the surface) are crushed and deformed by dislocation, and "nano-scale" fine grains appear, which greatly improves the high temperature resistance, corrosion resistance and wear resistance of the metal. performance;

(4) The "compressive stress" state is introduced on the surface of the rolling mandrel, which has a great inhibitory effect on the generation of fatigue cracks, which greatly improves the fatigue resistance of the surface of the mandrel, thus greatly improving the service life of the mandrel.

The method makes full use of the properties of metal cold work hardening, and through relatively simple design and improvement, the surface strengthening treatment of the mandrel can be realized, the performance of the mandrel can be greatly improved, the cost is very low, and the relevant steel pipe manufacturers can benefit a lot.

Using the process technology of the present invention can save the "high frequency quenching process on the surface of the mandrel rod" and the "chrome plating process on the surface of the mandrel rod", so the process technology of the present invention can reduce the pollution to the environment in the production process of the mandrel rod, and reduce the demand for energy.

On the basis of the above technical solutions, the present invention can also be improved as follows.

Preferably, after the step S5 and before the step S7, there is also a step S6 of chrome-plating the surface of the rolled or extruded round core bar.

The beneficial effect of adopting the above-mentioned further scheme is that the comprehensive hardness of the surface of the mandrel can be further improved.

The invention provides a repairing method for a defective mandrel, comprising the following steps: SF1, machining the defective mandrel, removing the surface defect layer, processing it to a new set size, and obtaining a flawless mandrel after machining ; SF5, to obtain the repaired mandrel, after SF1 and before SF5, there is a step SF3, one of cold rolling, warm rolling, cold extrusion and warm extrusion for the flawless core rod after machining deal with.

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

The technical effect of cold rolling, warm rolling, cold extrusion and warm extrusion technology for repairing the mandrel is manifested in the improvement of the surface quality of the mandrel, which is the same as the effect of the aforementioned mandrel manufacturing method, and will not be repeated here.

On the basis of the above technical solutions, the present invention can also be improved as follows.

Preferably, the processing to the new set size described in the SF1 refers to direct turning processing or surfacing and then turning processing;

The step of the direct turning processing is: directly turning the defective mandrel to a new set diameter, and the new set diameter is smaller than the original diameter of the defective mandrel;

The steps of turning after surfacing welding are: removing the defect layer on the surface of the defective mandrel bar to obtain a flawless bar, surfacing on the flawless bar to obtain a surfacing bar, and annealing the surfacing bar, The surfacing layer of the surfacing bar is machined to the new set diameter.

The beneficial effect of adopting the above-mentioned further scheme is that, according to the production situation, the defective mandrel can be reduced in diameter, or repaired with equal diameter.

In particular, for the repair process including the surfacing process, in the traditional repair process, after the surfacing layer is annealed and machining is completed, the entire machining repair work is over, but the core material of the mandrel itself is quenched and tempered. Processed, and the surfacing layer is the welding material that is directly cooled from the molten state to a solid state without undergoing the process of quenching and tempering. The difference is large. The surfacing layer in this state has poor high temperature resistance, wear resistance, corrosion resistance and fatigue resistance. During the process of steel pipe rolling, the surface of this type of surfacing repaired mandrel is prone to large fatigue. Cracks, and its life is up to 80--90% of the pure modulated mandrel; after adopting this scheme, cold rolling, warm rolling, cold extrusion or warm extrusion are used to cold work and harden the surfacing layer to make the surfacing layer The metal grains on the surface of the solder layer and the surface layer (a certain depth below the surface) are crushed, dislocated and deformed, and "nano-scale" fine grains appear, and the surface of the mandrel introduces a "compressive stress" state, which greatly improves the stacking performance. The welding layer has the properties of high temperature resistance, corrosion resistance, wear resistance and fatigue resistance, thereby greatly improving the service life of the mandrel after repair.

After adopting this scheme, the welding material itself does not need to choose high-end welding material (containing a variety of rare elements, such as cobalt, nickel, molybdenum, etc.), and the commonly used 1Cr13 welding material (or welding material with lower alloy) can also meet the requirements The required repair mandrel is produced, so the cost of surfacing can be effectively reduced by more than 50%.

Preferably, after the step SF3 and before the step SF5, there is a step SF4 to perform chrome plating on the surface of the flawless core bar after cold rolling, warm rolling, cold extrusion or warm extrusion.

The beneficial effect of adopting the above-mentioned further scheme is to further improve the comprehensive hardness of the surface of the mandrel.

The present invention provides a device for processing a mandrel, which is used to realize the aforementioned method for manufacturing a mandrel or the aforementioned method for repairing a defective mandrel, including a rolling device or a squeezing device for rolling or extruding the mandrel. , the rolling device or extrusion device is arranged on the tool table or sliding seat of the machine tool;

The rolling device is a rolling wheel or a rolling knife, and the rolling surface of the rolling knife can be a curved surface or a flat surface; the extrusion device is an extrusion die, and an independently set rolling device or extrusion device is set on the machine tool. It is the most simple to design and manufacture a rolling wheel device or extrusion device, which is directly installed on the tool table or sliding seat of the lathe used for processing the mandrel. When the mandrel is finished, the rolling or extrusion work can be started. .

It is also possible to directly use the rolls and their passes on the steel cold rolling, rolling, and hot rolling equipment as a rolling device or extrusion device for the mandrel; the steel cold rolling, rolling, and hot rolling equipment Rolling mill, longitudinal rolling mill, skew rolling mill, rotary straightening machine, cold drawing machine, cold rolling mill, push-reducing machine, spinning machine, etc., as long as the lower cross rolling mill, cross wedge rolling mill, vertical rolling mill, skew rolling mill, rotary straightening machine are adjusted The rolls and their pass types of the rolling mill, cold rolling mill and spinning machine can be used as a rolling device, or the parameters of the round hole outer die of the cold drawing machine and the rolling mill can be adjusted to be used as an extrusion device. For the rolling or extrusion of the mandrel, the above adjustment only involves the adjustment of the parameters, and does not require any improvement in the mechanical structure of the above-mentioned existing equipment.

Preferably, an ultrasonic vibration device or an electromagnetic vibration device is added to the rolling device or the extrusion device.

The ultrasonic vibration device or the electromagnetic vibration device can impact the surface of the mandrel rod in the rolling or extrusion process with high frequency and small amplitude, so that the surface quality of the mandrel rod after rolling or extrusion processing is better, and the core rod is further improved. The quality of the finish of the rod surface.

Description of drawings

1 is a schematic diagram of the layout of a rolling cutter when there is no mandrel support in Embodiment 1 of the present invention;

Figure 2 is a schematic diagram of the positional structure of the rolling cutter and the mandrel support under the first situation in Embodiment 1 of the present invention;

3 is a schematic diagram of the positional structure of the rolling cutter and the mandrel support under the second situation in Embodiment 1 of the present invention;

4 is a schematic diagram of the positional structure of the rolling wheel in Embodiment 2 of the present invention;

FIG. 5 is a schematic diagram of the layout of the extrusion device in Embodiment 3 of the present invention.

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

In the accompanying drawings, the list of component names represented by each number is as follows:

1. Mandrel; 21. Rolling wheel No. 1; 22. Rolling wheel No. 2; 23. Rolling wheel No. 3; 4. Rolling knife; ,thrust.

Detailed ways

The principles and features of the present invention will be described below with reference to the accompanying drawings. The examples are only used to explain the present invention, but not to limit the scope of the present invention.

Example 1:

A cold rolling equipment for processing mandrels, including a rolling device, the rolling device includes a rolling knife 4, as shown in FIG. On the tool holder of the machine tool, if the mandrel 1 to be processed is relatively short (non-slender rod), such as only 0.5 meters long, no other structure is needed. The mandrel 1 itself does not bend as a whole.

If the mandrel 1 to be processed is in the form of a slender rod, a mandrel support 5 should be provided on the opposite side of the rolling knife 4 to balance the pressure of the rolling knife 4 on the mandrel 1 and avoid the bending of the mandrel 1 caused by this pressure. As shown in Figure 2, a mandrel support roller is set on the opposite side. The mandrel support roller can balance the pressure of the rolling knife 4 to ensure that only the surface of the mandrel 1 is rolled and deformed, and the entire mandrel 1 itself will not be The overall bending occurs due to the pressure of this rolling blade 4 . Of course, multiple support rollers can be set up. As shown in Figure 3, two support rollers are set opposite the rolling knife 4. As long as the pressure of the rolling knife 4 is balanced, it can be ensured that the mandrel 1 will not be caused by rolling as a whole. The pressure of the knife 4 produces the overall bending deformation.

Example 2:

A cold rolling equipment for processing mandrels, including a 3-wheel rolling device, the layout of the 3-wheel rolling device is shown in Figure 4, including 3 rolling wheels, and the diameter of each rolling wheel is 20mm Left and right, evenly arranged along the circumference of the mandrel 1 to be processed, and the whole device is fixed on the tool table of the machine tool. Considering that the mandrel 1 is relatively long, three rolling rollers hug the mandrel 1 for rolling, so that the rolling pressure is balanced between the three rollers. The resultant force applied in the radial direction of the rod 1 is zero, that is, the rolling force will only cause the rolling deformation of the surface of the mandrel 1, and will not cause the overall bending of the mandrel 1, which will affect the machining accuracy.

As described in Example 1, it is not necessary to use three rolling wheels, and only one rolling wheel can be used. When one rolling wheel is used, if the mandrel 1 to be processed is relatively short (non-slender rod), If it is about 0.5 meters, there is no need for an additional mandrel support 5. The rigidity of the mandrel 1 is enough to withstand the pressure of the rolling wheel to ensure that the mandrel 1 itself does not bend; A mandrel support 5 is arranged at a position opposite to the rolling wheel, so that the mandrel support 5 can balance the pressure of the rolling wheel and ensure that the mandrel 1 is not bent and deformed as a whole. More rolling wheels may also be used, as long as the resultant force exerted by all rolling wheels on the mandrel 1 during the rolling process of the mandrel 1 is balanced, the mandrel 1 as a whole will not be bent and deformed.

In the rolling process, the rolls and their pass types on the stands such as the on-site cross-rolling mill, cross-cross rolling mill, longitudinal rolling mill, cross-rolling mill, rotary straightening machine, cold rolling mill, and spinning machine can also be directly selected as rolling devices. There is no need to add new equipment at this time, and only need to adjust the parameters of the roll pass, so the cost of on-site transformation is very low using this new process.

Example 3

A device for processing mandrels, including an extrusion device, the extrusion device is an annular circular hole outer die 6, the inner diameter of which is equal to the finished product diameter of the mandrel to be processed, and is smaller than the outer diameter of the mandrel to be processed by 0.1-0.3 mm (specifically determined according to the amount of extrusion), install the circular hole outer die 6 on the tool rest or sliding table of the machine tool, and provide a driving force F through the hydraulic system to drive the circular hole outer die 6 along the axis direction of the mandrel 1 Move to realize the extrusion of the mandrel 1 to be processed.

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

Example 4:

A manufacturing method of a moving mandrel, as shown in Figure 6, includes the following steps:

S1, prepare the blank;

S2, heat-treating and tempering the billet to obtain a quenched and tempered billet;

S3. Machining the quenched and tempered blank to obtain a round core bar;

S5. Use cold rolling equipment to perform cold rolling treatment on the surface of the round core bar;

S7, obtain the finished mandrel.

The improvement of the existing production equipment is very small by using this method. After canceling the "high-frequency quenching process on the surface of the mandrel" and the "chrome plating process on the surface of the mandrel", the surface of the traditional processing technology can still be obtained. The mandrel with comprehensive hardness and finish saves energy, reduces costs, and is more environmentally friendly. Of course, if the surface of the cold-rolled round core bar is chrome-plated after step S5, the comprehensive hardness of the surface of the core bar will be further improved, and the use effect of the core bar will be better.

Embodiment 5: The equal diameter repair method of the stopper mandrel:

A factory is specialized in repairing the mandrels of the limit mandrel continuous rolling mill. The diameter of the mandrels produced by the repaired mandrels is 192-460mm. The original mandrel repair and production process: used defective mandrels → machining: turning defective Fatigue layer of the mandrel → surfacing, generally using submerged arc welding process → annealing to eliminate the internal stress generated in the surfacing structure → machining, finishing to the required size and accuracy, and obtaining a round core bar → for the round mandrel The surface of the material is chrome-plated → the finished mandrel is obtained and used on the machine. Each time chrome plating takes more than 14 hours and causes environmental pollution.

Then use the process of the present invention: used defective mandrel → machining: turning the fatigue layer of the defective mandrel → surfacing, submerged arc welding → annealing, stress relief → machining, finishing to the required size and accuracy , get the round core bar → roll the surface of the round core bar → finished mandrel, use it on the machine.

Use the three-wheel type rolling device in Example 2, and assemble it according to the specifications of the mandrel. Among them, the No. 1 rolling wheel 21 and the No. 2 rolling wheel 22 do not move, and the No. 3 rolling wheel 23 can adjust the radial pressure. amount to meet different rolling requirements. Rolling 2 times: the first time: the rolling reduction on one side is 0.15mm; the second time: the rolling reduction on one side is 0.05mm. For a 12.5-meter-long mandrel, it only takes 2 hours to roll once, and 4 hours to roll it twice. Considerable time savings compared to the chrome plating process.

Compared with the original repair process: the surface hardness of the mandrel after rolling is increased by 18%, which is equivalent to the comprehensive hardness of the mandrel surface of the traditional chrome-plating process, and the smoothness reaches a level equivalent to that of the chrome-plated surface. Since the chrome plating process is omitted and the requirements for the welding material itself are reduced, the original welding material containing rare metals is replaced by the common welding material, the cost of the welding material is reduced by 50%, and the processing time is also saved. The cost of the mandrel is reduced by about 40--50% compared with the past, and it is environmentally friendly;

Example 5 After the repaired mandrel is used on the machine, the number of rolled steel pipes is increased by 20--50%, and the cost performance is greatly improved, and the cost performance is very high.

The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (10)

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.

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