RU2523179C2 - Production and operation of pilger mill composite mandrels for production of large- and medium-diameter hot-rolled pipes - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to pipe rolling and can be used at production of composite mandrels of Pilger mills. One-piece cores are made from continuously-cast billets or profiled special iron from carbon grades of steel. Said core is bored from one end to cut tight-hand thread while bulge shaped to truncated cone with larger base on core end is made at opposite end. Locking parts are made mechanically from mandrel rejects and forged pieces of steel "25Х2М1Ф" or steel resisting the impact effects to cut the thread at the end opposite the lock. Core and lock are screwed together to produce a prefabricated structure. Billets produced by forging or ESR casting are heated to ductility temperature and pierced at helical rolling mill to sleeved with ID larger than large bases of the core truncated cones by 15-20 mm. Said sleeve is fitted on said prefabricated structure till contact with lock cone to roll-and-knurl the sleeve on cores at Pilger mills. Thermal treatment of composite mandrel billets is carried out to produce 40-50 mm deep sorbite jacket on the surface. Then, said billets are machined to composite mandrels.

EFFECT: decreased consumption of heat-and-wear-resistant steel.

5 cl, 1 tbl

Description

The invention relates to pipe rolling production, and in particular, to a method for manufacturing a technological tool for pilgrim mills, in particular composite mandrels for rolling hot rolled pipes of large and medium diameters (325-550) mm with different wall thicknesses.

A known method of manufacturing the mandrels of pilgrim mills for pilgrim rolling of hot-rolled pipes, including casting ingots from steel grade 25X2M1F (SD-2), forging them into cylindrical billets (forgings) of 325-570 × 6000 mm in size with a yield of 2.25-2.50, rough machining with an allowance of 10-15 mm in diameter, taking into account the forging forgings during heat treatment, heat treatment of mandrel blanks, machining of mandrels to the final size with subsequent rolling or grinding of the surface and their operation until failure on the grid igneous cracks (patent RU No. 2055660, CL. B21B 21/00. 03/10/1992).

The disadvantage of this method is that mandrels with a carbon content of 0.24-0.32 fail, mainly due to surface hot cracks, as well as uneven abrasion along the length (loss of geometric dimensions). The disadvantages of this method is the complexity of the manufacture of mandrels forging on presses, followed by machining, heat treatment, machining and rolling in the roller of the working surface of the mandrel, the increased consumption of expensive heat-resistant wear-resistant steel grade 25X2M1F or heat-resistant steel with a ratio of components: carbon - 0.15- 0.23%; Manganese - 0.5-0.85%; chromium - 2.8-3.3%; vanadium - 0.10-0.25%; niobium - 0.01-0.015%; nitrogen - 0.005-0.015; iron - the rest, while the total percentage of Mn + Cr should be at least 3.7% (patent RU No. 2081199, CL. C22C 38/26. 06/10/1997). These mandrels are used for rolling hot-rolled tubes of various sizes with wall tolerances depending on the normative and technical documentation.

In the pipe industry, there is a known method for the manufacture and operation of mandrels of pilgrim mills of steel grade SD-2 (25X2M1F) for the production of hot-rolled pipes of large and medium diameters, including forging, heat treatment of mandrel blanks to obtain a sorbitol layer 40-50 mm deep on the surface, during operation before the intensive formation of a network of high-level cracks begins, the mandrels are grind to a smaller diameter until sorbitol and individual sections of perlite appear in the microstructure, the value of which is determined from the expression D _p = D _n -2Δ, where D _p - the minimum diameter of the mandrel after regrinding, mm; D _n - the initial diameter of the mandrel after manufacturing, mm; Δ is the thickness of the surface layer of the mandrel, which has a sorbitol structure, mm, the first regrinding of mandrels to a smaller diameter is performed through 0.75-0.80, the second through 0.5-0.55, and the third through 0.3-0.35 the average initial durability, after the third regrinding, the mandrels are operated until failure, and the amount of metal removal in diameter for each subsequent regrinding is increased by 1.2-1.3 times (patent RU No. 2238810. Cl. B21B 21/00, C21D 9 / 28.27.10.2004).

Despite the increase in the resistance of mandrels by more than 1.5 times, the disadvantages of this method of manufacturing mandrels is the complexity and increased consumption of expensive heat-resistant wear-resistant steel grade 25X2M1F.

A known method of manufacturing mandrels for hot pilgrim rolling pipes, including the manufacture of cores with solid shanks with the outer surface of the ends in the form of truncated cones connected by smaller bases, and tightly paired with the core cores (ed. Certificate. USSR No. 480319. Cl. B21B 25 / 00, 1973).

The disadvantages of this method of manufacturing mandrels are the increased consumption of core material, the need for accurate determination of the size of the original sleeve when planting the shell, sliding the shell during operation (rolling) from axial supporting forces.

In the pipe industry, a mandrel is also known, the inner cavity of which is made of variable taper along the length, the diameter at the end of the guide part is 0.78-0.85 of the outer diameter of the mandrel and 0.42-0.69 at the end of the section located from the end at a distance of 0 , 30-0.35 the sum of the lengths of the working and guide parts of the mandrel, and the ratio of the diameter of the cavity to the outer diameter of the mandrel is 0.19-0.29 (ed. Certificate of the USSR No. 1342547, Cl. B21B 21/00, Bull. No. 37. 1987).

The disadvantages of this design of the mandrel is the complexity of its manufacture and increased consumption of expensive metal. For mandrels with an outer diameter of 409/410 mm for rolling pipes with a size of 426 × 9-10 mm, the difference in the cones of the inner diameter along the length of the mandrel according to the copyright certificate should be ≈200 mm. It is impossible to roll such a mandrel blank at TPU 8-16 ″ with pilgrim mills, because the maximum difference between the inner diameter of the sleeve and the diameter of the mandrel, i.e. reduction should not exceed 40-45 mm. These mandrels can be made only by forging, followed by drilling and boring to the specified dimensions, and this, in turn, will lead to the loss of ≈30% of metal in the chips. In the process of machining the castle part of the hollow mandrel blanks, with a variable internal taper along the entire mandrel blank, we obtain a variable area along the castle, and in some cases, when milling cheeks at the end of the castle part adjacent to the working part, you can get a through hole, which will lead to weakening this section and uneven wear of the castle part of the mandrel.

The closest technical solution is a composite mandrel, the core of which has a through axial channel and is equipped with a thrust ring mounted on it in cooperation with an annular protrusion, under which a recess is made in the end of the wall of the working part, the outer diameter of the core is 0.7-0.75, and the diameter of its axial channel is 0.3-0.4 from the outer diameter of the working part of the mandrel (ed. certificate of the USSR No. 719720. Bull. No. 9. 1980).

The disadvantage of this design of the mandrel is the difficulty of manufacturing, namely, manufacturing by forging a workpiece from 25Kh2M1F steel with subsequent machining and drilling of a through hole, manufacturing a special thrust ring, heating a workpiece from 25Kh2M1F steel to ductility temperature, flashing it in a cross-helical rolling mill into the sleeve and rolling (knurling) the sleeves on the pilgrim mill to a given core, followed by machining to a predetermined size. Since the rolling (knurling) of the sleeve on the core takes place in rolls with an oval caliber or in rolls with tangential outlets, a tight fit of the cylindrical shirt around the entire perimeter of the core is not achieved. In the process of rolling pipes on the mandrels of this design, the cylindrical part (shirt) is intensively heated, which slides from the core due to the friction forces that arise when rolling and removing the mandrel from the pipe.

The objective of the proposed method is to develop the optimal design of the mandrels, the method of their manufacture, in particular hollow mandrels of maximum metal consumption, mandrel blanks for the manufacture of which can be produced in the conditions of OAO ChTPZ, i.e. in pilgrim installations, followed by the manufacture of hollow mandrels from them for pilgrim rolling of large and medium diameter hot rolled pipes, reduction in the consumption of heat-resistant wear-resistant steel, reduction in the cost of mandrels while increasing their resistance, and therefore, reduction in the cost of redistributing large and medium diameters of hot-rolled pipes with pilgrim camps.

The technical result is achieved by the fact that in the known method of manufacturing composite mandrels of pilgrim mills for the production of hot-rolled pipes of large and medium diameters, characterized in that they produce continuous cores from continuously cast billets or long products from carbon steel grades, which are drilled and cut from one end right screw thread, and at the other end, a thickening in the form of a truncated cone is performed, with a large base at the end of the core, mechanically made the lock parts from defective mandrels and forgings of steel grade 25X2M1F or from steel, resistant to impacts, with a threaded thread on the opposite end from the lock, the cores are connected to the lock part by screwing up the threaded joints to form a prefabricated structure, the workpieces are forged or electroslag remelted, made they are heated to a temperature of plasticity and flashed in a mill of cross-helical rolling into sleeves, the inner diameter of which is 1 larger than the large bases of the truncated core cones 5-20 mm, put the sleeve on the prefabricated structure until it touches the cone of the locking part, and on the pilgrim mills roll-knit the sleeves on the cores to form composite mandrel blanks with shirts, heat treat the composite mandrel blanks to obtain 40 mm deep sorbitol on the surface of the shirts -50 mm and the machining of composite mandrel blanks into composite mandrels, the length of blanks for piercing sleeves and the length of sleeves for knitting shirts for the manufacture of composite mandrel blanks yayut of expressions

where D _d - the outer diameter of the mandrel, mm; Δ is the allowance for machining a composite mandrel blank in a composite mandrel after knurling, mm; S _p - wall thickness of the shirt mandrel, mm; L _p - the length of the working part of the mandrel (the length of the rolled shirt), mm; K is a coefficient that takes into account the burning of metal during heating of blanks and ingots-blanks of ESR in methodical or ring furnaces for flashing them into sleeves in a cross-helical rolling mill; D _s - the diameter of the workpiece with central drilling for the manufacture of shirts, mm; S _z - wall thickness of the workpiece with central drilling, mm; R _s - the radius of the workpiece without central drilling, mm; D _g - the outer diameter of the sleeve for rolling the shirt, mm; S _g - the wall thickness of the sleeve, mm, the wall thickness of the shirts of the composite mandrels is determined from the expression S _p = K ₁ D _d , where K ₁ = 0.22-0.25 is the coefficient, the greater value of which is taken for mandrels of larger diameter, and the diameters cores from the expression D _c = K ₂ D _d , where K ₂ = 0.50-0.55 is the coefficient, the greater value of which is taken for mandrels of smaller diameter, the sleeve is rolled-rolled onto the core in the form of a shirt according to the technology: the caliber of the rolls is determined from the expression D _to = (D _d + 2Δ + h), where D _d - the outer diameter of the composite mandrel, mm; Δ is the allowance for machining a composite mandrel blank in the mandrel after rolling the shirt, mm; h = 15-20 - increase in caliber due to the breeding of rolls, mm; after running the pilgrim head, rolls are reduced by h / 2 and rolled-rolled shirt in caliber D _to = (D _d + 2Δ + h / 2); if during the secondary rolling-rolling, the shirt cannot be completely found on the core cone, then the rolls are reduced by h / 2 and the rolling process is carried out until the shirt is completely on the core cone, and the process of rolling the shirts onto the core is carried out by feeding the sleeves strains m ₁ = 20-25 mm, during secondary rolling-rolling, the feed rate is reduced to 0.75 m ₁ , and during subsequent rolling-rolling is reduced to 0.5 m ₁ , the greater value of which is taken when rolling composite mandrel blanks for manufacturing mandrels for pipe rolling bottom diameter.

The locking part of the mandrel is used to mount the mandrel in the lock of the feeding apparatus, it must have high resistance against friction and increased loads of shock action, it is determined constructively. The working part of the mandrel is selected from the maximum length of the liner and the width of the mandrel ring, during operation it experiences cyclic heating to 600-700 ° C with subsequent cooling to 100 ° C in baths with water and lubricant, as well as pressures up to 400-500 tons, depending on geometric dimensions of rolled pipes. The guide part of the mandrel is necessary for seed at the beginning of rolling, the size (length) of which depends on the path of rollback of the feeding apparatus and the end cone with a length of 20-50 mm.

The guide part of the mandrel on pipe rolling plants for rolling pipes of large and medium diameters should have a length, depending on the geometric dimensions of the pipes, from 1250 to 1450 mm, i.e. (0.27-0.32) of the total length of the mandrel.

A comparative analysis of the proposed method for the manufacture of composite mandrels of pilgrim mills for the production of hot-rolled pipes of large and medium diameters with a prototype shows that the inventive method is different in that the locking parts are made mechanically from defective mandrels and forgings of steel grade 25X2M1F or from steel that is resistant to shock, with a threaded thread on the opposite end from the lock, the cores are connected to the lock part by screwing up the threaded joints with the formation of a precast hands, make blanks by forging or casting by electroslag remelting, heat them to a plasticity temperature and sew them in a cross-helical mill into sleeves, the inner diameter of which is larger than the large bases of the truncated core cones by 15–20 mm, put the sleeve on the prefabricated structure until it touches the cone castle part, and on pilgrim mills produce rolling-knurling of sleeves on the cores with the formation of composite mandrel blanks with shirts, heat treatment of composite mandrels x blanks with obtaining on the surface of the shirts sorbitol with a depth of 40-50 mm and the machining of composite mandrel blanks into composite mandrels, the length of the blanks for piercing sleeves and the length of the sleeves for rolling the shirts for the manufacture of composite mandrel blanks are determined from the expressions

where D _d - the outer diameter of the mandrel, mm; Δ is the allowance for machining a composite mandrel blank in a composite mandrel after knurling, mm; S _p - wall thickness of the shirt mandrel, mm; L _p - the length of the working part of the mandrel (the length of the rolled shirt), mm; K is a coefficient that takes into account the burning of metal during heating of blanks and ingots-blanks of ESR in methodical or ring furnaces for flashing them into sleeves in a cross-helical rolling mill; D _s - the diameter of the workpiece with central drilling for the manufacture of shirts, mm; S _z - wall thickness of the workpiece with central drilling, mm; R _s - the radius of the workpiece without central drilling, mm; D _g - the outer diameter of the sleeve for rolling the shirt, mm; S _g - the wall thickness of the sleeve, mm, the wall thickness of the shirts of the composite mandrels is determined from the expression S _p = K ₁ D _d , where K ₁ = 0.22-0.25 is the coefficient, the greater value of which is taken for mandrels of larger diameter, and the diameters cores from the expression D _c = K ₂ D _d , where K ₂ = 0.50-0.55 is the coefficient, the larger value of which is taken for mandrels of smaller diameter, the sleeve is rolled-rolled onto the core in the form of a shirt using technology: the caliber of the rolls is determined from the expression D _to = (D _d + 2Δ + h), where D _d - the outer diameter of the composite mandrel, mm; Δ is the allowance for machining a composite mandrel blank in the mandrel after rolling the shirt, mm; h = 15-20 - increase in caliber due to the breeding of rolls, mm; after running the pilgrim head, rolls are reduced by h / 2 and rolled-rolled shirt in caliber D _to = (D _d + 2Δ + h / 2); if during the secondary rolling-rolling, the shirt cannot be completely found on the core cone, then the rolls are reduced by h / 2 and the rolling process is carried out until the shirt is completely on the core cone, and the process of rolling the shirts onto the core is carried out by feeding the sleeves strains m ₁ = 20-25 mm, during secondary rolling-rolling, the feed rate is reduced to 0.75 m ₁ , and during subsequent rolling-rolling is reduced to 0.5 m ₁ , the greater value of which is taken when rolling composite mandrel blanks for manufacturing mandrels for pipe rolling bottom diameter. Thus, these differences allow us to conclude that the criterion of "inventive step" is met.

Comparison of the proposed method for the manufacture of composite mandrels for the production of hot-rolled pipes of large and medium diameters not only with the prototype, but also with other technical solutions in the art did not reveal the signs that distinguish the claimed method from the prototype, which corresponds to patentability "inventive step".

The method was tested on a pipe-rolling installation with pilgrim mills 8-16 ′ ′ of OAO ChTPZ. Two experimental composite mandrels for pilgrim rolling of pipes with a size of 426 × 9-10 mm were made and tested. The castle parts of the mandrels were made of defective mandrels with a diameter of 409/410 mm in accordance with claim 1. Cores with a diameter of 230 mm were made of long products with a diameter of 260 mm from steel grade 20 in accordance with claim 1. At one end, the cores were drilled to a length (depth) of 200 mm and the right metric thread M150 was cut, and at the other end, a cone was made at a length of 250 mm with a large base of 260 mm at the end. The castle parts and cores were assembled-screwed into composite structures, which were alternately inserted (charged) by the castle parts into the mandrel heads. For shirts, forged blanks of 600 × 100 × 1,500 mm in size were used from steel grade SD-2, the geometric dimensions of which were calculated in accordance with paragraph 2 of the claims. The billets were heated in a methodical furnace to a temperature of 1270 ° C, stitched in a cross-helical rolling mill into sleeves measuring 610 × in. 190 × 1800 mm, the geometric dimensions of which were calculated in accordance with claim 2. Sleeves were alternately mounted on composite structures and rolled in caliber 434 mm into composite mandrel blanks. Rolling (knurling) of sleeves in mandrel blanks was carried out in accordance with paragraphs 4 and 5 of the claims. First, the rolling process was carried out in a caliber of 440 mm due to the rolls being fed with the feed of sleeves into the deformation zone m = 20-25 mm. In the process of rolling, composite mandrel blanks with a diameter of 432-434 mm were obtained. Shirts were not completely wound around the taper of the shanks. To reduce ovalization in the deformation zone, the roll was rolled and the shirts were rolled-rolled again in the caliber 434 mm with feeding mandrels into the deformation zone m = 15-18 mm. Shirts completely rolled over the lock part and the core cone. After rolling and cooling the composite mandrel blanks, measurements were made. The diameter of the mandrel blanks was 426-430 mm. Dorn blanks were heat treated. Then the mandrel blanks were cut from the ends to a length of 4585 mm, of which, after machining (turning), two mandrels with geometric dimensions were made according to claim 3. The wall thickness of the shirts was 90 mm, which corresponds to paragraph 3 of the claims for mandrels of this size. Experienced mandrels were handed over to pilgrim mill No. 2, where tests were completed with 2 solid mandrels made of 25X2M1F steel. The data on pipe rolling and the resistance of the pilgrim mill mandrels manufactured by the existing and proposed technologies are shown in Table 1. Table 1 shows that on solid mandrels 409/410 mm in size made of 25X2M1F steel, 4000 tons of pipes were rolled before the formation of the grid of open cracks. 426 × 10 mm. Then the mandrels were ground to a size of 390/391 mm, on which 2,000 tons of pipes with a size of 426 × 20 mm were rolled before the formation of a network of high-level cracks. After that, the mandrels were ground to a size of 360/361 mm, on which 1560 tons of pipes 377 × 9 mm in size were rolled. Then the mandrels were rejected according to a coarse grid of high-level cracks and the absence of a layer of sorbitol with further regrinding. The total number of rolled pipes on two mandrels manufactured using existing technology amounted to 7560 tons. The weight of two forgings for the manufacture of mandrels amounted to 10400 kg. The specific consumption of mandrel steel grade SD-2 for rolling one ton of pipes amounted to 1.38 kg. According to the proposed technology, 4400 tons of pipes of 426 × 10 mm in size were rolled on composite mandrels with a size of 409/410 mm. Then the mandrels were regrind to a size of 399/400 mm, on which 1900 tons of pipes with a size of 426 × 15 mm were rolled. Then the mandrels were ground to size 388/389, on which 1,500 tons of pipes 426 × 22 mm in size were rolled. Then the mandrels were ground to a size of 360/361 mm. 1100 tons of pipes 377 × 9 mm in size were rolled on these mandrels. After the mandrels were ground to a size of 314/315 mm, on which 1000 tons of pipes 325 × 8 mm in size were rolled. Since the thickness of the shirt after the last regrind was 42.5 mm, due to the subsequent thinning of the wall of the shirt, it was decided to reject the mandrels. Shirts were removed from these mandrels using a fire method and shirts were again rolled onto composite structures and composite mandrels with a diameter of 409/410 mm were made. The total number of rolled tubes on two composite mandrels manufactured using the proposed technology amounted to 9900 tons. The weight of two forgings for the manufacture of shirts is 6480 kg. The specific consumption of mandrel steel grade SD-2 for rolling one ton of pipes amounted to 0.65 kg.

Thus, the specific consumption of mandrel steel grade SD-2 when rolling pipes on mandrels manufactured by the proposed technology, decreased by more than 2.0 times.

Using the proposed method for the manufacture of composite mandrels of pilgrim mills for the production of hot-rolled pipes of large and medium diameters makes it possible to compensate for uneven temperature heating of the outer surface of the mandrel along its length, to reduce thermal stresses along the mandrel section during cyclic heating and cooling them in a lubricated bath, to reduce wear, and to increase their durability, in comparison with continuous mandrels, to reduce the metal consumption for their manufacture, to organize their production at TPU 8-16 ′ ′ of JSC “Chet Z "abandon the supply side, to reduce the cost of process tools (mandrel), and therefore the cost of hot-rolled tubes redistribution thumb and middle diameters for TPU pilger.

Claims (5)

1. A method of manufacturing composite mandrels of pilgrim mills for the production of hot-rolled pipes of large and medium diameters, characterized in that they produce continuous cores from continuously cast billets or rolled steel from carbon steel grades, which are drilled and cut from the right end from one end, and the other end is thickened in the form of a truncated cone, with a large base at the end of the core, the locking parts are mechanically made from defective mandrels and steel forgings m RKI 25X2M1F or of steel, resistant to impacts, with a threaded thread on the opposite end from the lock, the cores are connected to the lock part by screwing up the threaded joints with the formation of a prefabricated structure, the workpieces are forged or electroslag-melted by casting, heated to plasticity temperature and stitched into to a cross-helical rolling mill into sleeves, the inner diameter of which is larger than the large bases of the truncated core cones by 15-20 mm, put the sleeve on the prefabricated structure until the base with the cone of the castle part, and on the pilgrim mills, the sleeves are rolled-rolled to the cores to form composite mandrel blanks with shirts, the composite mandrel blanks are heat-treated to produce sorbitol structures on the surfaces of the shirts to a depth of 40-50 mm and the composite mandrel blanks are machined with obtaining compound mandrels. 2. The method according to claim 1, characterized in that the length of the blanks for flashing sleeves for the manufacture of composite mandrel blanks is determined from the expressions:
$$L_s=\frac{\left(D_d+0.5\Delta -S_p\right)\left(S_R+0.5\Delta \right)L_{R}K}{\left(D_s-S_s\right)S_s}$$

,
$$L_s=\frac{\left(D_d+0.5\Delta -S_p\right)\left(S_R+0.5\Delta \right)L_{R}K}{R_s^2}$$

,
and the length of sleeves for knitting shirts is determined from the expression:
$$L_g=\frac{\left(D_d+0.5\Delta -S_p\right)\left(S_R+0.5\Delta \right)L_{R}K}{\left(D_g-S_g\right)S_g}$$

,
where D _d - the outer diameter of the mandrel, mm,
Δ - allowance for machining a composite mandrel blank in a composite mandrel after knurling, mm,
S _p - wall thickness of the shirt mandrel, mm,
L _p - the length of the working part of the mandrel corresponding to the length of the rolled shirt, mm,
K is a coefficient that takes into account the fumes of metal during heating of blanks and ingots-blanks ESR in methodical or ring furnaces for flashing them into sleeves in a cross-helical rolling mill,
D _s - the diameter of the workpiece with central drilling for the manufacture of shirts, mm,
S _s - wall thickness of the workpiece with central drilling, mm,
R _s - the radius of the workpiece without central drilling, mm,
D _g - the outer diameter of the sleeve for rolling the shirt, mm,
S _g - wall thickness of the sleeve, mm 3. The method according to claim 1, characterized in that the wall thickness of the shirts of the composite mandrels is determined from the expression:
S _p = K ₁ D _d ,
where K ₁ = 0.22-0.25 - coefficient, a larger value which is taken for mandrels of larger diameter,
and the diameters of the cores are determined from the expression:
D _c = K ₂ D _d
where K ₂ = 0.50-0.55 - coefficient, a larger value which is taken for mandrels of smaller diameter. 4. The method according to claim 1, characterized in that when performing rolling-knurling of the sleeve on the core, the caliber of the rolls is determined from the expression:
D _to = (D _d + 2Δ + h),
where D _d - the outer diameter of the composite mandrel, mm,
Δ is the allowance for machining a composite mandrel blank in the mandrel after rolling the shirt, mm,
h = 15-20 - increase in caliber due to the breeding of the rolls, mm,
and after rolling the pilgrim head, the rolls are reduced by h / 2 and rolled - they roll the shirt in caliber D _to = (D _d + 2Δ + h / 2), and if the shirt is not completely worn on the core cone during the secondary rolling-rolling process, the rolls are reduced by h / 2 and the rolling process of the shirt is carried out until it is fully worn on the core cone. 5. The method according to claim 4, characterized in that the process of rolling the shirts onto the core is performed by feeding the sleeves to the deformation zone m ₁ = 20-25 mm, during secondary rolling-rolling, the feed rate is reduced to 0.75 m ₁ , and during subsequent rolling - the run-in is reduced to 0.5 m ₁ , the greater value of which is taken when rolling composite mandrel blanks for the manufacture of mandrels for rolling pipes of medium diameter.