RU2288053C2 - Method for producing cold-rolled large- and mean- diameter tubes of titanium base alloys - Google Patents

Abstract

FIELD: rolled tube production, namely rolling cold rolled large and mean diameter tubes of titanium base alloys from conversion welded blank, possibly in cold rolling mills.

SUBSTANCE: method comprises steps of producing conversion seamless or welded blanks, rolling them at one or more rerolling stages depending upon tube size and alloy type. Conversion tube blank for rolling cold rolled large and mean diameter tubes is produced by shaping in roll mill and by further welding its lengthwise edges in protective argon atmosphere. Conversion welded tube blank is rolled cold rolled tube of maximum diameter at elongation degree 1.2 - 1.4. At next rerolling stages elongation degree is increased by 0.05 - 0.20 till 1.9 - 2.3 for last rerolling stage. Invention provides possibility for producing high-quality large- and mean-diameter tubes of titanium base alloys according to ASTM B 862-02, lowered by 2.0 - 2.2 times consumption factor of titanium base alloys.

EFFECT: lowered cost of producing cold-rolled high quality large- and mean-diameter tubes of titanium base alloys.

2 cl, 1 tbl

Description

The invention relates to pipe production, namely, to rolling cold-rolled large and medium diameter pipes from titanium-based alloys from a welded billet, and can be used on cold rolling mills HPT 250 and HPT 450.

In the practice of pipe production, a method is known for the production of cold-rolled pipes of large and medium diameters (426-159) mm from titanium-based alloys from hot-rolled large-diameter pipe billets, including casting ingots with a diameter of 600-630 mm ESR, machining ingots (turning and drilling the central holes with a diameter of 100 mm), heating the ingots in muffles to a ductility temperature (1140-1180) ° С, piercing on a Kosovalkovy piercing mill with a drawing coefficient of 1.4-1.8, rolling on a pilgrim mill with a coefficient of hoses 2.8-3.8, straightening and machining of hot-rolled pipes with removal of external and internal defective layers of 8-10 mm (TU 14-3-1218-83 "Seamless hot-deformed pipes turned and bored from alloy grade 14 ″ and TI 158-Tr. TB1-64-2002 "Production of seamless hot-deformed pipes from alloy 14 according to TU 14-3-1218-83 and TU 14-3-1236-83 ″, Chelyabinsk, 2002).

The disadvantage of this method is the low yield (consumption coefficient of metal 1.8-2.5) due to the formation of surface defects (cracks due to the alpha layer) and the complexity of heating billets in special muffles, eliminating the possibility of ignition of billets made of titanium alloys when interacting with liquid dross.

In the production of seamless large-diameter seamless rolled tubes, large mass ingots are used, which require a long heating time, which results in gas saturation of the surface of the ingot (occurrence of an alpha layer). In the process of cross-screw piercing and rolling on a pilgrim mill under the action of tensile and compressive stresses, cracks arise in the alpha layer, which, under the influence of water and deformation stresses, which penetrate into them, develop deep into the body of the liners and pipes. To remove cracks from hot-rolled pipes, machining (boring and turning) to a depth of 10 mm is required, which requires additional costs for machine tools, and most importantly leads to significant losses of expensive titanium alloys.

In the practice of production of seamless cold-rolled pipes at HPT mills, it is recommended to reduce the outer diameter (reduction in diameter) in the range of 26-40 mm, which increases with increasing pipe diameter (V.Ya. Osadchy, A.S. Vavilin, V.G. Zimovets and A.P. Kolikov. Technology and equipment for pipe production. Moscow. "Internet Engineering", 2001, p. 481). This suggests that for rolling pipes with a diameter of 159 mm (average diameter) for one roll, a billet with a diameter of not more than 200 mm is required, and for pipes with a diameter of 426 mm (large diameter) a workpiece with a diameter of not more than 470 mm.

A known method of rolling cold-rolled tubes of titanium alloys, including the production of a sheet billet, forming a sheet billet into a tube billet, welding longitudinal edges, transverse rolling of a welded billet on a mandrel in a Kosovalkovy mill and subsequent rolling (ed. Certificate. USSR No. 499907, Cl. B 21 B 23/00, 1974).

The disadvantage of this method is that it is time-consuming due to the operation of rolling pipes on two types of rolling equipment, does not exclude the formation of defects on the outer and inner surfaces of the pipes in the form of marks on the border of fusion of the weld with the base metal, the complexity and lack of equipment for repair of the weld, as well as defects in the form of flaws of the weld due to the presence of an unremovised alfied layer from the weld. This process is acceptable only for the production of pipes from titanium alloys of small size, because There are industrial plants for the production of welded pipes of this assortment in a protective environment of argon.

The closest in technical solution is the method of rolling cold-rolled pipes from titanium alloys, including the production of a sheet billet, preparing the sheet edges for welding, forming a sheet billet into a tube billet, welding longitudinal edges, rolling on a cylindrical mandrel in a spiral (pitch angle less than 90 °) s in increments equal to the wall thickness of the finished pipe, with a degree of deformation along the wall of 30-50% (USSR Authors Certificate No. 893280, Cl. V 21 V 23/00, 1981).

The disadvantage of the above method for the production of a conversion tube billet for rolling cold-rolled large and medium diameters from titanium-based alloys is that it is also laborious, requires large capital expenditures and does not solve the main problem, namely the reduction of defects (stress concentrators) and their repair on the outer and inner surface of the pipes in the form of longitudinal marks along the boundary of fusion of the weld with the base metal and the flaw of the weld due to the alpha layer, which is removed from the pipes annogo assortment difficult and not economically feasible.

The objective of the proposed method for rolling cold-rolled pipes of large and medium diameters from titanium-based alloys is to master the production of cold-rolled pipes of large and medium diameters from titanium alloys from a welded pig billet, reduce the complexity of its manufacture and repair of welded joints, manufacture of cold-rolled pipes in accordance with ASTM B 862-02 and TU 14-158-135-2003, reduction of alloy consumption during redistribution: welded conversion pipe billet - cold rolled pipe.

This object is achieved by the fact that in the known method of rolling cold-rolled pipes of large and medium diameters from titanium-based alloys, including the production of converted welded billets, rolling them with one or two rifts, depending on the size and grade of the alloy, a converted billet for rolling cold-rolled pipes large diameter produced by molding on rollers with subsequent welding of the longitudinal edges in a protective environment of argon and rolled into a cold-rolled pipe with a maximum diameter of 1.2- 1.4, and in subsequent rolls, the hood is increased by 0.05-0.20 to 1.9-2.3 at the last roll.

The essence of the method lies in the fact that in order to reduce the consumption of titanium alloys when rolling cold-rolled pipes of large and medium diameters, welded pipe billets are used instead of seamless billets, and to reduce the complexity of their manufacture, reduce the complexity of repairing a welded joint, the billets are made by molding on rollers with subsequent welding of the longitudinal edges in a protective environment of argon, for rolling cold-rolled pipes of larger diameter, which are rolled from the elongation 1.2-1.4, and during subsequent rolls into pipes of medium diameter, the hood is increased by 0.05-0.20 to 1.9-2.3 at the last roll. Thus, the claimed method meets the criterion of "novelty."

Comparison of the proposed method not only with the prototype, but also with other technical solutions in the art did not allow them to identify signs that distinguish the claimed method from the prototype, which allows us to conclude that the criterion of "significant differences".

The method has been tested and implemented on the KhPT 250 and KhPT 450 mills of ChTPZ OJSC when rolling cold-rolled pipes of size 426 × 12 - 377 × 10 - 325 × 8 - 273 × 6 - 219 × 4.5 - 180 × 3 - 159 × 1, 5 mm from a welded pipe billet of 470 × 14.5 mm in size made of VT 1-0 alloy. Two conversion welded billets with a size of 470 × 14.5 × 4500 mm were manufactured at JSC "Plant PSK", Novosibirsk. Sheets were formed into tube blanks on rollers with a gap of 4.0 mm. The longitudinal edges were welded using a consumable electrode made of VT1-0 alloy in a protective argon medium. The billets were delivered to ChTPZ OJSC and rolled into pipes according to the proposed and existing technologies. The data on the rolling of cold-rolled large and medium-diameter pipes at the KhPT 250 and KhPT 450 mills of ChTPZ OJSC from the converted welded billets of VT1-0 alloy according to the existing and proposed technologies are given in the table. The table shows that the longitudinal welded billet according to the proposed technology was successively rolled into cold-rolled pipes of size 426 × 12 - 377 × 10 - 325 × 8 - 273 × 6 - 219 × 4.5 - 180 × 3 and 159 × 1.5 mm s hood ratios 1.33; 1.35; 1.45; 1.58; 1.66; 1.82 and 2.25 and compressions (reduction) in diameter, respectively 44; 49; 52; 52; 54; 39 and 21 mm, which is fully consistent with the claims. Pipes of all sizes in terms of geometric dimensions and mechanical properties met the requirements of ASTM B 862-02 and TU 14-158-135-2003. The expenditure coefficient of metal for redistribution ranged from 1.015 to 1.042, and the total expenditure coefficient for pipes of medium (final) diameter measuring 159 × 1.5 mm from the welded billet to the pipe was 1.153. According to existing technology, a welded straight-seam conversion billet should be rolled for two rolls into pipes of 426 × 12 and 377 × 10 mm in size. Since in Russia there are no longitudinal welding mills for pipes with a diameter of 377, 325 and 265 mm, and even more so for the production of welded pipes from titanium-based alloys in an argon protective environment, for the production of pipes of size 325x8 mm a seamless hot-rolled pipe billet of size 375 × was required 18 mm, which, after machining to a size of 365 × 10 × 6000 mm, was rolled into pipes of size 325 × 8 mm, followed by rolling into pipes of 273 × 6 mm in size. The expenditure coefficient of rolled metal was 1.024 and 1.035, and taking into account the machining of hot-rolled pipes, it was 1.854 and 1.960, respectively. For rolling pipes with sizes of 219 × 4.5, 180 × 3 and 159 × 2 mm according to the existing technology, it is possible to use hot-rolled mechanically processed (turned and bored) billets of 250 × 6 × 6000 mm in size. When using this workpiece, the expenditure coefficient of the metal in terms of redistribution was 1.025; 1.026 and 1.026, and taking into account the regrinding of blanks, respectively 2.409; 2,450 and 2,513. Thus, when rolling pipes with a size of 159 × 1.5 mm from a welded pipe billet for seven cuts, the total expenditure coefficient of VT1-0 alloy was 1.153, and according to the existing technology for three rolls from a seamless machined workpiece with a size of 250 × 6 × 6000 mm the total expenditure coefficient of the VT1-0 alloy was 2.536, i.e. a reduction in the expenditure coefficient by 1.383 or 2.2 times was obtained upon receipt of high-quality pipes in geometric dimensions and mechanical properties and a loss in productivity of mills ≈ 2 times. Since the cost of titanium-based alloys is much higher than the cost of mill downtime (mill hours), it is economically feasible to go along the path of saving alloys due to loss of mill productivity, especially when the mills of the KhPT 250 and KhPT 450 are not fully loaded.

Thus, the use of the proposed method for rolling pipes of large and medium diameters from titanium-based alloys will make it possible to produce high-quality pipes in accordance with ASTM B 862-02 and TU 14-158-135-2003 from a welded steel billet made for rolling pipes of maximum diameter , instead of a seamless conversion billet, significantly reduce the complexity of manufacturing a conversion billet, reduce the consumption coefficient of titanium alloys by 2.0-2.2 times during redistribution: a welded conversion billet for rollers of cold-rolled pipes of a larger diameter - a cold-rolled pipe of a size range from maximum to medium, and therefore, significantly reduce the cost of cold-rolled pipes of this size range from titanium-based alloys.

Data on the rolling of cold-rolled large and medium diameter pipes at the KhPT 250 and KhPT 450 mills of ChTPZ OJSC from the conversion billets of VT1-0 alloy according to the existing and proposed technologies Proposed technology Existing technology Type and dimensions of the conversion workpiece (mm) Pipe dimensions (mm) Koeffits. Hoods (μ) Diameter Compression (mm) Pipe length after trimming ends (mm) Consumption. coefficients metal Type and dimensions of the conversion workpiece (mm) Pipe dimensions (mm) Koeffits. hoods (μ) Diameter Compression (mm) Pipe length after trimming ends (mm) Consumption. coefficients metal Welded straight-line seam 470 × 14, 5 × 4500 426 × 12 1.33 44 5750 1,042 Welded straightforward. 470 × 14.5 × 4500 426 × 12 1.33 44 5750 1,042 377 × 10 1.35 49 7600 1,025 377 × 10 1.35 49 7600 1,025 325 × 8 1.45 52 10700 1,029 Seamless machining. 365 × 10 × 6000 325 × 8 1.40 40 8200 By proc. 1,024 s fur. arr. 1,854 273 × 6 1,58 52 16700 (8350 × 2) 1.016 Seamless machining. 315 × 8 × 6000 273 × 6 1,53 42 8900 By proc. 1,035 s fur. arr. 1,960 219 × 4.5 1.66 54 13600 13600 1.019 Seamless machining. 250 × 6 × 6000 219 × 4.5 1,52 31 8900 By proc. 1,025 s fur. arr. 2,409 180 × 3 1.82 39 12,200 × 2 12,200 × 2 1.015 180 × 3 1.82 39 15900 (7950 × 2) By proc. 1,026 with fur. arr. 2,450 159 × 1.5 2.25 21 10000 × 8 + 7300 × 4 1,035 s / c from the workpiece. 1,153 159 × 2 1,69 21 13100 × 2 By proc. 1,026 with fur. arr. 2,513

Claims (2)

1. The method of rolling cold-rolled pipes of large and medium diameters from titanium-based alloys, including the production of converted welded pipe billets, rolling them with one or two rifts, depending on the size of the tubes and alloy grade, characterized in that the converted tube billet for rolling cold-rolled pipes large diameters are produced by molding on rollers, followed by welding of longitudinal edges in a protective argon medium. 2. The method according to claim 1, characterized in that the welded pipe billet is rolled into a cold-rolled pipe of maximum diameter with a hood of 1.2-1.4, and during subsequent rolls, the hood is increased by 0.05-0.20 to 1.9 -2.3 at the last roll.