RU2386500C2 - Method for production of cold-rolled pipes of large and medium diametres of hardly-deformed grades of steels and alloys - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention is related to pipe-rolling production, namely to method for manufacturing of cold-rolled pipes of large and medium diametres from hardly-deformed grades of steel and alloys in mills HPT 250 and HPT 450 from conversion hot-rolled and hot-pressed pipes. Method includes hot rolling or pressing of conversion pipes, removal of defects having rolling origin by means of mechanical treatment of conversion pipes along inner and outer surfaces, chemical treatment and local repair of pipes surface for removal of stubborn defects, thermal treatment depending on grade of steel and alloy, cold rolling of conversion pipes along multi-stage routes, at the same time removal of defects having rolling origin is carried out after the first technological rolling from inner surface by means of floating chiseling, and from outer surface - by means of local repair or abrasive scraping, after floating chiseling and local repair of outer surface pipes are chemically treated and repeatedly repaired locally for removal of stubborn defects.

EFFECT: invention provides for manufacturing of cold-rolled pipes with large and medium diametres from hardly-deformed grades of steel and alloys with high accuracy of geometric dimensions, reduction of expensive metal consumption in average by 200-350 kg per each ton of manufactured pipes, higher probability of complete removal of defects having rolling origin in pipes, limited inventory of tools and equipment for mechanical treatment of pipes, and accordingly reduced cost of cold-rolled pipes from hardly-deformed grades of steel and alloys.

2 cl, 1 tbl

Description

The invention relates to pipe rolling production, and in particular to a method for manufacturing cold-rolled pipes of large and medium diameters from hard-deformed grades of steel and alloys, and can be used in the manufacture of cold-deformed pipes of large and medium diameters from hard-deformed grades of steel and alloys on mills ХПТ 250 and ХПТ 450 of hot-rolled and hot-pressed tubes.

In the practice of pipe production, there is a known method for the production of cold-rolled pipes of large and medium diameters (159-426) mm from hard-deformed steel grades and alloys from hot-rolled or extruded conversion pipes, which includes machining on the outer and inner surfaces (hard turning and boring to remove surface defects) hot deformed conversion pipes. The amount of removal during turning reaches 7-10 mm, and with a bore 6-8 mm. Further, the pipes are subjected to chemical treatment (etching and washing) and local repair of the surface to remove not removed defects, heat treatment depending on the grade of steel and alloy, cold rolling on multi-pass routes (TI 158-Tr. TB1-53-2002 “Production of seamless hot-deformed pipes made of corrosion-resistant steel grades with high surface quality according to TU 14-3R-197-2001 ”).

The disadvantage of this method of manufacturing cold-rolled pipes is the increased consumption of expensive metal (large metal removal during hard turning and boring), the reduced accuracy of cold-rolled pipes due to the lateral difference in the hard turning and boring of conversion pipes with a deviation forming straightness, which affects the difference in finished pipes.

Closest to the technical solution is a method for the production of cold-deformed pipes of large and medium diameters from hard-deformed steel grades and alloys from hot-rolled and hot-pressed tubes, which involves the use of floating turning and boring of hot-rolled steel tubes, further chemical treatment, local abrasive surface repair, and heat treatment in depending on the grade of steel and alloy, cold rolling on multi-pass routes. (TI 158-Tr. TB 5-23-2003 “Production of cold-deformed general-purpose pipes from carbon, alloy and corrosion-resistant steels.” TI 158-Tr. TB 5-44-2004 “Production of cold-deformed pipes from corrosion-resistant steels with high surface quality ").

The disadvantage of this method of manufacturing cold-rolled pipes of large and medium diameters from hard-deformed grades of steel and alloys is the increased consumption of metal, the low probability of complete removal of defects, which is due to the significant depth of surface defects of hot-deformed conversion pipes, the need for specialized tools and machines (machines for boring and turning large pipes, tool heads for turning pipes).

The objective of the proposed method for the production of cold-rolled pipes of large and medium diameters from hard-to-deform grades of steel and alloys is to reduce the consumption of expensive grades of steel and alloys, increase the percentage of pipe delivery from the first presentation by increasing the likelihood of complete elimination of surface defects, reduce the fleet of necessary equipment and tools for machining . The technical result is achieved by the fact that in the method for the production of cold-rolled pipes of large and medium diameters from hard-deformed grades of steel and alloys, including hot rolling or pressing of conversion pipes, removal of defects of rolling origin by mechanical processing of conversion pipes on the external and internal surfaces, chemical treatment and local repair pipe surfaces for removing non-removed defects, heat treatment depending on the grade of steel and alloy, cold rolling rub along multi-pass routes to the finished size, removal of defects of rolling origin is carried out after the first pass of cold rolling from the inner surface with a floating bore, and from the outer surface with local repair or abrasive peeling, after a floating bore and local repair of the inner and outer surfaces, the pipes are subjected to chemical processing and repeated local repair to remove not removed defects.

The essence of the method lies in the fact that since during cold rolling the depth of occurrence of surface defects of hot-deformed pipes decreases and depends on the degree of deformation, by machining the conversion pipes after the first pass at the CPT mill, the probability of complete elimination of surface defects increases and the metal removal rate decreases during mechanical processing, which improves the surface quality of pipes of the finished size and reduces the consumption of expensive metal. Improving the accuracy of the pipes is achieved by the fact that there is no turning of the outer surface, and therefore, redistributing pipes come to the subsequent roll with less lateral difference. Varying the size of the reduction in diameter during the first pass of cold rolling reduces the fleet of machines and tools for machining. After repairing the surface of the pipe, they undergo chemical and softening heat treatment, after which, if necessary, local surface repair is again performed. Then the pipes are rolled to the finished size along multi-pass routes.

The method has been tested and implemented on the KhPT-250 and KhPT-450 mills of ChTPZ OJSC in the production of cold-deformed pipes 219 × 10 mm in size from 06KHN28MDT-Sh alloy with technical requirements in accordance with GOST 9941.

The sequence of technological operations on the existing and proposed methods for the manufacture of cold-rolled pipes of large and medium diameters from hardly deformable grades of steel and alloys is presented in the table.

Existing production method The proposed method of production Technological operation Route Expense ratio Technological operation Route Expense ratio Fur. processing of hot-deformed conversion pipes (floating turning and boring, local repair) 377 × 30-369 × 21 1,424 Cold rolling pipes 377 × 30-325 × 28 1,1 Multi-pass cold pipe rolling 369 × 21-325 × 18-273 × 14-219 × 10 1,331 Fur. processing of cold-rolled pipes (floating bore, abrasive grinding, local repair) 325 × 28-325 × 23 1,197 Multi-pass cold pipe rolling 325 × 23-273 × 17-219 × 10 1.21 Total expense ratio 1,896 Total expense ratio 1,594

The table shows that the metal consumption in the manufacture of cold-rolled pipes of size 219 × 10 mm from an alloy of 06KHN28MDT-Sh grade from hot-rolled steel tubes of size 377 × 30 mm by the existing method is 1896 kg / t, while the proposed method allows the production of these cold-rolled pipes with metal consumption of 1,594 kg / t, that is, metal savings in the production of each ton of cold-rolled pipes of size 219 × 10 mm from 06KHN28MDT-Sh alloy from hot-rolled steel tubes of size 377 × 30 mm will be 302 kg, which is very significant, given the increased th the cost of hard-steels and alloys and industrial production of pipes of them.

Thus, the application of the proposed method for the production of cold-rolled pipes of large and medium diameters from hard-deformed grades of steel and alloys will reduce the consumption of metal of expensive grades of steel and alloys, increase the likelihood of complete elimination of surface defects of rolled origin, increase the accuracy of the geometric dimensions of cold-rolled pipes along the wall, and limit the size of the park tools and equipment for machining pipes and, as a result, reduce the cost of cold-rolled pipes from pipes nodeformiruemyh steels and alloys.

Claims (2)

1. Method for the production of cold-rolled pipes of large and medium diameters from hard-deformed grades of steel and alloys, including hot rolling or pressing of steel tubes, removal of defects of rolling origin by machining steel tubes on the outer and inner surfaces, chemical treatment and local repair of the surface of the pipes to remove unremoved defects, heat treatment depending on the grade of steel and alloy, cold rolling of conversion pipes along multi-pass routes to the finished pipe Measurement, characterized in that the removal of defects of rolling origin is performed after the first pass of cold rolling from the inner surface with a floating bore, and from the outer surface with local repair or abrasive grinding. 2. The method according to claim 1, characterized in that after the floating bore and local repair of the inner and outer surfaces of the pipe, they are subjected to chemical treatment and repeated local repair to remove unresolved defects.