RU2351417C2 - Method of pipe shell manufacture - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to method of tube round manufacturing and can be used while pipe shell manufacturing on continuous-casting plant with following its swaging by diameter in three-high skew-roll piercing mill. Method includes melting of blooms and ingots in electric or open-hearth furnace, its heating till the flexibility temperature, blooms rolling on section mills into pipe shell, ingots forging on press into forgings with removing of shrink and bottom parts, ends facing and its turning into feedstock or blank casting on continuous-casting plant with its slicing for length of cut, with its measured section is heated till the flexibility temperature and rolled in three-high skew-roll piercing mill per one or multiple passes into pipe shell with summary swaging by diameter from 8 till 40%, smaller summary swagings relates to sections of diameter 450-600 mm, and bigger - relates to sections of diameter 100-250 mm, measured castings are heated till the flexibility temperature in heater, using blank temperature after continuous casting, heater and three-high skew-roll piercing mill are installed in the flow after continuous-casting plant, for the first pass sections are swaged in three-high skew-roll piercing mill by diameter from 8 till 12%, and per each following passage swage is increased, properly - per 1-3%, while bigger values relate to sections of smaller diameter.

EFFECT: it is provided range of sizes expansion by pipe shells diameters excluding change of crystallisers on continuous-casting plant, increase in productivity of continuous-casting plants, improvement of pipe shell and hot-rolled pipes and its decrease in value.

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Description

The invention relates to metallurgical and pipe production, in particular to a method for the production of a round tube billet, and can be used in the manufacture of a tube billet at continuous steel casting plants, followed by its compression in diameter in a three-roll reversible oblique rolling mill.

In the practice of the metallurgical and pipe industries, there is a method of manufacturing seamless hot-deformed pipes of large and medium diameters for steam boilers, steam pipelines and manifolds of plants with high and supercritical parameters of steam in pipe rolling plants, with pilgrim mills from forged billets of steel grades 20, 15GS, 15XM, 12X1MF, 15Х1М1Ф, 12Х2МФСР, 10Х9МФБ, 12Х11В2МФ, 08Х16Н9М2, 12Х18Н12Т and 10Х13Г12БС2Н2Д2, with specified requirements for mechanical properties, including ingot smelting in electric and open-hearth furnaces ah, forging (structure compaction) of ingots into forgings with a weft from 2.0 to 3.0, depending on the steel grade, continuous casting of steel grades 20, 15GS, 12X1MF, 15X1M1F and 15XM with their subsequent forging into forgings with a minimum of at least 1.5, trimming the ends of the forgings with the removal of shrinkage and bottom parts, trimming the ends and drilling a central hole with a diameter of 100 ± 5 mm to remove liquation porosity and non-metallic inclusions (TU 14-1-2560-78 "Forged pipe blanks for boiler pipes") .

The disadvantage of this method is the high cost of the tube billet due to the high energy intensity of the process associated with heating and deformation (forging) of the ingots and UHF on the presses forgings, followed by trimming the ends of the forgings with the removal of shrinkage and bottom parts, trimming, turning and drilling of the central hole.

In the metallurgical industry, there is also a known method for the production of pipe billets from carbon, low alloy, and alloy steel, which involves the smelting of blooms in electric or open-hearth furnaces, heating them to plasticity temperature and rolling on high-quality mills into a pipe billet with a diameter of 70 to 270 mm (OST 14-21-21 -77 "Billet pipe made of carbon, low alloy, alloy and spring - spring steel. Technical requirements", reprinted in 2002).

The disadvantage of this method is the high cost of the pipe billet due to the high energy intensity of the process associated with heating and deformation of blooms on high-quality mills into a pipe billet, i.e. with the inclusion in the process of expensive and energy-intensive varietal mills.

In the metallurgical and pipe-rolling industries, there is a known method for the production of continuously cast tube billets from converter steel, which have been refined at the ladle furnace with neutral gas purging (TU 14-102-198-2002 "Continuously cast tube billets", GOST 1050-88 " Long products, calibrated, with special surface finish made of high-quality carbon structural steel ").

One of the disadvantages of this method is that on the installations of continuous casting of steel produce a round tube billet with an overrun of at least 100 mm in diameter, because the mold is an expensive unit, and their replacement is time consuming.

The closest technical solution is the method of screw rolling, including hot deformation of the ingots after casting at a crystallization temperature in their center, and on the outer surface lower by 300-500 ° C, with a compression of 2-8% in diameter (ed. Certificate of the USSR No. 660740 Bull. No. 17. 1979).

The disadvantage of this method of screw rolling is the need to install an oblique rolling mill at the metallurgical production areas at the end of the casting span, which is impractical for safety reasons, and this method is aimed only at improving the structure of the central part of the ingot.

The objective of the proposed method (invention) is to expand the size range of continuously cast billets in diameter without replacing molds in continuous steel casting plants, to increase the productivity of continuous steel casting plants, to improve the quality of pipe billets by compressing the billet mill in diameter without opening the inner cavity by rolling them into three-roll reverse mill oblique rolling in one or more passes with a total compression of from 8 to 40%.

The technical result is achieved by the fact that in the known method of manufacturing a pipe billet, including the smelting of blooms and ingots in electric or open-hearth furnaces, heating them to a plasticity temperature, rolling blooms on high-quality mills into a pipe billet, forging ingots on presses for forging, followed by trimming the ends of the forgings with the removal of shrinkage and bottom parts, trimming the ends and turning them into billets or casting billets on continuous steel casting plants with cutting them into measured lengths, heating measured continuously billets to plasticity temperature and rolling them in a three-roll reversible oblique rolling mill for one or several passes into pipe billets with a total diameter reduction of 8 to 40%, while for the first pass, continuously cast billets are crimped in a three-roll reversible oblique rolling mill by diameter up to 12%, and for each subsequent pass, the compression is increased, respectively, by 1-3%, with larger values refer to continuously cast billets of smaller diameter, smaller total reductions refer to continuously cast billets workpieces with a diameter of 450-600 mm, and large to continuously cast billets with a diameter of 100-250 mm, measured continuously cast billets are heated to the ductility temperature in the heating device, using the temperature of the workpieces after continuous casting, the heating device and a reversible three-roll oblique rolling mill are installed in flow after installation of continuous casting of steel.

Comparative analysis with the prototype shows that the inventive method for the production of a tube billet is characterized in that the continuous continuous cast billet is heated to a plastic temperature and rolled in a three-roll reversible oblique rolling mill in one or more passes into a tube billet with a total compression in diameter from 8 to 40 %, while for the first pass the continuously cast billets are crimped in a three-roll reversible oblique rolling mill in diameter to 12%, and for each subsequent pass, the compression is increased, respectively exactly, by 1-3%, with larger values referring to continuously cast billets of smaller diameter, smaller total reductions refer to continuously cast billets with a diameter of 450-600 mm, and large ones to continuously cast billets with a diameter of 100-250 mm, continuous cast billets are heated to the ductility temperature in the heating device using the temperature of the billets after continuous casting, and the heating device and the reversible three-roll oblique rolling mill are installed in the stream after the continuous casting is installed ki steel. These differences allow us to conclude that the criterion of "inventive step".

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 solution from the prototype, which corresponds to the patentability condition "inventive step".

Since there is no similar method and equipment in the proposed combination in world practice, an example of a specific implementation in a given period of time is not possible.

This method for the first time in world practice will allow for the industrial production of high-quality tubular billets of an expanded size range in diameters without replacing molds in continuous steel casting plants, to increase the productivity of continuous steel casting plants, to improve the quality of tube billets by compressing the billet mill by diameter without opening the inner cavity by rolling them in a three-roll reverse mill oblique rolling in one or more passes with a total compression of 8 to 40%, which, in echnom result, will improve the quality of hot-rolled tubes and reduce their cost.

Claims (4)

1. A method of manufacturing a tube billet, including the smelting of blooms and ingots in electric or open-hearth furnaces, heating them to a ductile temperature, rolling blooms on high-quality mills into a tube billet, forging ingots on presses into forgings, followed by trimming the ends of the forgings with the removal of shrinkage and bottom parts , trimming the ends and turning them into billets or casting billets at continuous steel casting plants with cutting them into measured lengths, heating the continuous continuously casted billets to a plasticity temperature and rolling and x in a three-roll reversible mill for oblique rolling in one or several passes into pipe billets with a total compression in diameter of 8 to 40%, while for the first pass, continuously cast billets are crimped in a three-roll reversible mill in diameter for up to 12%, and for each subsequent pass reduction is increased by 1-3%, respectively, and large values apply to continuously cast billets of smaller diameter. 2. The method according to claim 1, characterized in that the smaller total reduction refers to continuously cast billets with a diameter of 450-600 mm, and large to continuously cast billets with a diameter of 100-250 mm. 3. The method according to claim 1, characterized in that the measured continuously cast billets are heated to plasticity temperature in a heating device using the temperature of the billets after continuous casting. 4. The method according to claim 1, characterized in that the heating device and the reversible three-roll oblique rolling mill are installed in the stream after the installation of continuous casting of steel.