SU969758A1 - Method for producing high-strength electrically welded pipes - Google Patents

Description

The invention relates to the production of high strength oil-welded tubular pipes (casing).

Techniques are known for the production of electrically welded pipes of medium (and small) dimensions, including the following basic operations; continuous strip forming, high frequency edge welding, deburring, calibration 1.

The difference in the level of strength, ductility, and viscosity of the base metal of the pipe and the weld metal and the heat-affected zone is corrected by heat treatment to which either the whole pipe or the weld metal and heat-affected zone is subjected. However, the differences in structure and chemical composition that remain after heat treatment (usually normalization), as well as the presence of strong metal fiber curvature in the weld area (due to pressure welding), retain significant anisotropy of the mechanical properties around the perimeter of pipes, limiting their use in industry in particular for oil and gas production 21.

The closest in technical essence to the proposed is

A method of producing high-strength electric-welded pipes, including thermal hardening of welded pipes, hardening and tempering, followed by warm calibration and straightening to correct ovalization and curvature of the pipe. This technology allows to increase the level of strength properties of low carbon steels, as well as slightly reduce the difference in properties around the perimeter of the pipe 3.

At the same time, this technology does not ensure the achievement of inexpensive low-carbon (for example, with a content of 0.15-0.20% C) has become a complex of mechanical and technological properties that meet the requirements imposed, for example, on casing pipes of strength group L (yield strength is 65 kg / mm). It also does not provide the necessary uniformity of mechanical properties around the perimeter of the pipes, which is due to the above-mentioned characteristics of the pressure using radio frequencies. In the seam, near-weld zone and after heat treatment, lower toughness values are maintained than in the rest of the pipe, and often these values are lower than required l. In addition, the use of electric welded pipes as casing is prevented by the state of their inner surface. The removal of the internal flash in these tubes is either not performed at all or is not completely removed; attempts to completely remove internal deburring (on medium-diameter pipes often lead to the appearance of stress concentrators (scratches, grooves) on the inner surface of pipes. The purpose of the invention is to improve the complex of metal mechanical properties to achieve pain uniformity of properties around the perimeter of pipes and improve their inner surface This goal is achieved by the fact that according to the method of production of electric welded pipes, including strip molding, edge welding, complete or partial deburring, heating of pipes, x hardening and tempering, calibrating at tempering temperatures and warm straightening, the pipes after heating and before rolling are subjected to rolling on the mandrel with skewed rollers. The rolling is carried out with a degree of reduction on the pipe wall within 12-20%. The drawing shows a flow line. electric-welded pipes are produced in a production line, in which, after the pipe-welding mill 1 and the deburring device 2, a through-pass furnace 3 is installed to heat the pipes overflow by rolling and quenching, the mill 4 is a transverse-screw pipe piercing, cooling giving device (external and internal sprayers) 5, the straight-through furnace used for heating the pipe under rental, calibration and proper 7 8 mils, refrigerator 9. The method is carried out as follows. The pipes welded on the pipe-welding mill 1 with the outer and inner burrs completely or incompletely removed in the device 2 are subjected to heating up to the temperature of the meta-plate of Acj points at 100 + 50 ° С in the furnace 3, then they deform (roll) along the wall (and diameter) in the mill 4 cross-rolling rolling with compression on the mandrel (along the wall) by the value of 1220%. The rolled sections of the tubes coming out of the deformation zone are subjected to simultaneous external and internal cooling (from the quenching temperature) in the sprayers 5. After quenching, the tubes are transferred to the furnace 6 for tempering at metal temperatures in the range of 500-700 ° C, then they are subjected to warm calibration deformation of 10-15% in the calibration mill 7 and warm straightening in the correct mill 8 followed by cooling on the refrigerator 9. The deformation of the pipe along the wall with a compression of 12–20% during the rolling process improves the structure and arrangement of the metal fibers of the MVA zone, as a result of which the complex of mechanical properties is improved and their alignment takes place along the perimeter of the pipe. At the same time, all irregularities of the MVA zone, in particular, the protrusions that remain with incomplete removal of the bur, are smooth, the longitudinal grooves and the risks that arise, as a rule, during its complete removal. Bilateral water cooling of the pipe during the rapid rotation of the tube provides the formation of quenching structures for low carbon steel. Thermal calibration with a reduction rate of 10–15% after tempering at 500–700 s results in a significant comminution of the steel substructure, as a result of which, along with a further increase in the strength characteristics, high ductility and metal toughness are observed and a decrease is observed. Cold metal threshold threshold. Example. At the pipe-rolling plant at plant 250-2, VTMO carried out rolling and subsequent quenching of electric-welded straight conduit pipes of steel grade 20 of 146x7.4 mm in the amount of 15 pieces. Of these, 10 pipes with completely removed external and internal flash and 5 pipes with removed / flash. Heated in a ring furnace up to 1030 ° C, pipes with a length of 6 m at the transport speed are transferred by means of live rolls to the inlet side of the rolling machine No. 1 and immediately set into mill rolls, where they are deformed in diameter to 165 mm and compressed in wall to 6.5 mm (12 , 2%). During the rolling process, simultaneous two-sided cooling with water in the quenching device from 960 to 50 ° C is carried out at a speed of moving pipes of 0.5 m / s. After the forced removal of water from them, the pipes are then transferred to the thermal section, where they are heated in a sectional furnace for tempering up to 620 ° C (strength group E). After tempering, the pipes enter one by one into the calibration station, where at 600 ° C they are deformed in diameter up to 140 mm with wall thickening up to 7.0 mm. Calibrated pipes are transferred to a warm straightening at 500 ° C, and then to a shlepper refrigerator, where they are cooled to 50 ° C and collected in a pocket. Metallographic studies of the MVA metal, the heat-affected zone and the main body of the pipes show the uniformity of the resulting quenching structure.

(low carbon martensite). The quality of the surface of the pipes is also satisfactory.

Comparison of the properties of electric-steam pipes manufactured by the proposed method with electrowelded reinforced pipes obtained by the well-known ircnocoeoM and seamless pipes, which went through thermomechanical treatment from rolling heating, are given in Table. 1 (steel in all cases of carbon, composition,%: C 0.11; Mp 0.4; Si 0.15; P 0.011; S 0.032).

From the data table. 1 shows that the proposed method for the production of high-strength electric-welded pipes in comparison with the known tm provides a higher level and uniformity of mechanical and technological properties.

and in comparison with the production of high-strength, wasteless pipes - significantly greater accuracy of geometric dimensions.

Thus, the proposed method allows to eliminate defects in the weld zone, to achieve alignment of the structure and properties of the electric welded pipe along its perimeter and to ensure the production of reinforced critical pipes (for example, casing pipes) with the necessary complex of mechanical and technological properties using this low-carbon steel.

About the efficiency of the proposed method show comparative data table. 2

Table 1

Strength limit (E9 / kg / mm

, Impact viscosity (on transverse samples) of COP Kg / cm:

pipe body seam area

Shchi ± 3, 0 +3.0 Smooth grooves and risks

High resistance Low resistance hydrogen sulphide to hydrogen sulphide cracking cracking in the weld zone Note,

60.0

71.0

5 2

± 10.5

± 2.5 ± 5.0

With the remnants of grata.

Smooth

High hydrogen sulfide resistance; cracking

Table 1 - method of production by quenching and tempering of electric-welded pipes; 2- by means of high-temperature thermomehagzhsk treatment of the sleeveless tubes; 3- proposed.

Formula ieobtentenn

Claims (3)

1. Method for the production of high-strength electrically welded pipes, including strip molding, edge welding, complete or partial deburring, heating of pipes | quenching and tempering, calibrating at tempering temperatures and warm straightening, differing from the fact that, in order to improve the complex of mechanical properties and geometry of pipes, heated pipes are subjected to rolling on a mandrel with angled rolls before quenching. 2. A method according to claim 1. characterized in that the expansion is carried out with a degree of compression along the pipe wall in the range of 12-20%. Sources of information taken by the HE in the examination 1. Zhukovsky B.D. et al. Production of pipes by electric welding by the resistance method. Moscow, Metallurgists, 1953. 2.Gul ev GI, Voitselenok S.L. Quality of electric-welded pipes. M., Metallurgists, 1978, p. 97-122. 3.ProektUkrgipromeza. Arch. No. D116904, DI6905, D110249, 1974.