Method for the production of welded large diameter pipes

 

The invention relates to pipe manufacture and can be used in the manufacture of large diameter pipe welding method. The technical result of the invention the exception of the instability of the mechanical properties (impact strength) of a welded joint and heat affected zone, the alignment of their values to the level of the base metal or exceeding their values and exclusion of ovalization of the pipe ends. The technical result is achieved in that the weld seam before rolling heat in the inductor to a temperature AU₃+(120-200)^oFrom and after rolling the weld bead and heat-affected zone is heated in the coil to a temperature AU₃+(80-100)^oTo produce quenching in a water sprayer with a cooling rate of 70-100^oS and a vacation at a temperature AU₁-(30-80)^oC. 1 C.p. f-crystals, 1 table.

The invention relates to pipe production, in particular the production of welded pipes of large diameter.

In pipe production known method of manufacture of welded pipes of large diameter, comprising forming tubular workpieces, the welding of pipes and volumetric heat treatment - hardening high holidays (ed. mon. The USSR 450839, 1974).

and weld that reduces the operational reliability of the pipe due to insufficient resistance to brittle fracture (low toughness values) weld and ovalization ends with a volumetric heat treated pipes.

A method of producing welded large diameter pipes, where to ensure ravnopravnosti weld and base metal weld locally heated to temperatures (650-750)^oC and subsequent heating of the entire pipe for quenching produce until the seam temperature (920-1000)^o(Ed. mon. The USSR 742474, 1980).

However, this method of production of welded large diameter pipes(heat treatment) has not found industrial application due to the complexity of step heating, high energy consumption in heating the entire tube, and the uneven heating of the perimeter of the pipe (seam 920-1000^oC, and the pipe body 770-850^oC) leads to the loss of stability of circular profile, and a higher ovalization ends and the pipe body.

There is a method of manufacture of welded large diameter pipes, including forming, welding billets, heating of the welded connection to the temperature of hot deformation, the deformation of the weld with the degree of 10-40% and the volumetric thermal processing (and the resultant consumption of electrical energy, the ovalization of the ends and body of the pipe when the volumetric hardening.

The closest technical solution is the method of production of welded large diameter pipes, including forming, welding billets, heating of the welded joint to a temperature AU₃+(20-100)^oWith podstugivaniya welded connection to the temperature of A₃-(30-100)^oWith the deformation of the welded joint to a full rolling seam and air cooling with speed, providing recrystalization hot-deformed austenite (ed. mon. The USSR 1632988, 1991).

The disadvantage of this method is that the expansion of the weld to the level of the base metal at a temperature of 820-900^oWith leads to high loads, and heating-podstugivaniya-rolling and air cooling does not guarantee the stability of the mechanical properties (impact strength) of a welded joint and heat affected zone (HAZ) and the alignment of the mechanical properties of the weld and HAZ to the level of the base metal pipe.

The purpose of the proposed method of production of welded pipes of large diameter is to increase reliability by eliminating instability brittle R is the ESD of the metal and reduction of the load by rolling welded joint (weld).

This objective is achieved in that in the method of production of welded large diameter pipes, including forming, welding billets, heating of the welded joint to a predetermined temperature, hot deformation to a full rolling weld and cooling, the weld bead before rolling heat in the inductor to a temperature AU₃+(120-200)^oFrom and after rolling the weld and HAZ heated in the coil to a temperature AU₃+(80-100)^oTo produce quenching in a water sprayer with the cooling rate (70-100)^oS and a vacation at a temperature AC₁-(30-80)^oC.

The essence of the method lies in the fact that in order to reduce the load during rolling of the weld, eliminating the instability of the mechanical properties (toughness) weld and HAZ and the alignment of their values to the level of the base metal or exceeding their values heating of the weld and HAZ before rolling to produce temperature AU₃+(120-200)^oA subsequent thermal processing of these sections of pipe, including hardening at a temperature AU₃+(80-100)^oWith cooling rate (70-100)^oWith a second water sprayer and tempering at a temperature AC₁(30-80)^oC. Apostolicals fact, the weld seam and HAZ before rolling heat in the inductor to a temperature AU₃+(120-200)^oAfter rolling the weld and HAZ heated in the coil to a temperature AU₃+(80-100)^oWith, quenching produced in a water sprayer with cooling rate (70-100)^oWith a second, and a vacation at a temperature AU₁(30-80)^oC. Thus, the claimed method meets the criterion of "NOVELTY."

Comparison of the proposed method not only prototype, but also with other technical solutions in this field of technology is not allowed to reveal in them the features distinguishing the claimed method from the prototype, which allows to conclude that the criterion of "SUBSTANTIAL DIFFERENCES".

The method was tested and implemented in the welding shop at the line of weld pipes 1020-1220 mm in the manufacture of pipes of size 1020 x 12 mm steel grade PB-SQUARE strength class K60. For comparison, the experiment was carried out in three variants: 1. On existing technology TU 14-3R-04-94 "electric resistance welded steel Pipes, longitudinal diameter 530-1220 mm for gas and oil pipelines North of execution."

2. Copyright certificate of the USSR 1632988, CL 21 D 8/10,9/50.

3. The proposed technology.

For each option was brewed and isevidence in the table.

The table shows that the impact toughness of welded pipe connections (on the center seam), manufactured by TA-3P-04-94 was KCU-60^oWith from 0.99 to 4.9 kgfm/cm², KCV-60^oWith from 0.86 to 1.6, KCV-40^oFrom 0.63 to 5.3, a KCV-20^oWith from 2.0 to 6.2 kgfm/cm². These same indicators of the welded joint obtained after rolling the seam to the level of the base metal (ed. mon. The USSR 1632988), respectively 4,7-13,0; 3.3-8,0; 3.3-9,3 and 3.75-10,1 kgm/cm²i.e. toughness values on average increased by 2.2; 5,2; 3.9 and 1.7 times, but these values are significantly below the average of the actual values of the base metal, namely 2,38; 1,95; 2,39 and 2.72% respectively. At the same time of 10 tubes welded on author. mon. 1632988, 5 trumpets, the actual values of impact strength KCU-60^oAnd KCV-20^oWere below the normalized values on the worksheet (TU-1-5386-99).

On the proposed technology (method) heat welded connections before rolling was carried out before the temperature AU₃+(120-200)^o(The actual heating temperature was 1055-1065^oC). Then made the expansion of the weld to the level of the base metal. After rolling produced heat welded is connected to the Denia hot zone produced in the water sprayer with cooling rate (70-100)^oWith per second (the actual cooling rate was 80^oWith per second). After quenching the welded joint (weld and HAZ) was heated by the inductor to the tempering temperature of the AC₁-(30-80)^oC (in fact, 670-690^oC).

Testing of mechanical properties of the experimental tubes showed (see table), that the impact strength of the center seam at the test temperature KCU-60^oWith, KCV-60^oWith, KCV-40 and KCV-20^oWith significantly higher than that of the pipe after rolling the bead in the ed. mon. 1632988, respectively, in 3,69; 3.57; 4,19 and 4,37 times, and also above the average toughness of the base metal, respectively, 1.55; 1,83; 1,76 and 1.61 times. All toughness values on the center seam is significantly higher normalized values on the worksheet (TU-1-5386-99).

The use of the proposed method of production of welded pipes of large diameter will produce welded pipes of large diameter for the Northern version with mechanical properties of a welded joint at or significantly above the normalized values of the base metal.

Claims

1. Method for the production of welded large diameter pipes, including forming, welding billets, heating of the welded joint to a predetermined temperature of the roll is heated to a temperature AU₃+(120-200)C.

2. The method according to p. 1, characterized in that after rolling the weld bead and heat-affected zone is heated in the coil to a temperature AU₃+(80-100)To produce quenching in a water sprayer with cooling rate (70-100)S and a vacation at a temperature AU₁-(30-80)C.