EVALUATION OF STRESS-STRAIN STATE OF THE METAL ON THE BASIS OF MATHEMATICAL MODELING IN PRODUCTION OF LARGE DIAMETER PIPES

The analysis of slab forming processes under different schemes:  in rolls (RBE scheme), presses (UOE scheme) and stepwise forming  (JCOE scheme) shows that domestic and foreign plants of large-diameter pipe production for laying offshore pipelines use JCOE scheme.  The mathematical modeling of processes of plastic deformation of slab  in edge-bending press by JCOE scheme and on the stepwise forming  and calibration press of welded O-shaped pipe billet on a mechanical expander was made using the Deform 3D software. The results of  mathematical modeling of stress-strain state of the metal in pipe billets  and finished pipes are considered for all the technological production  process of large diameter pipes. It is shown that the plastic state of the  molded J-shaped slabs on forging equipment and at pipe calibration  is characterized by uneven stress-strain state (SSS) of the metal. Numerical results of the distribution of equivalent stress and strain rate on  the outer surface of the pipe of the size Dt × Sm  =  720×22  mm of K56  strength class have shown that pipe sections with more uneven SSS  have high values of residual stresses and strains, so in these areas was  noted an increase of diameter and roundness of the pipe relative to the  average. The results of experimental research of residual stresses in  pipes after expanding made at TESA 1020 and TESA 1420 confirm the  unstable distribution of stress-strain state in the cross-section of large  diameter pipes. In the weld joint σres reaches a value of +220  MPa  (JOE scheme) and +150  MPa (UOE scheme), which is (0.3  –  0.4)σt ,  whereas in the pipe metal σres  =  +40...45  MPa. Numerical calculations by the FEM model of out-of-roundness of pipe after expansion at various initial geometrical dimensions of the molded slabs are confirmed  by physical measurements of geometric dimensions on the installation  of automatic control. The modeling results have established that for the  construction of underwater gas pipeline according to normative documents the optimal geometric pipe shape and dimensional accuracy of  the inner diameter of large-diameter pipes can be achieved at expanding of the pipe billet with out-of-roundness of 5  mm. This ensures the  quality assembly and welding of the edges of connected pipes in the  pipeline. The results of computer simulation by the FEM model of the  stress-strain state of the plastic forming of pipe billet at manufacture by  JCOE scheme should be considered in the calculation of technological  parameters of pipe billet molding, tool calibration and press equipment  setting modes.

mathematical modeling,  parameters of stress-strained metal,   forming,  slab,  pipe calibration,  expander,  large diameter welded pipe

1. Mazur I.I., Ivantsov O.M. Bezopasnost’ truboprovodnykh system [Safety of pipeline systems]. Moscow: ITs ELIMA, 2004, 1104 p. (In Russ.).

2. Efron L.I. Metallovedenie v “bol’shoi” metallurgii. Trubnye stali [Metallography in large metallurgy. Pipe steels]. Moscow: Metallurgizdat, 2012, 696 p. (In Russ.).

3. Osadchii V.Ya., Kolikov A.P. Proizvodstvo i kachestvo stal’nykh trub [Production and quality of steel pipes]. Moscow: MGUPI,  2012, 370 p. (In Russ.).

4. Uryadov R.V., Khristoforov A.S. The use of three-roll plate bending  machine and rolls units for edges finish bending at the production of longitudinal welded large diameter pipes with a ratio of diameter/ wall thickness less than 30. In: Sb. trudov: Innovatsionnye tekhnologii v metallurgii i mashinostroenii [Innovative technologies in  metal lurgy and engineering: Coll. of papers]. Ekaterinburg: Izd-vo  Ural. Un-ta, 2014, pp. 414–422. (In Russ.).

5. Zvonarev D.Yu., Osadchii V.Ya., Romantsov A.I., Kolikov A.P.  Shaping of sheet to produce large-diameter welded pipe. Steel in Translation. 2016, vol. 46, no. 6, pp. 443–446. 

6. Deriks V., Genzer B. New technologies of cost-effective and flexible production of large diameter pipes. In: Trudy XIII Mezhdunar. nauch.-prakt. konf. “Truby-2005” [Proceedings of the XIII Intern.  Sci.-Pract. Conf. “Pipes-2005”]. Part. 1. Chelyabinsk: OAO “RosNITI”, 2005, pp. 105–108. (In Russ.). 

7. Wen S.W., Hilton P., Farrugia D.C.J. Finite element modeling of  a submerged arc welding process. Journal of Materials Processing Technology. 2001, vol. 119, pp. 203–209.

8. Kishiguchi T., Hosoda H., Ikuno Y . Pipe end round equipment and  control system (PERFECTS). Chin-Niittetsu-Sumikin Engineering Gino. 2013, no. 4, pp. 39–45.

9. Katsumi M., Kenji O. Steel products for energy industries. JFE Technical Report. 2013, vol. 43, no. 18, pp. 1–11.

10. Zvonarev D. Yu. Sovershenstvovanie protsessov podgibki kromok i shagovoi formovki svarnykh trub bol’shogo diametra dlya obespecheniya vysokoi tochnosti razmerov i form. Diss. kand. tech. nauk [Process improvement of edge-banding and step molding of  welded pipes of large diameter to ensure high accuracy of dimensions and shapes. Cand. Tech. Sci. Diss.]. Chelyabinsk: YuUrGU,  2015, 166 p. (In Russ.).

11. Galkin V.V., Cheburkov A.C., Pachurin G.V . Evaluation by mathematical modeling of stress-strain of metal billets made by stepwise  molding  method.  Sovremennye problemy nauki i obrazovaniya.  2013, no. 2, pp. 114–115. (In Russ.).

12. Kolikov A.P., Zvonarev D.Yu., Taupek I.M. Kadil’nikov S.V., Galimov M.R. Mathematical model of plastic forming of the slab for large diameter welded pipes. Report 2. Izvestiya VUZov. Chernaya metallurgiya = Izvestiya. Ferrous Metallurgy. 2016, vol. 59, no. 9,  pp. 615–621. (In Russ.).

13. Seleznev V.E., Aleshin V.V.,  Pryalov  S.N.  Osnovy chislennogo modelirovaniya magistral’nykh truboprovodov [Basics of numerical  modeling of pipelines]. Seleznev V.E. ed. Moscow: MAKS Press,  2009, 436 p. (In Russ.).

14. Danchenko V.N., Milenin A.A., Kuz’menko V.I., Grinkevich V.A.  Komp’yuternoe modelirovanie protsessov obrabotki metallov davleniem. Chislennye metody [Computer simulation of processes of  metal forming. Numerical methods]. Dnepropetrovsk: Sistemnye  tekhnologii, 2005, 448 p. (In Russ.).

15. Bogatov A.A., Nukhov D.Sh., P’yankov K.P. FEM-simulation of  plate rolling. Analysis of heterogeneity of the stress-strain state in  the deformation zone. In: Sb. trudov: Innovatsionnye tekhnologii v metallurgii i mashinostroenii [Innovative technologies in metallurgy  and engineering: Coll. of papers]. Ekaterinburg: Izd-vo Ural. Un-ta,  2014, pp. 185–189. (In Russ.).

16. ZV JCO. Certificate of state registration of computer program no.  2013660023, publ. 20.12.2013. (In Russ.)

17. Kolikov A.P., Zvonarev D.Yu. Simulation of expansion process of  welded large-diameter pipes. Stal’. 2017, no. 3, pp. 41–43. (In Russ.).

18. Kolikov A.P., Leletko A.S., Matveev D. V., Kulyutin S.A, Kadil’nikov S.V . Stress in welded pipe. Steel in Translation. 2014, vol. 44,  no. 11, pp. 808–812.