Three-roller continuous setting round process for longitudinally submerged arc welding pipes

In order to solve the problems of excess ovality and cross-section distortion of longitudinally submerged arc welding pipes after forming,a new three-roller continuous setting round process was proposed.This process can be divided into three stages:loading stage,roll bending stage and unloading stage.Based on the discretization idea,the mechanical model of the primary statically indeterminate problem of the longitudinally submerged arc welding pipes at the roll bending stage was established,and the deformation response was obtained.The simulation and theoretical results show that there are three positive bending regions and three reverse bending regions along the circumference of the pipe.The loading force of each roller shows growth,stability and downward trend with time.The error between the theoretical fitting curve and the simulated data point is very small,and the simulation results verify the reliability of the theoretical calculation.The experimental results show that the residual ovality decreases with the increase of the reduction,and the reduction of the turning point is the optimum reduction.In addition,the residual ovality of the pipe is less than 0.7%without cross-section distortion,which verifies the feasibility of this process.

Quality Control on Crimping of Large Diameter Welding Pipe

Crimping is used in production of large diameter submerged-arc welding pipes. Many researches are focused on crimping in certain manufacturing mode of welding pipe. The application scopes of research achievements become limited due to lack of uniformity in theoretical analysis. In order to propose a crimping prediction method in order to control forming quality, the theory model of crimping based on elastic-plastic mechanics is established. The main technical parameters are determined by theoretical analysis, including length of crimping, base radius of punch, terminal angle of punch, base radius of die, terminal angle of die and horizontal distance between punch and die. In addition, a method used to evaluate the forming quality is presented, which investigates the bending angle after springback, forming force, straight edge length and equivalent radius of curvature. In order to investigate the effects of technical parameters on forming quality, a two-dimensional finite element model is established by finite element software ABAQUS. The finite element model is verified in that its shapes error is less than 5% by comparable experiments, which shows that their geometric precision meets demand. The crimping characteristics is obtained, such as the distribution of stress and strain and the changes of forming force, and the relation curves of technical parameters on forming quality are given by simulation analysis. The sensitivity analysis indicates that the effects of length of crimping, technical parameters of punch on forming quality are significant. In particular, the data from simulation analysis are regressed by response surface method （RSM） to establish prediction model. The feasible technical parameters are obtained from the prediction model. This method presented provides a new thought used to design technical parameters of crimping forming and makes a basis for improving crimping forming quality.

Mathematical modeling and simulation application for a wheeled mobile robot applied on pipe welding

A geometric model was built to represent the position relation of a wheeled mobile robot relative to a pipe. The relationship between the deviation of falling off for the robot and the curvature of the pipe was formulated quantitatively. Based on the relationship, a mathematical model was derived and a fuzzy control algorithm for the robot was developed. Simulations were carried out to confirm the dynamic index and the validity of the mathematical model of the fuzzy control algorithm for seam tracking of pipe welding. Experiments for pipe welding with the mobile robot were also carried out to verify the algorithm, and the results showed that the seam has a good quality with a preferable appearance of weld.

Multi-objective optimization of crimping of large-diameter welding pipe

Crimping is widely adopted in the production of large-diameter submerged-arc welding pipes. Traditionally, designers obtain the technical parameters for crimping from experience or by trial and error through experiments and the finite element(FE) method. However, it is difficult to achieve ideal crimping quality by these approaches. To resolve this issue, crimping parameter design was investigated by multi-objective optimization. Crimping was simulated using the FE code ABAQUS and the FE model was validated experimentally. A welding pipe made of X80 high-strength pipeline steel was considered as a target object and the optimization problem for its crimping was formulated as a mathematical model and crimping was optimized. A response surface method based on the radial basis function was used to construct a surrogate model; the genetic algorithm NSGA-II was adopted to search for Pareto solutions; grey relational analysis was used to determine the most satisfactory solution from the Pareto solutions. The obtained optimal design of parameters shows good agreement with the initial design and remarkably improves the crimping quality. Thus, the results provide an effective approach for improving crimping quality and reducing design times.

MECHANICAL PROPERTIES OF LONGITUDINAL SUBMERGED ARC WELDED STEEL PIPES USED FOR GAS PIPELINE OF OFFSHORE OIL

Since the development of offshore oil and gas, increased submarine oil and gas pipelines were installed. All the early steel pipes of submarine pipelines depended on importing because of the strict requirements of comprehensive properties, such as, anti-corrosion, resistance to pressure and so on. To research and develop domes- tic steel pipes used for the submarine pipeline, the Longitudinal-seam Submerged Arc Welded （LSAW） pipes were made of steel plates cut from leveled hot rolled coils by both the JCOE and UOE （the forming process in which the plate like the letter “J”, “C”, “0” or “U” shape, then expansion） forming processes. Furthermore, the mechanical properties of the pipe base metal and weld metal were tested, and the results were in accordance with the corresponding pipe specification API SPEC 5L or DNV- OS-FI01, which showed that domestic LSAW pipes could be used for submarine oil and gas pipelines.

Finite element synthesized analysis of the forming process of spiral welded pipe

Numerical simulation concerning the forming and welding process of spiral welded pipe was conducted, which included three steps ： the first step was the stress analysis when the spiral was formed, and then the stress was regarded as initial condition of melding during the temperature field analysis in the process of welding, the last step was the thermal stress analysis of the weld seam after the welding was over. Moreover, when the steel strip was pushed, the stress was also calculated by non-linearity contact technology using Abaqus Software. By finite element modeling and calculating of the forming and welding process of the spiral welded pipe, the key points of the multi-fields synthetic simulating were studied and discussed.

Hot-rolled strips of up to 19 mm in thickness and their processing to helically welded large diameter pipes of grade X80

Hot-rolled wide strip for production of large diameter,heavy gauged(up to 19 mm) helical line pipe grade X80 was a priority development over the last three years.Microstructure,texture and mechanical properties of strips have been characterised.Also the welding conditions have been simulated.The favourable microstructure is achieved by the proper selection of an appropriate chemical composition of low carbon content and increased niobium micro alloying in combination with suitable strictly controlled hot-rolling parameters.The addition of niobium in combination with the adjustment of other alloying elements increases the recrystallisation stop temperature and thus makes it possible to apply a high temperature processing(HTP) concept.The homogeneous bainitic microstructure across the strip gauge is then formed during accelerated cooling on the run-out table of the hot-rolling mill.All results indicated excellent properties of these hot strips which make it suitable for spiral pipes of grade X80 for example 18.9mm×Φ1 220 mm at dimension.

The MFL Testing Methods for Welded Pipes

Steel pipes are categorized into seamless pipes and welded pipes,and particularly the welded pipes’ NDT(Non-Destructive Testing)has been a challenging problem.In the case,on the basis of the presentation of welded pipes,the analysis of its relevant testing key is carried out.Afterwards,the MFL(Magnetic Flux Leakage)methods for longitudinally welded line-pipes and for helically welded pipes are respectively proposed.Meanwhile,their relevant experiments are conducted,and finally the two technologies for the two types of welded pipes are verified well.

Review of the development of tube and pipe products at Baosteel over the past 30 years

The history of the development of the tube ＆ pipe division of Baosteel was reviewed in the article, focusing on the process of technical innovation and the product category enrichment. Thanks to the technical innovation, the Ф 140 product line has become the most efficient one in the world. With the advance of conglomeracy and the construction of the most advanced weld pipe line and the Ф460 premium quality finishing （PQF） line ,the catalogue of Baosteel tube ＆pipe products has covered the extensive range from the hot roll to cold roll, the seamless to the welded, and all of the product dimension scope from 25.4 mm to 610 ram. To meet the requirements of relevant industries such as energy ,transportation, machinery,ammunition and other relevant industries, the product variety is diverting from carbon steel to alloy steel, stainless steel and special alloys. As the Baosteel Steel Tubing Plant increased its number of production units, expanded its production capacity and developed new products ,it has grown into a pipe and tube supplier with global competitiveness.

Effect of strength matching on the reliability of welded pipe with circumferential surface crack

For different strength matching, the reliability index and failure probability of welded pressure pipe with circumferential surface crack were calculated using three dimensional stochastic finite element method. This method has overcome the shortcomings of conservative results in safety assessment with deterministic fracture mechanics method. The effects of external moment and the depth of the circumferential surface crack (a) on the reliability of pressure pipe were also calculated and discussed. The calculation results indicate that the strength matching has certain effect on the reliability of the welded pressure pipe with circumferential surface crack. The failure probability of welded pressure pipe with high strength matching is lower than that with low strength matching at the same conditions. The effects of strength matching on the failure probability and reliability index increased by adding external moment (M) and the depth of the circumferential surface crack (a).

Ultimate Bearing Capacity of Hollow Spherical Joints Welded with Circular Pipes under Eccentric Loads

The hollow spherical joints welded with circular pipes applied to the National Swimming Center of China are subjected to large bending moments, but the influence of bending moments is not considered in the design equations in Technical Specification for Latticed Shells. Based on the von Mises yield criterion, multilinear isotropic hardening rule and associated flow rule, the elasto-plastic finite element model is put forward to analyze the behavior of the joints, and a calculation method for the joints under bending moments or eccentric loads is proposed. It is shown by the analytical results of joint that the stiffening rib can improve the ultimate bearing capacity by 10% for joints under axial tensile load, by 40% for joints under axial compressive load, and by 50% for joints under bending moment. The unified calculation equations for joints with or without stiffening rib are put forward, which can be applied to calculating the ultimate bearing capacity of the hollow spherical joints with circular pipes under eccentric loads.

SIMULATION OF ROLL-FORMING PROCESSES OF WELDED PIPE

A multi- pumose simulation method for the roll- formign is proposed. The forming pro- cesses of welded pipes are systematically simulated by using the method. The three-dimensional cu rved surfaces of sheet metals in forming processes are mathema tically expressed by using the shape fonction S(X) which represents flow pattern of each part of sheet metal. Through optimis- ing t e parameter n in s(X), the best approximation of the deformation of sheet metal is derived and the minimum power of deformation is obtained. A mathematical procedure of this analysis is systematically foimulated. The simulation method can be applied to the analysis and simulation for various roll- forming processes of welded pipes observed in commercial production line.

INVESTIGATION ON BRITTLE FRACTUREPROPAGATION－ARRESTING CHARACTERISTICS OF STEEL PIPE

In order to study crack propagation-arresting characteristics of steel pipe construction, a new test installation was designed. The experiments of 20 steel pipes, pipes with longitudinally weld, pipes with circumferential weld and steel pipe with sleeve were conducted. The testing results indi- cated that circumferential weld in pipe with overrnatching weld had beneficial effect on crack prop- agation arrcsting propcrtics and the mechanical split sleeve can be used as crack arrester to prevent crack propagation.

Research on deformation characteristics of JCOE forming in large diameter welding pipe

In the present work, the JCOE forming is inves- tigated using the finite element （FE） method. A two- dimensional FE model is established for the plane strain condition by FE code ABAQUS, and the FE model is vali- dated by experiments. The aim of this research is to inves- tigate forming quality states in the JCOE forming process; in particular, the effects of technological parameters on form- ing quality are evaluated. Taking the JCOE forming process of X80 steel φ1 219 mm × 22 mm × 12 000 mmwelding pipe for instance, the deformation characteristics of JCOE forming are analyzed, in which the geometry of the formed pipe, residual stress distributions and effects of process parameters on JCOE forming quality can be obtained. Thus, the presented results of this research provide an effective approach to improve welding pipe forming quality.

Effects of Crack Opening Angle and External Loads on Reliability of Welded Pipe with Circumferential Crack

The reliability of welded pressure pipe with circumferential surface crack was calculated by using 3D stochastic finite element method.This method has overcome the shortcomings of conservative results in safety assessment with deterministic fracture mechanics method.The calculation of reliability was based on 3D elasticplastic stochastic finite element program which was developed by ourselves.The effects of variables such as fracture toughness,bending moment and depth of the circumferential surface crack on the structure reliability were also discussed.The calculation results indicate that the crack opening angle has certain effect on the reliability of the welded pipe.When the mean value of bending moment is 10kN·m,with the crack opening angle increasing from 30°to 180°,the failure probability of the welded pipe changes from 3.8379×10-8to 3.6943×10-6.When the mean value of bending moment is 15kN·m,with the crack opening angle increasing from 30°to 180°,the failure probability of the welded pipe changes from 3.986 5×10-6to 1.936 7×10-3.The bending moment has great effect on the reliability of the welded pipe.When the mean value of moment is changed from 10 to 15 kN·m,the failure probability of the welded pipe increases dramatically for the same circumferential crack opening angle.Regardless of changing of moment,the pipe has higher reliability if the crack opening angle is less than 60°.The method has put forward a new way for safety assessment of welded pipe with circumferential surface crack.

Numerical Study of the Forming Process of High Frequency Welded Pipe

The roll forming process is applied to the manufacturing of high frequency welded (HFW) pipes,section steels,etc. In this paper,the roll forming process of the HFW pipe is simulated with the finite element method (FEM). A user-defined material routine of the commercial finite element code ABAQUS/Explicit is developed,and the mixed hardening constitution model is realized through the user-defined material routine. Based on the mixed hardening constitutive equation,the numerical simulation of roll forming process of HFW pipe is performed. The evolutions of equivalent stress and strain are analyzed,and the calculated results are also compared between different hardening models. The results show that the different material hardening models have some important effects on the variation of equivalent stress and strain of strip steel during the simulation of the roll forming process.