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.

Effects of process parameters and die geometry on longitudinal welds quality in aluminum porthole die extrusion process

By using the rigid-visco-plasticity finite element method, the welding process of aluminum porthole die extrusion to form a tube was simulated based on Deform-3D software. The welding chamber height （H）, back dimension of die leg （D）, process velocity and initial billet temperature were used in FE simulations so as to determine the conditions in which better longitudinal welding quality can be obtained. According to K criterion, the local welding parameters such as welding pressure, effective stress and welding path length on the welding plane are linked to longitudinal welds quality. Simulation turns out that pressure-to-effective stress ratio （ρ/σ） and welding path length （L） are the key factors affecting the welding quality, Higher welding chamber best and sharper die leg give better welding quality. When H=10 mm and D=0.4 mm, the longitudinal welds have the best quality. Higher process velocity decreases welds quality. The proper velocity is 10 mm/s for this simulation. In a certain range, higher temperature is beneficial to the longitudinal welds. It is found that both 450 and 465℃ can satisfy the requirements of the longitudinal welds.

The Influence of Longitudinal Magnetic Field on the CO_2 Arc Shape

The COarc welding was carried out under a longitudinal magnetic field,and the arc shape has been studied by using a high-speed camera.From the camera images,we know that under the action of the longitudinal magnetic field,the upper end of the arc will constrict and the lower end of the arc will expand.It would become a bell-type shape and rotate at a highspeed in the optimum range of magnetic field parameters.The arc shape was simulated using a mathematical model,which was established based on experiment data and theoretical knowledge,and mechanism analysis has been carried out regarding the effect of longitudinal magnetic field on COwelding arcs.

Improving the fatigue performance of longitudinal welded joints by low transformation temperature electrodes

For a longitudinal welded joint, the tensile residual stresses are as high as the yield stress of the metal, so that the weld toes are sensitive to fatigue load. In this case a low transformation temperature electrode (LTTE) is one of the most useful methods used to improve the fatigue strength of the longitudinal welded joint, because the tensile residual stress is reduced or changed into compressive stress. Three kinds of longitudinal welded joints were selected to conduct fatigue tests. The tests results show that the fatigue strengths at 2×10 6 cycles of the joints welded with LTTE were improved by 41%, 47% and 59% respectively compared with those of the joints welded with E5015, and the fatigue lives at 162 MPa were improved by 9.9 times, 9.6 times and 46.8 times respectively. Furthermore, the LTTE method is not necessary to add process after welding and so that it can be valuable method to improve the fatigue performance of longitudinal welded joints.

Comparative study of weld residual stress on steel pipes with different weld types

This study developed a sequential coupling finite element procedure to predict residual stresses of steel pipes with longitudinal wela／ circumferential weld and spiral weld.The results show that the residual stress in heat affected zone（HAZ）is higher than that in weld for spiral weld pipe.For the circumferential weld pipe and spiral weld pipe,the residual stress in inner surface is higher than that in outer surface.However,for the spiral weld pipe,the residual stress in inner surface is smaller than that in outer surface.The hoop residual stress of circumferential weld pipe is higher than that of longitudinal weld pipe,while the axial residual stress of circumferential weld pipe is smaller than that of longitudinal weld pipe.The hoop stresses for circumferential weld pipe and axial stress for longitudinal weld pipe have exceeded the yield strength of base metal.With the increase of helix angle,the hoop stress decreases while the axial stress increases.For the spiral pipe（α=30° to 50°）,both the hoop stress and axial stress are relatively small.The spiral pipe（helix angle ranging from 30° to 50°） is helpful to reduce stress corrosion cracking（SCC） and it is recommended to manufacture the steel pipe.

Product development of Baosteel HFW 610 Mill

Baosteel's high-frequency electric resistance welded(HFW) 610 longitudinal seam mill(8 5/8″-24″, the yearly output 300000 t) and UOE 1422 longitudinal submerged arc welding(SAW) mill(20' -56',the yearly output 500000 t) are established in 2005 and 2008,respectively.Product specification covers whole of API 5CT standard and most of API 5L standard,terminating the history of manufacturing the medium and large size pipes at Baosteel.The yearly output increased from 1,200000 t to nearly 2000000 t.HFW 610 mill is oriented at mid size pipes,which are mainly linepipe and welded casing.The designed yearly output of HFW mill is 300000 t,including casing of 90000 t,linepipe of 180000 t,round structural pipe of 15000 t and rectangle structural pipe of 15000 t. The yearly output of oil casing line supporting the welding line is 120000 t,among which including welded casing and seamless casing of 30000 t.Baosteel's HFW 610 longitudinal seam mill was established on October 27,2005. After the equipment trial run In October,2005 - March,2006 and equipment function examination In April,2006 - June,2006,mass production started in July 2006.And in December 2006,monthly designed capacity was achieved,reaching to 30496.644 t in welding pipe and 28 349.939 t in finished pipe.The output of 2006,2007, 2008 and 2009 was 117 067 t,223 554 t,255 791 t,and 204 424 t,with the comprehensive yield ratio 79.4%, 87.8%,90.80%and 91.92%respectively.This study introduces Baosteel HFW 610 Mill which is the world class,energy conservation and environmental protection enterprise,including product orientation,process and new product development.

Experimental investigation and design of aluminum columns with longitudinal welds

This paper presents an experimental investigation of longitudinally welded aluminum alloy I-section columns subjected to pure axial compression.The specimens were fabricated using 6061-T6 heat-treated aluminum alloy.The test program included 20 column tests which were separated into 2 test series of different types of welding sections.Each test series contained 10 columns.All the specimens were welded using the Tungsten Inert Gas welding method.The length of the specimens ranged from 442 to 2433 mm in order to obtain a column curve for each test series.The observed failure mode for the column tests includes mainly flexural buckling around the minor axis and the major axis by applying support except for one column(ZP 1217-1)which buckled in the local zone and some columns which failed in the weld.The test strengths were compared with the design strengths predicted by the European Code and China Code for aluminum structures.The purpose of this paper is to present the tests results of two typically longitudinally welded I-section columns,and to check the accuracy of the design rules in the current specifications.