Alloy steel pipes and furnace tubes for petrochemical industry

The equipments and pipes serving at high temperature and pressure and the presence of hydrogen in the petrochemical industry are usually made of Cr-Mo steels.Cr9Mo pipes replacing Cr5Mo are widely used in many parts of/with high-sulfur crude oil refining equipment to meet the more demanding high temperature anticorrosion and oxidation resistance requirements.The mechanical property,creep rupture property and high temperature oxidation-resistant property of domestic Cr9Mo steel are at the same level as the similar foreign products.Three years applications indicate that domestic Cr9Mo steel can fully meet the service requirements of petrochemical industries.Finally,this paper presents the material selection guidelines for the key oil refining devices processing of low sulfur/high acid crude oil.

Theoretical and experimental study of the thermal strength of anticorrosive lined steel pipes

Bimetallic lined steel pipe(LSP) is a new anti-corrosion technology. It is widely used to transport oil, gas, water and corrosive liquid chemicals. At present, the hydroforming pressure for LSP has been investigated theoretically and experimentally by most researchers. However, there are a few reports on the thermal strength of bimetallic LSP. Actually, the bimetallic LSP will be subjected to remarkable thermal load in the process of three layer polyethylene(3PE) external coating. Reverse yielding failure may occur on the inner pipe of the bimetallic LSP when it suffers from remarkable thermal load and residual contact pressure simultaneously. The aim of this paper is to study the thermal load and strength of the bimetallic LSP. A mechanical model, which can estimate the thermal strength of the bimetallic LSP, was established based on the elastic theory and the manufacture of the bimetallic LSP. Based on the model, the correlation between the thermal strength of the bimetallic LSP and residual contact pressure and wall thickness of the inner pipe was obtained. Reverse yielding experiments were performed on the LSP(NT80SS-316L) under different thermal loads. Experiment results are consistent with calculated results from the theoretical model. The experimental and simulation results may provide powerful guidance for the bimetallic LSP production and use.

Numerical study on forming complex fitting body on end of integrated stainless steel pipe without welds

It is necessary to use the integrated stainless steel pipe having two fitting bodies without welds while train travelling at high speed. In order to form this type of integrated stainless steel pipe, the method of preforming combined finish forming process is developed. The preforming process is characterized by flaring combined upsetting for left fitting body which is like a flange, and is characterized by tube axial compressive process under die constraint for right fitting body which is like a double-wall pipe. The finite element simulations of the processes are carried out by software package DEFORM, and the results indicate that: 1) left or right fitting body can be formed by a two-step forming process without folding and under-filling defects; 2) by using two-step forming, strain and stress in left fitting body are larger than those in right fitting body, and deformation in right fitting body is more homogenous than the deformation in left fitting body; 3) two or more preforming steps may be needed for left fitting body considering the distributions of strain and stress.

Effect of Sacrificial Anode Protection for Steel Pipe Piles at Dandong Port

The sacrificial anode protection system for the steel pipe piles of the 3rd berth of Dandongwharf at Dandong port has operated for eight years.In this paper,the program design and the protectioneffect of the sacrificial anode protection system are presented.The results of various,inspections show thatthe piles are protected very satisfactorily.

A Dynamics Study of a Magnetic Flux Leakage(MFL) Signal and its Application to Defect Location Discrimination in Steel Pipes MFL Testing Equipment

Difference processing was used to the direct current magnetic flux leakage(DC-MFL) signal,emanating from the defects machined artificially on the internal and external surfaces of a steel pipe.Consequently,the location discriminating index δ was provided to identify the defect whether it is on the internal surface or the external one.Three characteristics,shape,depth and orientation of the defect,were discussed through a series of experiments on the artificial defects,such as transverse notches,oblique notches and pits on the steel pipe.The approach has been verified effective to address the defect location identifying problem,albeit the limits on the accuracy assessment to those natural defects on steel pipes in

The Vibration Controllability of 20~# Steel Pipe Excited by Unsteady Flow

An excited experiment system of 20# steel pipe was established with oil cylinder, 20# steel pipe, frequency converter, pump station and wave exciter generating unsteady flow artificially. The experimental results showed that the 20# steel pipe could vibrate with the excitation of unsteady flows, and the vibration was periodic, instead of a harmonic one. Particles on the front and rear positions of pipe vibrated synchronously, and the vibration intensity of the pipe's two ends was greater than in the middle. System pressure and wave exciter's frequency had much influence upon pipe's amplitude. Pipe's vibration frequency was little affected by system pressure, and its value was close to the wave exciter's. Therefore, the active control of pipe's vibration can be realized by setting system pressure and adjusting frequency converter's frequency.

Manufacture of Extra-Thin Wall Steel Pipe by LD Cluster Mill

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Ultimate Bending Capacity of Strain Hardening Steel Pipes

Based on Hencky's total strain theory of plasticity,ultimate bending capacity of steel pipes can be determined analytically assuming an elastic-linear strain hardening material,the simplified analytical solution is proposed as well.Good agreement is observed when ultimate bending capacities obtained from analytical solutions are compared with experimental results from full-size tests of steel pipes.Parametric study conducted as part of this paper indicates that the strain hardening effect has significant influence on the ultimate bending capacity of steel pipes.It is shown that pipe considering strain hardening yields higher bending capacity than that of pipe assumed as elastic-perfectly plastic material.Thus,the ignorance of strain hardening effect,as commonly assumed in current codes,may underestimate the ultimate bending capacity of steel pipes.The solutions proposed in this paper are applicable in the design of offshore/onshore steel pipes,supports of offshore platforms and other tubular structural steel members.

The current situation and prospect of oil steel pipe in China

The oil steel pipe in the petroleum industry is very important for its high price, large consumption volume and great effect on the development of petroleum industry. The oil steel pipe mainly includes oil well pipe (drill pipe, drill collar, casing and tubing etc.) and oil-gas transportation pipe. This paper is an attempt to make a comprehensive review on the current situation and prospect of the oil steel pipe in China, presenting the past , today and future of the China oil pipe. The first section is a historical review of the China oil pipe. The developing course and progress of the oil steel pipe products are presented. The second section is about the current situation of the China oil pipe. The general situation of the China’s steel pipe corporation and their products types, capability, etc. is introduced. The third section is about the prospect of the China oil pipe. This part mainly describes the new product research and development in China steel pipe corporations, which are facing more and more strict technical requirements of the petroleum industry in oil pipe, and reveals the prosperity of China’s steel pipe corporations.

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.

Mechanical characteristics of fused cast basalt tube encased in steel pipe for protecting steel surface

Because of the various excellent characteristics of cast basalt materials,such as,anti-corrosion,anti-wearing,good hardness,high chemical stability,of which steel may not possess,the steel-basalt composite pipes are used in severe environments for compensating the defects of steel.The limit of bending moment with which steel-basalt composite pipe may safely endure was calculated and the limit curvature of the composite pipe in the safe range was presented.The application temperature of steel-basalt pipe was examined due to a different coefficient among basalt,mortar and mild steel.

Experiments of Multi-element Composite Foundation with Steel Pipe Pile and Gravel Pile

A set of self-developed apparatus for foundation physical model were utilized to conduct model tests of the multi-element composite foundation with a steel pipe pile and several gravel piles. Some load-bearing characteristics of the multi-element composite foundation, including the curves of foundation settlement, stresses of piles, pile-soil stress ratio, and load-sharing ratio of piles and soil, were obtained to study its working performances in silty sand soil. The experimental results revealed that the multi-element composite foundation with steel pipe pile and gravel pile contributed more than the gravel pile composite foundation in improving the bearing capacity of the silty fine sand.

INVESTIGATION ON BRITTLE FRACTUREPROPAGATION－ARRESTING CHARACTERISTICS OF STEEL PIPE

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Effect of weld faying part groove shape on reduction of inner flash in steel pipe joints fabricated by friction welding

The groove shape of the weld faying part was investigated to obtain an ideal pipe frictiowelded joint that had a fracture in the base metal and no inner flash of it.The steel pipe had inner and outer diameters of 8.0 mm and 13.5 mm,respectively,and the weld faying surface was of a basic flat shape(butt)type.Moreover,stepped and tapered groove shapes were prepared.Pipe groove shapes were welded with a friction speed of 27.5 s_1 and a friction load of 2.79 kN.Joining phenomena during the welding process were observed,and the tensile strength of joints was evaluated.The joints,that fabricated with flat or step groove shapes,made with a friction time at which the friction torque reached the initial peak did not have the tensile strength of the base metal nor a fracture in the base metal.However,the joints fabricated with a friction time that reached past the initial peak had a large flash,and they contained a fracture in the base metal.In contrast,when joints were made with a gently tapered groove shape with a friction time reaching the time of the initial peak,they achieved a fracture in the base metal,despite having an extremely small inner flash.Therefore,the shape at the weld faying part was capable of reducing the flash exhausted from the weld interface.

Study on intelligent control technology for forming steel pipe of pipeline with JCO process

Based on plastic bending engineering theory and machine vision technology, the intelligent control technology for forming steel pipe with JCO process is presented in this paper. By ‘twice pre-bending method’ in the first forming step, the springback law can be obtained. With the springback law and the target angle, the exact punch displacement which determines the formed angle in each bending step is predicted. In the succedent forming steps, the bending process is carried out with the exact punch displacement by real-time revising the springback law. And the angle error in each forming step is calculated by comparing the actual formed angle with the target angle. By conducting compensation for the last angle error in the next forming step, each precise bending process step is realized. A system of intelligent control technology for forming the steel pipe was developed. A calibration method is proposed to calculate the exterior parameters of the CCD camera, in which the equilateral triangle is em-ployed as the calibrating board and only one image needs to be captured. A mathematical model, which converts the angle in the image into the actual formed angle, is derived. The experimental results showed that the ellipticity of the formed pipes was less than 1.5% and the high-quality pipes can be manufactured without the worker's operating experience by employing the in-telligent control technology.

Effect of microstructure on the low temperature toughness of high strength pipeline steels

Microstructure observations and drop-weight tear test were performed to study the microstructures and mechanical properties of two kinds of industrial X70 and two kinds of industrial X80 grade pipeline steels. The effective grain size and the fraction of high angle grain boundaries in the pipeline steels were investigated by electron backscatter diffraction analysis. It is found that the low temperature toughness of the pipeline steels depends not only on the effective grain size, but also on other microstructural factors such as martensite–austenite(MA) constituents and precipitates. The morphology and size of MA constituents significantly affect the mechanical properties of the pipeline steels. Nubby MA constituents with large size have significant negative effects on the toughness, while smaller granular MA constituents have less harmful effects. Similarly, larger Ti-rich nitrides with sharp corners have a strongly negative effect on the toughness, while fine, spherical Nb-rich carbides have a less deleterious effect. The low temperature toughness of the steels is independent of the fraction of high angle grain boundaries.

Development of pipeline steel at Baosteel over the last 20 years

This study reviews the development of Baosteel's pipeline steel over the last 20 years.Energy demand accelerates the development of high-grade pipeline steel as well as modern petroleum and natural gas pipeline construction.Pipeline steel is a kind of typical modern microalloyed steel produced via thermo-mechanical controlled processing.The development process of pipeline steel at Baosteel represents the course of the technological progress of pipeline steel in China.In the last two decades,Baosteel's pipeline steel has been developed from a single product of hot-rolled strips to a variety of products including hot-rolled strips,heavy plates,high-frequency electric resistance welded (HFW) pipes and U-ing-O-ing-Expanding(UOE) welded pipes.Moreover,the proportion of the HFW and the UOE welded pipes has been increasing year by year.UOE longitudinal submerged arc welding(SAW) pipes have become the leading product of strategic significance in Baosteel's pipeline steel family.Over the last 20 years,Baosteel's pipeline steel products have shifted from "ferrite+pearlite" X52 to "acicular ferrite" X70 and X80,and Baosteel has developed hydrogen-induced cracking (HIC) resistant pipeline steel.Baosteel's pipeline steel products have been applied in variety of geographical areas,including deserts,Gobi,mountains,plains as well as the ocean.And both the X100 and the X120 ultra high strength pipeline steels have been produced on a trial basis.Baosteel has accumulatively produced 6.5 Mt of pipeline steel for both domestic and overseas projects.Baosteel will continue strengthening its strategic cooperation with oil companies,and conducting research on ultra high strength pipeline steel,pipeline steel for strain-based design and submarine pipeline steel,etc.,so as to meet the need of construction in the future.