Clad Pipe Research Articles

Fracture assessments of clad pipe girth welds incorporating improved crack driving force solutions

This work addresses an evaluation procedure for the J-integral in pipeline girth welds with circumferential surface cracks subjected to bending load for a wide range of crack geometries and weld mismatch levels based on the GE-EPRI and the reference stress framework. The study also addresses evaluation of critical flaw sizes for a subsea flowline clad pipe having an undermatched girth weld made of UNS N06625 Alloy 625. The 3-D numerical analyses provide a large set of J-solutions in cracked pipes with mismatched girth welds with implications of the potential applicability of ECA procedures in welded cracked structural components.

Closed Analytical Expressions for Stress Distributions in Two-Layer Cylinders and Their Application to Offshore Lined and Clad Pipes

Closed-form analytical expressions are derived for the displacement field and corresponding stress state in two-layer cylinders subjected to pressure and thermal loading. Solutions are developed both for cylinders that are fully restrained axially (plane strain) and for cylinders that are axially loaded and spring-mounted. In the latter case, it is assumed that the combined two-layer cross section remains plane after deformation (generalized plane strain). The analytical solutions are verified by means of detailed three-dimensional finite element (FE) analyses, and they are easily implemented in, and suitable for, engineering applications. The chosen axial boundary conditions are demonstrated to be particularly relevant for pipeline and piping applications. By applying the exact solutions derived in the present study to typical offshore lined or clad pipelines, it is demonstrated that thermal expansion of the liner or clad layer may cause higher tensile hoop stresses in the pipe steel wall than accounted for in current engineering practice. It is shown that repeated cycles of start-up and shut-down phases for lined or clad pipelines cause significant plastic stress cycles in liners or claddings, which may pose a risk to the integrity of such pipelines.

Clad pipe for natural gas transportation

Clad pipe for natural gas transportation

Welding Procedure Development for Welding of High Strength Carbon Steel Cladded with Austenitic Stainless Steel 316L by Using Overmatching Filler Metal

This work aims to develop welding procedure for small diameter longitudinal welded clad pipe made from clad plate. High strength carbon steel base metal bonded with 316L stainless steel clad layer was used in this study. The dissimilar materials at the weld joint and accessibility limitation of small diameter present difficulty in welding process selection to achieve weld soundness. The joint and welding se¬quence are designed to avoid solidification cracking. Nickel base over matching filler is used on the clad side. Typical joint configuration is double V groove weld without clad peel back to minimize the number of passes inside the pipe. Firstly, welding is done on the carbon steel side by using Shielded Metal Arc Welding (SMAW) and Submerged Arc Welding (SAW) with carbon steel electrodes. Then, welding on the clad side is done by using ERNiCrMo-3 filler metal. Two different procedures for the clad side are studied. The first procedure is to weld the clad side by using Gas Tungsten Arc Welding (GTAW) and Gas Metal Arc Welding pulse current (GMAW-pulse) and another procedure is to weld the clad side by using the SAW procedure. Hot cracking was observed in the case of SAW procedure at the clad weld centerline due to high heat input and high level of dilution. Mechanical properties and microstructure are evaluated. Clad weld by use of GTAW and GMAW-pulse could give sound weld metal. The tensile and yield strength of all weld metal were found to be greater than that of base metal and 100% shear failures were observed. Charpy impact energy of weld and HAZ at -10°C was found to be over 100 joules. Hardness of weld and HAZ area are surveyed over the weld cross section to determine local hardening. Additionally intergranular corrosion testing was carried out on the clad weld side and then bend testing was done. No crack was observed. Therefore, GTAW and GMAW-pulse clad weld procedure could give required properties according to clad line pipe standard, reduce cost of production and increase productivity compared to the peel back method.

Effects of the inner mould material on the aluminium–316L stainless steel explosive clad pipe

The clad pipe played an important part in the pipeline system of the nuclear power industry. To prepare the clad pipe with even macrosize and excellent bonding quality, in this work, different mould materials were adopted to evaluate the effect of the constraint on the clad quality of the bimetal pipe prepared by explosive cladding. The experiment results indicated that, the dimension uniformity and bonding interface of clad pipe were poor by using low melting point alloy as mould material; the local bulge or the cracking of the clad pipe existed when the SiC powder was utilized. When the steel mould was adopted, the outer diameter of the clad pipe was uniform from head to tail. In addition, the metallurgical bonding was formed. Furthermore, the results of shear test, bending test and flattening test showed that the bonding quality was excellent. Therefore, the Al–316L SS clad pipe could endure the second plastic forming.

Electrochemical Studies of 316L/20G Clad Pipe Weld Joint Corrosion Behavior

To research the corrosion of clad pipe weld joint, commenting the welding processes of and analysis of the corrosion medium of clad pipe weld joint, using electrochemical impedance spectroscopy carried out the comparative analysis of Nyquist and bode diagram within the time limit of clad pipe weld joint. The results showed that: 316L/20G clad pipe weld joint in the sewage water up to two weeks, because of the passive film thickening, weld corrosion resistance up to the maximum, and then stabilized; Its resistance is slightly decreased, but still has a good corrosion resistance, therefore, 316L/20G clad pipe can be widely used in the sewage pipelines of oil and gas fields.

Mechanical behavior and wrinkling of lined pipes

The paper focuses on wrinkling of lined pipes (sometimes referred to as clad pipes) under bending loading, where a corrosion-resistant thin-walled liner is fitted inside a carbon–steel outer pipe. The problem is solved numerically, using nonlinear finite elements to simulate liner pipe deformation and its interaction with the outer pipe. Stresses and strains are monitored throughout the deformation stage, detecting possible detachment of the liner from the outer pipe and the formation of wrinkles. The wrinkling behavior of elastic and elastic–plastic (steel) lined pipes under bending is examined. The results indicate that the lateral confinement of the liner pipe due to the deformable outer pipe and its interaction with the outer pipe has a decisive influence on the wrinkling behavior of the lined pipe. It is also shown that the behavior is characterized by a first bifurcation in a uniform wrinkling pattern, followed by a secondary bifurcation. The values of corresponding buckling curvature are determined and comparison with available experimental results is conducted in terms of wrinkle height development and the corresponding buckling wavelength. The results of the present research can be used for safer design of lined pipes in pipeline applications.

Corrosion behavior of mechanical clad pipe welded joints in CO2‐saturated seawater under high temperature and high pressure

AbstractIn the present study, a new welding procedure was developed according to the welding difficulties of mechanical clad pipe. The effect of temperature on the corrosion product layer of stainless steel welded joints exposed to a CO2‐containing solution was investigated. The measurement techniques, such as scanning electron microscopy with energy dispersive spectrometry, X‐ray diffraction, and X‐ray photoelectron spectroscopy, were used to systematically characterize the morphology and composition of the corrosion product layer. The corrosion rates were calculated by weight loss method. The corrosion mechanisms are studied and discussed. The results showed that temperature is an important factor in the corrosion rate of mechanical clad pipe welded joints.

Independent testing confirms CermaClad™ CRA lowers corrosion rate by six times and exceeds API-5LD Clad Pipe Requirements

Independent testing confirms CermaClad™ CRA lowers corrosion rate by six times and exceeds API-5LD Clad Pipe Requirements

Analytical expressions for stress distributions in lined pipes: Axial stress and contact pressure interaction

Lined pipes are Carbon Manganese pipes (backing steel) with a thin liner of corrosion resistant alloy, mechanically bonded to the backing steel. Lined pipes are cheap to produce compared to clad pipes, where the liner is metallurgically bonded to the backing steel, but they are also more complex to design for. One particularly challenging aspect is to determine load/displacement levels for potential disbondment between the liner and the backing steel. In that context, the strength of the metallurgical bond between the backing steel and the liner in a lined pipe may have an important influence. The metallurgical bond may be characterized by residual stresses in the liner and the friction coefficient between the inner surface of the backing steel and the outer surface of the liner. Current industry testing practice to determine the magnitude of residual stresses is defined in API 5LD, but these tests fail to consider boundary effects and Poisson’s ratio effects which have a substantial impact on the measured stress levels. An analytical formulation for stress levels in the liner close to free boundaries, and interaction between axial and hoop stresses are presented in this paper and validated by detailed finite element analyses. This formulation provides excellent transparency in terms of understanding which physical parameters are important in the surface interaction between the liner and the backing steel, and, among several applications, they are a highly useful tool to reinterpret the test regimes suggested in API 5LD.

Performance Analysis on CRA-Clad Pipes Extruded from Bimetallic Centrifugal Castings

Recently a new method for manufacturing bimetal clad pipes is introduced, which can integrate centrifugal casting with extrusion technology organically. Through experimental study on microstructure and properties of bimetallic clad pipes manufactured by centrifugal casting and extruding, the results indicates that bimetal clad pipes with intact metallurgical interface have good bonding properties. Meanwhile wider interfacial zone will be favorable for reducing deformation stress. However there are still a few technical difficulties about the bimetallic clad pipe. Due to chemical composition and properties difference between backing materials and CRA layer, chemical elements will spread and microstructure will change during the process of production and even mechanical behavior of backing metal pipe and corrosion resistance of CRA layer will decline. To meet application requirements, appropriate heat treatment with bimetal clad pipes seems vita.

Cold model for process of a Ni-aluminide/steel clad pipe by a reactive centrifugal casting method

A novel method (reactive centrifugal casting method) to fabricate a Ni-aluminide/steel clad pipe has been proposed. Ni powder was placed on a spinning steel pipe, and Al liquid was poured into the steel pipe. The Al liquid and Ni powder exothermically reacted and produced a composite layer consisting of Ni-aluminides on the inner surface of the steel pipe. The heat generated by the exothermic reaction melted the inner surface of the steel pipe and bonded the composite layer to the steel. However, during the process, the Ni powder moves along the flow of the Al liquid. In this study, in order to obtain a better understanding of the Ni powder motion in the spinning steel pipe, a cold model centrifugal casting is employed. We focus on the effects of the angle between the spinning and horizontal axes on the type of centrifugal casters, because it is difficult to obtain the same data by the proper experiments.

Nickel-aluminides/steel clad pipe fabricated by reactive centrifugal casting method from liquid aluminum and solid nickel

A novel method to produce an aluminide/steel clad pipe has been proposed. The method is based on a combination of the self-propagating high-temperature synthesis (SHS) reaction and centrifugal casting, and is named the reactive centrifugal casting method. Nickel powder was placed on a rotating steel pipe, and aluminum liquid was poured into the steel pipe. The aluminum liquid and nickel powder exothermically reacted and produced a composite layer consisting of nickel aluminides on the inner surface of the steel pipe. The heat generated by the exothermic reaction melted the inner surface of the steel pipe and bonded the composite layer to the steel. It was found that increases in centrifugal force generated by rotating the steel pipe, the pouring temperature of the aluminum, and the preheating temperature of the nickel and steel remarkably promote the reaction between nickel and aluminum. In addition, the amounts of initial aluminum and nickel were found to play an important role in controlling the microstructure of the composite layer. Thus, the aluminide/steel clad pipe can be successfully fabricated by the proposed reactive centrifugal casting method.

Plastic Buckling Behavior of Clad Pipe in Longitudinal Compression.

Fabricating a part from sheet material not bulk is a good method from view point of energy consumption for processing and lightening the weight. Usually, deformed part from sheet material has almost constant thickness and sometimes needs to strengthen locally. One method for strengthening is to increase the thickness. First in this study, thin aluminum pipe was compressed longitudinally for thickening in a die. The pipe with large length buckled like bellows. The limit length without buckling was small and only from 3.5 to 4 times compared with the thickness. Then, clad pipe with two materials of aluminum and stainless steel was worked in the die with mandrel. The buckling behavior varied surprisingly according to the position of the two materials. In clad pipe of outer stainless steel and inner aluminum, the buckling behavior was almost the same as aluminum single pipe. However in clad pipe of outer aluminum and inner stainless steel, the outer aluminum deformed without space between the die and the workpiece, but the inner stainless steel buckled and deformed like bellows. By this new processing, we could get smooth outer surface with no defect and a structure of large elastic rigidness simultaneously.

Corrosion—Resistant, Two—Layer Sheet Rolled Stock and Clad Pipes. Production by the Electroslag Facing Method

The problem of protecting equipment from corrosion while simultaneously ensuring elevated mechanical characteristics is acute in petroleum refining and petrochemistry. Corrosion—resistant two—layer sheet steels have traditionally been widely used for manufacturing this equipment. Carbon or low—alloy steels selected as a function of the requirements for the mechanical properties of the articles are primarily the base layer of these steels. Corrosion—resistant steels of different brands, copper alloys (Monel, Inconel), nickel and nickel alloys, and titanium and its alloys are most widely used as the cladding layer which must be resistant to the aggressive effect of the environment.

塑性工学 熱間傾斜圧延法による異材管継手の開発

Metallurgically bonded transition joints which enable to connect reprocessing equipments made of superior corrosion resisitant valve metals (Ti-5Ta, Zr or Ti) to stainless steel piping are required for nuclear fuel reprocessing plants. The authors have developed dissimilar transition joints made of stainless steel and Ti-5Ta, Zr or Ti with an insert metal of Ta by the hot bond rolling process of clad bars and clad pipes, using a newly developed mill called “rotary reduction mill”.This report presents the manufacturing process of dissimilar transition joints produced from the clad pipe with three layers by the hot bond rolling. First, the method of hot bond rolling of clad pipe is proposed. Then, the mechanical and corrosion properties of the dissimilar transition joints are evaluated in detail by carrying out various tests. Finally, the rolling properties in the clad pipe method are discussed.

ブロークンピースによる軸対称残留応力測定法の提案

In failure analysis of a fractured component, estimation of residual stress distribution in the component before fracture is required. In this study, we propose a method to estimate the axisymmetric residual stresses in the original cylindrical component from its broken pieces. The method, which we refer to as broken piece method, employs an arc piece specimen and an axial piece specimen cut from the fractured component. The residual stresses are estimated from measured strains of the two pieces based on the equivalent inherent strain concept. The applicability of this method and appropriate dimensions of the piece specimens were theoretically discussed and experimentally verified by measuring residual stresses in a clad pipe. This method also applies to large cylindrical component case, where the residual stress measurement is quite difficult by using traditional measuring method with large cylindrical body specimen.

クラッド鋼管の強度設計手法に関する研究 (第2報) クラッド鋼管の曲げ座屈強度に及ぼす合せ材の影響

クラッド鋼管の強度設計手法に関する研究 (第2報) クラッド鋼管の曲げ座屈強度に及ぼす合せ材の影響

Design Concept of Clad Pipe Considering Effect of Clad Metal on Structural Integrity (Part 1)

Design Concept of Clad Pipe Considering Effect of Clad Metal on Structural Integrity (Part 1)

Ａｌｌｏｙ ６２５粉末クラッド鋼管の特性評価

A powder metallurgy (P/M) coextrusion process for superalloy-clad steel pipes has been developed. Composite billets consisting of an Alloy625 powder layer and a wrought steel hollow billet were hot-extruded and defect-free Alloy625/2 1/4Cr-lMo steel-clad pipes were experimentally produced in commercial production facilities. The pipes were proved to have an uniform layer of cladding in longitudinal and circumferential directions. The bonding properties of the P/M-clad pipe were evaluated in shear tests, tensile tests and bend tests. Ultrasonic evaluation was carried out on the full length of the clad pipe but no defects, such as disbonding or cracking at the interface, were found. Based on the results obtained, P/M superalloy-clad steel pipes would be applicable to oil-field line pipes and chemical plant tubes.