Low-carbon Pipe Steel Research Articles

Effect of Carbon and Manganese on Low-Carbon Pipe Steel Hydrogen-Induced Cracking Resistance

A favorable effect is established for reducing carbon and manganese content in low-alloy pipe steels of strength categories X56–X65 on the increase in hydrogen-induced cracking (HIC) resistance of thick-rolled sheet prepared by a thermomechanical treatment regime. This effect is due to a reduction in segregation structural inhomogeneity in the axial area of sheets in the form of a solid band of high-carbon structures.

Strain aging and the Bauschinger effect in low-carbon pipe steel

Strain aging and the Bauschinger effect in low-carbon ferrite–pearlite and ferrite–bainite pipe steel are studied. Steel with ferrite–bainite structure is more susceptible to strain aging and the Bauschinger effect. After alternating loading, strain aging develops, with increase in the yield point. After alternating loading of already aged steel, the Bauschinger effect appears; it is comparable with the effect in unaged steel.

Weld Properties of Low Carbon Steel Using Shielded Metal Arc Welding

Welding is basic part of the most modern assembly and manufacturing operations. Shielded metal Arc Welding process has hard facing and fabrication job application due to low cost electrode, increasing alloy transfer efficiency and low dilution with substrate without losing production capacity. SMAW electrode is coated with metal mixture called flux, which on decompose produce gases to restrict weld contamination, generating deoxidizers to disinfect the weld. The choice of electrode for SMAW lies on a number of factors, like weld material, welding direction and the preferred weld properties. The present paper investigate the microstructure and hardness properties of the Low carbon steel pipe welded using shielded metal arc welding with different electrode combinations.

Effect of Induction Heat Bending Process on the Properties of ASME SA106 Gr. C Carbon Steel Pipes

Recently, the bending process is greatly applied to fabricate the pipe line. Bending process can reduce welding joints and then decrease the number of inspection. Thus, the maintenance cost will be reduced. Induction heat bending process is composed of bending deformation by repeated local heat and cooling. By this thermal process, corrosion properties and microstructure can be affected. This work focused on the effect of induction heating bending process on the properties of ASME SA106 Gr. C low carbon steel pipes. Microstructure analysis, hardness measurements, and immersion corrosion test were performed for base metal and bended area including extrados, intrados, crown up, and down parts. Microstructure was analyzed using an optical microscope and SEM. Hardness was measured using a Rockwell B scale. Induction heat bending process has influenced upon the size and distribution of ferrite and pearlite phases which were transformed into finer structure than those of base metal. Even though the fine microstructure, every bent area showed a little lower hardness than that of base metal. It is considered that softening by the bending process may be arisen. Except of I2, intrados area, the others showed a similar corrosion rate to that of base metal. But even relatively high rate of intrados area was very low and acceptable. Therefore, it is judged that induction heat bending process didn’t affect boric acid corrosion behaviour of carbon steel.

OS1510-464 高ひずみ速度下における鋼円筒の爆発衝撃破壊特性

OS1510-464 高ひずみ速度下における鋼円筒の爆発衝撃破壊特性

Влияние теплой прокатки на структуру и механические свойства низкоуглеродистой трубной стали

This paper presents results of a research on the effect of warm rolling on structure and mechanical properties of the low-carbon pipe steel. The warm rolling results in formation of anisotropic ultra-fine grained (UFG) structure with average grain/subgrain size 0.5 µm in transverse direction and 20–30 µm along the rolling direction. The formation of ultra-fine grained (UFG) structure leads to 1.5 times increase in strength by comparison to fine-grained (FG) structure keeping the required level of ductility. It is shown that impact toughness at -196 °C in UFG steel is 15 times higher than that in initial FG condition. It was established that the total work of fracture at -196 °C increases due to growth of crack propagation distance in comparison to initial (FG) condition. Fractographic analysis of the sample after the test at -196 °C revealed that in the condition after rolling the mixed type of fracture surface is observed, and in the initial condition demonstrates completely brittle fracture. In both conditions of the materials at all temperatures tested appeared areas with the cleavage on the crack surface.

Application of low Ms temperature consumable to dissimilar welded joint

The welding of dissimilar joints is very common in systems used in oil exploration and production in deep sea waters. Commonly involves welding of low carbon steel pipes with low alloy steel forgings both with inner Inconel clad. The forged steel part undergoes a process of buttering with Inconel or carbon steel electrode before the weld of the joint. The buttering process is followed by a process of residual stresses relief. The conventional way of reducing the level of residual stresses in welded joints is to apply post welding heat treatments. Depending on the size and complexity of the parts to be joined, this can become a serious problem. An alternative technique for reducing residual stresses is to use an electrode that during the cooling process undergoes a displacive transformation at a relatively low temperature so that the deformation resulting from the transformation compensates the contraction during the cooling process, and, although many papers have been published in this direction using Fe–Cr–Ni alloys, most of them report a loss of toughness in the weld metal. Maraging steel is a family of materials with Ms temperature below 200°C and even without the final heat treatment of aging has superior mechanical properties to low alloy steels used in forgings. In this work, forged piece of AISI 4130 was buttered with Maraging 350 weld consumable and subsequently welded to ASTM A36 steel using Inconel 625 filler metal. In addition, the dissimilar base metal plates were welded together using Maraging 350 steel weld consumable. The levels of residual stress, and the toughness and microstructures of heat affected zone and weld metal were investigated.

Effect of Heat Treatments on Microstructure and Mechanical Properties of Low Carbon Steel Pipes Welded by Induction Process

In this work, the effect of isothermal heat treatments on microstructure evolution and mechanical properties after welding by induction of A37 pipeline steel have been studied by scanning electron microscopy, hardness measurements, and tensile tests. Microstructural evolution in welded joint was identified after isothermal annealing from 200 until 900 °C.

Ratcheting response of dented pipes under monotonic and cyclic axial loadings

Offshore pipelines are usually subject to hostile environments. Temperature changes and repetitive start-up/shutdown in offshore pipelines generate cycles of axial compression and relaxation. Consequently, the pipes may become subject to loading magnitudes that could cause them to locally buckle and wrinkle, and if subject to repeated loading, they could undergo ratcheting. Pipelines could also be subject to damage in the form of dents. This form of damage would have a profound effect on a pipe’s ratcheting response when subjected to cyclic loading. In this article, the ratcheting response of locally dented pipes that were subject to axially applied cyclic loading has been experimentally investigated. Scaled pipes (tubes) were first laterally indented with a cylindrical indenter and then were subjected to a monotonic axial compressive load that initiated small amplitude wrinkles on them. The pipes were subsequently subjected to repeated axial strain. The experiments were conducted on low carbon steel pipes (API 5L-grade B), with Do/t ≃ 35, which were indented to three different indentation depths. Significant variation in pipes’ responses was observed, and the number of cycles prior to collapse dramatically decreased by as much as 75% when the indentation depth was marginally increased.

Application of ultra-smooth composite diamond film coated WC–Co drawing dies under water-lubricating conditions

A specific revised HFCVD apparatus and a novel process combining HFCVD and polishing technique were presented to deposit the micro- and nano-crystalline multilayered ultra-smooth diamond (USCD) film on the interior-hole surface of WC–Co drawing dies with aperture ranging from d1.0 mm to 60 mm. Characterization results indicate that the surface roughness values (Ra) in the entry zone, drawing zone and bearing zone of as-fabricated USCD coated drawing die were measured as low as 25.7, 23.3 and 25.5 nm, respectively. Furthermore, the friction properties of USCD films were examined in both dry sliding and water-lubricating conditions, and the results show that the USCD film presents much superior friction properties. Its friction coefficients against ball-bearing steel, copper and silicon nitride balls (d4 mm), is always lower than that of microcrystalline diamond (MCD) or WC–Co sample, regardless of the lubricating condition. Meanwhile, it still presents competitive wear resistance with the MCD films. Finally, the working lifetime and performance of as-fabricated USCD coated drawing dies were examined under producing low-carbon steel pipes in dry-sliding and water-lubricating conditions. Under the water-lubricating drawing condition, its production significantly increases by about 20 times compared with the conventional WC–Co drawing dies.

Analysis of the elastic-plastic behavior of pressurized internal cracks in welded joints of low carbon steel pipes

It was analyzed the elastic-plastic behavior of areas with pressurized planar internal cracks extending from the pattern metal region in the heat affected zone to the welding metal in welding joints of low carbon pipes subject to internal pressure. Using the ANSYS 8.0[TM] software, three-dimensional simulation of geometrical models of pipes containing the internal pressurized cracks was performed. The finite element method with non linear strain conditions was employed, considering the kinematic hardening rule and the real material properties for every location. The fracture paths and expressions to calculate the pressure in the crack and in the pipe that lead to fracture of the cracked area were obtained.

Inheritance of misorientations and model of formation of bainite structure in low-doped steels under the influence of austenite deformation

The structure and spectra of misorientation in carbide-free bainite low-carbon low-doped pipe steel are studied. It is demonstrated that the increase in the portion of low-angle misorientations in deformed steel is due to the fact that bainite inherits the deformation structure of austenite. A model of computation of the kinetics of bainite transformation of deformed austenite is proposed which facilitates forecasting of the average size of structural element with preset misorientation depending on the mode of thermomechanical treatment.

Mechanical Characteristics of Low-Carbon-Steel Pipe Bent by Local Induction Heating with Small Bending Radii

small radius of curvature from 1.5­2.0 diameter ratio (DR) have been investigated. Our pipe material was low carbon steel (SA106Gr-B) having the chemical compositions of 0.3C, 0.29Mn, 0.4Cr, and 0.4Cu (mass%). The high cycle fatigue, microstructure, hardness, and residual stress of two bent sections ®extrados and intrados regions ®were compared with those of the raw material section. Low carbon steel pipes have better fatigue characteristics at the bent section than at the raw material section. The improvements in the fatigue strength of specimen resulted from grain refinement and phase transformation, while compressive residual stress at surface of bent pipe remained by thermo-mechanical processing can give better fatigue properties in fields. [doi:10.2320/matertrans.MF201123]

Special features of the evaluation of the weldability of low-carbon high-strength pipe steels

The special features of the weldability of high-strength low-carbon microalloyed steels are investigated.

Measurement of the hysteresis characteristics of pipe steels under elastic and plastic tensile strain

The changes in the shape and characteristics of the major and asymmetric hysteresis loops of low-carbon pipe steels under the action of elastic and plastic tensile strains were studied. The hysteresis loop segments that experienced the most considerable transformations under the tension of a material were determined. The possibilities of the inspection of tensile strains by the coercive return magnetization and the magnetic field corresponding to a fixed magnetization on the descending branch of a hysteresis loop were shown.

Structure and properties of low-carbon pipe steel after pneumatic testing

The structure and properties of low-carbon pipe steel with ferrite-bainite structure subjected to pneumatic tests are investigated. The relation between the properties determined in static and dynamic loading and the results of the pneumatic tests is considered. It is found that the structure of steel not subjected to pneumatic tests includes large bainite sections and coarse martensite-austenite inclusions.

Classification of low-carbon pipe steel microstructures

The expediency of classifying the microstructure of low-carbon pipe steels is demonstrated. The main structures that should be considered in its development are investigated.

A Novel Carbon Steel Pipe Protection Based on Radial Basis Function Neural Network

Problem statement: The cost due to corrosion Damage have estimated to be 3-4% of their gross national product which significantly Countries problem around the world. Approach: In this study, a novel carbon steel pipe protection based on RBFNN was proposed. The RBFNN used to predict the minimum current density required in impressed current cathodic protection to protect low carbon steel pipe. Learning data was performed by using a 30 samples test with different concentration C%, temperature T, distance D and pH. The RBFNN model has four input nodes representing the (concentration C%, temperature T, distance D and pH), eight nodes at hidden layer and one output node representing the min. current density. Results: Generalization test used 5 data samples taken from the experimental results other than those data samples used in the learning process to check the performance of the neural network on these data. Conclusion: In addition, the experimental results indicate that proposed system can be used successfully to obtain minimum cathodic protection current density to protect low carbon steel pipes.

Influence of the plastic-deformation temperature on the structure and properties of low-carbon pipe steel

Influence of the plastic-deformation temperature on the structure and properties of low-carbon pipe steel

3D thermal finite element analysis of single pass girth welded low carbon steel pipe-flange joints

This paper presents a detailed computational procedure for predicting the complete thermal history including transient temperature distribution during girth welding and subsequent post weld cooling of low carbon steel pipe flange joints. Using the FE code ABAQUS, 3-dimensional non-linear heat transfer analysis is carried out to simulate gas metal arc welding (GMAW) process. ANSI Class #300 flange is used with a 6 mm thick, 200 mm long and 100 mm nominal diameter pipe. Joint type is a single ‘V-groove’ butt joint with a 1.2 mm root opening. FORTRAN subroutine is utilized for the application of volumetric heat flux from the weld torch using Goldak’s double ellipsoidal heat source model, which is based on Gaussian power density distribution. Temperature dependent thermal properties as well as phase change effects have also been accounted. Apart from comprehensive discussion on the thermal history, in-depth analysis of the axial temperature profile at four different sections on both sides of the weld joint is presented. The simulated results showed that the temperature distribution around the implemented heat source model is steady when the weld torch moves around the circumferential joint. The present simulation model can be used as a proper tool to investigate the effect of different GMAW process parameters.