Strength Of Carbon Steel Research Articles

Effects of Hydrogen Sulfide on the Corrosion Behavior of High Strength Steel in Alkaline Solutions

The effects of hydrogen sulfide (H2S) on the corrosion of high strength carbon steel have been studied due to their relevance to the oil and natural gas industries. Since H2S behaves as an acid in aqueous solutions, the presence of dissolved H2S results in a decrease in pH through dissociation into H+(aq) and HS-(aq) ions. It is known that the effects of sulfide on iron oxidation dependent on the solution pH. For example, at very low pH the metal surface is free of corrosion products and resulting in high rates of active corrosion. In a pH region from 3 to 5, the addition of H2S can result in an initial increase in corrosion rate that decreases over time as a protective iron sulfide layer forms and passivates the metal. Our goal was address the corrosion processes on high strength carbon steel due to H2S at high pH values. In-situ electrochemical corrosion measurements were performed for high strength low alloy steel in 5 %wt. NaCl solution at 85 °C. The solution pH was tested from 7 and 12 to simulate conditions that may be present for drill pipes operating in deep-well environments. Exposure for each sample was at least 60 hours to allow for the observation of steady-state behavior. It was found that the calculated corrosion rate dramatically increased from around 3 mm y-1 or less to over 10 mm y-1 as the solution pH fell below 9, which is an event that could occur if pH control is temporarily lost during gas or oil extraction operations.The change in corrosion rate corresponded to an observed change in the electrochemical impedance spectroscopy (EIS) behavior, with a shift from two well-defined time constants at more alkaline conditions to what appeared to be a single low-frequency time constant at more neutral pH. Varying the rate of stirring in the test vessel did not appear to change the corrosion behavior across the pH range tested, suggesting that the corrosion process was not diffusion limited.The results were correlated to previous work that found the mechanical failure mechanism to shift from stress corrosion cracking at alkaline conditions to hydrogen induced cracking over a similar pH range. This would suggest that changing the pH alters the nature of the corrosion process, possibly by changing the mechanism or the nature of the corrosion product film. Thermodynamic modeling has been performed to investigate the stable corrosion products and aqueous species at each condition. Pourbaix diagrams suggest that corrosion products shift from iron sulfides to iron oxides as the solution pH is increased.

Dynamic Characteristic of AlN Precipitate in Production of High Strength and Low Carbon Steel in FTSR Technology

Study on Dynamic characteristic of AlN precipitate in Production of High Strength and Low Carbon Steel in FTSR technology. Results calculated by dynamical model indicate that part of the AlN particles precipitate in casting slab rapidly which because the increasing precipitation driving force offered by increasing local concentration of Al caused by dendritic segregation in thin slab.

Characteristics of Deposition Precipitation Process in Production of High Strength and Low Carbon Steel in FTSR

Precipitation characteristics of second phase in HSLC steel produced by FTSR technology have been researched by TEM and EDS in this article. And preliminary research of precipitation conditions of second phase particles in thermodynamics and dynamics have been took. The results indicate that: there’re second phase particles precipitated dispersively in hot rolled HSLC steels by FTSR technology. These particles mainly contain particles of Al2O3、MnS and AlN. Thermo dynamical analysis declares that most of the Al2O3 and all of the MnS、 AlN particles are precipitated in solid state. That’s why the precipitation process is slowed down by the diffusion velocity of the elements in solid, and thinner particles are precipitated while the material is in solid state than in liquid state.

Failure Investigation of Hydrogen Blistering on Low-strength Carbon Steel

The current study assesses the root causes of hydrogen blisters on low strength carbon steel equipment. For this purpose, some experiments including hardness test, non-destructive test (NDT), metallography, and fractograpghy are conducted. The microstructure of two blisters is assessed by means of optical microscopy and scanning electron microscopy (SEM). The microstructural studies show that the steel plate has some inclusions and banded ferrite/pearlite structure. The energy dispersive x-ray spectroscopy (EDS) results indicate that these inclusions mainly contain Mn, S, Al, Ca, and Si. The results show that the inclusions and planar imperfections found in the NDT have been the nucleation locations for blisters in the plate. Remediation action plans are recommended to prevent further occurrence and growth of hydrogen blisters.

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.

Influence of sulfate reducing bacterial biofilm on corrosion behavior of low-alloy, high-strength steel (API-5L X80)

The utilization of high strength carbon steels in oil and gas transportation systems has recently increased. This work investigates microbiologically influenced corrosion (MIC) of API 5L X80 linepipe steel by sulfate reducing bacteria (SRB). The biofilm and pit morphology that developed with time were characterized with field emission scanning electron microscopy (FESEM). In addition, electrochemical impedance spectroscopy (EIS), polarization resistance (Rp) and open circuit potential (OCP) were used to analyze the corrosion behavior. Through circuit modeling, EIS results were used to interpret the physicoelectric interactions between the electrode, biofilm and solution interfaces. The results confirmed that the extensive localized corrosion activity of SRB is due to a formed biofilm and a porous iron sulfide layer on the metal surface. Energy Dispersive Spectroscopy (EDS) revealed the presence of different sulfide and oxide constituents in the corrosion products for the system exposed to SRB.

Influence of Pseudomonas on corrosion and mechanical properties of carbon steel in sea water

In order to separate the effects of a specific microbial species (Pseudomonas) in sea water on carbon steel, a comparative study of the corrosion and mechanical properties of AISI 1045 carbon steel in natural sea water, sterile sea water and Pseudomonas inoculated sea water was carried out using tensile testing, mass loss experiments and microscopy. The results of mass loss showed that the corrosion rate of the specimens in the single Pseudomonas system was faster than that in sterile sea water but slower than in natural sea water. Microscopy revealed that a loose corrosion product layer formed on the surface of carbon steel, and micropitting corrosion occurred underneath the corrosion product. Energy dispersive X-ray analysis of this deposit indicated that iron and oxygen were the main components, and a large amount of carbon, which most likely originated from the bacteria and its exopolymer, could also be detected. The tensile strength of carbon steel was reduced by the action of Pseudomonas, but hydrogen embrittlement was not found.

Analysis of microstructure and mechanical properties of different high strength carbon steels after hot stamping

Usage of high strength steels may reduce the weight of automobiles and improve the crash safety and low down the gas emissions. Besides cold forming, hot stamping has gained much interest for the production of car body components. Boron alloyed steels have been the point of focus for the materials choice in hot stamping. In this paper, four high strength non-boron alloyed steels were hot stamped using water and nitrogen cooling media. Microstructural analyses, lateral and surface hardness profiling as well as tensile tests of hot stamped samples were performed. These steels provided yield strength (Y.S.) values of 600–1100MPa and ultimate tensile strength (U.T.S.) values of 900–1400MPa. Increasing cooling rates, i.e. by using nitrogen cooled punch (NCP) during hot stamping resulted in mostly martensitic microstructure and maximum strength, while hot stamping using water cooled punch (WCP) resulted in maximum formability index due to presence of some ferrite phase.

Prediction of residual stresses in high strength carbon steel pipe weld considering solid-state phase transformation effects

In this paper, prediction of axial and hoop residual stresses produced in high strength carbon steel pipe weld was made by employing a sequentially coupled 3-D thermal, metallurgical and mechanical FE model. Solid-state phase transformation during welding was incorporated into the FE model by allowing for volumetric changes and the associated changes in yield stress induced by austenitic and martensitic transformations. In the FE model, temperature-dependent thermo-physical and mechanical properties were considered, and phase transformation plasticity was also taken into account. The results showed the importance of incorporating solid-state phase transformation in the simulation of the pipe welding.

Steel Research Institutions in China

Steel Research Institutions in China

Effect of Specimen Configuration and Loading Types on Fatigue Life of an Annealed 0.42% Carbon Steels

In the present study, a unified crack growth law based on the small fatigue crack growth law was investigated using specimens with different configurations and loading types for the annealed 0.42% carbon steel. Then, a convenient prediction method of fatigue life was proposed. This small fatigue crack growth rate was uniquely determined by the modified small crack growth law, , despite of changing for specimen configurations and loading types. The constants of can be estimated by an empirical equation of without stress/strain gradient. Considered the effect of stress gradient for different specimen configurations and loading types, the stresses under bending loadings and specimen configurations was calculated from that under push-pull loading. Therefore, the fatigue life of the specimens with different configuration and under different loading types can be simply estimated through the fatigue crack growth law based on the only tensile strength of carbon steels. The availability of proposed method was confirmed experimentally by the results of several carbon steels.

Measurement and prediction of hydrogen embrittlement in high strength carbon steel

Hydrogen embrittlement tests were performed on 0·254 mm diameter BS 5216 M4 high strength carbon steel wire using constant loads to give initial tensile stresses in the range 48–91% ultimate tensile stress. The wires were electrolytically charged with hydrogen in 4%H2SO4 at current densities of 75 and 150 mA cm–2. The failure times at each applied stress and charging rate were displayed on Weibull statistical plots and shown to correlate with a diffusion model of hydrogen transport. At high stresses, crack initiation occurred rapidly and the failure time was controlled by the rate of inward hydrogen diffusion to maintain a threshold concentration for crack propagation. At low applied stresses, crack initiation required a higher hydrogen concentration and occurred more slowly. In this case, the failure time was controlled by the size and location of the significant microstructural flaw at which crack initiation occurred. The model enabled failure times to be predicted in specimens with differing dimensions.

Finite element simulation of the residual stresses in high strength carbon steel butt weld incorporating solid-state phase transformation

This paper presents a sequentially coupled three-dimensional (3-D) thermal, metallurgical and mechanical finite element (FE) model to simulate welding residual stresses in high strength carbon steel butt weld considering solid-state phase transformation effects. The effects of phase transformation during welding on residual stress evolution are modeled by allowing for volumetric changes and the associated changes in yield stress due to austenitic and martensitic transformations. In the FE model, phase transformation plasticity is also taken into account. Moreover, preheat and inter-pass temperature are included in the modeling process. Based on the FE model, the effects of solid-state phase transformation on welding residual stresses are investigated. The results indicate the importance of incorporating solid-state phase transformation in the simulation of welding residual stresses in high strength carbon steel butt weld.

Influence of tool steel microstructure on origin of galling initiation and wear mechanisms under dry sliding against a carbon steel sheet

The drive to reduce lubrication in sheet metal forming (SMF) operations has increased the interest to study the contact between polished tool materials sliding over relatively rough sheet surfaces. Commonly, transfer of sheet material to the tool surface occurs by adhesive wear. In the present work, a study of wear showed that the origination of the damage was complex and several simultaneous wear mechanisms were operative, even though friction did not change remarkably. A low strength carbon steel sheet was tested under dry sliding conditions against conventionally ingot cast and powder metallurgy cold work tool steels. The sheet was sputtered with a thin gold layer, which acted as a marker helping to reveal details of the wear mechanisms. Initial sliding was characterized by local adhesive wear with transfer of sheet material, predominantly, to the metallic matrix of the tool. Seemingly, the carbides have less adhesion to the sheet material than the steel matrix. Subsequently, materials transfer resulted in gradual coverage of carbides with formation of a semi-continuous thin layer of sheet material on the tools surface. Further sliding led to initiation of local microscratching of the sheet surface due to formation of lumps of sheet material adhered to the tool. Comparison of the two different tool steels revealed that the amount of adhered sheet material depended on amount, size and distribution of carbides and was higher for the ingot cast steel with coarser carbide phase. The advantage of the powder metallurgy steel was associated to removal of adhered material from the tool due to a higher amount and a more homogeneous distribution of finer carbides.

Effect of the morphology and size of iron carbide on the fatigue strength of carbon steels

The effect of the morphology and size of iron carbide in a high-carbon steel on the fatigue strength and critical crack opening is considered. The increase in the fatigue strength induced by a decrease in the pearlite size in medium-and high-carbon steels is caused by the fact that the time of formation of nonuniformities in a uniform dislocation distribution shifts toward high total strains.

Pressurized Water Corrosion Resistance of Carbon Steels and Their Nondestructive Characterization

This study dealt with the corrosion resistance for the carbon steels under a pressurized water atmosphere at the elevated temperature. The nondestructive test was also used to evaluate the damage degree of corrosion test specimen. The corrosion test for carbon steels was carried out at the temperature of 200 °C under a water pressure of 10 MPa. The corrosion time for carbon steel was changed up to 20 weeks. The strength of carbon steel by the degree of corrosion was investigated by a tensile test. The carbon steel showed an average tensile strength of about 500 MPa after the corrosion period of 20 weeks, accompanying the weight loss of about 2.5 %. The attenuation coefficient of ultrasonic wave can be utilized as useful parameters to inspect the corrosion damages of carbon steels.

2020 ナノインデンテーションにおける高強度鋼の変形特性に及ぼす水素の影響(S16-2 物理的・力学的現象,S16 インデンテーションの物理と応用)

Nanoindentation was used to study the effect of dissolved hydrogen on the nano plastic deformation in engineering steel. In this study, the results of high strength steel, SCM435 and carbon steel, S15C were discussed. We focused on the hydrogen effect on both onset and the resistance of plastic deformation at nano scale. Nano hardness was found to be increased with increasing in hydrogen content in SCM435 steel. The displacement burst of indentation curve was observed in both materials. The result of SCM435 steel, however, exhibited large scatter due to the large surface roughness. We, thus, investigated the displacement burst which occurred in the same grain of S15C steel. The result revealed that hydrogen increased the indentation force which induced displacement burst. Contrary to this, this force value decreased with a decrease in hydrogen content.

201 偏心軸圧縮荷重を受ける有孔薄肉正方形短柱鋼管の局部座屈強度に関する実験的研究 : 第2報長方形開口の場合(G.S.:材料力学I)

201 偏心軸圧縮荷重を受ける有孔薄肉正方形短柱鋼管の局部座屈強度に関する実験的研究 : 第2報長方形開口の場合(G.S.:材料力学I)

Two Approaches to the Problem of A. Griffith on the Strength of Solids

Two approaches to the development of physical models of fracture of solid bodies with cracks are compared, i.e., an energy approach based on the model of A. Griffith and a force approach considering breakage of atomic bonds at the tip of ideally sharp crack. It is shown that it is expedient to amend the contribution of the process of breakage of interatomic bonds into the spent energy by introducing a factor equal to 3 into the classical Griffith formula. An original “force” model of fracture of solid bodies due to ideally sharp cracks of natural origin with allowance for the factor of “rigidity” of interatomic bonds at the tip of the crack is suggested. Results of theoretical computations by both models are compared with experimental data presented in the literature. Explanation of the effect of nanosize cracks on the strength of carbon steels and on the strength of cracked glass tubes and bulbs in Griffith's experiments is suggested as an example.

High strength and low yield ratio carbon steel bar processed by thermomechanical rolling

Adding alloying elements or refining grain size are the common means to increase the strength of steels. By refining ferrite grains down to ~1μm through thermomechanical rolling, a high strength and low yield ratio (the ratio of yield strength to tensile strength) steel bar with good impact toughness has been developed from an ingot with a similar chemical composition to that of mild steel. The steel bar consisted of large ferrite grains (1 – 15μm), small ferrite colonies (smaller than ~1μm), and martensite. The tensile strength, 0.2% offset yield strength, yield ratio, uniform tensile elongation, and elongation up to fracture of the developed steel were: 856 MPa, 478 MPa, 0.558, 11.6%, and 19.1%, respectively. The absorbed energy in Charpy impact test at -40°C was 134 J. The toughness and strength of the steel can be adjusted by varying the volume fractions of the large ferrite grains, small ferrite colonies, and martensite.