Carbon Low Alloy Steel Research Articles

Close-to-Reality Sliding-Corrosion Test-Rig for Oilfield Application

Sliding-corrosion phenomena play a crucial role in reducing the lifetime of tubings in the oil production industry. The aim of the present work is to develop and apply a close-to-reality test rig to describe the tribological performance of low-alloyed Carbon-steel (C-steel) under sliding-corrosion conditions in O2-free environment. The proposed test rig is highly relevant for the oil production industry and has been designed at the Austrian Competence Center for Tribology (AC²T). The benefit of this equipment is that it allows the setting of the CO2 atmosphere at a certain partial pressure while simultaneously varying the pH-value, Cl− ion concentration, and temperature of the electrolyte solution. Pure corrosion phenomena are investigated within a designed coupon box where conditions of steam, electrolyte injection, static, and dynamic flow are controlled. In addition to the corrosive environment, a tribological reciprocating sliding contact is implemented between tubing segments and coupling samples. Within this study, a commercially available low-alloyed C-steel was selected as base material for the tubing, which was tribologically stressed under reciprocating sliding contact against spray metal coated couplings. The results show a high influence of the steel microstructure on the performance of low-alloyed C-steel tubings under sliding-corrosion. Additionally, the dominant damage mechanisms that are observed in real field applications could be successfully reproduced by experimental simulation using this newly designed close-to-reality test rig.

Uncovering carbide on carbon steels by use of anodic galvanostatic polarization and its effect on CO2corrosion

A galvanostatic method was used to accelerate pre-corrosion of three low-alloyed carbon steels. The resulting surface morphology, cathodic reaction rates and corrosion rates, and the cathodic reaction mechanism are discussed. The method is suited to accelerate pre-corrosion; however, significant self-corrosion must be taken into account. Surface roughening and increasing amounts of uncovered cementite, associated with increasing metal loss, increases cathodic reaction rates. The cathodic reaction is under mixed chemical and diffusional control in the pH range of these experiments (pH < 4.8). H2CO3 is regarded as an additional source of H+. Although the dissociation of H2CO3 is restricted by the slow hydration of CO2, its presence enhances the corrosion rates.

The effects of process parameters for joining of AISI 1010-Cu alloys by friction welded

In this study, the effects of process parameters for joining of AISI 1010 low carbon steel and copper alloys by friction welded were investigated. Low carbon steel and commercial copper each of 12 mm diameter was used to fabricate the joints. The friction welding tests were carried out using a direct-drive type friction welding machine which was designed and manufactured for this purpose by us. After friction welding, in order to determine the microstructural changes that occurred, the interface regions of the welded specimens were examined by means of OM, SEM, EDS and X-Ray analysis. Microhardness and tensile tests were conducted to determine the mechanical properties of the welded specimens. The experimental results indicated that AISI 1010 low carbon steel could be joined to copper using the friction welding technique and for achieving a welding with a sufficient strength, the friction time has to be held as short as possible, while the rotational speed, friction and forging pressure has to be as high as possible. Tensile strength values also confirmed this result and at the interface did not occurred intermetallic phases. The maximum tensile strength of 294,67 MPa could be obtained for the joints welded under the welding conditions of rotation speed of 2300 rpm, friction pressure of 40 MPa, forging pressure of 80 MPa, friction time of 6 s and forging time of 3 s.

Influence of DIT Parameters on the Cementite Spheroidization in a Low-Alloy Medium Carbon Steel

The influence of strain, strain rate, and temperature on deformation-induced transformation (DIT) in a low-alloy medium carbon steel is studied. The strain promotes the nucleation of ferrite (deformation-induced ferrite) and also pearlite (deformation-induced pearlite), this last being characterized by a fine interlamellar spacing and morphological instability. At strains e > 0.5, intragranular nucleation activates and further ferrite nucleation over the newly created α/γ interface takes place, which gives rise to the precipitation of cementite (deformation-induced cementite) at the ferrite boundaries. Soft annealing treatments have been performed on the microstructures obtained by DIT, and the degree of spheroidization has been quantified by image analysis techniques. In comparison to non-deformed conditions, the application of DIT results in a higher degree of spheroidization after soft annealing. Moreover, the EBSD analysis denotes that ferrite grain size refinement is achieved with respect to non-deformed conditions. The degree of spheroidization is highly influenced by the applied strain level and subsequent holding temperature.

Relationships among microstructure, precipitation and mechanical properties in different depths of Ti–Mo low carbon low alloy steel plate

Ti–Mo low carbon low alloy steel plate with 25mm in thickness was produced through hot rolling in laboratory condition. Relationships among microstructure, precipitation and mechanical properties in different depths were investigated and the results revealed that substructures, such as dislocations and low angle boundaries, could vary the process of precipitation and finally made the mechanical properties changed from different depths. Mainly influenced by the high cooling rate during γ–α phase transition process, surface region of the plate was characterized by quasi-polygonal ferrite and large (Ti,Mo)C carbides (>10nm). However, due to the relatively low cooling rate, some polygonal ferrite formed in the 1/2 thickness region, leading to the promotion of cluster precipitation. Different with the large (Ti,Mo)C carbides heterogeneously nucleated in the substructures, small (Ti,Mo)C carbides (∼2nm) embedded in the precipitation cluster could homogeneously nucleate in the matrix and exhibited a coherent or semi-coherent interface. Besides, the fact that Ti/Mo atomic ratio increased with the size of (Ti,Mo)C carbides further confirmed the promoting effect of Mo during the nucleation process. Different with the Orowan strengthening mechanism, the movement of dislocation could traverse precipitation clusters. The formation of TiN during smelting process is harmful to the mechanical properties, thus a better performance can be achieved through the reasonable control of it.

EFFECT OF FILLER METALS ON THE MECHANICAL PROPERTIES OF DISSIMILAR WELDING OF STAINLESS STEEL 316L AND CARBON STEEL A516 GR 70

This paper describes an investigation on the effect of using three different filler metals to weld two dissimilar metals namely, stainless steel 316L and low alloy carbon steel A516 gr 70. Manual Gas Tungsten Arc welding (GTAW) with three filler metals including ER 80S-Ni1, ER309L, ER NiCrMo-3 were selected to weld the two metals. Radiography and penetrant tests were performed on the welded metals to ensure the surface and internal soundness of the welds based on the tensile tests results, all the specimens failed at the carbon steel A516 gr 70 base metals with fully ductile fracture mode (cup and cone). Welded samples using Inconel 615 filler metal has the highest strength of 512 MPa while other samples show almost similar strength of 481 and 487 MPa. The tensile strength of all the welded samples is found to be in between the tensile strength of the base metals. Micro-hardness test showed that ER80S-Ni1weld has the highest hardness, meanwhile hardness profile of ER309L presented a sharp drop in the stainless steel side and ER NiCrMo-3 weld metal illustrated hardness above the two base metals with fewer variations across the weld metal.

Electrochemical Corrosion Behavior of High Strength Carbon Steel in H2S-Containing Alkaline Brines

The electrochemical corrosion behavior of high strength low alloy carbon steel API S-135 was investigated using in-situ electrochemical measurements, ex situ surface analyses, and software modeling in the alkaline brines at pH of 7.9, 10.7, and 12.4 and at four different P H2S equal to 0 kPa, 0.83 kPa, 8.3 kPa, and 69 kPa at 85 oC. Linear polarization resistance (R pol) at steady state increased as pH increased from 7.9 to 12.4 at lower P H2S whereas R pol decreased and then increased at higher P H2S. The fastest corrosion rate (CR) was 0.26 mm yr-1 at pH 10.7 with P H2S 69 kPa, and the slowest CR was 0.0053 mm yr-1 at pH 12.4 with P H2S 0.83 kPa. The correlation between the primary species, corrosion products, localized corrosion and R pol were discussed. The experimental CR and corrosion products were compared with the modeling CR and Pourbaix diagram.

On the formation of metallic glass coatings by means of Cold Gas Spray technology

Novel Cold Gas Spray technology has been used to build-up coatings of Fe-base metallic glasses on low alloyed carbon steel. Impact morphologies have been studied demonstrating extensive shear band formation but also homogeneous plastic flow in the metallic glass particles despite high strain rates, 108–109 s−1, involved in the technique. Interestingly, thick coatings with good deposition efficiencies have been built-up in conditions of homogeneous flow. Coating formation is discussed in terms of fundamentals of dynamics of undercooled liquids, plastic flow mechanism and crystallization kinetics of metallic glasses. Therefore, the method herein established is valid for any metallic glass.

Effect of Heat Treatment Process on Mechanical Properties of a Medium Carbon Low Alloy Steel

Effect of heat treatment processes on the microstructure and mechanical properties of a medium carbon low alloy steel was studied by means of color metallography, XRD and mechanical tests.The adopted heat treatment processes included air quenching and then austempering in salt bath, watercooling and then austempering in salt bath, as well as directly austempering in salt bath. The results show that after treatments according to the above three processes the steel may exhibited microstructure composed of different amount of bainite and martensite, and better mechanical properties in comparison with the cast ones, i.e. its impact toughness and hardness were increased by 92%-183% and 31%-55% respectively. For the case of air cooling and then austempering in salt bath, the amount of bainite decreased gradually with the increase of air cooling time while the amount of martensite progressively increased, correspondingly its hardness and impact toughness showed a tendency of increase and decrease respectively.The mechanical performance of the medium carbon low alloy steel is closely related to the ratio of bainite to martinsite in the microstructure. It is noted that the steel with a duplex microstructure of 50%-60% bainite and 30%-40% martensite exhibited an optimal comprehensive mechanical performance.

Evaluation of the corrosion protection of steel by anodic processing in metasilicate solution using the scanning vibrating electrode technique

Anodic processing in metasilicate solution was investigated for the improvement of the corrosion resistance of various steels, namely F111 low alloy carbon and 304 stainless steels, as well as on galvanized steel cut edges. The efficiency of the prior electrochemical treatment for each material was tested during their exposure to naturally-aerated aqueous chloride solutions of different aggressiveness. Analysis was performed using the scanning vibrating electrode technique (SVET) in order to detect local ionic current distributions over the samples under study associated to the corrosion reactions. The onset of corrosion processes was greatly inhibited after anodic processing with metasilicate on both the low alloy carbon steel and the galvanized steel cut edge. Conversely, SVET analysis of unbiased 304 steel samples tested in 0.1M chloride-containing solution did not show differences between pristine and metasilicate-treated surfaces. Differences in the electrochemical reactivity between treated and non-treated 304 steel surfaces were only observed after partial removal of the corresponding passive layers under operator-controlled polarization.

SPEED DEPENDENCE OF ACOUSTIC VIBRATION PROPAGATION FROM THE FERRITIC GRAIN SIZE IN LOW-CARBON STEEL

Purpose. It is determining the nature of the ferrite grain size influence of low-carbon alloy steel on the speed propagation of acoustic vibrations. Methodology. The material for the research served a steel sheet of thickness 1.4 mm. Steel type H18T1 had a content of chemical elements within grade composition: 0, 12 % C, 17, 5 % Cr, 1 % Mn, 1, 1 % Ni, 0, 85 % Si, 0, 9 % Ti. The specified steel belongs to the semiferritic class of the accepted classification. The structural state of the metal for the study was obtained by cold plastic deformation by rolling at a reduction in the size range of 20-30 % and subsequent recrystallization annealing at 740 – 750 ° C. Different degrees of cold plastic deformation was obtained by pre-selection of the initial strip thickness so that after a desired amount of rolling reduction receives the same final thickness. The microstructure was observed under a light microscope, the ferrite grain size was determined using a quantitative metallographic technique. The using of X-ray structural analysis techniques allowed determining the level of second-order distortion of the crystal latitude of the ferrite. The speed propagation of acoustic vibrations was measured using a special device such as an ISP-12 with a working frequency of pulses 1.024 kHz. As the characteristic of strength used the hardness was evaluated by the Brinell’s method. Findings. With increasing of ferrite grain size the hardness of the steel is reduced. In the case of constant structural state of metal, reducing the size of the ferrite grains is accompanied by a natural increasing of the phase distortion. The dependence of the speed propagation of acoustic vibrations up and down the rolling direction of the ferrite grain size remained unchanged and reports directly proportional correlation. Originality. On the basis of studies to determine the direct impact of the proportional nature of the ferrite grain size on the rate of propagation of sound vibrations in the low-carbon alloy steel. The directly proportional nature of influence of ferrite grain size on the speed propagation of acoustic vibrations in low-carbon alloy steel on the basis of the conducted researches is defined. The paper is shown that at increasing in the size of the recrystallized ferrite grain the degree of influence the texture from the previous cold plastic deformation by rolling increases. Practical value. The received results on nature determination of influence of ferrite grain size on the speed propagation of acoustic vibrations can be the useful by development of techniques of non-destructive testing of metal materials quality. The special value the specified technique of measurement acquires in the conditions of line production of metal constructions.

Microstructure based flow stress modeling for quenched and tempered low alloy steel

Abstract Quenching and tempering (Q&T) process is commonly applied in part making industries for improving mechanical properties of carbon low alloy steels. After Q&T, microstructure of the steel consists of temper martensite and carbide precipitations. In this work, material modeling for describing flow stress behavior of the SNCM439 alloy steel under different tempering conditions was introduced. Microstructure based models were developed on both macro- and micro-scale. The models were afterwards applied in FE simulations for predicting stress–strain responses of the tempered steels. For the macroscopic model, the Ludwik equation was used, in which precipitation strengthening depending on particle size was incorporated by the Ashby–Orowan relationship. For the microscopic model, representative volume elements (RVEs) were generated considering microstructure characteristics of the examined steels. Flow curves of the individual constituents were described based on dislocation theory and chemical compositions. The FE simulations of tensile tests and RVE simulations under uniaxial tension were performed using the introduced models. The influences of the carbide precipitations on mechanical behavior of the tempered steels were investigated. The resulted effective stress–strain curves were determined and compared with the experimental ones. Both macroscopic and microscopic approaches accurately predicted mechanical properties and strain hardening behaviors of the tempered steels.

Rapid surface hardening and enhanced tribological performance of 4140 steel by friction stir processing

Tribological performance of steel materials can be substantially enhanced by various thermal surface hardening processes. For relatively low-carbon steel alloys, case carburization is often used to improve surface performance and durability. If the carbon content of steel is high enough (>0.4%), thermal treatments such as induction, flame, laser, etc. can produce adequate surface hardening without the need for surface compositional change. This paper presents an experimental study of the use of friction stir processing (FSP) as a means to hardened surface layer in AISI 4140 steel. The impacts of this surface hardening process on the friction and wear performance were evaluated under both dry and lubricated contact conditions in reciprocating sliding. FSP produced the same level of hardening and superior tribological performance when compared to conventional thermal treatment, using only 10% of the energy and without the need for quenching treatments. With FSP surface hardness of about 7.8GPa (62 Rc) was achieved while water quenching conventional heat treatment produced about 7.5GPa (61 Rc) hardness. Microstructural analysis showed that both FSP and conventional heat treatment produced martensite. Although the friction behavior for FSP treated surfaces and the conventional heat treatment were about the same, the wear in FSP processed surfaces was reduced by almost 2× that of conventional heat treated surfaces. The superior performance is attributed to the observed grain refinement accompanying the FSP treatment in addition to the formation of martensite. As it relates to tribological performance, this study shows FSP to be an effective, highly energy efficient, and environmental friendly (green) alternative to conventional heat treatment for steel.

REGULATION OF MULTI-PHASE MICROSTRUCTURE AND MECHANICAL PROPERTIES IN A 700 MPa GRADE LOW CARBON LOW ALLOY STEEL WITH GOOD DUCTILITY

Low carbon and low alloy steels require good combination of strength and ductility to ensure safety and stability of structures. Heat treatment in intercritical area can not only produce multi-phase microstructure,but also lead to the redistribution of alloying elements in different phases. Multi-step intercritical heat treatment is favorable to obtain retained austenite that is stabilized by repeated enrichment of alloying elements in reversed austenite and nanometer-sized precipitate that are primarily formed during tempering. Excellent mechanical properties are contributed by transformation-induced-plasticity effect of retained austenite and precipitation hardening effect of nanometer-size precipitates. In this work, the microstructural evolution and relative mechanical properties were investigated in a low carbon low alloy steel processed by a three-step heat treatment, namely, intercritical annealing, intercritical tempering and tempering. The microstructure was a typical dual- phase microstructure consisting of intercritical ferrite and bainite/martensite after intercritical annealing, and primarily comprised of intercritical ferrite, tempered bainite/martensite and retained austenite after intercritical tempering. Retained austenite with volume fraction of 29% distributed at the ferrite/bainite(martensite) boundaries and betweent bainitic/martensitic laths. Retained austenite was stabilized by enrichment of C, Mn, Ni and Cu in reversed austenite during the reversion transformation process. Nb C precipitates with average size of 10 nm was formed in ferrite matrix and bainite/martensite, while Cu- containing particles in size range of 10~30 nm precipitated in ferrite and retained austenite during intercritical tempering and tempering process. The morphology of Nb C precipitates was spherical, elliptical and irregular, and copper precipitates were spherical. With the combination of transformation- induced- plasticity(TRIP) effect of retained austenite and precipitation hardening, the steel possessed outstanding mechanical properties: yield strength 700 MPa, tensile strength 900 MPa, uniform elongation 20%, and total elongation 30%.

Wear on overlay welded HCWI vs. quenched and tempered low alloyed carbon steels evaluated with granite in a laboratory drum test machine

This present test evaluates wear resistance of overlay welded High Chromium White Iron (HCWI) in comparison with quenched and tempered low alloyed carbon steels within a hardness range between 400 and 700HBW. The HCWI overlay material had a carbon content in the range of 3–5% and a chromium content of 20–25%. The wear performance was evaluated by the use of two different sizes of granite rocks. This test was undertaken in a laboratory drum machine, which aimed to resemble typical conditions expected within raw material flows in mines and quarries. The secondary aim of the investigation was to further evaluate the material selection process by comparing ore, residuals and aggregates from real-world mining sites with the respective wear resistant materials being employed. The drum machine used had a diameter of 800mm and a width of 100mm. The drum rotated on a horizontal axle, which lifted the aggregate to a certain height, thus creating a sliding motion. Each test evaluated 34 samples, attached at the inner side of the drum shell. The samples were installed inside a depressed holder to protect against unwanted edge wear. The holders were specifically designed to fit hard materials such as HCWI. The HCWI overlay material was ground flat at the top and cracks were sealed with epoxy. The experimental results demonstrated how different size of abrasives resulted in significantly different wear responses on the tested materials and that the developed test method can provide valuable information in the selection of wear resistant material.

해양파이프라인 비파괴검사를 위한 와전류 센서 개발

Regular high-strength carbon steel is currently the most commonly used pipe material for onshore and offshore pipelines. The corrosion of offshore pipelines is a major problem as they age. The collapse of these structures as a result of corrosion may have a heavy cost is lives and assets. Therefore, their monitoring and screening is a high priority for maintenance, which may ensure the integrity and safety of a structure. Monitoring risers and subsea pipelines effectively can be accomplished using eddy current inspection to detect the average remaining wall thickness of corroded low-alloy carbon steel pipelines through corrosion scaling, paint, coating, and concrete. A test specimen for simulating the offshore pipeline is prepared as a standard specimen for an analysis and experiment with differential bobbin eddy current sensors. Using encircling coils, the signals for the defect in the simulated specimen are analyzed and evaluated in experiments. Differential bobbin eddy current sensors can diagnose the defects in a specimen, and experiments have been carried out using the developed bobbin eddy current sensor. As a result, the most optimum coil parameters were selected for designing differential bobbin eddy current sensors.

Development of γ′-Fe4N Phase Control Technology and Low-Carbon Alloy Steel for High-Strength Nitrided Gear

Development of γ′-Fe₄N Phase Control Technology and Low-Carbon Alloy Steel for High-Strength Nitrided Gear

SUMITOMO SM90XS

Abstract Sumitomo SM90XS is a low alloy carbon steel for use in oil country tubular goods as a material suitable for sour service. This datasheet provides information on physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming. Filing Code: CS-187. Producer or source: Nippon Steel and Sumitomo Metal Corporation.

Effect of Ausforming Temperature on Bainite Transformation of High Carbon Low Alloy Steel

The effect of ausforming temperature on bainite transformation of high carbon low alloy steel was studied by in situ experiments using a Gleeble 3500 thermal and mechanical testing system. Morphology and crystallography of ausforming bainite were examined by scanning electron microscopy (SEM) and electron backscattered diffraction (EBSD). It has been found that deformation at all temperatures range from 230°C to 600°C can accelerate low temperature bainite transformation, and transformation rate increased with deformation temperature reduced. Quantitative X-ray analysis shows that the volume fraction of retained austenite was about 35.84% after deformation and isothermal transformation for 20 hours, it was approximately the same amount with austempering bainite transformation process (no strain) which austenite volume fraction was about 32.01%. Low temperature bainite formation can be accelerated with a smaller increase amount of retained austenite by deformation at a low temperature range of 230~600 oC.

Microstructural control and mechanical properties in friction stir welding of medium carbon low alloy S45C steel

Critical control of the welding conditions produced a fine ferrite–martensite duplex structure with the martensite volume fraction of around 33% in friction stir welding (FSW) of medium carbon (0.45wt% C) low alloy steel sheets. This microstructure provides the preferable combination of tensile strength and ductility. The findings were achieved to clarify the effect of the welding speed on the weldability. The fraction of low angle grain boundaries (LAGBs) decrease with increasing welding speed. At the welding speed of 400mm/min, the top region microstructure consists of lath martensite, while the bottom region shows a fine ferrite–pearlite structure. This microstructural variation can be linked with the distribution of the peak temperatures along the thickness of the weld. Additionally, it was shown that a non-contact thermal imaging system can be used as an effective tool for the online monitoring of several kinds of weld decays.