Plain Low Carbon Steel Research Articles

On the use of thermomechanical processing to enhance the strength-ductility-toughness balance of plain low-carbon steel

This study aimed to fabricate a dual-phase (DP) steel with a combination of high strength-ductility-toughness by thermomechanical processing for industrial applications. Accordingly, the effects of 40 % cold deformation and intercritical annealing temperature on the microstructural evolution and tensile properties of low-carbon steel were studied. The microstructure of dual-phase steels consisted of ferrite (α) and martensite (α'), however, the morphology of martensite was different. With increasing the intercritical annealing temperature, the martensite fraction increased gradually from 0.41 at 770 °C to 0.51 at 860 °C. Also, the increase of martensite fraction from 0.41 to 0.51 caused a decrease in the martensite carbon concentration from 0.174 to 0.142 wt%. All dual-phase steels had a larger hardness than the as-received steel. When the temperature of annealing increased from 770 °C to 860 °C, the yield strength enhanced from 370.4 to 496.3 MPa, the ultimate tensile strength improved from 642.0 to 809.2 MPa, the total elongation decreased slightly from 31.8 % to 29.8 %, and the energy absorption increased from 190.0 to 217.6 J/cm3. The work hardening rate of all DP samples was considerably higher than other samples. Unlike initial, quenched, and rolled samples, the DP steels exhibited three-stage strain hardening behavior with increasing the true strain. For all dual-phase steels, a perfect ductile fracture was observed, with numerous uniform deep and coarse dimples. The dominant mechanism in the fabricated dual-phase steels was interface decohesion.

Achieving Fine-Grained Microstructure and Superior Mechanical Property in a Plain Low-Carbon Steel Using Heavy Cold Rolling Combined with Short-Time Heat Treatment

Achieving Fine-Grained Microstructure and Superior Mechanical Property in a Plain Low-Carbon Steel Using Heavy Cold Rolling Combined with Short-Time Heat Treatment

Extraordinary strength–ductility–toughness in Fe–0.08C plain low-carbon steel via introducing weblike martensite: Towards the third generation

The effect of large-strain cold rolling followed by intercritical annealing on the microstructure and mechanical properties of plain low-carbon steel was investigated. The grain size of ferrite reduced from 38 μm (for the as-received steel) to about 4 μm (for the dual-phase steel). The martensite phase was connected in 3D space in the dual-phase steel and a weblike structure of martensite was created. The stress-strain curve of dual-phase steel represents the continuous yield behavior without any distinct evidence of the yield point phenomenon. By introducing weblike martensite into the microstructure and refining α grains, the yield strength, ultimate tensile strength, and tensile toughness significantly increased to 740 MPa, 1062 MPa, and 193 J cm−3, respectively. The fracture surface of the DP sample had a dimpled appearance, indicating a ductile fracture mode. The results of the present work indicated that a low-cost plain low-carbon DP steel composed of weblike martensite and fine-grained ferrite exhibits extraordinary strength–ductility–toughness balance. Therefore, the dual-phase steel produced in the present work, by moving towards the third generation, can find wide applications in the automotive industry.

Comparison of Temperature Distribution between TWIP and Plain Carbon Steels during Wire Drawing

The effect of the thermal properties of steels on wire drawing behavior has been investigated to understand and improve the wire drawing process. Finite element analysis and experimental tests were conducted to analyze the temperature distribution of the deformed specimens with different thermal properties. The thermal properties of twinning-induced plasticity (TWIP) steel were measured and compared with those of plain carbon steel. Based on the measurement of thermal properties, wire drawing behaviors were systematically compared with thermal conductivity of the specimen (k) using plain low-carbon steel with high k and TWIP steel with low k. The results revealed that the k of TWIP steel was approximately one third of that of low-carbon steel, and the thermal expansion coefficient of the TWIP steel was approximately 50% higher than that of low-carbon steel in the temperature range of 26-400 °C. The temperature distributions in the wire strongly depended on the k of the wire during wire drawing. TWIP steel exhibited higher maximum temperature, and took a longer time to attain the equilibrium temperature than low-carbon steel during wire drawing owing to the low k. The maximum temperature of the die increased with decreasing k of the wire, indicating that die wear can increase with decreasing k of the wire. Therefore, reducing the drawing speed is suggested for a wire with low k, such as high-alloyed metals, especially for TWIP steels.

The effect of inter critical heat treatment on mechanical and wear properties of AISI 1015 steel

ABSTRACT Dual-phase (DP) steels mainly consist of ferrite and martensite phases. In this paper, DP steel was developed by inter-critical heat treatment followed by water quenching using AISI 1015 steel which is a type of plain low carbon steel. After developing DP steel, the mechanical and wear properties of AISI 1015 have been investigated. Inter-critical heat treatment was done at four different temperatures 740°C, 770°C, 800°C, 830°C in a muffle furnace. After SEM, it was found that the percentage of martensite increases with the heating temperature in the dual-phase region followed by water quenching. The results revealed that inter-critical heat treatment increased the tensile and hardness properties but decreased the ductility as the temperature increased. For wear properties, it was concluded that the specimen heat-treated at higher temperature showed a higher wear rate due to lower ductility. This was due to higher ductility at a lower temperature in comparison to lower ductility at a higher temperature. So, basically, the percentage of martensite affects the properties of dual-phase steel.

Prediction of the formation of carbide network on grain boundaries in carburizing of 18CrNiMo7-6 steel alloys

With the increasing surface carbon content during the carburizing process, undesirable carbide networks are generally formed on the surface and in the near-surface region of the mechanical parts composed of plain low carbon steels. Therefore, it is of great significance to predict the formation conditions of carbide networks in advance and thereby avoid their appearance. The effect of carbon concentration and grain size on the formation of carbide networks of 18CrNiMo7-6 steel alloys has been investigated in this work. The results show that the network carbide of the 18CrNiMo7-6 steel alloys after carburizing was mainly composed of cementite. Grain size has a significant effect on the formation of carbide network for 18CrNiMo7-6 steels during carburizing due to the preferential diffusion of excess carbon through the grain boundaries. Grain growth behavior of the 18CrNiMo7-6 steels during different pseudo-carburizing process was investigated to build the relationship between grain size and process parameters of time and temperature. On the other hand, a mathematical model including variables of process time and temperature was established to predict the critical volume fraction of carbides forming networks by estimating the grain size of the 18CrNiMo7-6 steel alloys in the carburizing process. And the critical carbon concentration for forming carbide networks could be further calculated through the thermodynamic simulation. The results indicate that carbide network could be restrained by adjusting the process parameters of temperature, time and carbon concentration before carburizing with reasonable accuracy.

Grain-to-Grain Interaction Effect in Polycrystalline Plain Low-Carbon Steel within Elastic Deformation Region.

A grain is surrounded by grains with different crystal orientations in polycrystalline plain low-carbon steel. The grain is constrained by its adjacent grains in the tension process. The interaction of the grain with the adjacent grains was investigated within the elastic deformation region. The following results have been obtained: (1) the Young’s modulus of a grain without consideration of grain-to-grain interaction is denoted as the inherent Young’s modulus; when the inherent Young’s modulus of a grain is equal to the Young’s modulus of the bulk material, there is almost no interaction between the grain and its adjacent grains; when a grain has a great difference between its inherent Young’s modulus and the Young’s modulus of the bulk material, its grain-to-grain interactions increase significantly; (2) the grain-to-grain interaction is mainly caused by the difference in the inherent Young’s modulus between the grain and its adjacent grains; the misorientation angle between the grain and its adjacent grains has almost no effect on the grain-to-grain interaction.

Effect of ultra-fast cooling on microstructure and mechanical properties in a plain low carbon steel

Effect of ultra-fast cooling on microstructure and mechanical properties in a plain low carbon steel

Effect of ultra-fast cooling on microstructure and mechanical properties in a plain low carbon steel

Effect of ultra-fast cooling on microstructure and mechanical properties in a plain low carbon steel

Study on the influence of temperature and vibration on indications of liquid penetrant testing of A516 low carbon steel

Abstract Liquid penetrant test (LPT) is one of the easiest and effective crack detection methods used in industries as it can be used to check a wide range of materials except porous materials. It is based on the capillary rise principle and used to detect surface discontinuities. In the present work, the effect of vibration and temperature on the effectiveness of Liquid Penetrant test on plain low carbon steel A516 Grade 70 is presented, which would give us a clear insight about the role of temperature and vibration on the indications produced in LPT. It is observed that at higher vibration and higher temperature combination, the indication is the largest.

Heterogeneous Distribution of Microstrain Evolved During Tensile Deformation of Polycrystalline Plain Low Carbon Steel

On a macroscale, the stress–strain curve of polycrystalline steel exhibits perfectly linear behavior in the elastic tension region. We observed that the strain distribution within grains is inhomogeneous in the range of the elastic deformation region. Microstrain concentrates at some local sites which are at and near the grain boundaries or in the interior of the grains. The microstrain is pseudo-periodic, and its period increases with applied stress, tending to approach the grain size. In addition to the tension-strain concentration, the compression-strain concentration is even present in the elastic region. The pseudo-periodic and inhomogeneous microstrain is attributed to the orientation heterogeneity of grains in polycrystalline steel.

A new 1.2 GPa-strength plain low carbon steel with high ductility obtained by SRDR of martensite and intercritical annealing

In the current research, a new technique to produce ultra-high strength ferrite-martensite dual phase (DP) steels with high ductility was developed for a low-cost plain low carbon steel with 0.16 wt% C. A combination of austenitization, water quenching, single-roll drive rolling (SRDR), and intercritical annealing at 830 °C for three different holding times was used. The microstructure and mechanical properties of DP samples were investigated. It was found that the martensite islands were very uniformly distributed in both RD–TD and RD–ND planes of DP steels due to performing the SRDR process. The average sizes of the martensite islands for the holding times of 1 (DP1), 5 (DP5), and 15 (DP15) min were 7.1, 11.6, and 15.8 μm, respectively. Also, the volume fraction of martensite was about 0.29, 0.47, and 0.68 for the DP1, DP5, and DP15 steels, respectively. With increasing the annealing time, the hardness, strength, and ductility increased. The DP15 showed a superior hardness (354.1 H V) strength (1172.5 MPa) and high ductility (13.5%). The martensite phase in the DP15 steel exhibited remarkable plastic deformation because its hardness decreased by reducing the carbon content and therefore the strain hardening ability of the martensite phase increased. Achieving superior strength with high ductility in the DP15 was attributed to the uniform distribution of martensite caused by the SRDR process. As the holding time increased to 15 min, two stages of strain hardening transformed to one stage owing to increasing the ability of strain hardening of martensite with lower carbon content. All DP steels mainly consisted of dimples indicating the ductile fracture, however, some cleavage facets were observed on the fracture surfaces. In DP1 and DP5 steels voids formed mainly by decohesion at the ferrite-martensite interface. With increasing the holding time to 15 min, the severity of decohesion decreased due to increasing the critical strain required for the formation of voids through interface decohesion.

Interaction between Microalloying Additions and Phase Transformation during Intercritical Deformation in Low Carbon Steels

Heavy gauge line pipe and structural steel plate materials are often rolled in the two-phase region for strength reasons. However, strength and toughness show opposite trends, and the exact effect of each rolling process parameter remains unclear. Even though intercritical rolling has been widely studied, the specific mechanisms that act when different microalloying elements are added remain unclear. To investigate this further, laboratory thermomechanical simulations reproducing intercritical rolling conditions were performed in plain low carbon and NbV-microalloyed steels. Based on a previously developed procedure using electron backscattered diffraction (EBSD), the discretization between intercritically deformed ferrite and new ferrite grains formed after deformation was extended to microalloyed steels. The austenite conditioning before intercritical deformation in the Nb-bearing steel affects the balance of final precipitates by modifying the size distributions and origin of the Nb (C, N). This fact could modify the substructure in the intercritically deformed grains. A simple transformation model is proposed to predict average grain sizes under intercritical deformation conditions.

Quality characteristics optimization in CNC end milling of A36 K02600 using Taguchi’s approach coupled with artificial neural network and genetic algorithm

This study investigates surface roughness and energy consumption in a CNC end milling of plain low carbon steel (mild steel) A36 K02600 using a carbide end mill cutter. Taguchi’s L9 orthogonal array was adopted for designing the experimental runs considering several process parameters viz. cutting velocity, Feed rate, spindle speed and cutting depth in order to study their influence on the quality characteristics. Optimal control parameter combinations for minimizing surface roughness and energy consumption were evaluated from signal to noise ratio. Analysis of variance revealed the contribution of control factors on the quality characteristics. Numerical predictive models using linear regression and artificial neural network were developed to envisage the responses accurately. Multi-objective Genetic Algorithm optimization was exploited in order to obtain a specific set of control parameter which would optimize both the responses simultaneously. This study concludes that spindle speed (68.24% contribution) and feed rate (92% contribution) are the most responsible variables for surface quality and energy consumption respectively. The outcome of artificial neural network model and genetic algorithm confirm that both quality characteristics can be optimized simultaneously and Taguchi’s robust design approach is a successful tactic for optimizing machining parameters to achieve desired surface quality at low energy consumption. Improvement in surface quality and reduction in energy consumption were found to be 27.79% and 30% respectively. Low carbon steel is extensively accepted by the industries for its wide variety of which make this study physically viable.

Effect of Pressure and DCT on Microstructure and Strength of Diffusion Bonds of PLCS-HSLAS

In the present study, eight pairs of samples were used in four groups for diffusion bonds of plain low carbon steel (PLCS) to high strength low alloy steel (HSLAS) so that, diffusion bonding was performed on two groups without pressure and two groups with the pressure of 2 MPa. Then, the groups alternatively underwent deep cryogenic treatment at -196°C (DCT) for 10 h; finally, all the groups were tempered at 150°C for 1 h. The results show under the non-pressure conditions, DCT had a positive effect on the bond strength because population density of carbide increased from 1400000 to 2300000 mm-2. While under the pressure conditions, the DCT led to 59% decrease in the bond strength because discontinuity on the bond metal increased from 7 to 15 percent. In addition, in the absence of DCT, applying pressure during diffusion bonding caused the strength of the bond to increase 25.8%, the reason of which could be attributed to the increase in the bond length from 160 to 220 μm, or the larger bond metal. It is found that discontinuity in bond metal, population density of carbides and bond's length are three main factors to affect the bond strength. The role of discontinuity in bond metal is negative while the others are positive. Finally, to increase bond strength just one of these two operations (pressure during diffusion bonding or DCT after diffusion bonding) must be used.

Distribution of Stress in Deformation Zone of Niobium Microalloyed Steel

Microalloyed steels today represent a significant part of total world production and processing of steel. Although widely used, there are scarce data on the stress distribution in the deformation zone of these steels. Research was carried out on two steel grades, both low-carbon structural steels with the same basic chemical composition, with one of them additionally microalloyed with niobium. Differences in the stress distribution in the deformation zone between two tested steels were continuously observed and measured using the methods of digital image correlation and thermography. It has been found out that niobium microalloyed steel has significantly more complex material flow and stress distribution in the deformation zone when compared to the plain low carbon steel.

Effect of Intercritical Heat Treatment on Mechanical Properties of Plain Carbon Dual Phase Steel

Mechanical properties of DP (Dual Phase) steels are greatly influenced by the microstructural features such as grain size, morphology and martensite volume fraction (V m %). These microstructural features can be altered by changing the soaking time and temperature within intercritical zone. Present study aims to study the effect of intercritical annealing temperature and soaking time on V m % and its effects on mechanical properties of plain low carbon steel grade (AISI 1020) steel having ferrite-martensitemicrostructure. Nine DP steel specimens with various amount of martensite were produced via intercritical heat treatment. Mechanical properties including TS (Tensile Strength), hardness and toughness were characterized and co-related with martensite volume fraction. It was found that increasing the intercritical annealing temperature and soaking time increases the V m %. The optimum TS and hardness were found at 64V m % and then decrease with further increase in V m %. The toughness was found to have linear relationship with V m %.

Effect of vacuum level on microstructure and mechanical properties of titanium–steel vacuum roll clad plates

Vacuum roll cladding (VRC) was used to bond pure titanium (Ti) plate to a plain low carbon steel (Q345) with the aim of obtaining a high-quality Ti–steel clad plate. The effect of interfacial compound on the microstructure and mechanical properties of Ti–steel clad plate was studied by electron probe microanalysis, scanning electron microscopy, X-ray diffraction and shear test. The clad plates were heated at 850 °C for 120 min and welded at different levels of vacuum. The results indicated that the cracked zone of the bonded interface decreased significantly with the increase in the level of vacuum during welding. Welding at atmospheric pressure, the randomly distributed TiN damaged the continuity of TiC and the uniformly diffused region of Ti and Fe at the bonded interface, while welding in vacuum of 1 × 10−2 Pa, maximum shear strength of 298 MPa was obtained because of the decrease in TiN content.

Experimental Investigation of the Effect of Quenching Temperature on Fatigue Life of Plain Low-Carbon Steel

This study presents an experimental study of the effect of quenching temperature from the inter-critical region (a the standard high speed rotating beam test was adapted for this purpose. It was found that there is a direct relation between quenching temperature from the inter-critical region and fatigue life; the fatigue life can be increased up to 625% by increasing the quenching temperature to 850°C. This finding is important as it enhances much the ability of the AISI 1010 steel to resist fatigue failure.

Bainite Formation in Low Carbon Steel by Thermomechanical Control Process

Continuous cooling transformation (CCT) behavior of plain low carbon steel was investigated. Based on the obtained results, allotriomorphic ferrite and high volume fraction of bainite structure has been obtained by controlled deforming in the finish rolling temperature (higher than Ae3) and controlled cooling. The formation of bainite would lead to an enhanced strength of the low carbon steel and the steel possesses a good combination of strength and ductility.