Carbon Steel Grades Research Articles

Express evaluation of welded joints cool resistance

Low-temperature instrumented indentation tests of welded joints are carried out. The effect of metal cooling on indentation diagrams and metal hardness is investigated. Impact strength tests with a gradual decrease in temperature with the identification of the cold brittleness threshold and determination of the critical brittleness temperature for several structural steels are performed. For an express evaluation of a metal cold resistance, the parameter γ is proposed, which is equal to the ratio of hardness at a given low temperature to hardness at room temperature. The relation between the parameter γ and the temperature coefficient of hardness, which is included in the equation describing low-temperature dependence of hardness, is established. For several grades of carbon and alloy steels, the relation between the parameter γ and the critical brittleness temperature T0.4, determined by the criterion value of impact strength KCV = 0.4 MJ/m2, is established. For welded joints obtained by electron beam welding and arc welding, the values of T0.4 are determined by the parameter γ in various local zones, including parent metal, heat-affected zone and weld metal. The possibility of establishing the acceptable operation temperature of welded joints using the obtained distributions of the critical brittleness temperature T0.4 is shown.

Fabrication of clean cut surface on high strength steel using a new shaving die design

A shaving process is commonly applied to achieve a smooth cut surface thorough the workpiece thickness and a square cut-edge, also known as a finishing operation. However, this process is rarely successful for high-strength steel sheets, which is a major problem. In the present study, finite element method (FEM) simulation was used to clarify the main causes of this problem by comparing the shaving mechanisms between medium carbon steel grade SPCC (JIS) and high-strength steel grade SPFH 590 (JIS). Results show that in the case of SPFH 590 based on material flow, stress distribution, and strain distribution analyses, the shaved chip was difficult to form by sliding along the punch face. Moreover, the tensile stress generated in the shearing zone was increased and readily generated cracks. The shaving process was developed in the present study by generating the cutting-edge angle and rake radius on the punch. The cutting edge angle was designed to generate high compressive stress in the cutting-edge vicinity and shearing zone, and the rake radius was designed to tear a shaving allowance off and move it along the rake radius instead of moving downward along the punch movement direction, thereby decreasing the tensile stress in the shearing zone. Under these mechanisms, the increases in the generated tensile stress in the shearing zone could be delayed, and cracks could thus be prevented. The effect of the punch geometry on the cut surface characteristics and cutting forces were also investigated. Laboratory experiments were performed to validate the FEM simulation results. Experimental results agreed well with the FEM simulation results. Therefore, a smooth cut surface thorough the workpiece thickness of high-strength steel sheets could be successfully achieved by using the developed shaving process.

ДОСЛІДЖЕННЯ ВПЛИВУ ШВИДКОСТІ ОХОЛОДЖЕННЯ ПРИ ЗАТВЕРДІННІ БЕЗПЕРЕРВНОЛИТОЇ ЗАГОТОВКИ НА ОСОБЛИВОСТІ ДЕНДРИТНОЇ СТРУКТУРИ ВУГЛЕЦЕВОЇ СТАЛІ

The analysis of the formation process of the cast structure of carbon steel grade EA1N (EN 13261: 2009 + A1: 2010 (Е)) after the completion of its crystallization with a change in a wide range of metal cooling rate during solidification of a continuously cast billet (ССB) with a diameter of 470 mm has been carried out. The effect of the cooling rate during the solidification of ССB Ø 470 mm on the parameters of the chemical heterogeneity of the distribution of silicon and manganese in the microstructure of carbon steel has been shown. It has been determined that the effect of the metal cooling rate during the solidification of the investigated CCB on the size of dendritic crystals is described by the inversely proportional relationship: у = 510,85 х-0,156. With a change in the cooling rate of the metal during solidification from 106 до 1 ℃ / min, the size of the dendrites in the direction from the surface to the central layers of the CCB Ø 470 mm increased by ~ 8 times, and the density of the dendritic structure of carbon steel EA1N decreases by 64 times. In this case, the nature of its dependence on the intensity of heat removal is the opposite nature of the change in the size of dendrites. It has been established that by varying the cooling rate in the range 1 – 106 ℃ / min, one can achieve a significant change in the average size and density of dendritic crystals while maintaining the constancy of the volume fraction of segregation areas of silicon and manganese ~ 23% in carbon steel (~ 0.4 % wt. C). The results of X-ray spectral analysis of samples of ССB Ø 470 mm made of carbon steel grade EA1N showed that the maximum content of silicon and manganese is characteristic of the former spaces between the first-order dendritic branches, their minimum content is for the former dendritic branches. At the same time, the amount of these elements in steel microvolumes, which are the former spaces between the second-order dendritic branches, is on average 50 % more than in the former dendritic branches. It has been determined that in the entire investigated range of cooling rates 1 – 106 ℃ / min, the coefficients of dendritic segregation КдI and КдII of silicon and manganese change insignificantly and amount to 1.8-1.9 and 1.5 for КдI and КдII, respectively. In this case, the values of the coefficients КдI and КдII for both elements are practically constant in both pearlite and ferrite. It has been proven that both silicon and manganese have high diffusion mobility only at sufficiently high temperatures, when steel is in a solid-liquid state. Based on the results of X-ray microanalysis, it has been established that the heterogeneity of the distribution of chemical elements, which is formed as a result of dendritic segregation of silicon and manganese, is the primary and constant component of the microstructure of carbon steel.

Low-cycle fatigue of stainless steel plates under large plastic strain demands

The low-cycle characteristics of structural subassemblies under large cyclic strains play an important role in contemporary seismic design. Obtaining these characteristics can lead to an understanding of a structure's degradation and nonlinear response behaviour, and can serve as a basis for developing efficient numerical models to predict seismic collapse mechanisms. The austenitic stainless tubular grade of steel has shown promise in terms of strain hardening character, structural overstrength and ductility, but existing test data is limited or constrained to small plastic strains, which is hardly useful in earthquake engineering applications. This article presents an experimental study designed to characterize the hysteresis of stainless steel plates under large inelastic cyclic strains and to assess their potential use in buckling-restrained brace components for seismic applications. Axial coupons machined from austenitic Grade 304L stainless steel and from regular carbon steel Grade 350WT were tested under uniaxial tensile loading, as well as constant and variable strain amplitude cyclic loadings. Results of the uniaxial tests confirmed higher ductility and strain hardening capacity for the stainless steel plates compared to those of carbon steels. These results were subsequently used to validate a novel technique based on image analysis to derive the true stress-strain characteristics. The stainless steel Grade 304L plates showed higher cyclic hardening but shorter low-cycle fatigue life compared to the carbon steel. Parameters for representing the low-cycle fatigue behavior of these materials, useful for developing a cyclic plasticity hardening numerical model, were derived from the test data.

Development and testing of a steel regulating thermostatic valve

A steel thermostatic valve group has been designed from a more affordable, cheaper domestic material - structural carbon steel grade PS08, which makes it possible to improve the manufacturability, installation, ease of the developed product operation, and reduce production costs. As a prototype, bronze thermostatic valves with threaded connections of foreign manufacturers were used, other geometrical parameters were determined by the production manufacturability. The results of the thermostatic valve steel body new design studies for two-pipe water heating systems are presented. A 3D model was built using the Solidworks design and graphics package, optimizing the geometric, mass, and strength valve characteristics. The application Solidworks Flow Simulation calculated the pressure loss in the digital 3D-model of the valve, its hydraulic characteristic was calculated. According to the numerical experiment results, a physical model of the valve group was manufactured and tested on a pouring stand. A comparison of the hydraulic characteristics of the digital and physical models was made, improvements to the design were made, and the purity of the internal surfaces was improved. A series of tests was carried out to determine the hydraulic characteristics for the regulating mechanism various values adjustment. In the heating season 2018 - 2019, full-scale tests were carried out at the operating facility with the installation of a valve and a thermal head on experimental convectors. The internal air average temperature measurements showed that the air temperatures in all the rooms with the same settings of the thermostatic head were within the acceptable limits. Therefore, the control quality of the pilot valve was adequate. The experimental thermostatic valve group was launched into small-scale production for the field tests in the buildings for various purposes.

Analyzing the Features of Non-Metallic Inclusion Distribution in Ø410 mm Continuously Cast Billets of Low Carbon Steel Grades

The paper reports findings on the morphology of non-metallic inclusions in low carbon pre-peritectic and peritectic steel grades used for the fabrication of seamless pipes. It is demonstrated that the distribution of non-metallic inclusions over the cross section area of continuously cast billets is of a step-like nature conditioned by the features of billet solidification. In all the steels analyzed the non-metallic inclusions are presented by oxides, sulfides and complex oxi-sulfides not larger than 2 μm.

Evaluation of a High-Frequency Induction Heating Assisted Friction Stir Welding Process on Carbon Steel Sheets

Friction stir welding of carbon steel causes tool wear and system deformation issues because of its relatively high strength compared to aluminum. As a countermeasure, additional high-frequency induction heating is suggested to solve this problem. An inline high-frequency induction heating assisted friction stir welding process was studied on 450 MPa and 980 MPa grade carbon steel sheets. As a pre-experiment, the heating performance of the high-frequency induction heating system was quantified. Then the effective welding speed range, vertical load history, and weldment performance were investigated to evaluate the characteristics of the process. Those results were compared with a conventional friction stir welding process conducted under equivalent process conditions. For the 440 MPa steel, about 40% faster maximum welding speed was achieved by applying the 4 kW induction heating. No tensile strength degradation of the weldment was found. Also, the maximum vertical load was decreased by 26% compared to the conventional friction stir welding process. No significant degradation of hardness was observed in the welds on 440 MPa and 980 MPa steel. Key words: High-frequency induced heating, Friction stir welding, Carbon steel, Welding speed, Vertical load

Investigation of artificial pit growth in carbon steel in highly alkaline solutions containing 0.5 M NaCl under oxic and anoxic conditions

We report an investigation of artificial pit growth (APG) in P355QL2 Grade Carbon Steel in the highly alkaline, synthetic concrete pore solution [sat. Ca(OH)2/NaOH of pH of 13.5] + 0.5 M NaCl under both “oxic” and “anoxic” environmental conditions. The corrosion potential of the external surface, as well as the coupling currents flowing between the external surface and the pit tip and pit walls of the segmented carbon steel specimens under the selected conditions, were measured as a function of time and pit aspect ratio. The findings were interpreted in terms of the Differential Aeration Hypothesis (DAH).

The semiconductor properties of passive films and corrosion behavior of stainless steel reinforcing bars in simulated concrete pore solution

The vulnerability of concrete reinforcing steels to corrosion when depassivation occurs, typically in the presence of chloride, makes it important to understand the nature of the steels’ passive films. In Part I of the study, electrochemical techniques and Mott–Schottky analysis were used to investigate these films formed on five different grades of stainless steel and carbon steel reinforcing bars exposed to simulated concrete pore solution. The influence of the steel composition and surface finish on Mott–Schottky plots and the electronic properties are discussed in relation to the steels’ corrosion resistance. A p-type semiconductor behavior was observed in the stainless steel alloys in the cathodic potential regions and an n-type in the anodic potential regions. The n-type behavior is similar to that observed in the carbon steel. The electronic and electrochemical properties of the austenitic grades were superior to the duplex grades. The molybdenum-containing grades, 316LN and 2205, did not show the expected superior properties compared to molybdenum-free grades, 304L and 2304. Also, the replacement of nickel by manganese in the 24100 alloy was not found to be detrimental. The as-received bars showed electronic and electrochemical properties that are more realistic to field conditions than those of the polished cross-sections.

Evaluation of combined heat treatment techniques of testing hardness and tensile strength of mild carbon steel commonly used in Nigeria

This study investigated effect of combined heat treatment on the hardness and tensile strength of 0.25 - 0.35 grade of medium carbon steel. Heat treatment at 900 °C for four hours was done and six specimens of each were then quenched in water. Results showed that the hardness and tensile strength ranged from 113.7 to 184.4 HB and from 383.84 to 621.2 N/mm 2 , respectively, for hardening temperature from 700 to 950 °C; and were from 180.2 to 125.5 HB and 594.7 to 4143 N/mm 2 , respectively, when the steel was quenched from 900 °C for tempering temperatures from 250 to 600 °C. The result of tempering (from 250 to 600 °C) when previously quenched (from 850 °C) steel showed decreasing values of hardness (from 400 to 248 HB) and of tensile strength (from 1320 to 819 N/mm2). The microstructure of the normalized sample was observed to be finer and more homogenized than the one observed in the as-rolled condition of the sample. This invariably led to the higher hardness and tensile strength values recorded. Keywords: Hardness, Tensile strength, quenching, microstructure, ferrite

Carbon steel and stainless steel bolted connections undergoing unloading and re-loading processes

ABSTRACT A total of 50 bolted connections of carbon steel and stainless steel subjected to monotonic loading and cyclic loading conditions were investigated. The connection specimens were fabricated from carbon steel grades 1.20 mm G500 and 1.90 mm G450, as well as cold-formed stainless steel types EN 1.4301 and EN 1.4162 with nominal thickness 1.50 mm. In the monotonic tests, the specimens were tested under a constant loading rate by the displacement control test method, while in the cyclic tests, the specimens having the same dimensions as those in the monotonic tests were subjected to loading, unloading and re-loading processes, where displacement control and load control test methods were used. The results obtained from the cyclic tests were compared with those obtained from the monotonic tests. It was found that the ultimate loads obtained from the cyclic tests were, on average, larger than those obtained from the monotonic tests for carbon steel bolted connections; this was in contrast with the compared results for stainless steel bolted connections. The elongations corresponding to the ultimate loads obtained from the cyclic tests were, on average, larger than those obtained from the monotonic tests for both carbon steel and stainless steel, which may indicate that the loading processes in the cyclic tests generally delayed the bolted connection specimens from reaching the ultimate loads. Generally, the failure modes in the cyclic tests were consistent with those in the monotonic tests for the same specimen series, where the specimens mainly failed in the connection plate bearing.

Effect of pH in SRB (ATCC 7757) Growth for Oil and Gas API X 70 Steel Pipes

In the oil and gas industry, pipeline is the major transportation medium to deliver the products. According to [1] containment of pipeline loss to indicate that corrosion has been found to be the most predominant cause for failures of buried metal pipes. MIC has been identified as one of the major causes of underground pipeline corrosion failure and Sulphate Reducing Bacteria (SRB) are the main reason causing MIC, by accelerating corrosion rate. The objectives of this study is to study the SRB growth, Desulfovibrio desulfuricans ATCC 7757 due to pH and determine the optimum value controlling the bacteria growth on the internal pipe of carbon steel grade API X70. The result shows that the optimum SRB growth is at range pH 5-5 to 6.5 and the exposure time of 7 to 14 days. At pH 6.5 the maximum corrosion rate is 1.056 mm/year. Corrosion phenomena on carbon steel in the study proven had influence by pH and time. From this result pitting corrosion strongly attack at carbon steel pipe. In the future project, it is recommended to study the effect of different pipe location for example the pipeline under seawater.

Polyaniline-modified graphene oxide nanocomposites in epoxy coatings for enhancing the anticorrosion and antifouling properties

We report on the anticorrosion and antifouling properties of epoxy-based polyaniline (PANI)–graphene oxide nanosheets (GONs) paint coatings. PANI-based nanocomposites with different fractions of GONs were synthesized by an in situ polymerization process. Well-dispersed GONs were prepared using a modified Hummers’ method in the presence of (NH4)2S2O8 as an effective oxidant. We employed a spontaneous in situ polymerization at a constant temperature of 0°C using an ultrasonic bath to produce homogenous PANI-GON nanocomposites as characterized by X-ray diffraction (XRD), Fourier transfer infrared spectroscopy (FTIR), and field-emission scanning electron microscopy (FESEM) techniques. The nanocomposites were incorporated into an epoxy resin with different fractions to form epoxy/PANI-GON paint coatings. The epoxy/PANI-GON dip coated on a carbon steel (grade St-37) substrate exhibited significant improvement of the anticorrosion and antifouling properties. Epoxy-12 wt% PANI-GON coating revealed the highest corrosion resistance of 2.70 × 106 Ω cm2 after 192-h immersion in saline water measured by electrochemical impedance spectroscopy (EIS) technique. Such high corrosion resistance was attainable by inhibiting the diffusion process against the corrosive environment. Furthermore, higher protection against fouling was observed for epoxy 6 and 12 wt% PANI/GON as the most efficient antifouling composite coatings.

Experimental investigation of carbon steel and stainless steel bolted connections at different strain rates

A total of 36 carbon steel and stainless steel bolted connections subjected to shear loading at different strain rates was experimentally investigated. The connection specimens were fabricated from carbon steel grades 1.20 mm G500 and 1.90 mm G450, as well as cold-formed stainless steel types EN 1.4301 and EN 1.4162 with nominal thickness 1.50 mm. The connection tests were conducted by displacement control test method. The strain rates of 10 mm/min and 20 mm/min were used. Structural behaviour of the connection specimens tested at different strain rates was investigated in terms of ultimate load, elongation corresponding to ultimate load and failure mode. Generally, it is shown that the higher strain rate on the bolted connection specimens, the higher ultimate load was obtained. The ultimate loads were averagely 2-6% higher, while the corresponding elongations were averagely 8-9% higher for the test results obtained from the strain rate of 20 mm/min compared with those obtained from the lower strain rates (1.0 mm/min for carbon steel and 1.5 mm/min for stainless steel). The connection specimens were generally failed in plate bearing of the carbon steel and stainless steel. It is shown that increasing the strain rate up to 20 mm/min generally has no effect on the bearing failure mode of the carbon steel and stainless steel bolted connections. The test strengths and failure modes were compared with the results predicted by the bolted connection design rules in international design specifications, including the Australian/New Zealand Standard (AS/NZS4600 2018), Eurocode 3 - Part 1.3 (EC3-1.3 2006) and North American Specification (AISI S100 2016) for cold-formed carbon steel structures as well as the American Specification (ASCE 2002), AS/NZS4673 (2001) and Eurocode 3 - Part 1.4 (EC3-1.4 2015) for stainless steel structures. It is shown that the AS/NZS4600 (2018), EC3-1.3 (2006) and AISI S100 (2016) generally provide conservative predictions for the carbon steel bolted connections. Both the ASCE (2002) and the EC3-1.4 (2015) provide conservative predictions for the stainless steel bolted connections. The EC3-1.3 (2006) generally provided more accurate predictions of failure mode for carbon steel bolted connections than the AS/NZS4600 (2018) and the AISI S100 (2016). The failure modes of stainless steel bolted connections predicted by the EC3-1.4 (2015) are more consistent with the test results compared with those predicted by the ASCE (2002).

Residual stresses prediction on clad pipeline girth welds through numerical simulation

It is generally known that different welding processes induce residual stresses into the weld joints, which may have a negative impact on fatigue and durability or other aspects of the in-service performance. This effect is of high interest in offshore pipeline girth welds, since they are typically not subjected to PWHT (Post Weld Heat Treatment). Although different methods of experimental measurements of the residual stresses are available their application in real context is extremely challenging or not convenient for several reasons, as a matter of example often the weld location and surface can make it problematic to access with the equipment, the execution of the measurements in a true non-destructive way is not feasible or more simply the execution of weld samples with very expensive equipment as the one used in offshore pipelines is not economical. In addition to this the stress field within or in the proximity of welds is of very complex and variable character and there appears a high level of plasticity, which makes the interpretation of local experimental measurements very difficult. For these reasons the prediction of residual stresses using numerical simulation of the welding process is today a very interesting and cost-efficient alternative. In this paper authors present the work where thermo-metallurgical and mechanical analysis of the thermal effects of the welding process using FEM based solver SYSWELD was done in order to determine residual stress field after girth welding of pipes made of carbon steel grade API 5LD X65 with internal alloy 625 cladding. The simulated process involves the execution of several external weld passes in gas metal arc welding technology and root re-melting with plasma arc welding process. Further variant simulations of the process were executed in order to evaluate the impact on residual stress field changing selected process parameters, namely the welding sequence. The use of numerical simulation finally allowed a deeper understanding of residual stresses field generation phenomena for the specific and quite complex welding process conditions.

Corrosion of High Carbon Steel by Bacteria under Aerobic and Anaerobic Conditions

The role of microbes in the corrosion of metals is due to the chemical activities (metabolism) associated with the microbial growth and reproduction. A lot of researches have shown that enormous loss of resources and even lives has been experienced in many countries of the world due to corrosion. There is therefore need to device a means of combating this menace so as to save different countries of the world including Nigeria the cost encured due to corrosion. This research has helped to determine the role of bacteria in the corrosion of high carbon steel under aerobic and anaerobic conditions was investigated using sulphate reducing bacteria and other aerobes. A sample of high carbon steel grade of chemical composition: 96% iron (Fe), 1.08% carbon (C), 0.349% silicon (Si), 0.841% manganese (Mn), 0.005% phosphorus (P) and 0.005% sulphur (S), was obtained in the form of steel plate. Eighteen (18) samples of the high carbon steel were prepared. Standard microbiological methods were used to isolate aerobic and anaerobic bacteria isolates. The microbes isolated from the soil included; aerobes (Bacillus species, Pseudomonas species) and anaerobes (Desulfovibrio species, Thiobacillus species). The role of bacteria in the corrosion of high carbon steel was estimated using the weight loss technique and the electrochemical potential measurement technique. Eighteen samples of a high carbon steel of known compositions were exposed to sulphate reducing bacteria under different environments (aerobic, anaerobic and control). The physical and chemical changes were examined and monitored on weekly basis for six weeks. It was observed that the coupons immersed in the media with sulphate reducing bacterium underwent fast activation and numerous corrosion sites were formed on the surfaces. The average corrosion rate for six weeks (42 days) period of time as determined by the weight loss method and electrochemical testing were found to be 0.0004595 mm/year, -0.712 mV in aerobic environment, 0.0005646 mm/year, -0728 mV in anaerobic environment and 0.0004458 mm/year, -0702 mV in the control or reference environment (distilled water environment). High carbon steel was found to corrode more only in the anaerobic environment. In view of this, high carbon steels were found to be relatively more corrosion resistant than mild and medium carbon steels and may be suitable for application in industries such as the petrochemical industry. Therefore, treating the environment with chlorine but with caution as solutions of chlorine gas in water is corrosive to steels while the use of bactericides or biocides to arrest the action of microbes is important.

Forecasting the mean flow stress of carbon and low-alloy steels in hot rolling on a strip mill

The effectiveness of the initial setup of the mill stands depends on the accuracy of the calculation of the mean flow stress of the rolled metal, the value of which is determined not only by the deformation parameters, but also depends on the chemical composition of the steel and the structural transformations of the rolled metal. This article proposes a mathematical model for the prediction of the mean flow stress of carbon and low-alloy steels during hot rolling on a strip mill, which allows to take into account, along with the deformation parameters, the content of chemical elements in the steel and the processes of recrystallization of the metal during deformation and during inter-pass times. The adequacy of the model was checked by comparing the results of the calculation of mean flow stress with the experimental data obtained by rolling of 100 strips 2-12 mm thick of 16 grades of carbon and low-alloy steels on a broadband mill 2000 NLMK. The influence of dynamic, metadynamic and static recrystallization on the mean flow stress of carbon and low-alloy steels in the mill stands is estimated. It is shown that taking into account the processes of recrystallization of the deformed metal can significantly improve the accuracy of the prediction of the mean flow stress.

Study on cyclic constitutive model and ultra low cycle fracture prediction model of duplex stainless steel

This paper calibrates micromechanical fracture models for duplex stainless steel in order to study its fracture behaviour under seismic loading, characterized by large strain ultra low cyclic conditions. In this investigation, smooth round bars and notched round bars were subject to monotonic and cyclic loading. Monotonic and cyclic loading constitutive models were calibrated against smooth round bar test tests. The fracture toughness parameters of the void growth model (VGM), the stress modified critical strain (SMCS) model and the cyclic void growth model (CVGM) were calibrated against the notched round bar tests. Furthermore, the skeleton curve, hysteresis loop and characteristic length of duplex stainless steel were also investigated. The test results indicate that duplex stainless steel exhibits cyclic hardening behaviour under cyclic loading, and the subsequent numerical simulation successfully captured this behaviour. The toughness parameters of duplex stainless steel are generally higher than those for carbon steel grades Q345B and Q460, which demonstrates that duplex stainless steel has better toughness. All the experimental results provide useful data for the prediction of ultra low cycle fatigue (ULCF) fracture of duplex stainless steel.

Study the effect of cooling medium on the torsion resistance and hardness of medium carbon steel

In this paper, the effect of the cooling medium on the strength of torsion and hardness is discussed. The specimen used in this study is of medium carbon steel grade. The carbon percentage was determined as 0.55% C through the Arl spectroscopy instrument. The specimen dimension is 6 mm in diameter, gauge length is 76 mm and the total length is 144 mm. Different cooling mediums such as water, air, furnace atmosphere and oil were used to determine the effect of cooling speed on mechanical properties, specifically the torsion strength and hardness. In all treatments, the holding period was 30 minutes. From the results, cooling in the furnace atmosphere had the greatest impact on the resistance of the torsion of the carbon steel from other cooling methods. The non-heat-treated sample was the least resistant between the samples whereas the water-cooled sample had the highest in terms of their scratch resistance according to the results of the hardness device.

ANALISIS PERBANDINGAN KEKERASAN PERMUKAAN POROS AXLE SHAFT JENIS MATERIAL S-43 YANG DILAKUKAN DENGAN PROSES INDUKSI HARDENING PADA MESIN 12-9 B “KORA NETUREN”

Hardening process is the process of hardening in a material heated above the critical temperature and then cooled quickly (quenched) to reach room temperature in order to improve hardness and strength of a material. Hardening process carried out on all the tools and some equipment or machine parts that have a major benefit is to obtain a higher hardness. This research was conducted on 447 SNCM alloy steel which is a medium carbon steel grade that is equal to 0:30 to 0:38%. This type of steel can be hardened by heat treatment process that is by heating the steel at a temperature of 500 o C, for 1 hour as the preheating temperature (preheated). Then proceed to the process of hardening, namely austenising temperature with 900 o C with holding time 2 hours and cooled with oil and then water in tempering with holding time 1 hour at 300 o C, 400 o C and 500 o C. From research result obtained using the Vickers hardness values that increase occurred in materials that undergo a process of hardening at 900 o C cooling using water media, whereas the lowest hardness value occurs in the original material.