A steel of grade C55 with a bright surface and homogeneous mechanical properties, and a method for obtaining this steel.

Abstract

The invention relates to a steel of grade C55 with a bright and oxide-free surface, suitable for use in applications requiring high strength and surface quality, such as automotive, machine manufacturing, spring and blade production, and a method for obtaining this steel.

Description

C55 HAS A GLOSSY SURFACE AND HOMOGENEOUS MECHANICAL PROPERTIES. A STEEL BELONGING TO A HIGH-QUALITY CLASS AND THE PROCESS OF OBTAINING THIS STEEL. A METHOD TECHNICAL FIELD The invention is suitable for applications requiring high strength and surface finish, such as in the automotive, machinery manufacturing, spring and blade production industries. Suitable for use in application areas requiring high quality, with a bright and oxide-free surface texture. possessing a steel classified as C55 quality grade and a method for obtaining this steel. It is related. PREVIOUS TECHNIQUE C55 steel grade has a medium-high carbon content (0.52–0.60% C by weight); it is heat-treatable. It belongs to the group of biodegradable carbon steels. These steels have high tensile strength, It stands out with its hardenability and wear resistance properties and is used in automotive parts, springs, In the production of components subjected to mechanical stress, such as blades, shafts, and gears. It is widely used. C55 grade steels generally conform to EN 10083-2 and EN standards. It is defined under the 10132-4 standards and is available in hot or cold rolled form. It is available. Thanks to its low phosphorus (P) and sulfur (S) content, it provides satiety and The machinability balance is maintained through heat treatments such as annealing, quenching, and tempering. By controlling the microstructure, ferrite-pearlite or martensitic structures can be obtained. This Therefore, C55 grade steels are very versatile in terms of strength and surface quality. They are considered a group of materials that are adaptable to various applications. One of the main technical problems encountered during the production of C55 grade steels. The first is surface oxidation and scale residues. The high carbon content of these steels, This causes an oxide layer to easily form on the surface during the rolling and annealing stages. This is especially true in the pickling process step of the current technique, where 10% by weight is used. A 12% HCl solution is not able to completely remove this oxide layer, leaving some on the surface. It leaves behind microscopic scale residues and oxidized areas. These residues, This leads to the formation of microcracks and roughness on the surface during subsequent rolling steps. Classification: General Classification: Public 2 This leads to an increase in oxide residues. Furthermore, these types of oxide residues negatively affect the surface gloss of the product. It affects and prevents adhesion in surface treatments such as galvanizing, painting or coating. This can cause surface problems. Therefore, in C55 grade steels, the surface... Making it oxidation-free and homogenous presents a significant technical challenge. Another technical problem is the measurement of the mechanical properties of steels in this grade. The lack of homogeneity observed throughout is the issue. This is applied in production lines using current technology. Single-stage annealing process allows sufficient carbon diffusion in high-carbon steels. It is unable to provide a balanced distribution of ferrite and pearlite phases throughout the steel. This leads to differences in distribution, especially in the inner and outer layers of large coils. Due to different thermal conductivity rates, the homogeneity of the microstructure is disrupted, which reduces the tensile strength. and causes variations in elongation values. This problem is particularly prevalent in cold weather. Out-of-tolerance mechanical behaviors in shaping and tempering processes after rolling and This leads to surface undulations. Minimizing such differences during production is crucial. This is critical in C55 grade steels, where high strength and surface quality are targeted. It is important. Another major challenge encountered in the production of C55 grade steels is cold rolling. Uncontrolled deformation during processing and thickness tolerance problems are among the issues. Reduction ratios of 30–50% applied in traditional rolling lines, especially This is insufficient to achieve the desired level of grain fineness in high-carbon steels. However, increasing the reduction ratio increases the internal stresses of the material. This increases the risk of cracking. Additionally, the cooling used during rolling... imbalances in lubrication conditions, surface roughness and thickness variations This situation causes the formation of a reverse rolling mill, especially one operating at high speeds. This leads to an increase in thickness tolerance zones and surface smoothness in the systems. This leads to its deterioration. In addition, annealing atmosphere and temperature control are also important in the production of C55 grade steels. This is another crucial technical problem. Inert or nitrogen-based solutions are commonly used in industry. Since mixed atmospheres cannot ensure the complete removal of oxygen, annealing Afterwards, oxidation or dulling occurs on the surface. Annealing temperature When homogeneity is disrupted, grain growth and carbon segregation occur in the material structure. This is observed, which leads to undesirable imbalances between tensile strength and ductility. Classification: General Classification: Public 3 This precision in the annealing process opens up the surface of high-carbon steels. This is one of the most critical stages that directly affects its quality. Finally, surface roughness control and residue removal are performed during the tempering and rolling stage. Stress relief cannot be adequately achieved with the methods currently available in the field. C55 Standard tempering forces in the range of 100–150 tons applied to grade steels, It is unable to completely correct the micro-undulations on the surface, and at the same time, it is not sufficient. It is unable to provide voltage relief. This situation results in a lack of surface gloss in the final product. This can lead to differences and the initiation of microcracks. Also, after lubrication... Because surface homogeneity cannot be fully achieved, the products cannot be subjected to further processing (e.g. suitability (cold forming or surface coating) is decreasing, the final quality standard It cannot be achieved. As one of the studies carried out in this technical field, publication number US3630723 A1 The patent application relates to machinable alloy steels. Specifically, the patent application... S20C, S30C, as defined according to Japanese Industrial Standards (JIS) or SAE standards, Carbon steels such as S45C and S55C, as well as Ni-Cr, Cr-Mo, and Cr-based machinable steels. This includes steels. These steels contain specific percentages of carbon (0.20–0.56% by weight), It contains silicon (0.24–0.33% by weight) and manganese (0.35–0.78% by weight). Alloy steel also contains nickel, chromium, and molybdenum. The main innovative aspect of the invention is... These steels contain oxide inclusions and a certain amount of calcium. One of the reasons is that their processability has been improved thanks to this contribution. Another aspect of patents is... Calcium and oxide inclusion control in machining operations (e.g., turning, It is aimed at developing steels that facilitate milling and have a high surface quality. Another study conducted in this technical field is published under the publication number JPH06306654 A. The patent concerns the degreasing of steel strips used in a continuous annealing line and It relates to a method for cleaning. Alkaline is used in traditional methods. Base-based degreasing solutions leave residue on the surface, causing quality defects after annealing. However, this also creates high costs in wastewater treatment. In this patent, however... Before using alkaline solutions, the steel strip is first pre-washed with high-pressure hot water. It is subjected to this process, then cleaned by brushing under hot water, and finally again... Final cleaning is performed by spraying high-pressure, oil-free hot water. This ensures a thorough surface treatment. Classification: General Classification: Public 4 Effective degreasing is achieved without leaving residue, and pattern formation occurs after annealing. This prevents and significantly reduces wastewater treatment costs. In conclusion, surface oxidation and microstructure problems occur in the industrial production of C55 grade steels. Lack of homogeneity, internal stresses due to deformation, thickness tolerance defects and related technical problems such as insufficient brightness are experienced. The problems arise because, although the products have the same chemical composition, the production parameters are precise. When not controlled, this leads to instability in the final product quality. A BRIEF DESCRIPTION OF THE INVENTION During the production of steels included in the C55 grade, especially surface quality and microstructure are considered. Various technical problems are encountered in terms of homogeneity and mechanical stability. The high carbon content of these steels causes surface changes during the rolling and annealing process steps. This leads to oxidation and the formation of scale deposits, which in turn increases surface roughness. This increases the risk and causes adhesion problems in subsequent processes. Furthermore, the existing full annealing, rolling and tempering conditions applied in production methods As a result of not being able to optimize it, the tensile strength and elongation values ​​are measured in meters. Differences are observed throughout. This affects the mechanical stability of the steel and the surface. It negatively affects its integrity. Accordingly, the invention covers the treatment of surface oxidation and scaling in the production of C55 grade steels. remnants, internal structural instability, and variability in mechanical properties throughout the measurement. In order to eliminate problems such as these, chemical and thermal processes in the production line... It involves a method in which mechanical processes are optimized in a harmonious way. The invention relates to cold rolling, pickling, and other processes, particularly in steels with high carbon content. By interactively controlling the annealing and tempering stages, the surface is... It ensures that the surface is oxide-free, homogeneous, and shiny. It also provides tensile strength. Maintaining fundamental mechanical properties such as strength and elongation throughout the production process It aims to achieve this. In this context, the invention addresses processes that are dealt with separately in classical production methods. the steps should be considered in relation to each other, each process step being linked to the next It envisages optimization in a way that will ensure internal structural integrity. Thus, the surface reduction of roughness, complete removal of scale layer, deformation Eliminating internal stresses caused by warping and improving the brightness, homogeneity, and strength of the final product. Classification: General Classification: Public 5 This makes it possible to achieve a high quality standard in this regard. This invention... this approach addresses the long-standing surface quality issues encountered in the production of C55 grade steels. By providing a systematic solution to mechanical instability problems, existing techniques It aims to provide improvements in areas where it is lacking. DETAILED DESCRIPTION OF THE INVENTION In this detailed description, the subject of the invention is high-carbon steels belonging to the C55 grade class. improved in terms of surface quality, oxidation-free and mechanical stability during production It is related to a method for obtaining steels with specific properties and only with examples that will not have any limiting effect on a better understanding of the subject It is explained. The primary goal of this invention is to ensure the optimum chemical composition of the steel to be produced. The aim is to create a steel that is classified as C55 grade and has a medium-high carbon content. It belongs to the group of malleable carbon steels with the following composition. Invention The chemical composition included will maintain the stability of the microstructure under heat treatment, and It has been determined in a way that will provide the desired homogeneity in terms of surface quality. Within this scope, the carbon content for steel is determined to be between 0.52% and 0.60% by weight. The specified weight value increases the hardenability and strength properties of the steel, while excessive It is maintained at a balanced level to prevent embrittlement. This carbon content in the steel... Determining the ferrite-perlite ratio by weight to ensure it is at the desired level after the remediation process. It allows for control and the simultaneous preservation of tensile strength and ductility. It provides. The silicon element in the steel discussed in the invention is 0.15%–0.35% by weight. It is found in this range and, in addition to its deoxidizing function, this element contributes to the elasticity of steel. It has a positive effect on improving the modulus and yield strength of the steel in question. In the invention, the steel in question... The manganese content is selected to be between 0.60% and 0.90% by weight. This weight-based value increases the hardenability of the steel in question, resulting in finer particles within its structure. It contributes to the formation of perlite structures, thereby increasing tensile strength, and Internal structural homogeneity is being improved. However, this is due to the ratio of carbon by weight. By balancing these elements together, care is taken to preserve the toughness of the material. Classification: General Classification: Public 6 The phosphorus and sulfur alloying elements present in the steel covered by the invention. The total percentage by weight is kept below 0.05%, and the percentage by weight of each is at most... It is limited to 0.025% by weight. These two elements are present at low levels. Preservation reduces the tendency to crack, especially at high temperatures, and improves surface quality. It contributes to its preservation. It also includes secondary alloys such as chromium, nickel, and copper. The elements will not exceed 0.40%, 0.10%, and 0.40% by weight, respectively. This is how it is limited. The controlled presence of these elements causes mild corrosion to the steel. It provides resistance while also ensuring stability in mechanical properties. The steel covered by this invention has high weight values ​​thanks to its chemical composition. While maintaining the stiffness and strength advantages provided by the carbon content, it offers a low weight advantage. The presence of phosphorus and sulfur in the values ​​affects surface homogeneity and processability. It shows improved performance. In addition, the specified manganese value by weight is thermal. It is possible to obtain a finer-grained and more balanced microstructure after processing. This enables deformation control and surface quality in subsequent processing steps. This facilitates optimization. Therefore, the resulting chemical composition is standard. The chemical properties of C55 grade steels remain within these limits. Specifically designed to provide an optimum balance of strength, ductility, and surface quality. It offers an adapted composition. Furthermore, the chemical composition of the steel discussed here... Its composition is also given in Table 1. Element Weight Ratio (%) C (Carbon) 0.52 – 0.60 Si (Silicon) 0.15 – 0.35 Mn (Manganese) 0.60 – 0.90 P (Phosphorus) ≤ 0.025 S (Sulfur) ≤ 0.025 Cr (Chromium) ≤ 0.400 Ni (Nickel) ≤ 0.100 Cu (Copper) ≤ 0.400 Other impurities (Al, N, etc.) in trace amounts. Table 1. Chemical composition of the steel described in the invention. Classification: General Classification: Public 7 The invention optimizes the chemical composition of the steel and the process steps. This ensures homogeneous stability and repeatability in mechanical properties. The aim is to obtain steel in the annealed and tempered final state. The aim is for it to meet specific strength and ductility values ​​in its form. This This includes fundamental properties of steel such as tensile strength, yield strength, elongation rate, and hardness. Mechanical parameters are controlled within specific ranges. The steel in question has a tensile strength in the range of 480–600 MPa and a yield strength of... The target mechanical strength is in the range of 350–450 MPa. These values ​​maintain the strength provided by the high carbon content of the steel while also preserving ductility. This ensures that the elongation of the steel obtained is kept at a sufficient level. The goal is for their values ​​to be at least 15%. This value reflects shaping capability and It represents a balanced structure in terms of cold workability. On the other hand, obtained The hardness value of the steel to be produced is in the range of 150–190 on the Brinell scale (HB). This range is determined so that the steel is neither too brittle nor too soft. It prevents further damage and creates a suitable intermediate hardness level for subsequent processes. Parameters in the annealing, rolling and tempering process steps within the scope of the invention By optimizing it, the mechanical values ​​obtained remain constant throughout the production process. The aim is to achieve a tensile strength difference of ±3% along the entire length. The aim is to prevent this from happening and to keep the deviation in elongation values ​​within ±1.5%. Thanks to this approach, intra-product homogeneity and mechanical consistency between different coils are ensured. This ensures that the resulting steel has stable strength and ductility. It exhibits performance, along with surface quality, in automotive, machinery and spring manufacturing, etc. It is becoming suitable for application areas requiring precise tolerances. Furthermore, the invention... The mechanical strength values ​​of the steel targeted to be obtained within this scope are given in Table 2. is provided. Tolerance Throughout Production Mechanical Properties Target Value Range (Within the meter) Tensile Strength 480 – 600 MPa ±3 % Yield Strength 350 – 450 MPa ±3 % Elongation ≥ 15% ±1.5% Hardness 150 – 190 HB ±5 HB Table 2. Mechanical strength values ​​of the target steel. Classification: General Classification: Public 8 The aim of this invention is to address the technical issues encountered in the production of C55 grade steels. The goal is to develop solutions for each problem, with each methodological step being specific to the process. The technical solutions to be obtained will involve chemical composition, surface preparation, rolling, annealing, and It is based on optimizing the tempering processes as a whole. Thus surface quality and mechanical stability compared to current production methods in the technology Significant improvements are being achieved compared to previous years. One of the most common problems encountered in C55 grade steels is surface defects. In order to remove oxidation and scale residues, the pickling step in the invention is repeated. It is structured. The current production lines use 10–12% HCl by weight. instead of a solution, the invention includes a solution containing HCl in the range of 16–20% by weight. A higher concentration solution is used. This preference is for hot rolling. subsequently, a thick and stable scale layer forms on the steel surface, with a higher profile. It ensures efficient dissolution at high speeds. On the other hand, as a production process step, the pickling process is carried out at a temperature range of 70–80 °C. This is being carried out. Under these conditions, the iron oxide layer on the surface is completely removed. This process ensures the dissolution and removal of scale residues. Following this, the surface The rinsing and drying steps are carried out in a controlled manner to activate the surface. This prevents surface fracture and microcracks during the subsequent rolling stage. The risk of oxidation or decay is minimized, resulting in an oxidation-free, glossy surface. is being done. The problem of lack of homogeneity observed throughout the measurement in mechanical properties is the invention. This is eliminated by the two-stage bright annealing process applied within the scope of this. Annealing The process is carried out in a 100% hydrogen atmosphere and in two stages. Hydrogen gas is preferred. The reason for this is that hydrogen's thermal conductivity is much higher than that of nitrogen, which is an alternative atmosphere. The higher temperature and the relatively low dew point temperature are the characteristics of this feature. During the annealing process, heat spreads more quickly and evenly along the windings of the steel coil, It also prevents the surface from reacting with oxygen. Thus A bright and oxide-free surface is obtained. The reason for performing the annealing process in two stages within the scope of this invention is that, single Uncontrolled and localized grain formation along the coil during stepped high-temperature application. Classification: General Classification: Public 9 Growth is a risk of occurrence. The first stage lasts 4–7 hours at a temperature range of 480–520 °C. During this stage, internal stresses are reduced in a controlled manner and slowly within the steel structure. Recrystallization nuclei are forming in a balanced manner. The second stage is 720–740 This process takes place in the °C temperature range and lasts 12–16 hours, during which time carbon diffusion occurs. homogenization and a controlled one from the nuclei formed in the first stage Growth is taking place. The fact that the annealing process is carried out in a bell-type furnace makes the method two-stage. This makes it necessary. If the temperature is raised directly to 730 °C in a single step, the coil... The outer windings immediately begin recrystallization and grain growth, but the inner coil... Because the coils reach this temperature later, they lag behind in microstructural transformation. This situation leads to irregularities in grain size and mechanical properties throughout the measurement. It opens up the temperature difference between all regions of the coil thanks to the two-stage application. This is reduced, the same recrystallization conditions are ensured in the inner and outer windings, and thus A homogeneous grain structure is obtained. Annealing is followed by slow cooling over 3–5 hours. termination both increases internal structural homogeneity and prevents surface oxidation. It completely prevents its formation. The invention covers deformation hardening and thickness increase that occurs during cold rolling. For tolerance problems, a multi-pass reversible rolling process step is applied. The rolling process step is performed in 6 to 9 passes. For each pass... The reduction ratio is between 5% and 10%, while the total thickness reduction ratio is in the range of 40% to 70%. The pressure force in cold rolling processes is between 1800–2200 tons. The rolling speed is determined to be in the range of 900–1100 m / min. These parameters, boron oil ensures the formation of a homogeneous grain structure under high deformation. Overheating is prevented by using a cooling system based on cooling. This ensures surface smoothness and thickness. Tolerance and internal stress balance are optimized. Within the scope of the invention, a bright annealing furnace is completely designed for annealing atmosphere and temperature control. It is configured to operate in a hydrogen atmosphere. Hydrogen gas is a substitute for oxygen. By ensuring its removal from the environment, it guarantees the formation of an oxide-free surface and Surface gloss is enhanced thanks to the system being operated at a low dew point. The dual-stage temperature profile facilitates the relief of internal stresses and the diffusion of carbon. It helps to balance the grains, thus preventing grain growth in the internal structure. Classification: General Classification: Public 10 The invention covers the control of surface roughness in the temper rolling process step and A high-pressure tempering system for relieving residual stresses is described in the invention. It is used. The constant pressing force is in the range of 230–270 tons, and the tensioning force is 3000–6000 tons. It is applied in the kgf range. The surface roughness of the rollers used is 0.2–3.2 Ra. These values ​​are selected within a range; these values ​​eliminate micro-undulations on the surface and It is suitable for achieving homogeneous brightness. This invention is the subject of this discussion. The surface roughness values ​​of steels obtained by rolling are in the range of 0.3 to 1.5 Ra. This is the value. Electrostatic lubrication in the range of 0.8–1.2 g / m² after the application of the process step. The treatment step is applied, which protects the surface against oxidation and ensures long-term durability. It ensures the maintenance of stability under storage conditions. The production line, structured in this way, achieves C55 quality thanks to its interconnected process steps. Long-standing problems in this class of steel include surface oxidation, microstructural heterogeneity, and thickness. It eliminates technical problems such as tolerance deviations and surface roughness. This This enables the reproducible production of bright, oxide-free, and mechanically homogeneous steels. This makes it possible to do so. - Obtaining steel in strip form through preparation and pre-treatment steps. To obtain the steel described in this invention, the first step is to determine the targeted chemical composition. The preparation process involves the carbon, manganese, and silicon contained in the steel. The ratios of elements such as chromium, nickel, phosphorus, and sulfur are precisely adjusted. This lays the metallurgical foundation for subsequent processes. Production is generally electrical. This process is carried out in arc furnaces or converter-type furnaces. Scrap steel or direct steel is used. Reduced iron is melted to obtain liquid steel. In this melting process, carbon, With the addition of manganese and silicon, the chemical composition is approximately at the target values. It is brought in. Then the liquid steel is taken to the ladle metallurgy stage, where it is processed in the ladle furnace. and gas removal processes are applied under vacuum. In this way, oxygen, hydrogen and Gases like nitrogen are removed, and the amounts of phosphorus and sulfur are also reduced. This As a result of these processes, the levels of gas and impurities in the steel are brought under control, and The elements are ensured to have a homogeneous distribution. The chemical composition of the steel that is intended to be obtained within the scope of the invention has not been previously determined. As stated, carbon is 0.52–0.60% by weight, silicon is 0.15–0.35% by weight, and by weight... Classification: General Classification: Public 11 Manganese 0.60–0.90%, phosphorus maximum 0.025% by weight, sulfur maximum 0.025% by weight, Chromium by weight, maximum 0.40%, nickel by weight, maximum 0.10%, and copper by weight... It is prepared to contain 0.40%. As the next step, after the chemical composition reaches the desired values... Liquid steel is solidified in slab or bloom form by continuous casting. Casting During this process, the solidification rate and cooling rate are carefully controlled, preventing segregation and thickening. The formation of a granular structure is prevented. As is known in the field of technology, the solidified semi-finished products... Subjected to homogenization annealing process carried out in the temperature range of 1100–1250 °C. is held in place. In this process step, internal stresses are relieved and the alloy elements are bonded to the billet. Even distribution is ensured throughout. After the homogenization process, the logs are formed into slabs. They are fed into the hot rolling line, where they are rolled in several passes to determine their thickness. It is reduced and formed into flat strip coils. However, during hot rolling... Due to the high temperature, a thick and hard oxide layer forms on the surface. Rolling After the process is complete, the strips are wound into coils. This scale on the surface most of them by water spraying, brush cleaning or mechanical scraping methods are removed. After this preliminary cleaning process, the coils are removed in a controlled manner. It is cooled and the remaining scale on the surface is embrittled. Then the coils It is passed through a mechanical surface breaking line called a scalebreaker, at this stage The surface is loosened by breaking off large pieces of the oxide layer. This allows the steel to... The ribbon coil is being prepared for chemical surface treatment. - Performing pickling processes on the obtained steel strips for coils. The innovative aspect of the invention lies primarily in the optimizations performed during these process steps. It begins with this. The aim of this process step is to remove scale and oxide from the surface of the steel strip coil. The complete removal of the layers. After the coil ends are joined by end welding. Then the strip line progresses along the coil pickling line. The strip is located on the coil surface. The scale layer is first mechanically broken in the scalebreaker unit. Then, steel As part of this process step, the strip is placed in an acid bath containing 16–20% HCl, and It is processed within a temperature range of 70–80 °C. These temperature and concentration conditions, effective dissolution of iron oxide layer and complete surface cleaning This is achieved by rinsing the strip coil with deionized water after pickling, followed by hot air. Classification: General Classification: Public 12 It is dried and a thin layer of protective oil is applied to its surface. Thus The surface is activated and prepared for the next rolling stage. - Applying cold rolling processes to the resulting steel strip into coils. The strip coil prepared after pickling is thinned by reducing its thickness and refining its internal structure. to a multi-pass reversible rolling line for the purpose of reducing and homogenizing the particles The rolling process is carried out in 6 to 9 passes, and the total... The reduction ratio is kept between 40–70%. Average reduction ratio for each pass. It varies between 5% and 10%. The pressing force in cold rolling processes is 1800– It is applied at a value in the range of 2200 tons and the rolling speed is 900–1100 m / min. It is a value within a range. These parameters ensure the homogeneous thinning of the steel and It ensures that deformation hardening is kept under control. Cooling and lubrication. A boron oil-based emulsion is used for this, thus stabilizing the surface temperature and Surface quality is preserved. - Performing bright annealing processes after the rolling process. Cold-rolled steel strip coil, with its homogeneous microstructure and surface brightness. To achieve this, it undergoes a two-stage bright annealing process. Annealing The process is carried out entirely in a 100% hydrogen atmosphere, and oxygen is removed. By removing these substances, an oxide-free surface is obtained. The first stage lasts 4–7 hours at a temperature range of 480–520 °C, during which time carburization occurs. The precipitates are stabilized and the internal stresses of the material are partially relieved. Second The stage lasts 12–16 hours at a temperature range of 720–740 °C, involving carbon diffusion. The structure is stabilizing and the ferrite-pearlite structure is becoming homogenized. The annealing process takes 3–5 hours. The process is completed by slow cooling, thereby increasing surface gloss and preventing oxidation. It is completely prevented. - Application of temper rolling processes Improving surface smoothness and eliminating residual stresses after annealing. The tempering and rolling process is applied. During this stage, a constant pressing force of 230–270 is applied. Classification: General Classification: Public 13 In the tonnage range, the tensile strength is maintained between 3000–6000 kgf. The surface roughness of the rollers is 2.3–2.7 Ra. Under these conditions, steel strip The coil is subjected to a low-rate plastic deformation, creating micro-undulations on the surface. The color is removed and uniformity of brightness is ensured. At the same time, this process is done using cold It eliminates the deformation stresses that occur after rolling and the material It reduces the risk of cracking during shaping. - Performing the lubrication process The tempering process is applied to the surface of the steel obtained after the rolling process using an electrostatic method. A protective oil layer is applied in the range of 0.8–1.2 g / m². This oil layer protects the surface. This prevents it from coming into contact with oxygen and prevents oxidation during storage or shipment. It prevents out-of-tolerance measurements by controlling surface roughness. They are sorted, and then mechanical test specimens are taken. Thus, mechanical and Surface quality control is ensured, resulting in a final product with a bright and oxide-free surface. One of the most important technical results obtained is the surface oxide-free and bright appearance of the steel. It is a significant improvement in the level. The invention uses a high concentration (by weight) Double-stage polishing carried out with 16–20% HCl pickling and 100% hydrogen atmosphere. Thanks to the annealing process, oxygen and iron oxide residues are completely removed from the surface. is removed. The reducing effect of hydrogen gas occurs during annealing when oxygen is on the surface. It inhibits the reaction and thus preserves the metallic shine. As a result, A homogeneous, reflective shine is obtained on the steel surface, and the surface roughness is 2.3– It is fixed in the range of 2.7 Ra. This property is particularly important for surface treatments (e.g. Phosphating, galvanizing, paint coating) is a great advantage for parts that will undergo these processes. It provides. Another technical result is the achievement of intracellular homogeneity and mechanical stability. Double During the stepped annealing process, thanks to the first stage carried out at 480–520 °C Carbide precipitations are stabilized, then a second treatment is applied in the range of 720–740 °C. With each step, carbon diffusion becomes completely homogenized. This process sequence involves ferrite-pearlite. By regulating the distribution, the tensile strength and elongation values ​​remain constant throughout the measurement. This ensures that the tensile strength difference in the steels produced within the scope of the invention is ±3%. The elongation difference can be kept within ±1.5% limits. These values ​​are consistent with the classic C55. Classification: General Classification: Public 14 The variability observed in steels is less than half of what it should be. Thus, throughout the product... The strength distribution becomes balanced, and fracture and forming behaviors are controlled. It reaches an acceptable level. On the other hand, thickness tolerances and surface Improving its smoothness is also one of the important advantages brought by the invention. Multi-pass In a reversible rolling system, the rolling process is carried out in 6–9 passes. It provides a total reduction ratio of 40–70% and a pressing force of 1800–2200 tons. It varies between them. These conditions ensure that the deformation is uniform throughout each pass. It allows for dissipation, and also prevents overheating thanks to the boron oil-based cooling system. and surface undulations are prevented. This controlled deformation reduces the thickness of the steel. By reducing the grain size along its length, it creates microstructural balance, thus reducing thickness. Deviations can be kept within tight tolerances such as ±0.02 mm. This is especially true for high-performance systems. Dimensional precision in applications requiring accuracy, such as springs, blades, and automotive components. It increases determination. The invention also ensures long-term stability and repeatability in mechanical properties. It also provides an advantage. The tempering applied during rolling is in the range of 230–270 tons. constant compressive force and tensile force in the range of 3000–6000 kgf, microscopically on the surface. It effectively relieves internal stresses caused by deformation while eliminating fluctuations. This reduces the risk of steel cracking during shaping. The desired gloss on the surface is maintained over time. 0.8– applied after tempering. Electrostatic lubrication in the range of 1.2 g / m² prevents the surface from coming into contact with oxygen during storage. It also prevents oxidation during transport, extending the product's shelf life. The steel produced using this manufacturing method is mechanically stable, has a bright surface, and It exhibits a non-oxidizing character. Tensile strength is 480–600 MPa, yield strength is 350– The tensile strength is fixed at 450 MPa and the elongation rate is at a minimum of around 17%. Additionally, the hardness value is 150– By maintaining a strength range of 190 HB, an optimum balance is achieved in terms of machinability and wear resistance. These values ​​have been provided for C55 grade steels in terms of mechanical and surface properties. This signifies a superior level of quality. The steel obtained in this way possesses... thanks to its surface quality, mechanical strength, ductility and microstructural homogeneity properties It has a wide range of industrial applications. Especially its high strength and good performance are important factors. Preferred in sectors requiring formability, wear resistance and aesthetic surfaces. is being done. Classification: General Classification: Public 15 The resulting steel has a bright and oxide-free surface structure, resulting in high mechanical strength. Thanks to its properties, it is used in many industrial fields. In the automotive sector... mechanical parts such as engine components, gears, axles, brake systems, clutch elements, and springs It is preferred in components subjected to stress. Surface quality, galvanizing, High compatibility with coating processes such as phosphating and electrostatic painting. It provides this in the field of machine manufacturing, where high strength and dimensional stability are required. It is used in components such as shafts, cams, pins, and press parts. The balanced nature of steel. Its robust and durable structure ensures a long service life in systems operating under impact and vibration. It provides high performance. Thanks to the high carbon content in spring and blade production, it is elastic. Modulus and hardenability characteristics stand out, suspension springs, saw teeth and It is actively used in the production of cutting tools. Its bright surface structure, PVD and It forms a suitable substrate for thin film coatings such as CVD, cutting tools and It eliminates the need for pre-coating preparation in molds. It also saves energy. Fasteners, piston rods, and chains are also used in the defense and agricultural machinery sectors. This steel can be used in shafts and components requiring high impact resistance. Its strength, surface quality, and stable structure make it suitable for a wide range of industrial applications. It offers. The scope of protection of the invention is specified in the claims attached hereto, and these details are strictly adhered to. The explanation cannot be limited to those given for illustrative purposes. Because a technically skilled person... the person, without deviating from the main theme of the invention, in light of what has been described above, similar It is clear that these structures can emerge. Classification: General Classification: Public

Claims

1. Preparation of the chemical composition of the steel, slab or by continuous casting method. Solidified in bloom form, then flattened into strip form by hot rolling. the process of bringing in and loosening the scale layer by mechanical surface breaking including steps, with a dimensionally homogeneous mechanical structure and a non-oxidizing and bright surface. a method for obtaining C55 grade steels with stability Its distinguishing feature is that it includes the following steps: - steel strip with a relaxed surface coil, 16% to 20% by weight immersed in an acid bath containing hydrochloric acid in a range of 70 to Applying the pickling process step at a temperature range of 80 °C, - the thickness of the steel strip coil prepared after the pickling process by reducing and internally refining the particles. between 6 and 9 passes to ensure homogenization. The application of the multi-pass reversible cold rolling process and a total thickness reduction ratio between 40% and 70% to be carried out, - internal structural homogeneity of the steel strip coil after the cold rolling process. and in order to obtain an oxide-free surface, in a 100% hydrogen atmosphere, 480 to Temperature range of 520 °C for 4 to 7 hours and 720 to 760 °C Two levels of brightness that will last for 12 to 16 hours. subjected to annealing process, - surface smoothness and residue of the steel strip coil after annealing process To relieve stresses, a compressive force between 230 and 270 tons is required. It undergoes a tempering and rolling process underneath.

2. A method that conforms to Claim 1, characterized by the fact that it is applied after the pickling process and cold. The rinsing process is carried out sequentially with deionized water and then with hot air before the rolling process. This includes drying and applying protective oil to the surfaces.

3. A method that conforms to one of the previous requirements, characterized by its cold rolling process. The step is performed between 6–9 passes, and the reduction ratio is given for each pass. It should be in the range of 5-10%. Classification: General Classification: Public 17 4. A method suitable for one of the previous requirements, characterized by cold rolling. The pressure force in these operations should be between 1800 and 2200 tons.

5. A method suitable for one of the previous requirements, characterized by cold rolling. the rolling speed in the processes is between 900 and 1100 m / min It is the fact that.

6. A method suitable for one of the previous requirements, characterized by its temper rolling process. In these processes, the surface roughness of the rollers is in the range of 2.3 to 2.7 Ra. It is the fact that.

7. A method suitable for one of the previous requirements, characterized by its temper rolling process. In these processes, the tension force of the rollers is between 3000 and 6000 kgf. It is the fact that.

8. A method that conforms to one of the previous requirements, characterized by its temper rolling process. 2 Afterwards, a protective oil is applied to the surface of the steel at a concentration ranging from 0.8 to 1.2 g / m³. It is the implementation.

9. Obtained by a method conforming to one of the requirements 1-8 and belonging to quality class C55. It is made of steel, and its characteristic feature is that it contains... Carbon (C) 0.52% to 0.60% by weight. silicon (Si) contains 0.15% to 0.35% by weight. manganese (Mn) 0.60% to 0.90% by weight, Phosphorus (P) maximum 0.025% by weight, Sulfur (S) maximum 0.025% by weight, Chromium (Cr) maximum 0.40% by weight, nickel (Ni) maximum 0.10% by weight, It is characterized by containing a maximum of 0.40% copper (Cu) by weight.

10. A steel conforming to Claim 9, with a tensile strength of 480 to 600 MPa. within the range of 350 to 450 MPa yield strength and at least elongation rate The required percentage is 15%, and the hardness value should be between 150 and 190 HB on the Brinell scale. 35 Classification: General Classification: Public 18 11. A steel suitable for stem 9 or 10; for automotive, machinery, spring, cutting tool, mold, In the energy, defense, and agricultural machinery industries; especially engine components, Gears, axles, brake systems, clutch components, springs, shafts, cams, pins, press parts, chain shafts and components requiring high impact resistance It is used in obtaining it. Classification: General Classification: Public