An alloy steel for the back of a bimetallic saw blade and its manufacturing method

Abstract

An alloy steel for the backing body of a bimetallic saw blade, comprising the following components and wt%: C: 0.29–0.33%, Si: 0.22–0.28%, Mn: 0.95–1.05%, P: ≤0.015%, S: ≤0.002%, Als: 0.03–0.05%, Cr: 3.80–3.90%, Mo: 1.20–1.30%, V: 0.30–0.40%, Ni: 0.60–0.70%. The production method includes: desulfurization of molten iron; converter smelting; bottom argon blowing followed by LF furnace refining; RH vacuum treatment; casting into billets; heating the billets; rough rolling; finish rolling; and cooling followed by coiling. While ensuring a yield strength of 1150-1250 MPa, a tensile strength of 1900-2000 MPa, and an elongation A ≥ 11%, the alloy content is relatively low, the alloy is simple, and it can be continuously cast into billets through converter smelting without heat treatment. It also achieves a hardness of 1000-1100 HV and has good weldability. The working hours of the prepared saw blade can be increased by at least 30%.

Description

Technical Field

[0001] This invention relates to a high-alloy tool steel and its manufacturing method, specifically to alloy steel for bimetallic saw blade backing and its manufacturing method. Background Technology

[0002] Bimetal saw blades use high-speed steel as the saw tooth material, and the saw teeth are welded to the saw blade back body as a single unit. Saw blades are mainly used for cutting difficult-to-machine materials such as carbon steel, alloy steel, structural steel, non-ferrous metals, stainless steel, die steel, and nickel-based alloys. The saw blade back body material must meet the environmental requirements of high heat resistance and high wear resistance for the saw blade teeth, therefore requiring high strength and high toughness, excellent hardenability and quenchability. Simultaneously, its weldability to the saw teeth must be guaranteed.

[0003] Currently, the high-alloy steel used for the backing body of saw blades is primarily produced by electric arc furnace steelmaking followed by ingot casting. This ingot is then welded to the saw teeth to form the saw blade. The production process for high-alloy steel for the backing body is not only time-consuming and inefficient, resulting in low hardness, but also, due to weld performance issues, the hardness of the backing steel after welding to the saw teeth is only a few hundred HV. This leads to a short service life for the saw blade, typically no more than 150 working hours. These issues represent a bottleneck in the current preparation and use of saw blades. The reason for using electric arc furnace steelmaking instead of converter steelmaking is that converter smelting of high-alloy steel is extremely difficult. Converter smelting cannot effectively solve the heat balance control problems associated with using ordinary molten iron and scrap steel, nor can it address the issue of adding high-alloy steel. Furthermore, converter smelting cannot meet the requirements for extremely low phosphorus and sulfur content, minimal inclusions, and extremely high steel purity in high-alloy steel. Therefore, electric arc furnace steelmaking is used instead of high-cost raw materials with low impurity content.

[0004] The reason for using ingot casting instead of continuous casting is that continuous casting of high-alloy steel is extremely difficult. Due to the high alloy content, the liquidus temperature is very low, reducing the critical strain of the billet and altering the brittle temperature range, thus increasing crack sensitivity and making the billet very prone to cracking. Furthermore, because of the high alloy content, the high-temperature mechanical properties and solidification characteristics differ significantly from conventional steel. When casting high-alloy steel, the outer solidified shell is thinner, resulting in very high internal stress that easily leads to shell cracking and leakage – a significant technical challenge. Because other plants could not overcome these technical difficulties, they chose ingot casting. Ingot casting involves pouring molten steel into a mold, allowing it to solidify, cool, and be demolded to obtain the billet. Since ingot casting requires creating a mold for each pour and then demolding after cooling, it occupies a large area, takes a long time, and has low production efficiency.

[0005] As retrieved:

[0006] Chinese patent application CN200610013084.8, entitled "High-alloy steel seamless pipe and its production method," discloses a high-alloy steel seamless pipe and its production method. The chemical composition (wt%) of the high-alloy steel seamless pipe is: C 0.08–0.12, Si 0.20–0.50, Mn 0.30–0.60, Cr 8–9.5, Mo 0.85–1.05, Al 0.01–0.04, Ni 0–0.4, Cb 0.06–0.10, P < 0.02, S < 0.010, V 0.18–0.25, N 0.03–0.07, with the balance being Fe. The production method involves using sponge iron and scrap steel as raw materials for steelmaking, melting them into molten steel in an electric arc furnace, refining them outside the ladle and degassing them under vacuum, and then continuously casting them into circular tube billets. The cooled continuously cast tube billets are then heated in an annular heating furnace for hot centering, hot piercing, continuous stretching and rolling, heat treatment, and finally flaw detection. Although this document describes a high-alloy product, uses sponge iron, and employs an electric arc furnace for smelting, its production cost is high, and it is only applicable to the field of seamless steel pipes. Therefore, it is not considered a substitute for the product field to which this invention pertains.

[0007] Chinese patent application CN200710052539.1, entitled "A Mixing Method for High-Quality Low-Phosphorus and Low-Sulfur High-Alloy Steel," discloses a mixing method for high-quality low-phosphorus and low-sulfur high-alloy steel. The method involves continuously oxidizing molten iron or pig iron from a blast furnace and charging it into an electric furnace or converter for smelting. Specifically, it involves simultaneously charging ferroalloys or recycled materials into another induction furnace or electric furnace for continuous charging. The molten iron from the aforementioned electric furnace or converter and the ferroalloys from the induction furnace or electric furnace are then mixed in a ladle for ladle refining, followed by ingot casting. This invention is simple and standardized to operate, low in cost, and can continuously smelt high-alloy steel with an alloy ratio greater than 5%. It completely solves the problem of uncontrollable phosphorus, five harmful elements, and trace harmful elements in high-alloy steel produced using ordinary smelting methods. It is particularly suitable for smelting tool steel, stainless heat-resistant steel, blade steel, valve steel, high-speed tool steel, and high-temperature alloys. It uses steel ingot mold casting, and the mold making cost is very high and the cycle is very long. It cannot be adapted to large-scale production, the production efficiency is extremely low, and the steel ingots produced by mold casting have great limitations.

[0008] Chinese patent application CN200810079601.0, entitled "A Method for Smelting High Alloy Steel," discloses a method for smelting high alloy steel. The method involves adding molten iron and scrap steel to an electric furnace or converter to melt them into crude steel. Once the crude steel reaches the required composition, it is added to an LF ladle refining furnace. Simultaneously, the molten alloy is also added to the LF ladle refining furnace to refine the alloy steel. When the alloy steel reaches the required composition, it is tapped. The key feature is the use of a medium-frequency induction furnace for melting the alloy, ensuring complete melting within the furnace. After reaching the required temperature, the crude steel from the electric furnace or converter is tapped, and the medium-frequency induction furnace also taps the steel. The alloy steel is then poured into the LF refining ladle, which then proceeds to the LF refining station for further refining. This high alloy steel smelting method requires less investment, significantly shortens the smelting time, and substantially improves alloy recovery rate and quality. Different composition systems and applications result in varying yield strengths and tensile strengths in the steel. The process is extremely complex, as it relies on medium-frequency induction furnaces for alloy melting due to the inability to properly control steelmaking temperatures. These furnaces are unconventional equipment, unavailable in most steel mills, and are very expensive.

[0009] Chinese patent application CN200910008966.9, entitled "High-Efficiency Short-Process Production Line for High-Alloy Steel and High-Alloy Steel Composite Materials," discloses a high-efficiency short-process production line for high-alloy steel and metal materials coated with high-alloy steel. The high-alloy steel includes materials such as nickel-based superalloys. This production line is designed for high-alloy steel grades that cannot be continuously cast or rolled, or where continuous casting quality cannot be guaranteed, or where continuous casting billets require extensive grinding. Specifically, this invention relates to three types of production lines: high-efficiency short-process production lines for high-alloy steel and metal composite plates, pipes, and bars coated with high-alloy steel. Its key feature is that different smelting equipment in the smelting workshop can flexibly handle different steel grades, and all billet casting equipment is liquid metal electroslag casting equipment. These devices can flexibly produce high-quality slabs and composite slabs, hollow tubes and composite tubes, as well as round billets and composite round billets. Slabs are combined with reversible roughing and finishing rolling, supplemented by online pre-rolling heating and heat-insulating roller conveyors to flexibly produce high-alloy plates. Pipes are flexibly produced in combination with extrusion presses, and bars are flexibly produced in combination with Y-type three-roll continuous rolling. It is designed for high-alloy steel grades that cannot be continuously cast or rolled, or where the quality of continuous casting cannot be guaranteed, or where continuous casting billets require extensive grinding. All of its billet casting equipment is liquid metal electroslag casting equipment.

[0010] Chinese patent application number CN200910310243.4, entitled "Manufacturing Method of High Alloy Steel Seamless Pipe", discloses a manufacturing method for high alloy steel seamless pipe. The aim is to provide a method for manufacturing seamless steel pipes with high strength, high toughness, high temperature resistance and corrosion resistance using high alloy steel with specific composition, which can meet the needs of industries such as power and petrochemical. The molten steel composition for manufacturing high-alloy steel seamless pipes, obtained through batch smelting, is as follows by weight percentage: C: 0.08–0.12%, Si: 0.20–0.50%, Mn: 0.30–0.60%, Cr: 5.0–7.5%, Mo: 0.85–1.05%, Al: 0.005–0.040%, Ni < 0.40%, Cu: 0.05–0.20%, V: 0.18–0.25%, Ti: 0.10–0.15%, Nb: 0.06–0.10%, N: 0.03–0.07%, Ca < 0.0015%, P < 0.020%, S < 0.003%, with the remainder being iron. The process employs continuous casting and rolling, followed by normalizing and tempering heat treatment. After sizing and hot straightening, the finished high-alloy steel seamless pipes are obtained through flaw detection. Its existence not only results in a high alloy cost, but also in a high process cost, which requires a heat treatment process of normalizing followed by tempering to ensure the performance of the steel. It is used to manufacture seamless steel pipes. Summary of the Invention

[0011] The present invention aims to overcome the shortcomings of the existing technology and provide an alloy steel for bimetallic saw blade backing, which ensures a yield strength of 1150-1250MPa, a tensile strength of 1900-2000MPa, an elongation A≥11%, a relatively low alloy content, a simple alloy, and can be continuously cast into billets through converter smelting without heat treatment. It also achieves a hardness of 1000-1100HV and has good weldability. The resulting saw blade working cycle can be increased by at least 30%, and the same applies to its production method.

[0012] Measures to achieve the above objectives:

[0013] An alloy steel for the backing of a bimetallic saw blade, comprising the following components and weight percentages: C: 0.29–0.33%, Si: 0.22–0.28%, Mn: 0.95–1.05%, P: ≤0.015%, S: ≤0.002%, Als: 0.03–0.05%, Cr: 3.80–3.90%, Mo: 1.20–1.30%, V: 0.30–0.40%, Ni: 0.60–0.70%, with the balance being Fe and unavoidable inclusions.

[0014] Preferably, the weight percentage content of Cr is 3.80% to 3.86%.

[0015] Preferably, the weight percentage content of V is 0.32% to 0.37%.

[0016] A method for producing an alloy steel backing for a bimetallic saw blade, comprising the following steps:

[0017] 1) Desulfurization of molten iron, desulfurization target: S≤0.001%,

[0018] 2) Conduct converter smelting and control the following: the final smelting temperature is 1630-1650℃, and the final oxygen content is 0.05-0.07%; the slag discharge from the converter is ≤40m; during the tapping process, aluminum ferrooxidant is added first for deoxidation, with the addition amount ensuring that the Al content in the steel is 0.050-0.080%; then, low-carbon ferrochrome is added at 29-33 kg / ts, and ferrovanadium is added at 6.7-8.0 kg / ts.

[0019] 3) After bottom argon blowing, the steel is refined in the LF furnace, and the temperature of the molten steel in the LF furnace is controlled at 1500-1510℃;

[0020] The refining process in the LF furnace is carried out in the following five stages: The first stage is the deep desulfurization stage, in which lime and aluminum granules are added to create a reducing slag for desulfurization, and the sulfur content in the molten steel is controlled to be less than or equal to 1.

[0021] 0.0015%; Heating at a rate of 4–5 °C / min to a temperature not lower than 1570 °C.

[0022] And the heating time is 15 to 25 minutes;

[0023] The second stage is the Cr composition stage: before adding Cr, the molten steel is heated to a temperature of not less than 1600℃.

[0024] During this period, carbon ferrochrome is added in batches, with a total amount of 37.0 to 41.0 kg / ts and each batch added at 3.5 to 5.5 kg / ts. The number of batches added is calculated based on the principle that the temperature of the molten steel drops by 1°C for every 0.5 kg / ts of low-carbon ferrochrome added, so as to reduce the temperature of the molten steel by 70 to 80°C.

[0025] The third stage is the fine-tuning of other alloys. During this stage, the Si composition is controlled at the lower end of the range, and the Al content is controlled at 0.040-0.060%. At the end of LF refining, the Al content is controlled at 0.030-0.050% by feeding aluminum wire.

[0026] The fourth stage is the temperature adjustment stage: when the LF refining is completed, the temperature is controlled at 1560-1570℃. However, if the temperature is higher than the controlled range, bottom blowing argon is used to cool it down. If the temperature is lower than the controlled range, heating is used to raise the temperature.

[0027] 4) Perform RH vacuum treatment. During this period, the vacuum cycle time is controlled at 35-40 min, the vacuum degree is controlled at ≤15 Pa, and the temperature is controlled at 1520-1530℃ at the end of the vacuum treatment.

[0028] 5) Vacuum circulation time is 35-40 minutes, vacuum degree is controlled at ≤15Pa, and vacuum end temperature is controlled at 1520~1530℃;

[0029] 6) Casting and billet formation under the protection of protective slag: During this period, the billet pulling speed is controlled at 0.9–1.0 m / min, and the fluctuation range of the molten steel level in the crystallizer is within ±3 mm; the taper of the crystallizer is controlled at 1.15–

[0030] 1.22%, the cooling water flow rate of the wide face of the crystallizer is 4400~4500L / min, the cooling water flow rate of the narrow face of the crystallizer is 630~640L / min; the superheat of molten steel is ≤20℃, and the temperature of the tundish is 1500~1510℃;

[0031] 7) Heat the billet and control the billet temperature at 1280-1320℃ when it enters the furnace;

[0032] 8) Perform rough rolling and control the rough rolling temperature at 1080~1120℃;

[0033] 9) Perform finish rolling and control the final rolling temperature at 900-940℃ to end the rolling process;

[0034] 10) After cooling, the product is wound up, and the winding temperature is controlled at 680-720℃.

[0035] The physical properties of the protective slag are required to be: alkalinity of 0.8 to 0.9, viscosity of 0.07 to 0.17 Pa·S at 1300℃, and melting point of 1000 to 1060℃.

[0036] The role and mechanism of each raw material and main process in this invention

[0037] Carbon (C): To meet the mechanical properties of steel, the microstructure of the steel described in this invention requires a structure of martensite + retained austenite + a small amount of carbides. Carbon can play a role in solid solution strengthening, which helps to improve the strength of steel. However, too much carbon will reduce the plasticity and toughness of steel, causing the steel to fracture. Therefore, the more suitable carbon addition is 0.29-0.33%.

[0038] Manganese (Mn): Manganese strengthens the solid solution of steel, refining its grains after heat treatment, thereby increasing the steel's strength and hardness. Manganese improves the weldability and toughness of steel, resists deformation and shrinkage during hot and cold treatment, and reduces cracking and deformation. Manganese has a converging effect on grain boundaries, inhibiting intergranular microcracks. Therefore, the optimal manganese addition amount is 0.95–1.05%.

[0039] Silicon (Si): Silicon can be used as a reducing agent and deoxidizer in steelmaking. Silicon can improve the strength and hardness of steel. Silicon forms silicides with iron, and these silicides have high hardness, which can improve the tensile strength of steel. However, silicon should not be added in excessive amounts, as it will reduce plasticity. The suitable amount of silicon added is 0.22% to 0.28%.

[0040] Chromium (Cr): Significantly improves the hardenability and tempering stability of steel, resulting in excellent comprehensive mechanical properties after quenching and tempering. It has a secondary hardening effect, significantly increasing the strength and hardness of steel. It also improves the wear resistance, high-temperature mechanical properties, and surface finish of steel. However, as the chromium content continues to increase, the strength, hardness, and plasticity of the steel will decrease. Therefore, the chromium content should not be too high; a suitable chromium addition is 3.80–3.90%.

[0041] Molybdenum (Mo): Mo acts as a solid solution strengthener, improving the strength and ductility of steel. Mo can form various alloys with elements such as carbon, chromium, and nickel in steel, enhancing grain boundary strength and stability, thereby increasing the steel's strength and hardness. Mo can refine the grain size of steel, resulting in a more uniform microstructure, thus improving its toughness and tensile strength. It can eliminate or reduce temper brittleness caused by other elements, improving the steel's impact toughness and hardenability. However, excessive molybdenum content will reduce the steel's oxidation resistance and increase its resistance to deformation during hot working. Therefore, the optimal molybdenum addition is 1.20–1.30%.

[0042] Nickel (Ni): Ni enhances the strength of steel through solid solution strengthening and precipitation strengthening. Solid solution strengthening involves dissolving nickel in the steel, increasing its lattice constant and elastic modulus, making it harder and more durable. Precipitation strengthening involves forming a large amount of supersaturated solid solution in the steel, increasing its grain boundary density and dislocation density. The combination of these two strengthening mechanisms allows steel to achieve higher strength and hardness. Ni can lower the critical transformation temperature and reduce the diffusion rate of elements in steel, thus improving its hardenability. Ni exhibits certain stability at high temperatures, making it less prone to deformation and hot cracking during heating, thereby improving the heat resistance and creep life of steel, as well as its fatigue limit and fatigue life. Ni can also improve the corrosion resistance, wear resistance, and toughness of steel. Therefore, the optimal Ni addition amount is 0.60–0.70%.

[0043] Vanadium (V): V can refine the microstructure and grain size of steel, increase the grain coarsening temperature, reduce the overheating sensitivity of steel, significantly improve the red hardness, hardness, and wear resistance of steel, improve the tempering stability of steel, and produce a secondary hardening effect, increasing the strength and toughness of steel. The suitable V addition amount should be 0.30-0.40%.

[0044] Aluminum (Al): Aluminum is a major deoxidizing element in steel, refining grains and fixing nitrogen in steel, thereby significantly improving its impact toughness. Aluminum can improve the wear resistance and oxidation resistance of steel, but its disadvantage is that it affects the hot working and weldability of steel. The suitable Al addition amount in this invention is 0.03–0.05%.

[0045] Phosphorus (P): P easily leads to phosphorus dendrite segregation in cast billets, increases grain boundary brittleness, increases crack sensitivity, and causes internal cracks; phosphorus also deteriorates the toughness and plasticity of steel, and produces "cold brittleness" at low temperatures, which worsens weldability. Therefore, the phosphorus content in steel should be reduced as much as possible.

[0046] Sulfur (S) easily causes hot brittleness, reduces the ductility and toughness of steel, and reduces weldability; therefore, the sulfur content in steel should be reduced as much as possible.

[0047] The reason this invention controls the final temperature of the converter smelting process at 1630–1650℃ and the final oxygen content at 0.05–0.07% is that the main raw materials for converter steelmaking are molten iron and scrap steel. If the final smelting temperature is too low, the scrap steel cannot be completely melted. If the final smelting temperature is too high, it is not conducive to the removal of phosphorus from the molten steel, leading to excessive phosphorus levels; dephosphorization requires a relatively low temperature. If the final oxygen content is too low, the oxidizing power of the molten steel is insufficient, which is not conducive to the removal of phosphorus. If the final oxygen content is too high, it will cause over-oxidation of the molten steel, resulting in high nitrogen levels and rapid erosion of the converter walls.

[0048] The reason why this invention controls the addition of low-carbon ferrochrome at 29-33 kg / ts and ferrovanadium at 6.7-8.0 kg / ts after deoxidation with aluminum and ferrochrome during the converter tapping process is that adding alloys after deoxidation with aluminum and ferrochrome during the converter tapping process prevents the alloying elements from being oxidized and resulting in low yield, and facilitates the full melting of the alloy, thereby improving the yield.

[0049] The reason why this invention controls the amount of slag discharged from the converter to be ≤40m is to improve the purity of the molten steel. During the tapping process, aluminum and iron are added for deoxidation. The amount added is based on the principle that the Al content in the steel is 0.050-0.080%. This is to prepare reducing slag in advance for subsequent desulfurization, and the slag must be reducible for subsequent desulfurization.

[0050] The present invention is carried out in the following five stages during the refining process in the LF furnace: The first stage is the deep desulfurization stage, in which lime and aluminum particles are added to form a reducing slag for desulfurization, and the S in the molten steel is controlled to be ≤0.0015%; the temperature is raised to not less than 1570℃ at a heating rate of 4-5℃ / min, and the heating time is 15-25min. The reason for making it the first stage is that deep desulfurization of LF requires high temperature, high basicity, and high reducing slag. If it is placed later, the temperature will drop rapidly with the addition of a large amount of alloy, which is not conducive to deep desulfurization. The second stage is the Cr composition adjustment stage: before adding Cr, the molten steel is heated to a temperature not lower than 1600℃; during this period, low-carbon ferrochrome is added in batches, with a total amount of 37.0-41.0 kg / ts and each batch added at 3.5-5.5 kg / ts. The number of batches added is calculated based on a 1℃ temperature drop in the molten steel for every 0.5 kg / ts of low-carbon ferrochrome added, aiming to lower the steel temperature by 70-80℃. The reason for choosing the second stage for Cr composition adjustment is that after the first stage of deep desulfurization, high temperature is not required, and a large amount of low-carbon ferrochrome can be added for cooling. At this time, the slag layer is conducive to the addition of alloys (as the LF treatment progresses, the slag layer gradually thickens, which is not conducive to the addition of large amounts of alloys). The large amount of low-carbon ferrochrome added is beneficial. The alloy is added in batches to prevent agglomeration and facilitate melting. The third stage involves fine-tuning other alloys. During this stage, the Si composition is controlled at the lower end of the range, and Al is controlled at 0.040-0.060%. At the end of LF refining, aluminum wire is used to feed Al to 0.030-0.050%, and the composition is fine-tuned to meet the requirements. The fourth stage is the temperature adjustment stage: at the end of LF refining, the temperature is controlled at 1560-1570℃. However, if the temperature is higher than the controlled range, bottom blowing argon is used to cool it down. If the temperature is lower than the controlled range, heating is used to raise the temperature. The temperature control at the end of LF refining is to provide the required temperature for the next process.

[0051] The reason this invention controls the vacuum circulation time to 35–40 minutes, the vacuum level to ≤15 Pa, and the temperature at the end of the vacuum cycle to 1520–1530°C is to strictly control the circulation time and vacuum level parameters during the vacuum circulation process. This further reduces the nitrogen content in the steel, further removes harmful impurities and gases, and improves the purity of the molten steel, thereby improving the various properties of the steel. Controlling the temperature at the end of the vacuum cycle to 1520–1530°C is to control the superheat during continuous casting.

[0052] The reason this invention controls the billet casting speed to 0.9–1.0 m / min, the molten steel level fluctuation in the crystallizer to within ±3 mm, the crystallizer taper to 1.15–1.22%, the cooling water flow rate on the wide side of the crystallizer to 4400–4500 L / min, and the cooling water flow rate on the narrow side of the crystallizer to 630–640 L / min; the molten steel superheat to ≤20℃, and the tundish temperature to 1500–1510℃ is because this steel is extremely difficult to cast continuously, and leaks are prone to occur. Therefore, ingot casting is more commonly used in the industry. Controlling these parameters is to avoid defects such as longitudinal cracks, edge cracks, and center segregation in the continuously cast billet. A casting speed below 0.9 m / min can easily cause billet stagnation, which can damage the continuous casting machine. A casting speed above 1.0 m / min can easily lead to leaks. When the molten steel level fluctuation in the crystallizer exceeds ±3mm, it can easily cause secondary contamination of the molten steel by slag entrapment. A crystallizer taper below 1.15 or above 1.22 can easily cause cracks in the cast billet, leading to its scrap. Excessive control of the cooling water flow rate on both the wide and narrow sides of the crystallizer can result in a thinner billet shell at the crystallizer outlet, increasing the risk of steel leakage. Excessive superheat of the molten steel and excessively high tundish temperature can easily cause center segregation in the cast billet.

[0053] The reason this invention controls the furnace inlet temperature to be between 1280 and 1320°C is that excessively low temperatures result in low toughness, while excessively high temperatures lead to defects such as oxidation, deformation, porosity, and cracks on the inlet surface, affecting quality and increasing energy consumption.

[0054] Compared with the prior art, the present invention ensures a yield strength of 1150-1250MPa, a tensile strength of 1900-2000MPa, and an elongation A≥11%, while having a relatively low alloy content and a simple alloy. It can be continuously cast into billets through converter smelting without heat treatment, and also achieves a hardness of 1000-1100HV. Furthermore, it has good weldability. The working hours of the prepared saw blade can be increased by at least 30% compared to the existing less than 150 working hours, i.e., more than 200 hours. Detailed Implementation

[0055] The present invention will now be described in detail:

[0056] Table 1 is a list of chemical components of the various embodiments and comparative examples of the present invention;

[0057] Table 2 is a list of the main process parameters for each embodiment and comparative example of the present invention;

[0058] Table 3 is a list of performance test results for each embodiment and comparative example of the present invention.

[0059] The various embodiments of the present invention are produced according to the following steps.

[0060] 1) Desulfurization of molten iron, desulfurization target: S≤0.001%,

[0061] 2) Conduct converter smelting and control the following: final smelting temperature at 1630–1650℃, final oxygen content at 0.05–0.07%; slag discharge from converter tapping ≤40m³; during tapping, aluminum ferrooxide is first added for deoxidation, with the addition amount ensuring Als in the steel is between 0.050–0.080%; subsequently, according to…

[0062] Add 29–33 kg / ts of low-carbon ferrochrome and 6.7–8.0 kg / ts of ferrovanadium.

[0063] 3) After bottom argon blowing, the steel is refined in the LF furnace, and the temperature of the molten steel in the LF furnace is controlled at 1500-1510℃. The LF furnace refining process is carried out in the following five stages: The first stage is the deep desulfurization stage, in which lime and aluminum particles are added to form a reducing slag for desulfurization, and the sulfur content in the molten steel is controlled to be less than or equal to 1500-1510℃.

[0064] 0.0015%; Heating at a rate of 4–5 °C / min to a temperature not lower than 1570 °C.

[0065] And the heating time is 15 to 25 minutes;

[0066] The second stage is the Cr composition stage: before adding Cr, the molten steel is heated to a temperature of not less than 1600℃.

[0067] During this period, carbon ferrochrome is added in batches, with a total amount of 37.0 to 41.0 kg / ts and each batch added at 3.5 to 5.5 kg / ts. The number of batches added is calculated based on the principle that the temperature of the molten steel drops by 1°C for every 0.5 kg / ts of low-carbon ferrochrome added, so as to reduce the temperature of the molten steel by 70 to 80°C.

[0068] The third stage is the fine-tuning of other alloys. During this stage, the Si composition is controlled at the lower end of the range, and the Al content is controlled at 0.040-0.060%. At the end of LF refining, the Al content is controlled at 0.030-0.050% by feeding aluminum wire.

[0069] The fourth stage is the temperature adjustment stage: when the LF refining is completed, the temperature is controlled at 1560-1570℃. However, if the temperature is higher than the controlled range, bottom blowing argon is used to cool it down. If the temperature is lower than the controlled range, heating is used to raise the temperature.

[0070] 4) Perform RH vacuum treatment. During this period, the vacuum cycle time is controlled at 35-40 min, the vacuum degree is controlled at ≤15 Pa, and the temperature is controlled at 1520-1530℃ at the end of the vacuum treatment.

[0071] 5) Vacuum circulation time is 35-40 minutes, vacuum degree is controlled at ≤15Pa, and vacuum end temperature is controlled at 1520~1530℃;

[0072] 6) Casting and billet forming under the protection of protective slag: During this period, the billet pulling speed is controlled at 0.9–1.0 m / min.

[0073] The fluctuation range of the molten steel level in the crystallizer is within ±3mm; the taper of the crystallizer is controlled between 1.15% and 1.22%.

[0074] The flow rate of cooling water on the wide side of the crystallizer is 4400-4500 L / min, and the flow rate of cooling water on the narrow side of the crystallizer is 630-640 L / min; the superheat of molten steel is ≤20℃, and the temperature of the tundish is 1500-1510℃.

[0075] 7) Heat the billet and control the billet temperature at 1280-1320℃ when it enters the furnace;

[0076] 8) Perform rough rolling and control the rough rolling temperature at 1080~1120℃;

[0077] 9) Perform finish rolling and control the final rolling temperature at 900-940℃ to end the rolling process;

[0078] 10) After cooling, the product is wound up, and the winding temperature is controlled at 680-720℃.

[0079] Table 1. List of chemical components (wt%) of each embodiment and comparative example of the present invention.

[0080]

[0081] Table 2. List of main process parameters for each embodiment and comparative example of the present invention.

[0082]

[0083] Continued from Table 2-1

[0084]

[0085] Continued from Table 2-2

[0086]

[0087] Continued

[0088] Table 2-3

[0089]

[0090] Continued from Table 2-4

[0091]

[0092] Continued from Table 2-5

[0093]

[0094]

[0095] Table 3. Statistical table of main performance tests of various embodiments and comparative examples of the present invention.

[0096]

[0097] As shown in Table 3, by strictly controlling the process parameters such as hot metal desulfurization, converter smelting, LF refining, RH vacuum, continuous casting, and hot rolling, the high-alloy tool steel described in this invention can achieve the performance requirements of a yield strength of 1150–1250 MPa, a tensile strength of 1900–2000 MPa, an elongation A ≥ 11%, and a hardness of 1000–1100 HV. This solves the problem of continuous casting of high-alloy steel using a continuous casting machine while ensuring the quality of the cast billet. Furthermore, it exhibits good weldability, and the working hours of the prepared saw blades can be increased by at least 30%, all exceeding 200 working hours.

[0098] This specific embodiment is merely a best example and is not intended to limit the implementation of the technical solution of the present invention.

Claims

1. A method for producing alloy steel for the backing body of a bimetallic saw blade, comprising the following steps: 1) Desulfurization of molten iron, desulfurization target: S≤0.001%, 2) Conduct converter smelting and control the following: the final smelting temperature is 1630-1650℃, and the final oxygen content is 0.05-0.07%; the slag discharge from the converter is ≤40m; during the tapping process, aluminum ferrooxidant is added first for deoxidation, with the addition amount ensuring that the Al content in the steel is 0.050-0.080%; then, low-carbon ferrochrome is added at 29-33 kg / ts, and ferrovanadium is added at 6.7-8.0 kg / ts. 3) After bottom argon blowing, the steel is refined in the LF furnace, and the temperature of the molten steel in the LF furnace is controlled at 1500-1510℃; The refining process in the LF furnace is carried out in the following five stages: The first stage is the deep desulfurization stage, in which lime and aluminum particles are added to form a reducing slag for desulfurization, and the S in the molten steel is controlled to be ≤0.0015%; the temperature is raised to not less than 1570℃ at a heating rate of 4~5℃ / min, and the heating time is 15~25min. The second stage is the Cr composition stage: before adding Cr, the molten steel is heated to a temperature of not less than 1600℃. During this period, carbon ferrochrome is added in batches, with a total amount of 37.0 to 41.0 kg / ts and each batch added at 3.5 to 5.5 kg / ts. The number of batches added is calculated based on the principle that the temperature of the molten steel drops by 1°C for every 0.5 kg / ts of low-carbon ferrochrome added, so as to reduce the temperature of the molten steel by 70 to 80°C. The third stage involves fine-tuning other alloys. During this stage, the Si composition is controlled at the lower end of the range, and the Al content is controlled at 0.040–0.060%. At the end of LF refining, aluminum wire is fed to maintain the Al content at 0.030–0.050%. The fourth stage is the temperature adjustment stage: when the LF refining is completed, the temperature is controlled at 1560-1570℃. However, if the temperature is higher than the controlled range, bottom blowing argon is used to cool it down. If the temperature is lower than the controlled range, heating is used to raise the temperature. 4) Perform RH vacuum treatment. During this period, the vacuum cycle time is controlled at 35-40 min, the vacuum degree is controlled at ≤15 Pa, and the temperature at the end of the vacuum treatment is controlled at 1520-1530℃. 5) Casting and billet forming under the protection of protective slag: During this period, the billet pulling speed is controlled at 0.9–1.0 m / min, and the molten steel in the crystallizer… The surface fluctuation range is within ±3mm; the taper of the crystallizer is controlled at 1.15~1.22%; the cooling water flow rate of the wide face of the crystallizer is 4400~4500L / min; the cooling water flow rate of the narrow face of the crystallizer is 630~640L / min; the superheat of molten steel is ≤14℃; and the temperature of the tundish is 1500~1510℃. 6) Heat the billet and control the heating temperature of the billet between 1280 and 1320℃; 7) Perform rough rolling, and control the rough rolling temperature at 1080~1120℃; 8) Perform finish rolling and control the final rolling temperature at 922-940℃ to end the rolling process; 9) After cooling, the winding is wound up, and the winding temperature is controlled at 701~713℃; The alloy steel used for the bimetallic saw blade back body has the following composition and weight percentage content: C: 0.29-0.32%, Si: 0.22-0.28%, Mn: 0.96-1.05%, P: ≤0.009%, S: ≤0.0017%, Als: 0.03-0.05%, Cr: 3.80-3.90%, Mo: 1.20-1.30%, V: 0.30-0.40%, Ni: 0.60-0.70%, with the balance being Fe and unavoidable inclusions.

2. The method for producing alloy steel for the back body of a bimetallic saw blade as described in claim 1, characterized in that: The physical properties of the protective slag are required to be: alkalinity of 0.8 to 0.9, viscosity of 0.07 to 0.17 Pa·S at 1300℃, and melting point of 1000 to 1060℃.

Images