A bimetallic band saw back material steel X32, a preparation method and application thereof

Abstract

The application provides a bimetallic band saw back material steel X32, a preparation method and application. The bimetallic band saw back material steel X32 is composed of the following components in percentage by mass: C 0.28-0.35%, Si 0.15-0.35%, Mn 0.8-1.2%, Cr 3.6-4.0%, Mo 1.0-1.4%, Ni 0.6-0.9%, V 0.3-0.5%, Nb 0.025-0.055%, Al 0.01-0.06%, P 0.007-0.015%, S 0.0007-0.0017%, and the rest is Fe and inevitable impurity elements. The yield strength is 1250-1450 MPa, the tensile strength is 1900-2200 MPa, and the elongation is 9-17%. The preparation method is simple, suitable for large-scale production, and has a good effect on improving the cutting capacity of the bimetallic band saw.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of saw blade back material steel production, in particular to a bimetallic band saw blade back material steel X32, a preparation method and application. BACKGROUND

[0002] The bimetallic band saw has many mechanical performance advantages such as good flexibility, strong fatigue resistance, ability to withstand great tension, high tooth ductility, etc., so that it has obvious advantages over traditional disc saws and bow-shaped reciprocating saws in terms of cutting efficiency, energy saving and environmental protection, material consumption reduction, and machining precision, etc. Compared with traditional bow-shaped reciprocating saws and disc saws, the bimetallic band saw not only improves cutting precision and working efficiency, reduces material and power consumption, but also solves the problem of sawing large-section workpieces.

[0003] The bimetallic band saw blade back material steel has high alloy content and high smelting technical difficulty. The long-term use of mold casting production restricts production efficiency, increases production cost, and is not conducive to large-scale production and manufacturing due to low automation. With the progress of continuous casting equipment and technology, the existing continuous casting process simplifies the production process and reduces environmental pollution, but due to the high alloy content, a long refining power supply time and smelting time are required, which leads to continuous casting waiting for molten steel, mismatching of production rhythm, reduction of production efficiency, and low tensile strength. Moreover, the molten steel cleanliness is unstable, which affects the quality of the billet.

[0004] Therefore, it is necessary to provide a bimetallic band saw blade back material steel X32, a preparation method and application to solve the technical problems of low production efficiency, low tensile strength and unstable molten steel cleanliness. SUMMARY

[0005] The main purpose of the present application is to provide a bimetallic band saw blade back material steel X32, a preparation method and application, which aims to solve the technical problems of low production efficiency, low tensile strength and unstable molten steel cleanliness of the bimetallic band saw blade back material steel X32 in the prior art.

[0006] To achieve the above-mentioned purpose, the present application provides a bimetallic band saw blade back material steel X32. The chemical composition of the bimetallic band saw blade back material steel X32, in terms of mass percentage, is as follows: C 0.28-0.35%, Si 0.15-0.35%, Mn 0.8-1.2%, Cr 3.6-4.0%, Mo 1.0-1.4%, Ni 0.6-0.9%, V 0.3-0.5%, Nb 0.025-0.055%, Al 0.01-0.06%, P 0.007-0.015%, S 0.0007-0.0017%, and the rest is Fe and inevitable impurity elements.

[0007] The yield strength of the double-metal band saw back material steel X32 is 1250-1450 MPa, the tensile strength is 1900-2200 MPa, and the elongation is 9-17%.

[0008] The preparation method of the double-metal band saw back material steel X32 comprises the following steps:

[0009] The target molten steel is obtained by subjecting the furnace charge to converter smelting, LF refining, and RH refining, and the double-metal band saw back material steel X32 is obtained after the target molten steel is continuously cast into a slab.

[0010] The furnace charge contains molten iron, scrap steel, molybdenum-iron alloy, and nickel-iron alloy.

[0011] The step of LF refining comprises:

[0012] In the process of smelting the converter molten steel into the LF refining furnace, a first mass of alloy is added to the LF refining furnace in batches to obtain a mixed solution of refined molten steel.

[0013] Each batch of added alloy is a second mass of alloy, the LF refining furnace is heated to a first temperature before each addition of the second mass of alloy, and argon stirring is started after the addition. The first temperature is greater than or equal to 1580°C; the interval time of each batch of added second mass of alloy is greater than or equal to 5 minutes; the argon gas flow is 800-1200 L / min, and the argon stirring time is 3-5 min.

[0014] Each batch of added second mass of alloy is 1.0-1.5 tons of chromium-iron alloy or 0.2-1.5 tons of one or more of silicon-iron, manganese-iron, vanadium-iron, molybdenum-iron, and nickel-iron alloy.

[0015] The step of RH refining comprises:

[0016] The refined molten steel is sent into the RH refining furnace in a vacuum environment, and niobium-iron alloy is added for refining to obtain a mixed solution, which is the target molten steel.

[0017] The pressure of the vacuum environment is less than or equal to 133 Pa; the refining time is greater than or equal to 15 minutes; and the mass of the added niobium-iron alloy is 0.025-0.055% of the mass of the target molten steel.

[0018] According to the embodiments of the present application, the step of converter smelting comprises:

[0019] After the furnace charge is added to the converter, oxygen is introduced for blowing for 5-10 minutes, the high-phosphorus slag in the early stage of the converter is poured out, and then lime is added to the converter for smelting, and the liquid after the impurities are separated is the converter molten steel.

[0020] The pressure of the oxygen blowing is 1.1-1.35 MPa, and the mass fraction of phosphorus in the converter liquid steel is less than 0.011%.

[0021] According to the embodiment of the application, the first mass of alloy is 4-6% of the target liquid steel mass.

[0022] According to the embodiment of the application, after the last batch of the second mass of alloy is added, the solution is discharged after stirring and mixing for at least 8 min, and the solution is the refined liquid steel.

[0023] According to the embodiment of the application, the vacuum environment is an extreme vacuum, and the niobium-iron alloy is added to the refined liquid steel within the first 3 min of the extreme vacuum; the niobium element yield is greater than or equal to 94%.

[0024] According to the embodiment of the application, in the step of manufacturing a slab by continuous casting, the target liquid steel is continuously cast into a continuous casting billet; wherein argon blowing is performed on a tundish for 30-50 L, and the superheat is controlled to be 12-35 DEG C, and the continuous casting speed is 1.0 m / min.

[0025] Application of the double-metal band saw back material steel X32 in improving the cutting capacity of the double-metal band saw.

[0026] The application has the following beneficial effects:

[0027] The double-metal band saw back material steel X32 has suitable chemical composition and content, wherein the yield strength is 1250-1450 MPa, the tensile strength is 1900-2200 MPa, and the elongation is 9-17%. The alloy elements such as Cr, Mn, V, Ni, Mo and Nb are added to ensure the product performance.

[0028] The above process is simple, shortens the smelting time, reduces energy consumption and cost, is convenient to operate, has high production efficiency, is suitable for large-scale production, and produces the double-metal band saw back material steel X32 with high yield strength, high tensile strength and high cleanliness, which has a good effect in improving the cutting capacity of the double-metal band saw. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only show some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of the drawings shown.

[0030] Figure 1 It is a metallographic inclusion microscope graph of the double-metal band saw back material steel X32 prepared in Example 1.

[0031] Figure 2 is a metallographic microscope graph (100 times magnification) of the double-metal band saw back material steel X32;

[0032] Figure 3 is a metallographic microscope graph (500 times magnification) of the double-metal band saw back material steel X32.

[0033] The implementation, functional features and advantages of the present application will be further described with reference to the accompanying drawings. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work are within the protection scope of the present application.

[0035] In addition, the technical solutions in the embodiments of the present application can be combined with each other, but it must be based on that a person of ordinary skill in the art can realize the combination. When the combination of the technical solutions appears to be contradictory or unachievable, it should be considered that the combination of the technical solutions does not exist, and is not within the protection scope of the present application.

[0036] The present application provides a double-metal band saw back material steel X32, the chemical components of the double-metal band saw back material steel X32 are as follows in mass percentage: C 0.28-0.35%, Si 0.15-0.35%, Mn 0.8-1.2%, Cr 3.6-4.0%, Mo 1.0-1.4%, Ni 0.6-0.9%, V 0.3-0.5%, Nb 0.025-0.055%, Al 0.01-0.06%, P 0.007-0.015%, S 0.0007-0.0017%, and the rest is Fe and inevitable impurity elements.

[0037] The yield strength of the double-metal band saw back material steel X32 is 1250-1450 MPa, the tensile strength is 1900-2200 MPa, and the elongation is 9-17%.

[0038] The present application obtains the double-metal band saw back material steel X32 with the yield strength of 1250-1450 MPa, the tensile strength of 1900-2200 MPa and the elongation of 9-17% by regulating the element composition and content. The alloy elements such as Cr, Mn, V, Ni, Mo and Nb are added to ensure the product performance.

[0039] The application also provides a preparation method of the bimetallic band saw back material steel X32.

[0040] The target molten steel is obtained by subjecting the furnace charge to converter smelting, LF refining and RH refining, and the bimetallic band saw back material steel X32 is obtained after the target molten steel is continuously cast into a slab.

[0041] The furnace charge contains molten iron, scrap steel, molybdenum iron alloy and nickel iron alloy.

[0042] In some embodiments, the converter smelting is used for preliminary removal of impurities and adjustment of components to provide a basic condition for subsequent refining; the LF refining is used for further adjustment of components, temperature and purity to ensure the uniformity and purity of the molten steel; and the RH refining is used for removal of gas and further reduction of carbon content to improve the purity and quality of the molten steel.

[0043] Through the synergistic effect of the three processes, the target molten steel with high quality, low impurities and high purity can be produced to meet the production requirements of high-end steel.

[0044] According to the embodiments of the application, the step of converter smelting comprises:

[0045] After the furnace charge is added to the converter, oxygen is introduced for blowing for 5-10 minutes, and then lime is added to the converter for smelting after the high-phosphorus slag in the early stage of the converter is poured out, and the liquid after separation of impurities is the converter molten steel.

[0046] The pressure of the oxygen blowing is 1.1-1.35 MPa, and the mass fraction of phosphorus in the converter molten steel is less than 0.011%.

[0047] In some embodiments, before smelting, the mass of molten iron, scrap steel, target molten steel and molybdenum iron alloy and nickel iron alloy to be added is calculated, the molybdenum iron alloy and nickel iron alloy are added in the scrap steel tank and placed behind the scrap steel, so that the molybdenum iron alloy and nickel iron alloy can be added to the converter smelting on the scrap steel, which can make the molybdenum iron alloy and nickel iron alloy closer to the high-temperature area and high-stirring area in the converter smelting process, and is beneficial to rapid melting and complete melting in the converter smelting process. It is ensured that there is no un-melted molybdenum iron alloy and nickel iron alloy in the converter when the converter smelting is completed.

[0048] In some embodiments, the operation mode of the converter smelting adopts front furnace slag + front slag pouring, and through blowing of oxygen, the C, P and S elements in the molten iron are oxidized by oxidation reaction, and are separated in the form of gas or into the slag to reduce the content of impurity elements.

[0049] In some embodiments, the converter retains about 5 tons of converter slag before smelting, and after the converter is filled with scrap steel and molten iron, the converter is blown for 5-10 minutes, then the high-phosphorus converter slag is poured out, and then the smelting is restarted by adding lime to improve the dephosphorization rate of the converter. This operation mode can use high-phosphorus molten iron to smelt low-phosphorus molten steel to reduce the content of phosphorus.

[0050] In some embodiments, lime is added as a desulfurizing agent to convert sulfur into sulfide into the slag, thereby reducing the sulfur content.

[0051] In some embodiments, the front furnace slag retention + front slag pouring operation mode is adopted to effectively improve the dephosphorization rate of the converter smelting X32 steel by optimizing the composition of the slag and utilizing rapid dephosphorization in the low-temperature stage, while reducing the production cost. At the same time, the converter is left with steel during tapping to prevent high-phosphorus converter slag from entering the ladle, which would cause phosphorus increase during LF refining process and affect the cleanliness of the molten steel, and also improve the smelting efficiency.

[0052] In the converter smelting process, the high temperature and intense stirring in the converter during blowing are used to quickly melt molybdenum iron and nickel iron alloy, which saves smelting time and reduces energy consumption compared to adding molybdenum iron and nickel iron alloy in the ladle.

[0053] According to the embodiments of the present application, the step of LF refining includes:

[0054] During the process of transferring the converter molten steel into the LF refining furnace for smelting, a first mass of alloy is added to the LF refining furnace in batches to obtain a mixed solution as the refined molten steel.

[0055] Wherein, the amount of each batch is a second mass of alloy, before adding the second mass of alloy each time, the LF refining furnace is heated to a first temperature, and argon stirring is started after adding. The first temperature is ≥ 1580℃; the interval time of each batch of second mass of alloy is ≥ 5 minutes; the gas flow of argon is 800-1200 L / min, and the argon stirring time is 3-5 min.

[0056] The second mass of alloy added in each batch is 1.0-1.5 tons of chromium iron alloy or 0.2-1.5 tons of one or more of silicon iron, manganese iron, vanadium iron, molybdenum iron, and nickel iron.

[0057] In some embodiments, during the process of transferring the converter molten steel into the LF refining furnace, the LF furnace is immediately powered to heat up. After the converter molten steel temperature is raised to 1580℃, the power is turned on for heating. If the converter molten steel temperature is lower than 1510℃, the power is turned on again for heating. This repeated power-on, batch addition of alloy, and argon stirring operation. Utilizing the stirring force generated by the flow of converter molten steel during tapping and bottom argon blowing to quickly melt the alloy, reduces the LF refining furnace smelting time, and improves the cleanliness of the molten steel.

[0058] Specifically, the first mass of alloy is added in batches, each batch adding 1.0-1.5 tons of ferrochrome alloy or 0.2-1.5 tons of one or more of ferrosilicon, ferromanganese, ferrovanadium, ferromolybdenum, and ferronickel alloy. The interval between each batch of alloy addition is ≥5 minutes. The impact of the converter molten steel under high temperature and oxidizing environment causes the alloy to quickly melt and uniformly distribute, reducing the oxidation loss of the alloy. Preventing a large amount of alloy from being added at one time prevents the solidification of the molten steel surface in the ladle and further affects the temperature of the molten steel in the LF refining furnace. At the same time, it also reduces environmental pollution during power transmission and improves the cleanliness of the refined molten steel.

[0059] According to the embodiments of the present application, the first mass of alloy is 4-6% of the target molten steel mass.

[0060] In some embodiments, to obtain the steel X32 for the double-metal band saw back material according to the present application, the chemical composition and content are controlled, so the first mass of alloy is adjusted according to the target molten steel mass to obtain the chemical composition according to the present application.

[0061] According to the embodiments of the present application, after the last batch of the second mass of alloy is added, the mixture is stirred for at least 8 minutes, and the solution discharged from the furnace is the refined molten steel.

[0062] In some embodiments, after the last batch of alloy is added, sufficient stirring is performed to ensure that the interval between the last batch of alloy addition and the molten steel leaving the LF refining furnace is ≥8 minutes. For example, the time from when the composition of the refined molten steel is qualified to when the molten steel leaves the LF refining furnace is ≥8 minutes, to ensure that the alloy is fully melted and uniformly distributed, the target composition is adjusted, the alloy yield is improved, the purity of the refined molten steel is optimized, the molten steel quality and production efficiency are effectively improved, and the cost is reduced.

[0063] According to the embodiments of the present application, the step of RH refining includes:

[0064] The refined molten steel is sent into the RH refining furnace in a vacuum environment, and niobium-iron alloy is added for refining, and the resulting mixture is the target molten steel.

[0065] The pressure of the vacuum environment is ≤133 Pa; the refining time is ≥15 minutes; and the mass of the added niobium-iron alloy is 0.025-0.055% of the mass of the target molten steel.

[0066] In some embodiments, after the ladle containing the refined molten steel reaches the working position of the RH refining furnace, the RH refining furnace is immediately subjected to a vacuum operation to ensure that the pressure of the vacuum environment of the RH furnace is ≤133 Pa and that the refining time of the refined molten steel in the RH refining furnace is ≥15 minutes, thereby improving the cleanliness of the refined molten steel.

[0067] In some embodiments, the vacuum environment is an ultimate vacuum, and the ferro-niobium alloy is added within the first 3 minutes of the ultimate vacuum treatment. Because the melting point of the ferro-niobium alloy is high, by circulating the ferro-niobium alloy in the RH refining furnace with the refined steel for a refining time of ≥15 minutes, it can be ensured that the ferro-niobium alloy is fully melted and uniformly distributed in the molten steel, and the oxidation loss of the ferro-niobium alloy can be reduced, and the recovery rate thereof is improved. In addition, after the ferro-niobium alloy is added, the inclusions in the molten steel need a certain time to float and be removed. By prolonging the circulating time, the circulating action of the RH furnace can be utilized to make the inclusions fully float, thereby improving the purity of the refined molten steel, and ensuring the uniformity and stability of the composition of the molten steel.

[0068] According to the embodiments of the present application, the vacuum environment is an ultimate vacuum, and the ferro-niobium alloy is added within the first 3 minutes of the ultimate vacuum treatment; the recovery rate of niobium element is ≥94%.

[0069] According to the embodiments of the present application, in the step of continuously casting the target molten steel into a slab, the target molten steel is continuously cast into a continuously cast slab; wherein the argon blowing of the tundish is 30-50L, and the superheat is controlled to be 12-35℃, and the continuous casting speed is 1.0 m / min.

[0070] In some embodiments, a double-flow slab continuous casting machine is used for continuous casting. After the ladle containing the target molten steel reaches the continuous casting machine, the tundish is closed for baking, and an argon pipeline is placed into the tundish. The tundish of the continuous casting machine is opened for argon blowing operation, and the argon blowing is maintained for more than 3 minutes, and the argon blowing of the tundish is 30-50L. When the ladle containing the target molten steel reaches above the tundish, the ladle is opened to cast the target molten steel into the tundish, and the target molten steel enters the tundish filled with argon. This can effectively reduce the contact between the target molten steel and oxygen in the air before the casting starts, and can avoid the generation of oxidized inclusions, thereby improving the cleanliness of the target molten steel. After the casting starts, the pulling speed of the continuous casting machine is gradually increased to 1.0 m / min, and the double-metal band saw back material steel X32 is cast at a constant pulling speed of 1.0 m / min. The constant pulling speed can reduce the inclusion defects such as slag entrapment in the continuous casting mold caused by the fluctuation of the pulling speed, and improve the surface quality of the X32 cast slab and hot-rolled steel coil.

[0071] In the process, the heat generated during the converter smelting and the stirring of oxygen blowing are controlled to quickly melt the ferromolybdenum and nickel-iron alloy, reduce the energy consumption of the smelting process, and shorten the smelting time; cooperate with the temperature of the LF refining furnace, and add the chromium-iron, manganese-iron, vanadium-iron and other alloys in batches, effectively prevent the alloy from coagulating into a shell on the surface of the molten steel in the ladle after a large amount of alloy is added at one time, improve the heating efficiency of the LF refining furnace, and improve the cleanliness of the refined molten steel; then cooperate with the RH refining furnace to add niobium-iron alloy, refine the grain of the double-metal band saw back material steel X32, improve the metal yield of the niobium-iron alloy, reduce the alloy cost, also improve the strength and toughness of the double-metal band saw back material steel X32, avoid the target molten steel from contacting oxygen through argon blowing in the tundish, and perform continuous casting into a slab, thereby ensuring the cleanliness of the double-metal band saw back material steel X32, and obtaining the double-metal band saw back material steel X32 with high yield strength, high tensile strength and high cleanliness.

[0072] The process method is simple, the smelting time is shortened, the energy consumption and cost are reduced, the operation is convenient, the production efficiency is high, it is suitable for large-scale production, and the double-metal band saw back material steel X32 with high yield strength, high tensile strength and high cleanliness is prepared, which has a good effect in improving the cutting ability of the double-metal band saw.

[0073] The application of the double-metal band saw back material steel X32 or the double-metal band saw back material steel X32 prepared by the above preparation method in improving the cutting ability of the double-metal band saw.

[0074] In some embodiments, the double-metal band saw back material steel X32 is made into a double-metal band saw after cold rolling, in the cutting experiment, the cutting ability is improved by 16%, which shows that the niobium fine-grain strengthening can produce a double-metal band saw blade with high toughness and long service life. The double-metal band saw back material steel X32 has a good application in improving the cutting ability of the double-metal band saw.

[0075] In order to further understand the present application, examples are given as follows:

[0076] Example 1

[0077] A 210-ton oxygen converter is used, 175 tons of molten iron and 40 tons of scrap steel are loaded into the converter, 5 tons of ferromolybdenum and 1.6 tons of nickel plate are loaded into the tail of the scrap steel tank for loading the converter scrap steel. The converter smelting operation mode adopts the front furnace slag + inverted front slag operation, after the converter is loaded with scrap steel and molten iron, the front blowing is blown for 5-10 minutes, then the front high-phosphorus converter slag is poured out, and the smelting is carried out again by adding lime, the converter is determined according to the slag detector when tapping, and a small amount of converter molten steel is reserved in the converter.

[0078] After the ladle containing the converter molten steel is sent into the LF refining furnace, the power is immediately turned on to heat up, and the temperature of the converter molten steel is raised to above 1580℃. Then, 9 tons of ferrochrome, 1.5 tons of ferrovanadium, 1 ton of metallic manganese, 0.3 tons of ferrosilicon and 0.2 tons of aluminum block are added into the ladle through the feeding system in 8 batches for alloying, and the interval time of each batch of alloy addition is ≥5 minutes. After the alloy is added, argon stirring is started for 3-5 minutes to obtain the refined molten steel. When the composition of the refined molten steel is detected to be qualified, the time for the refined molten steel to leave the LF refining furnace is ≥8 minutes. The composition of the refined molten steel is: C 0.3214%, Si 0.2298%, Mn 1.005%, Cr 3.874%, Mo 1.321%, Ni 0.7351%, V 0.3562%, Al 0.0672%, and the rest is Fe and unavoidable impurity elements.

[0079] After the ladle containing the refined molten steel reaches the working position of the RH refining furnace, the RH refining furnace vacuum pumping operation is immediately started to ensure that the pressure value under the limit vacuum condition of the RH furnace is ≤133 Pa. Then, 100 Kg of ferro-niobium alloy is added to the refined molten steel under the limit vacuum condition, and the circulation time of the ferro-niobium alloy in the refined molten steel is ≥12 minutes. At the same time, the refining time of the refined molten steel under the limit vacuum condition of the RH refining furnace is ≥15 minutes to improve the cleanliness of the molten steel and obtain the target molten steel. The composition of the target molten steel is: C 0.3194%, Si 0.2341%, Mn 1.001%, Cr 3.855%, Mo 1.334%, Ni 0.7302%, V 0.3611%, Nb 0.029%, Al 0.0594%, P 0.0138%, S 0.0017%, and the rest is Fe and unavoidable impurity elements.

[0080] After the ladle containing the target molten steel reaches the continuous casting machine, the intermediate ladle roasting is turned off, the argon pipeline is put into the intermediate ladle, the intermediate ladle argon blowing operation of the continuous casting machine is started, and the argon blowing is maintained at 30-50 L. When the ladle containing the target molten steel reaches above the intermediate ladle, the ladle is opened to cast the molten steel into the intermediate ladle. After the casting is started, the continuous casting machine is cast at a constant casting speed of 1.0 m / min to obtain the double-metal band saw back material steel X32.

[0081] Through testing, the yield strength of the double-metal band saw back material steel X32 is 1450 MPa, the tensile strength is 2130 MPa, and the elongation is 12%.

[0082] Example 2

[0083] A 210-ton oxygen converter was used, with 174 tons of molten iron and 44 tons of scrap steel charged into the converter. Five tons of molybdenum iron and 1.6 tons of nickel plate were added to the tail of the scrap steel tank. The converter smelting operation mode adopted the front furnace slag + back slag operation. After the converter was filled with scrap steel and molten iron, the front blowing lasted for 5-10 minutes, then the front high phosphorus converter slag was poured out, and the smelting was restarted by adding lime. The converter was determined by the slag detector and a small amount of converter water was retained in the converter.

[0084] After the ladle containing the converter water was sent to the LF refining furnace, the power was immediately turned on to heat it up. When the temperature of the converter water was raised to above 1580℃, 9 tons of chromium iron, 1.5 tons of vanadium iron, 1 ton of manganese iron, 0.3 tons of silicon iron and 0.2 tons of aluminum block were added to the ladle through the feeding system in 7 batches for alloying. The interval time for each batch of alloy addition was 3 minutes. After the alloy was added, argon gas stirring was started for 3-5 minutes to obtain refined molten steel. When the composition of the refined molten steel was detected to be qualified, the time to leave the LF refining furnace was ≥8 minutes. The composition of the refined molten steel was: C 0.3237%, Si 0.2321%, Mn 1.047%, Cr 3.868%, Mo 1.304%, Ni 0.7298%, V 0.3512%, Al 0.0649%, and the rest was Fe and unavoidable impurity elements.

[0085] After the ladle containing the refined molten steel reached the RH refining furnace working position, the RH refining furnace vacuum pumping operation was immediately started to ensure that the pressure value under the limit vacuum condition of the RH furnace was ≤133 Pa. 100Kg of niobium iron alloy was added to the refined molten steel under the limit vacuum condition. The circulation time of the niobium iron alloy in the refined molten steel was ≥12 minutes. At the same time, the smelting time of the refined molten steel under the limit vacuum condition of the RH refining furnace was ≥15 minutes to improve the cleanliness of the molten steel and obtain the target molten steel. The composition of the target molten steel was: C 0.3201%, Si 0.2335%, Mn 1.042%, Cr 3.879%, Mo 1.325%, Ni 0.7301%, V 0.3578%, Nb 0.031%, Al 0.0553%, P 0.0117%, S 0.0010%, and the rest was Fe and unavoidable impurity elements.

[0086] After the ladle containing the target molten steel reached the continuous casting machine, the intermediate ladle roasting was turned off, the argon gas pipeline was put into the intermediate ladle, the argon gas blowing operation of the intermediate ladle of the continuous casting machine was started, and the argon gas blowing was maintained at 30-50L. When the ladle containing the target molten steel reached above the intermediate ladle, the ladle was opened to pour the molten steel into the intermediate ladle. The target molten steel entered the intermediate ladle filled with argon gas. After pouring, the continuous casting machine was poured at a constant speed of 1.0m / min to obtain the double-metal band saw back material steel X32.

[0087] Through testing, the yield strength of the double-metal band saw back material steel X32 was 1408MPa, the tensile strength was 2068MPa, and the elongation was 12%.

[0088] Comparative Example 1

[0089] Compared with Example 1, the step of adding ferro-niobium alloy into the refining molten steel under the limit vacuum of RH refining furnace was omitted.

[0090] In the obtained molten steel, C was 0.3148%, Si was 0.2404%, Mn was 0.9658%, Cr was 3.9317%, Mo was 1.3585%, Ni was 0.7147%, V was 0.3644%, Al was 0.0493%, Nb was 0.0010%, P was 0.0119%, S was 0.0015%, and the rest was Fe and inevitable impurity elements.

[0091] It was tested that the yield strength of the obtained steel was 1208 MPa, the tensile strength was 1879 MPa, and the elongation was 8.5%.

[0092] Comparative Example 2

[0093] Compared with Example 1, the number of LF furnace alloying was reduced to 6 times, and the step of adding ferro-niobium alloy into the refining molten steel under the limit vacuum of RH refining furnace was omitted.

[0094] In the obtained molten steel, C was 0.3166%, Si was 0.2443%, Mn was 1.0224%, Cr was 3.9233%, Mo was 1.3464%, Ni was 0.7136%, V was 0.3597%, Al was 0.0497%, P was 0.0121%, S was 0.0011%, and the rest was Fe and inevitable impurity elements.

[0095] It was tested that the yield strength of the obtained steel was 1179 MPa, the tensile strength was 1798 MPa, and the elongation was 8.0%.

[0096] Based on the classification and rating rules of non-metallic inclusions according to international or national standards (such as GB / T 10561, ISO 4967, ASTM E45), by detecting A / B / C / D fine series and coarse series, the smelting process can be optimized. Among them, referring to Table 1, the non-metallic inclusions of the double-metal band saw back material steel X32 prepared in Example 1 and Example 2 were detected.

[0097] Table 1 Non-metallic inclusion related parameters of double-metal band saw back material steel X32

[0098]

[0099] In summary, the bimetallic band saw back material steel X32 prepared in Example 1 has a yield strength of 1450 MPa, a tensile strength of 2130 MPa, and an elongation of 12%. The content of corresponding non-metallic inclusions is low. Compared with Example 1, the addition amount of the material is appropriately changed in Example 2, and the bimetallic band saw back material steel X32 obtained has a yield strength of 1408 MPa, a tensile strength of 2068 MPa, and an elongation of 12%. The detection of the content of corresponding non-metallic inclusions shows that it is slightly increased compared with Example 1. Referring to Figure 1 the metallographic inclusion microscope image of the bimetallic band saw back material steel X32 prepared in Example 1, Figure 2 the metallographic structure microscope image (100 times magnification) of the bimetallic band saw back material steel X32, and Figure 3 the metallographic structure microscope image (500 times magnification) of the bimetallic band saw back material steel X32. Among them, Figure 2 and Figure 3 the metallographic structures with different magnifications, Figure 2 at 100 times magnification, slight banded structure can be seen. After magnification of 500 times, referring to Figure 3 martensite structure can be seen. That is, the bimetallic band saw back material steel X32 described in the application has a martensite structure. Compared with Example 1, the comparative examples 1-2 omit the process steps, and the yield strength, tensile strength and elongation of the obtained steel are all decreased. Therefore, the bimetallic band saw back material steel X32 described in the application needs to be combined with the corresponding chemical composition and parameters, process steps and corresponding parameters to prepare the bimetallic band saw back material steel X32 with high yield strength, high tensile strength and high cleanliness described in the application. Moreover, the process method is simple, which shortens the smelting time, reduces the energy consumption and cost, is easy to operate, has high production efficiency, is suitable for large-scale production, and has a good effect in improving the cutting capacity of the bimetallic band saw.

[0100] In the above technical solution of the application, the above is only the preferred embodiment of the application, and does not limit the patent scope of the application. Any equivalent structural transformation made by using the content of the application specification and drawings, or direct / indirect application in other related technical fields is included in the patent protection scope of the application.

Claims

1. A method for preparing X32 steel for bimetallic band saw backing, characterized in that, The chemical composition of the bimetallic band saw backing steel X32, by mass percentage, is as follows: C 0.28~0.35%, Si 0.15~0.35%, Mn 0.8~1.2%, Cr 3.6~4.0%, Mo 1.0~1.4%, Ni 0.6~0.9%, V 0.3~0.5%, Nb 0.025~0.055%, Al 0.01~0.06%, P 0.007~0.015%, S 0.0007~0.0017%, with the remainder being Fe and unavoidable impurity elements; The bimetallic band saw backing material uses X32 steel with a yield strength of 1250~1450MPa, a tensile strength of 1900~2200MPa, and an elongation of 9~17%. The method for preparing the bimetallic band saw backing material of steel X32 includes the following steps: The furnace charge is smelted in a converter, refined in LF and RH to obtain the target molten steel. The target molten steel is then continuously cast into slabs to obtain the bimetallic band saw backing steel X32. The furnace charge contains molten iron, scrap steel, ferromolybdenum alloy, and ferronickel alloy; The steps involved in LF refining include: During the process of transferring the molten steel obtained from the converter smelting into the LF refining furnace, the first mass of alloy is added to the LF refining furnace in batches to obtain a mixed solution as refined molten steel. Each batch of alloy is added in the form of a second mass. Before each addition of the second mass of alloy, the LF refining furnace is heated to a first temperature, and argon gas stirring is started after the addition. The first temperature is ≥1580℃; the interval between each batch of alloy added is ≥5 minutes; the argon gas flow rate is 800~1200L / min; and the argon gas stirring time is 3~5 minutes. The second alloy added in each batch is 1.0 to 1.5 tons of ferrochrome alloy or 0.2 to 1.5 tons of one or more alloys selected from ferrosilicon, ferromanganese, ferrovanadium, ferromolybdenum, and ferronickel. The steps of the RH refining process include: The refined molten steel is fed into an RH refining furnace in a vacuum environment, and ferroniobium alloy is added for refining to obtain a mixed liquid, which is the target molten steel. Wherein, the pressure of the vacuum environment is ≤133 Pa; the refining time is ≥15 minutes; and the mass of the added ferroniobium alloy is 0.025~0.055% of the mass of the target molten steel. The vacuum environment is an ultimate vacuum. During the first 3 minutes of the ultimate vacuum, niobium-iron alloy is added to the refined steel; the niobium yield is ≥94%.

2. The method for preparing X32 steel for bimetallic band saw backing material according to claim 1, characterized in that, The converter smelting steps include: After adding the furnace charge to the converter, oxygen is introduced for blowing for 5 to 10 minutes. After pouring out the high-phosphorus slag from the early stage of the converter, lime is added to the converter for smelting. The liquid after separating the impurities is the converter steel. The oxygen blowing pressure is 1.1~1.35MPa, and the phosphorus mass fraction in the converter molten steel is less than 0.011%.

3. The method for preparing X32 steel for bimetallic band saw backing material according to claim 1, characterized in that, The first mass of alloy is 4 to 6% of the mass of the target molten steel.

4. The method for preparing X32 steel for bimetallic band saw backing material according to claim 1, characterized in that, After the last batch of the second-quality alloy is added, stir and mix for at least 8 minutes. The resulting solution is the refined molten steel.

5. The method for preparing X32 steel for bimetallic band saw backing material according to claim 1, characterized in that, In the step of continuously casting to form a slab, the target molten steel is continuously cast to obtain a continuously cast slab; wherein, 30~50L of argon is blown into the tundish and the superheat is controlled at 12~35℃, and the continuous casting speed is 1.0m / min.

6. The application of X32 steel for bimetallic band saw backing material prepared by the preparation method according to any one of claims 1 to 5 in improving the cutting capability of bimetallic band saws.

7. Bimetallic band saw backing steel X32 prepared by the preparation method according to any one of claims 1 to 5.

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