Low-alloy steel grinding ring for ball mill and preparation method of low-alloy steel grinding ring

Abstract

The invention discloses a low-alloy steel grinding ring for a ball mill and a preparation method. The chemical components of the grinding ring are unique, the C content is 0.42-0.46, and the grinding ring contains a plurality of alloy elements in a specific proportion and 2Kg of rare earth. The corners are designed to be R15 arcs, and stress concentration is reduced. During preparation, high-quality cold-rolled sheets are selected and smelted through a medium-frequency induction furnace, and tapping and pouring temperatures and heat treatment temperatures of all stages are accurately controlled. The hardness of the grinding ring reaches HRC48-50, the mechanical performance is excellent, sigma b is 1000-1500 MPa, sigma s is larger than or equal to 350 MPa, A is larger than or equal to 10%, and delta is larger than or equal to 15%. Compared with a traditional grinding ring, the abrasion resistance is greatly improved, the working time is prolonged from 2000 hours to 3000 hours, the crack tendency and abrasion are remarkably reduced, the equipment replacement frequency is reduced, the unit energy consumption and the use investment cost are reduced, and the economic benefits and the market competitiveness of enterprises are effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgy and mechanical manufacturing, and in particular to a low alloy steel grinding ring for a ball mill and a preparation method thereof. Background Art

[0002] In the operation system of the ball mill, the grinding ring, as a key grinding component, undertakes the important task of material grinding. Its performance is directly related to the working efficiency and production capacity of the ball mill. The grinding ring is a consumable part of the coal mill in the pulverizing industry, and its consumption is relatively large.

[0003] In current industry applications, the production and use of grinding rings face many challenges. According to industry standards, the chemical composition range of traditional grinding rings is C: 0.38-0.45, Si: 0.30-0.60, Mn: 0.80-1.0, Cr: 0.80-1.2, Mo: 0.20-0.30, P, S ≤ 0.035. However, grinding rings manufactured based on this chemical composition have a high tendency to crack during the manufacturing process, which not only increases the scrap rate in the production process and increases production costs, but may also cause the service life of the grinding ring to be greatly reduced after installation and use due to further development of cracks.

[0004] At the same time, the hardness of traditional grinding rings is relatively low, and they are prone to cracking during long-term use. The wear resistance of the material also needs to be improved. The low hardness and wear resistance require frequent replacement of grinding rings, which not only increases equipment downtime, reduces production efficiency, but also leads to a decrease in production capacity. Frequent replacement of grinding rings also means that more manpower and material costs need to be invested, thereby increasing the operating costs of the enterprise.

[0005] In summary, developing a grinding ring with high hardness, better wear resistance, low crack tendency and long service life has become a key issue to be urgently solved in the field of ball mills. Summary of the invention

[0006] The present invention aims to overcome the many deficiencies of grinding rings in the prior art and provide a low alloy steel grinding ring for a ball mill with high hardness and good wear resistance. At the same time, the present invention is also committed to providing a grinding ring preparation method that further improves the mechanical properties by optimizing the chemical composition and adopting a specific process, so as to reduce the crack tendency of the grinding ring, extend its service life, reduce the number of equipment replacements, and reduce the investment cost.

[0007] Chemical composition of low alloy steel grinding ring

[0008] The low alloy steel grinding ring of the present invention has the following chemical components by weight percentage: C: 0.42-0.46, Si: 0.50-0.60, Mn: 0.90-1.0, Cr: 1.0-1.1, Ni: 0.40-0.50, Mo: 0.20-0.30, V: 0.09-0.10, Al: 0.02-0.03, Ti: 0.05-0.07, P≤0.015, S≤0.015, 2 kg of rare earth, and the remaining components are Fe and residual elements.

[0009] Structural design of grinding ring

[0010] In order to reduce the stress concentration phenomenon during the grinding ring quenching, the corners of the grinding ring are designed to be an R15 arc structure.

[0011] Preparation method of low alloy steel grinding ring

[0012] Raw material selection: Select high-quality cold-rolled sheets, resolutely do not add any recycled materials, and conduct spectral analysis to accurately determine the composition content of scrap steel.

[0013] Melting: Add cold-rolled steel scrap into the medium frequency induction furnace. When the molten steel is fully melted, take a sample immediately for spectral analysis to determine the chemical composition of the molten steel. According to the analysis results, add the corresponding alloy material accurately. Then, let the molten steel settle in the furnace for 30 minutes, and take a sample again for spectral analysis of the chemical composition. When the composition fully meets the requirements of the present invention, tap the steel at a furnace temperature of 1620-1640°C. When tapping the steel, quickly add the aluminum block and rare earth into the ladle, followed by a 10-15 minute calming operation.

[0014] Pouring: Closely monitor the temperature of the molten steel. When the temperature drops to 1530-1550℃, start the pouring operation. After the pouring is completed, let the grinding ring cool naturally in the sand mold and demould it after 72 hours. It should be noted that the temperature of the grinding ring itself should not be lower than 350℃ during demoulding, and the pouring riser should be cut immediately after demoulding.

[0015] Heat treatment: After cutting the pouring and riser, the grinding ring is placed in the furnace for annealing heat treatment, and the annealing temperature is strictly controlled at 880-900℃. After annealing, the grinding ring is cooled to 300℃ in the furnace, and then directly tempered at 550-600℃. After tempering, the grinding ring is naturally air-cooled to below 200℃.

[0016] Processing and flaw detection: Rough processing is performed on the grinding ring. After rough processing, UT and MT flaw detection technology are used to conduct comprehensive flaw detection on the grinding ring to ensure that there are no defects inside the grinding ring.

[0017] Final treatment: After passing the flaw detection, the grinding ring is subjected to quenching treatment at 900-920℃ and tempering treatment at 420-440℃. After tempering, the grinding ring is allowed to cool naturally to below 35℃.

[0018] Testing: Professional hardness testing and mechanical property testing methods are used to strictly test the grinding ring to ensure that its various properties fully meet the predetermined chemical composition and mechanical property requirements of the present invention.

[0019] Beneficial effects of the present invention:

[0020] 1. The low alloy steel grinding ring prepared by the method of the present invention has a hardness of HRC48-50 and good toughness and plasticity. Its mechanical properties are excellent, σb: 1000-1500MPa, σs≥350MPa, A≥10%, δ≥15%. This effectively reduces the crack tendency of the grinding ring when it is subjected to greater pressure and impact, greatly improving the reliability and stability of the grinding ring.

[0021] 2. Through careful adjustment of the type and content of alloy elements and unique heat treatment process, the wear resistance of the grinding ring of the present invention has been greatly improved. In actual use, the wear of the grinding ring is significantly reduced, effectively extending the service life of the grinding ring. The working time of the grinding ring is greatly increased from the original 2000 hours to 3000 hours, reducing the number of equipment shutdowns due to grinding ring replacement and improving production efficiency.

[0022] 3. The extension of the service life of the grinding ring directly reduces the number of equipment replacements, and reduces the cost of enterprises in the purchase and replacement of grinding rings and production losses caused by downtime. At the same time, due to the excellent performance of the grinding ring of the present invention, the unit energy consumption of the ball mill can be effectively reduced, further saving production costs for the enterprise and improving the economic benefits and market competitiveness of the enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 It is a schematic diagram of the three-dimensional structure of an embodiment of the present invention;

[0025] Figure 2 It is a schematic diagram of the cross-sectional structure of an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. At the same time, it is explained here that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments, and those skilled in the art may also adopt other alternatives to implement some known technologies; and the accompanying drawings are only for more specific description of the embodiments, and are not intended to specifically limit the present invention.

[0027] It should be noted that the references to "one embodiment", "an embodiment", "an exemplary embodiment", "some embodiments" and the like in the specification indicate that the embodiments described may include specific features, structures or characteristics, but not every embodiment may include the specific features, structures or characteristics. In addition, when a specific feature, structure or characteristic is described in conjunction with an embodiment, it should be within the knowledge of a person skilled in the art to implement such feature, structure or characteristic in conjunction with other embodiments (whether or not explicitly described).

[0028] In general, a term can be understood, at least in part, from its use in context. For example, depending, at least in part, on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in the singular sense, or can be used to describe a combination of features, structures, or characteristics in the plural sense. Additionally, the term "based on" can be understood as not necessarily intended to convey an exclusive set of factors, but can instead, depending, at least in part, on the context, allow for the presence of other factors that are not necessarily explicitly described.

[0029] See also Figure 1 to Figure 2

[0030] A low alloy steel grinding ring for a ball mill. The chemical composition of the low alloy steel grinding ring is as follows by weight percentage: C: 0.42-0.46, Si: 0.50-0.60, Mn: 0.90-1.0, Cr: 1.0-1.1, Ni: 0.40-0.50, Mo: 0.20-0.30, V: 0.09-0.10, Al: 0.02-0.03, Ti: 0.05-0.07, P≤0.015, S≤0.015, 2 kg of rare earth, and the remaining components are Fe and residual elements.

[0031] Specifically, the corners of the grinding ring are all rounded structures with a radius of 15 mm.

[0032] A method for preparing a low alloy steel grinding ring for a ball mill comprises the following steps:

[0033] Step 1: Select high-quality cold-rolled sheet without adding any recycled materials, and use spectral analysis to determine the content of scrap steel in the cold-rolled sheet;

[0034] Step 2: Put the selected cold-rolled steel scrap into the medium-frequency induction furnace, and after the molten steel in the furnace is fully melted, perform spectral analysis to determine the chemical composition of the molten steel; determine the type and amount of alloy materials to be added based on the chemical composition and add them; after settling in the furnace for 30 minutes, perform spectral analysis again to determine the chemical composition of the molten steel; when the composition meets the predetermined requirements, tap the steel at a furnace temperature of 1620-1640°C, add aluminum blocks and rare earths to the ladle during tapping, and then perform a 10-15 minute calming operation;

[0035] Step 3: When the temperature of the molten steel is in the range of 1530-1550°C, the pouring operation is started; after the pouring is completed, the grinding ring is allowed to cool naturally in the sand mold, and the sand mold is opened for demoulding after 72 hours, and the pouring riser is cut off when the grinding ring temperature is not lower than 350°C;

[0036] Step 4: After the pouring and riser are cut off, the grinding ring is placed in a furnace for annealing heat treatment, and the annealing temperature is set at 880-900℃; after the annealing is completed, the grinding ring is cooled to 300℃ in the furnace, and then tempering heat treatment is carried out, and the tempering temperature is controlled at 550-600℃. After the tempering is completed, it is naturally air-cooled to below 200℃;

[0037] Step 5: Rough machining is performed on the grinding ring. After the rough machining is completed, the grinding ring is inspected by using UT and MT flaw detection technology to ensure that there are no defects inside the grinding ring.

[0038] Step 6: After the flaw detection is qualified, the grinding ring is quenched at 900-920℃, and then tempered at 420-440℃. After tempering, it is naturally air-cooled to below 35℃;

[0039] Step 7: Use hardness test and mechanical property test methods to test the grinding ring to ensure that the various properties of the grinding ring meet the predetermined chemical composition and mechanical property index requirements.

[0040] Example 1

[0041] Before melting, select high-quality cold-rolled sheet materials without adding any recycled materials, and analyze their chemical composition to confirm the content of scrap steel; take cold-rolled sheet scrap steel and add it to the medium-frequency induction furnace. After it is fully melted, take samples and analyze the chemical composition of the melted molten steel. According to the purpose of the project, after determining the chemical composition of the molten steel, determine the corresponding alloy materials to be added according to the composition of the molten steel. After settling in the furnace for 30 minutes, sample the spectral chemical composition again. After the composition meets the requirements of this project, tap the steel at a furnace temperature of 1620-1640℃. When tapping, add aluminum blocks and rare earths into the ladle, and then calm it for 10-15 minutes. Measure the temperature and start pouring when the molten steel temperature reaches 1530-1550℃. After pouring, the grinding ring is cooled naturally in the sand mold. After 72 hours, it is unpacked and demolded. The temperature of the grinding ring itself shall not be lower than 350℃. Then the pouring riser is cut. After cutting, it is put into the furnace for annealing heat treatment. The annealing temperature is 880-900℃. After annealing, it is cooled to 300℃ in the furnace and directly tempered. The tempering temperature is 550-600℃. After tempering, it is naturally air-cooled to below 200℃; then rough machining is carried out. After rough machining, UT and MT flaw detection are performed. If there are no internal defects, 900-920℃ quenching treatment and 420-440℃ tempering treatment are carried out. After tempering, it is naturally air-cooled to below 35℃. Hardness test and mechanical property test are performed to see if they meet the chemical composition and mechanical property requirements of the project.

[0042] Example 1 Alloy composition and performance table:

[0043] C Si Mn P S Cr Ni Mo V Ti Re HRC σb σs A δ 1 0.441 0.548 0.941 0.013 0.012 0.051 0.431 0.229 0.09 0.065 2Kg 49 1356 375 12 16 2 0.42 0.38 0.825 0.03 0.02 0.025 / 0.209 0.002 / / 42 933 333 11 19

[0044] Serial number 1 is the alloy composition of this project, and serial number 2 is the original chemical composition.

[0045] The present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention. In order to make the public have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can fully understand the present invention without the description of these details. In addition, in order to avoid unnecessary confusion about the essence of the present invention, well-known methods, processes, procedures, components and circuits are not described in detail.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A low alloy steel grinding ring for a ball mill, characterized in that: The chemical composition of the low alloy steel grinding ring is calculated by weight percentage: C: 0.42-0.46, Si: 0.50-0.60, Mn: 0.90-1.0, Cr: 1.0-1.1, Ni: 0.40-0.50, Mo: 0.20-0.30, V: 0.09-0.10, Al: 0.02-0.03, Ti: 0.05-0.07, P≤0.015, S≤0.015, rare earth 2Kg, and the remaining components are Fe and residual elements.

2. The low alloy steel grinding ring for ball mill according to claim 1, characterized in that: The corners of the grinding ring are all rounded structures with a radius of 15 mm.

3. A method for preparing a low alloy steel grinding ring for a ball mill, characterized in that: The following steps are involved: Step 1: Select high-quality cold-rolled sheet without adding any recycled materials, and use spectral analysis to determine the content of scrap steel in the cold-rolled sheet; Step 2: Put the selected cold-rolled steel scrap into the medium-frequency induction furnace, and after the molten steel in the furnace is fully melted, perform spectral analysis to determine the chemical composition of the molten steel; determine the type and amount of alloy materials to be added based on the chemical composition and add them; after settling in the furnace for 30 minutes, perform spectral analysis again to determine the chemical composition of the molten steel; when the composition meets the predetermined requirements, tap the steel at a furnace temperature of 1620-1640°C, add aluminum blocks and rare earths to the ladle during tapping, and then perform a 10-15 minute calming operation; Step 3: When the temperature of the molten steel is in the range of 1530-1550℃, start the pouring operation; after the pouring is completed, let the grinding ring cool naturally in the sand mold, open the sand mold for demoulding after 72 hours, and cut off the pouring riser when the grinding ring temperature is not lower than 350℃; Step 4: After the pouring and riser are cut off, the grinding ring is placed in a furnace for annealing heat treatment, and the annealing temperature is set at 880-900℃; after the annealing is completed, the grinding ring is cooled to 300℃ in the furnace, and then tempering heat treatment is carried out, and the tempering temperature is controlled at 550-600℃. After the tempering is completed, it is naturally air-cooled to below 200℃; Step 5: Rough machining is performed on the grinding ring. After the rough machining is completed, the grinding ring is inspected by using UT and MT flaw detection technology to ensure that there are no defects inside the grinding ring. Step 6: After the flaw detection is qualified, the grinding ring is quenched at 900-920℃, and then tempered at 420-440℃. After tempering, it is naturally air-cooled to below 35℃; Step 7: Use hardness test and mechanical property test methods to test the grinding ring to ensure that the various properties of the grinding ring meet the predetermined chemical composition and mechanical property index requirements.

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