Preparation method of CADI wear-resistant material for grinding section

Abstract

The invention belongs to the technical field of casting, and particularly relates to a preparation method of a CADI wear-resistant material for a grinding section, which comprises the following specific steps: producing the grinding section by adopting a CADI material; the CADI grinding section is heated through a continuous push rod type heat treatment production line; a quenching cooling medium is changed into tap water from isothermal quenching oil, so that the CADI grinding section is quickly cooled to bainite transformation temperature and then is discharged by utilizing the characteristic of high cooling speed of a water medium, and in the process, oil steam pollution can be avoided, and meanwhile, the potential fire hazard that an oil pool catches fire is reduced; staying in the air to reduce the temperature difference between the surface and the core part of the CADI grinding section; and the CADI grinding section is pushed into an isothermal tempering furnace to be subjected to isothermal treatment in air. In the process of preparing the CADI grinding section, a heat treatment quenching cooling medium is changed into tap water from original isothermal quenching oil, so that the pollution influence of oil steam on the environment can be solved, the potential risk of ignition of an oil pool can be eliminated, and the cost investment can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of casting, in particular to a method for preparing a CADI wear-resistant material for a grinding segment. Background Art

[0002] The crushing and grinding in the grinding ball mill are achieved through the grinding medium. The filling rate, gradation and shape of the grinding medium are the key to improving the grinding efficiency. At present, the grinding medium shape is spherical and cylindrical, and the first and second stage grinding is mainly spherical, and the third stage fine grinding is mainly cylindrical. In the third stage of the mining ball mill, low chromium alloy castings (YB / T093-2005 low chromium alloy cast iron grinding) are mostly used in China. According to the standard requirements: The surface Rockwell hardness of low chromium alloy cast iron grinding section should be above HRC50.

[0003] The surface Rockwell hardness of the low-chromium alloy cast iron grinding section should be no less than HRC48 when the nominal diameter is less than 35mm; and no less than HRC45 when the diameter is ≥35mm. The crushing rate should be no more than 1.0%.

[0004] In actual production, the surface hardness of low-chromium alloy cast iron grinding segments is below HRC50. The impact value is 1-2J, so the crushing rate is greater than 1%, resulting in high wear. In view of the actual use of domestic grinding segments, the technology of producing CADI grinding balls was transplanted to the production of grinding segments, and the grinding segments made of CADI material were developed. After actual use in mines, the wear was reduced by 30-40% compared with the low-chromium alloy cast iron grinding segments, and they were applied and promoted in mine ball mills.

[0005] CADI grinding segment: A proper amount of carbide-forming elements are added to ductile iron, and a ductile iron grinding segment containing acicular ferrite, carbon-rich austenite, graphite nodules and a proper amount of carbides is obtained through austempering, referred to as CADI grinding segment.

[0006] At present, most of the heat treatment of CADI materials produced in China adopts salt bath isothermal quenching, but the salt bath isothermal quenching equipment is relatively complicated, and the salt vapor emitted by sodium nitrate and potassium nitrate at high temperature is highly corrosive, which has an adverse effect on the environment. The quenched workpiece also needs to be rinsed with water, so water treatment equipment is also equipped. The equipment purchase cost and production cost are high. For low value-added grinding sections, using this process and equipment is not competitive.

[0007] Another isothermal heat treatment process is to use isothermal quenching oil continuous cooling + residual heat isothermal process, but the oil quenching process will also produce oil vapor and oil residue, causing environmental pollution. After quenching, the surface of the workpiece will be adhered to a layer of oil, which will continue to burn and produce oil smoke during the isothermal tempering process. Therefore, the heat treatment production line must be equipped with an oil fume purification device. At the same time, the oil pool has the potential risk of fire, so a new quenching medium must be found.

[0008] Based on the above, a method for preparing CADI wear-resistant material for grinding segments is invented. Summary of the invention

[0009] To solve the above technical problems, according to one aspect of the present invention, the present invention provides the following technical solutions: A method for preparing a CADI wear-resistant material for a grinding section comprises the following specific steps: Step 1: Use CADI material to produce the grinding section; Step 2: Use a continuous push rod heat treatment production line to heat the CADI mill section; Step 3: Change the quenching cooling medium from isothermal quenching oil to tap water, so as to take advantage of the fast cooling speed of water medium and quickly cool the CADI grinding section to the bainite transformation temperature before discharging water. In this process, oil vapor pollution will be avoided and the potential fire hazard of oil pool fire will be reduced; Step 4: Stay in the air to reduce the temperature difference between the surface and the core of the CADI mill; Step 5: Push the CADI grinding section into the isothermal tempering furnace for isothermal treatment in air.

[0010] As a preferred solution of the method for preparing a CADI wear-resistant material for a grinding segment described in the present invention, the water temperature is controlled at 30-50°C during water quenching of the CADI grinding segment.

[0011] As a preferred solution of the method for preparing a CADI wear-resistant material for a grinding segment described in the present invention, the time for which the CADI grinding segment is in water is 10-30 seconds.

[0012] As a preferred solution of the method for preparing a CADI wear-resistant material for a grinding section described in the present invention, the surface temperature of the outlet water of the CADI grinding section is controlled at 180-250°C.

[0013] As a preferred solution of the method for preparing a CADI wear-resistant material for a grinding segment described in the present invention, the cooling time of the CADI in air is 30-100 seconds.

[0014] As a preferred solution of the method for preparing a CADI wear-resistant material for a grinding segment described in the present invention, the residual heat isothermal treatment time of the CADI grinding segment is controlled within 180-360 minutes.

[0015] Compared with existing technologies: The present invention adopts CADI material to produce grinding segments, which can greatly reduce the wear of the grinding segments. In addition, by changing the heat treatment quenching cooling medium from the original isothermal quenching oil to tap water during the preparation of the CADI grinding segments, it can not only solve the pollution effect of oil vapor on the environment, but also eliminate the potential danger of oil pool fire and reduce the cost investment. DETAILED DESCRIPTION

[0016] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below.

[0017] Embodiment 1: The present invention provides a method for preparing a CADI wear-resistant material for a grinding section, comprising the following specific steps: Step 1: Use CADI material to produce the grinding section; Step 2: Use a continuous push rod heat treatment production line to heat the CADI mill section; Step 3: Change the quenching cooling medium from isothermal quenching oil to tap water, so as to take advantage of the fast cooling speed of water medium and quickly cool the CADI grinding section to the bainite transformation temperature before discharging water. In this process, oil vapor pollution will be avoided and the potential fire hazard of oil pool fire will be reduced; Step 4: Stay in the air to reduce the temperature difference between the surface and the core of the CADI mill; Step 5: Push the CADI grinding section into the isothermal tempering furnace for isothermal treatment in air.

[0018] In the above steps, the quenching line and the tempering line will be linked according to the set production rhythm, and in the quenching process, it will be required to make clear process regulations for various parameters such as the maximum heating temperature, heating time, water medium temperature, cooling time in water, water outlet temperature, equalization time in air, isothermal temperature, isothermal time, etc. of different diameter grinding sections, so as to formulate a complete heat treatment process specification, which will be executed by PLC to reduce the influence of human factors; among them, the water temperature of the CADI grinding section is controlled at 30°C during water quenching; the time of the CADI grinding section in water is 10 seconds; the surface temperature of the water outlet of the CADI grinding section is controlled at 180°C; the residual heat isothermal treatment temperature of the CADI grinding section is controlled at 200°C; the residual heat isothermal treatment time of the CADI grinding section is controlled at 180 minutes; the cooling time of CADI in the air is 30 seconds.

[0019] Embodiment 2: The present invention provides a method for preparing a CADI wear-resistant material for a grinding section, comprising the following specific steps: Step 1: Use CADI material to produce the grinding section; Step 2: Use a continuous push rod heat treatment production line to heat the CADI mill section; Step 3: Change the quenching cooling medium from isothermal quenching oil to tap water, so as to take advantage of the fast cooling speed of water medium and quickly cool the CADI grinding section to the bainite transformation temperature before discharging water. In this process, oil vapor pollution will be avoided and the potential fire hazard of oil pool fire will be reduced; Step 4: Stay in the air to reduce the temperature difference between the surface and the core of the CADI mill; Step 5: Push the CADI grinding section into the isothermal tempering furnace for isothermal treatment in air.

[0020] In the above steps, the quenching line and the tempering line will be linked according to the set production rhythm, and in the quenching process, it will be required to make clear process regulations for various parameters such as the maximum heating temperature, heating time, water medium temperature, cooling time in water, water outlet temperature, equalization time in air, isothermal temperature, isothermal time, etc. of different diameter grinding sections, so as to formulate a complete heat treatment process procedure, which will be executed by PLC to reduce the influence of human factors; among them, the water temperature of the CADI grinding section is controlled at 40°C during water quenching; the time of the CADI grinding section in water is 20 seconds; the surface temperature of the water outlet of the CADI grinding section is controlled at 215°C; the residual heat isothermal treatment temperature of the CADI grinding section is controlled at 250°C; the residual heat isothermal treatment time of the CADI grinding section is controlled at 270 minutes; the cooling time of CADI in the air is 65 seconds.

[0021] Embodiment 3: The present invention provides a method for preparing a CADI wear-resistant material for a grinding section, comprising the following specific steps: Step 1: Use CADI material to produce the grinding section; Step 2: Use a continuous push rod heat treatment production line to heat the CADI mill section; Step 3: Change the quenching cooling medium from isothermal quenching oil to tap water, so as to take advantage of the fast cooling speed of water medium and quickly cool the CADI grinding section to the bainite transformation temperature before discharging water. In this process, oil vapor pollution will be avoided and the potential fire hazard of oil pool fire will be reduced; Step 4: Stay in the air to reduce the temperature difference between the surface and the core of the CADI mill; Step 5: Push the CADI grinding section into the isothermal tempering furnace for isothermal treatment in air.

[0022] In the above steps, the quenching line and the tempering line will be linked according to the set production rhythm, and in the quenching process, it will be required to make clear process regulations for various parameters such as the maximum heating temperature, heating time, water medium temperature, cooling time in water, water outlet temperature, equalization time in air, isothermal temperature, isothermal time, etc. of different diameter grinding sections, so as to formulate a complete heat treatment process specification, which will be executed by PLC to reduce the influence of human factors; among them, the water temperature of the CADI grinding section is controlled at 50°C during water quenching; the time of the CADI grinding section in water is 30 seconds; the surface temperature of the water outlet of the CADI grinding section is controlled at 250°C; the residual heat isothermal treatment temperature of the CADI grinding section is controlled at 300°C; the residual heat isothermal treatment time of the CADI grinding section is controlled at 360 minutes; the cooling time of CADI in the air is 100 seconds.

[0023] After the performance test of the CADI mill segment prepared above, the data comparison is shown in the following table: In summary, after use, embodiment 2 has the best effect.

[0024] In the present invention, the cooling time and water outlet temperature of austinite cast balls of different specifications in water are specified as follows: In the present invention, when the quenched casting section is subjected to temperature equalization treatment and then enters the isothermal tempering furnace, and isothermal treatment is performed using the residual heat of the casting section, the isothermal treatment process is controlled as follows: Although the present invention has been described above with reference to the embodiments, various modifications may be made thereto and parts thereof may be replaced by equivalents without departing from the scope of the present invention. In particular, as long as there is no structural conflict, the various features in the embodiments disclosed in the present invention may be used in combination with each other in any manner, and the fact that these combinations are not exhaustively described in this specification is only for the sake of omitting space and saving resources. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for preparing CADI wear-resistant material for grinding segments, characterized in that: The specific steps are as follows: Step 1: Use CADI material to produce the grinding section; Step 2: Use a continuous push rod heat treatment production line to heat the CADI mill section; Step 3: Change the quenching cooling medium from isothermal quenching oil to tap water, so as to take advantage of the fast cooling speed of water medium and quickly cool the CADI grinding section to the bainite transformation temperature before discharging water. In this process, oil vapor pollution will be avoided and the potential fire hazard of oil pool fire will be reduced; Step 4: Stay in the air to reduce the temperature difference between the surface and the core of the CADI mill; Step 5: Push the CADI grinding section into the isothermal tempering furnace for isothermal treatment in air.

2. The method for preparing a CADI wear-resistant material for a grinding segment according to claim 1, characterized in that: The water temperature of the CADI mill section is controlled at 30-50°C during water quenching.

3. The method for preparing a CADI wear-resistant material for a grinding segment according to claim 1, characterized in that: The CADI mill section is in water for 10-30 seconds.

4. The method for preparing a CADI wear-resistant material for a grinding segment according to claim 1, characterized in that: The surface temperature of the outlet water of the CADI mill section is controlled at 180-250°C.

5. The method for preparing a CADI wear-resistant material for a grinding segment according to claim 1, characterized in that: The cooling time of the CADI in air is 30-100 seconds.

6. The method for preparing a CADI wear-resistant material for a grinding segment according to claim 1, characterized in that: The isothermal treatment time of the residual heat of the CADI mill section is controlled within 180-360 minutes.

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