A production method of high-chromium cast iron wear-resistant roller sleeve

Abstract

The application discloses a production method of a high-chromium cast iron wear-resistant roller sleeve and belongs to the cast technology field.The production method of the high-chromium cast iron wear-resistant roller sleeve is characterized in that specific metal is added on the basis of high-chromium material, and the production method has more uniform crystal phase organization distribution, smaller and denser crystal grains and better quenching hardenability.Compared with common high-chromium roller sleeves, the product has higher hardness, better toughness, excellent wear resistance and long service life, greatly reduces the replacement frequency of the wear-resistant roller sleeve, improves the use cost performance of customers, has the characteristics of high hardness, high toughness and high wear resistance, and is wear-resistant, tough and mechanically strong.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of casting, and particularly relates to a production method of a high-chromium cast iron wear-resistant roller sleeve. BACKGROUND

[0002] The material commonly used for the roller sleeve of a coal mill in a thermal power plant is usually wear-resistant cast iron. The normal service life of a set of roller sleeves is 8-12 months, and the coal blocks used for power generation in the power plant often contain a large amount of coal gangue, which further aggravates the wear of the roller sleeves. Under normal circumstances, a small power plant needs to replace at least 18 roller sleeves per year due to wear, and the procurement cost of each roller sleeve is about 60,000 yuan. The annual cost for replacing the roller sleeves is more than 1 million yuan. When the wear of the mill plate lining plate and the roller sleeve reaches about 20 mm, the hourly output of the coal mill will be reduced to 70% of the original, and the roller sleeve of the coal mill needs to be replaced in time. During the operation of the roller sleeve, the vibration of the coal mill and the wear of the roller sleeve will cause stress concentration, resulting in cracks on the roller sleeve, and even the breakage of the roller sleeve. The domestic thermal power plant needs to replace about 2,000 types of roller sleeves every year. Therefore, improving the service life of the roller sleeve and reducing the replacement cost of the roller sleeve are the most concerned and valued problems of the power plant, and have very important research value and good market prospect. For example, in the early stage of the establishment of Harbin Thermal Power Plant in 1959, the total of 9 domestic medium-speed coal mills were equipped in the milling system, each mill was equipped with 3 roller sleeves, and the total number of roller sleeves was 27. A new production method of a high-chromium cast iron wear-resistant roller sleeve needs to be developed urgently. Industrial application experiments show that the service life of the wear-resistant roller sleeve prepared by using an alumina particle reinforced hyper-eutectic high-chromium cast iron composite material in a cement raw mill vertical mill can be more than twice that of the original high-chromium cast iron roller sleeve. The technical personnel in the field urgently need to develop a production method of a high-chromium cast iron wear-resistant roller sleeve to meet the existing use requirements and performance requirements. SUMMARY

[0003] The purpose of the application is to provide a production method of a high-chromium cast iron wear-resistant roller sleeve to solve the existing problems.

[0004] The application is implemented by the following technical scheme:

[0005] A production method of high-chromium cast iron wear-resistant roller sleeve, comprising the following steps: first step, forming shell and core by phenolic resin coated sand through shell machine and core machine, placing dried sand core, closing box, completing casting model, placing furnace charge in medium frequency furnace for smelting to form molten iron, smelting temperature is 1450-1500 DEG C, wherein the composition of the molten iron is C2.6-2.9%, Si0.6-1.2%, Mn0.6-0.8%, P≤0.1%, S≤0.1%, Cr22-24%, Ni0.5~0.8%, Cu0.8-1.0%, Mo1.8-2.0%, the rest is Fe and inevitable impurity elements, total 100%; second step, after the molten iron is transferred into the ladle, argon blowing refining is needed for the molten steel in the ladle, argon blowing time is 3-5 minutes, and pouring into the casting model for forming; third step, after forming, natural cooling to 250-300 DEG C, and cleaning the casting; fourth step, after sand dropping, the semi-finished product is put into a shot blasting machine for removing surface impurities; fifth step, surface build-up welding: using diameter 3.0-4.0mm build-up welding flux-cored wire and AH20 flux as build-up welding materials, the composition of the welding flux-cored wire is C6-7.50%, Si1.5-1.80%, Mn1.3-1.50%, Cr26-32.0%, Ni0.5-1.00%, Mo5-7.50%, S≤0.025%, P≤0.030%, Fe balance.

[0006] Further, the fourth step shot blasting process is conveying speed 4.5 m / min, 0.425-0.71 mm cast steel shot projection speed 50-60 m / s, projection angle 30 DEG ~ 60 DEG, shot blasting amount 250 kg / min, coverage 95%.

[0007] Further, the build-up welding uses GP-100-C3 high-frequency induction build-up welding heating equipment, maximum output power 100 kW, output oscillation frequency 200-250 kHz, anode voltage 8.5-9.0 kV, anode current 5.0-5.1 A, grid voltage 0.9-1.1 kV, grid current 1.0-1.2 A, heating time 30 s.

[0008] Further, the second step deoxidizer accounts for one thousandth to two thousandth of the weight of the molten iron, and the deoxidizer is silicon-calcium alloy.

[0009] Further, the second step argon blowing rate is 3-4 m3 / min, the pouring speed is controlled to be 3-5 kg / s, and the pouring temperature is 1420-1450 DEG C.

[0010] C, Cr elements are the most important in the material composition selection, they are the key factors to determine whether the hardness of the casting meets the standard. The role of carbon is the largest, it can increase the amount of cementite, thereby improving wear resistance, but the toughness is reduced, therefore for the larger impact of the casting, its content cannot be too high. Chromium promotes the formation of carbide and increases the hardness of carbide, chromium and carbon, silicon, thereby can greatly improve the wear resistance and impact toughness, also need to control the cracking tendency of the casting. Molybdenum enters part of the carbide, another part of the austenite, the amount of dissolved molybdenum can improve the hardenability, when used with copper, its effect of improving hardenability is greater, in addition, it also has a certain help to improve the hardness of the casting. Manganese can expand the austenite phase region.

[0011] Nickel does not dissolve in carbide and enters austenite completely, which can fully play its role in improving hardenability, promote the formation of martensite or bainite matrix, in addition, nickel can also promote graphitization.

[0012] The production method of high chromium cast iron wear-resistant roller sleeve is based on high chromium material, through the addition of specific metal, it has more uniform crystal phase organization distribution, smaller and denser crystal grains, better hardenability. Compared with ordinary high chromium roller sleeve, this product has higher hardness, better toughness, excellent wear resistance and long service life, greatly reduces the replacement frequency of wear-resistant roller sleeve and improves the use cost-effectiveness of customers, has the characteristics of high hardness, high toughness and high wear resistance, not only wear-resistant, but also has toughness and mechanical strength. DETAILED DESCRIPTION

[0013] The application will be described in detail below with specific examples, but it is not limited to the application. Example 1

[0014] Step 1: Select a kgps-1.0t-630 medium-frequency centerless induction corundum lining electric furnace. Use fresh feedstock or unsintered old lining material mixed with 10% 170-mesh fused magnesia and 5-10% water glass for the furnace collar and taphole. Compact the mixture and harden it by heating or blowing CO2. First, add a mixture of scrap steel and slag-forming material to the furnace chamber, filling it to 1 / 3 of its depth. Operate the furnace at 60% power. After the material melts, increase the power to 100%, adding and melting the material simultaneously. During the adding process, prevent the material from accumulating. After the scrap steel is melted and cleared, high-carbon ferromanganese and medium-carbon ferromanganese alloys are added. Only after the alloys melt can silicon-calcium alloys be added for precipitation and deoxidation. Samples are taken for chemical analysis, and after adding more alloys, the chemical composition is: C 2.6–2.9%, Si 0.6–1.2%, Mn 0.6–0.8%, P ≤0.1%, S ≤0.1%, Cr 22–24%, Ni 0.5–0.8%, Cu 0.8–1.0%, Mo 1.8–2.0%, with the remainder being Fe and unavoidable impurities, totaling 100%. After heating, silicon-calcium particles with a particle size no larger than 10mm are added for final deoxidation, and the ladle is prepared for tapping. The silicon-calcium particles account for 0.2% of the weight of the molten iron. The melting temperature is 1450–1500℃. Before use, the ladle needs to be dried in a baking furnace for 3–4 hours, reaching a temperature of 750℃ after baking. After the molten steel is melted and transferred to the ladle, it needs to be refined by argon blowing within the ladle for 3 minutes. The argon blowing rate is 3~4 m3 / min, and the pouring speed is controlled within the range of 50 kg / s. The sand core is placed in the baking oven for baking, with a baking temperature of 80℃ and a baking time of 1 hour. The overhead crane LD5-15.92-A3 is used. Operators must wear masks, gloves, and other protective equipment and check that the equipment is functioning properly. The vertical parting molding machine CX-Ⅱ207 uses coated sand to make the shell, and the core shooting machine FPG600 makes the sand core. For the mold assembly: remove burrs from the inside of the upper and lower sand box cavities and bake the cavity surface with a dryer to remove moisture; first, use the overhead crane to lift the lower sand box to the designated platform for placing the sand box; place the dried sand core, then use the overhead crane to lift the upper sand box, align the assembly, and lock both ends of the sand box; finally, lift the sand box platform into the pouring position in front of the furnace. Step 2, Pouring: Before use, the ladle is dried in a baking oven for 4 hours, until the temperature reaches 850℃. The ladle is then moved to the sand box and pouring in front of the riser. The pouring speed should follow a slow-fast-slow rhythm, starting slowly and then increasing the speed. When 2 / 3 of the ladle has been poured, it should be slowly closed. When the molten iron fills the sand box and riser, rice husk ash or covering agent should be added to the riser for insulation. After pouring, the ladle should be kept warm in the sand for at least 5 minutes. Then, the fasteners of the sand box should be unlocked, and the sand box should be lifted and neatly placed in the sand cleaning area. After pouring, depending on the thickness of the casting wall, oxygen should be blown into the riser within 30 minutes to extend the time of maintaining the high temperature of the riser. One riser should be blown into each product for 1 minute.Before pouring, the temperature of the molten iron in the ladle is measured by a hand-held thermocouple temperature measuring gun, the pouring speed is 3-5 kg / s, the pouring temperature is 1420-1450℃; the third step, after forming, naturally cooling to 250-300℃, cleaning the castings; the fourth step, after shakeout, the semi-finished product enters the QR3210 shot blasting machine to remove surface impurities, the pad conveying speed is 4.5 m / min, the 0.425 mm of Kaite S-170 cast steel shot blasting speed is 60 m / s, the blasting angle is 60°, the shot blasting amount is 250 kg / min, the coverage is 95%; the fifth step, surface build-up welding: using a diameter of 3.0-4.0 mm of build-up welding wire and AH20 flux as build-up welding material, the composition of the welding core wire is C6-7.50%, Si1.5-1.80%, Mn1.3-1.50%, Cr26-32.0%, Ni0.5-1.00%, Mo5-7.50%, S≤0.025%, P≤0.030%, Fe balance, the build-up welding uses a GP-100-C3 high-frequency induction build-up welding heating equipment, the maximum output power is 100 kW, the output oscillation frequency is 200-250 kHz, the anode voltage is 8.5-9.0 kV, the anode current is 5.0-5.1 A, the grid voltage is 0.9-1.1 kV, the grid current is 1.0-1.2 A, the heating time is 30 s.

[0015] Product: impact toughness impact performance ≥ 5J / m2; hardness ≥ 58HRC. The sand sticking, oxide skin and the like on the inner cavity and outer surface of the high-grade cast iron roller sleeve are cleaned, the surface is flat and smooth, the surface roughness meets the requirements of Ra≤50μm in GB / T6060.1. There are no cracks, shrinkage holes, pores, slag and other defects reducing strength or damaging appearance. The cast iron roller sleeve is heat treated, and the surface is free of sand sticking and other defects after precision cleaning and shot blasting. Example 2

[0016] Step 1: Select a kgps-1.0t-630 medium-frequency centerless induction corundum lining electric furnace. Use fresh feedstock or unsintered old lining material mixed with 10% 170-mesh fused magnesia and 5-10% water glass for the furnace collar and taphole. Compact the mixture and harden it by heating or blowing CO2. First, add a mixture of scrap steel and slag-forming material to the furnace chamber, filling it to 1 / 3 of its depth. Operate the furnace at 60% power. After the material melts, increase the power to 100%, adding and melting the material simultaneously. During the adding process, prevent the material from accumulating. After the scrap steel is melted and cleared, high-carbon ferromanganese and medium-carbon ferromanganese alloys are added. Only after the alloys melt can silicon-calcium alloys be added for precipitation and deoxidation. Samples are taken for chemical analysis, and after adding more alloys, the chemical composition is: C 2.6–2.9%, Si 0.6–1.2%, Mn 0.6–0.8%, P ≤0.1%, S ≤0.1%, Cr 22–24%, Ni 0.5–0.8%, Cu 0.8–1.0%, Mo 1.8–2.0%, with the remainder being Fe and unavoidable impurities, totaling 100%. After heating, silicon-calcium particles with a particle size no larger than 10mm are added for final deoxidation, and the ladle is prepared for tapping. The silicon-calcium particles account for 0.2% of the weight of the molten iron. The melting temperature is 1450–1500℃. Before use, the ladle needs to be dried in a baking furnace for 3–4 hours, reaching a temperature of 750℃ after baking. After the molten steel is melted and transferred to the ladle, it needs to be refined by argon blowing within the ladle for 3 minutes. The argon blowing rate is 3~4 m3 / min, and the pouring speed is controlled within the range of 50 kg / s. The sand core is placed in the baking oven for baking, with a baking temperature of 80℃ and a baking time of 1 hour. The overhead crane LD5-15.92-A3 is used. Operators must wear masks, gloves, and other protective equipment and check that the equipment is functioning properly. The vertical parting molding machine CX-Ⅱ207 uses coated sand to make the shell, and the core shooting machine FPG600 makes the sand core. For the mold assembly: remove burrs from the inside of the upper and lower sand box cavities and bake the cavity surface with a dryer to remove moisture; first, use the overhead crane to lift the lower sand box to the designated platform for placing the sand box; place the dried sand core, then use the overhead crane to lift the upper sand box, align the assembly, and lock both ends of the sand box; finally, lift the sand box platform into the pouring position in front of the furnace. Step 2, Pouring: Before use, the ladle is dried in a baking oven for 4 hours, until the temperature reaches 850℃. The ladle is then moved to the sand box and pouring in front of the riser. The pouring speed should follow a slow-fast-slow rhythm, starting slowly and then increasing the speed. When 2 / 3 of the ladle has been poured, it should be slowly closed. When the molten iron fills the sand box and riser, rice husk ash or covering agent should be added to the riser for insulation. After pouring, the ladle should be kept warm in the sand for at least 5 minutes. Then, the fasteners of the sand box should be unlocked, and the sand box should be lifted and neatly placed in the sand cleaning area. After pouring, depending on the thickness of the casting wall, oxygen should be blown into the riser within 30 minutes to extend the time of maintaining the high temperature of the riser. One riser should be blown into each product for 1 minute.Before pouring, the temperature of the molten iron in the ladle is measured by a handheld thermocouple temperature measuring gun, the pouring speed is 3-5 kg / s, and the pouring temperature is 1420-1450℃; the third step, after forming, naturally cooling to 250-300℃, cleaning the casting; the fourth step, after shakeout, the semi-finished product enters the QR3210 shot blasting machine to remove surface impurities, the pad conveying speed is 4.5 m / min, the 0.425 mm open Tai S-170 cast steel shot blasting speed is 60 m / s, the blasting angle is 60°, the shot blasting amount is 250 kg / min, and the coverage is 95%; the fifth step, surface build-up welding: using a diameter of 3.0-4.0 mm build-up welding wire and AH20 flux as the build-up welding material, the composition of the welding wire is C6-7.50%, Si1.5-1.80%, Mn1.3-1.50%, Cr26-32.0%, Ni0.5-1.00%, Mo5-7.50%, S≤0.025%, P≤0.030%, Fe balance, the build-up welding uses a GP-100-C3 high-frequency induction build-up welding heating device, the maximum output power is 100 kW, the output oscillation frequency is 200-250 kHz, the anode voltage is 8.5-9.0 kV, the anode current is 5.0-5.1 A, the grid voltage is 0.9-1.1 kV, the grid current is 1.0-1.2 A, and the heating time is 30 s.

[0017] Product: impact toughness impact performance ≥ 5J / m2; hardness ≥ 58HRC. The inner cavity and outer surface of the high-grade cast iron roller sleeve are cleaned of sand, scale and other impurities, and the surface is smooth and clean. The surface roughness meets the requirements of GB / T6060.1 Ra≤50μm. There are no cracks, shrinkage holes, pores, slag and other defects that reduce strength or damage appearance. The cast iron roller sleeve is heat treated, and the surface is free of sand and other defects after precision cleaning and shot blasting.

[0018] Note: The test block is prepared according to the shape of the single cast iron roller sleeve. According to the engineering conditions, production habits and other factors of the supplier, one of the impact test block or knock-off test block in GB / T1348 is selected. The impact test block is poured, cooled and heat treated according to the requirements of GB / T8263-2010 heat treatment specification. The impact test block is selected on the cross-section of the single cast test block or the body of the casting; the shape and size of the impact test block are specified in GB1348 8.6. Mechanical property test Hardness test Brinell hardness test is performed according to the provisions of GB / T231.1-231.3. Rockwell hardness test is performed according to the provisions of GB / T231.3-2018 Part 3.

Claims

1. A method for producing a high-chromium cast iron wear-resistant roller sleeve, characterized in that, Includes the following steps: The first step involves using a shell-making machine and a core-making machine to fabricate the shell and core using phenolic resin-coated sand. After the sand core is dried, the casting mold is assembled, completing the casting model. The furnace charge is then placed in an induction furnace for smelting to form molten iron at a melting temperature of 1450–1500℃. The composition of the molten iron is: C 2.6–2.9%, Si 0.6–1.2%, Mn 0.6–0.8%, P≤0.1%, S≤0.1%, Cr 22–24%, Ni 0.5–0.8%, Cu 0.8–1.0%, Mo 1.8–2.0%, with the remainder being Fe and unavoidable impurities. The first step involves 100% pure iron; the second step involves transferring the molten iron into a ladle, where it is then refined by argon blowing for 3-5 minutes before being poured into a casting mold; the third step involves allowing the casting to cool naturally to 250-300℃ and cleaning the casting; the fourth step involves removing the sand after the casting process and then blasting the semi-finished product in a shot blasting machine to remove surface impurities; the fifth step involves surface surfacing: using 3.0-4.0mm diameter flux-cored welding wire and AH20 flux as surfacing materials, the flux-cored welding wire having the following composition: C 6-7.50%, Si 1.5-1.80%, Mn 1.3-1.50%, Cr 26-32.0%, Ni 0.5-1.00%, Mo 5-7.50%, S≤0.025%, P≤0.030%, and Fe balance.

2. The method for producing a high-chromium cast iron wear-resistant roller sleeve according to claim 1, characterized in that, The fourth step of the shot blasting process is as follows: conveying speed 4.5m / min, 0.425~0.71mm cast steel shot blasting speed 50~60m / s, blasting angle 30°~60°, shot blasting amount 250kg / min, and coverage rate 95%.

3. The method for producing a high-chromium cast iron wear-resistant roller sleeve according to claim 1, characterized in that, The welding process uses a GP-100-C3 high-frequency induction welding heating device with a maximum output power of 100kW, an output oscillation frequency of 200~250kHz, an anode voltage of 8.5~9.0 kV, an anode current of 5.0~5.1 A, a gate voltage of 0.9~1.1 kV, a gate current of 1.0~1.2A, and a heating time of 30 s.

4. The method for producing a high-chromium cast iron wear-resistant roller sleeve according to claim 1, characterized in that, The second step involves a deoxidizer comprising one to two-thousandths of the weight of the molten iron, and the deoxidizer is a silicon-calcium alloy.

5. The method for producing a high-chromium cast iron wear-resistant roller sleeve according to claim 1, characterized in that, The second step involves an argon blowing rate of 3-4 m / s. 3 / min, control the pouring speed at 3~5kg / s and the pouring temperature at 1420~1450℃.