Thermal simulation method and device for solidification structure of hollow chilled cast iron roll
Through the hot simulation device for solidification structure of hollow cold hard cast iron rolls, the solidification process of the roll is simulated, and the problem of thin white hole layer of the roll is solved, efficient and low-cost research is achieved, and the roll material and process are optimized based on scientific basis, and the roll material and process are improved. hardness and toughness.
Patent Information
- Application Number
- CN202411430553.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-14
- Publication Date
- 2025-01-14
AI Technical Summary
During the production process of hollow cold hard cast iron rolls, the thin white hole layer of the roll affects the yield rate, resulting in a decrease in service life. The existing research relies on physical anatomy to be expensive and inefficient, which limits the improvement of roll quality.
A thermal simulation method and device for solidification structure of hollow cold hard cast iron rolls was designed. By simulating the local solidification conditions of the roll, using sand boxes, cold iron blocks and thermocouples, the different areas of the rolls from the surface layer to the core were simulated at different cooling rates. The solidified tissue distribution provides accurate experimental data to support process improvements.
It has realized efficient and low-cost simulation of the roll solidification process, significantly improved the research efficiency and production level, provided scientific basis to optimize the roll material and process, successfully reproduced the white mouth, hemp mouth and gray mouth tissue distribution of the roll, and improved the roll hardness and toughness.
Smart Images
Figure CN119304129A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of metal casting, and particularly relates to a method and a device for thermally simulating the solidification structure of a hollow chilled cast iron roll. Background Art
[0002] Hollow chilled cast iron rolls play a vital role in the manufacturing industry, especially in the packaging, textile, paper and rubber industries. However, their unique hollow structure and high-performance requirements for the working environment make the production of such rolls quite challenging, and the yield rate is relatively low. Among them, the thin white layer of the roll is the main factor affecting its yield rate, which seriously reduces the service life of the roll.
[0003] There are many factors that affect the solidification structure of hollow chilled cast iron rolls, mainly including pouring temperature, metal mold temperature and chemical composition. Ideally, the surface of the hollow chilled cast iron roll should be white cast iron structure, the middle transition area should be pitted cast iron structure, and the core should be gray cast iron structure. The large amount of cementite distributed in the white cast iron structure is the key to the high hardness and good wear resistance of the roll surface, while the graphite in the gray cast iron structure gives the core of the roll good toughness and impact resistance. Therefore, for hollow chilled cast iron rolls, not only is it required that the white cast iron layer has sufficient thickness, but also has good hardness and wear resistance. At the same time, the thickness of the gray cast iron layer in the core should be as large as possible to improve the toughness of the roll.
[0004] At present, the research on hollow chilled cast iron rolls mainly relies on the method of physical dissection. By dissecting the rolls, researchers can visually observe the internal structure distribution of the castings, which provides a valuable reference for process improvement. However, the physical dissection method is costly, labor-intensive, and has a long production cycle, so many factories are deterred and give up this method. This also leads to certain restrictions on the development of hollow chilled cast iron rolls in the direction of high quality. Summary of the invention
[0005] The technical problem to be solved by the present invention is to provide a method and device for thermal simulation of the solidification structure of a hollow chilled cast iron roll. The method is convenient and reliable, and can accurately reveal the internal structure of the roll, providing strong support for process improvement and quality control.
[0006] The technical solution of the present invention is:
[0007] A device for simulating the solidification structure of a hollow chilled cast iron roller comprises a sand box, a heat preservation cover is arranged on the top of the sand box, a riser is opened in the middle of the heat preservation cover, a pouring cup is arranged on the top of the heat preservation cover, and a sand mold is filled in the sand box, wherein the sand mold comprises an upper sand mold and a lower sand mold, a cold iron block is embedded and installed in the lower sand mold, a mold cavity is arranged in the upper sand mold, a thermocouple I is inserted horizontally through the sand box body and the lower sand mold at a position of the sand box corresponding to the cold iron block and extends to the center position of the cold iron block, and a thermocouple II is inserted horizontally through the sand box body and the upper sand mold at a position of the sand box corresponding to the mold cavity and extends into the mold cavity.
[0008] Furthermore, a first positioning groove is provided at the bottom of the sand box, and a boss matching the first positioning groove is provided at the bottom of the cold iron block.
[0009] Furthermore, the thermocouple I and the thermocouple II located in the cavity are both covered with glass protection tubes.
[0010] Furthermore, a second positioning groove is provided on the top of the cold iron block.
[0011] A method for thermally simulating the solidification structure of a hollow chilled cast iron roll by using the above-mentioned hollow chilled cast iron roll solidification structure thermal simulation device is to reproduce the solidification structure distribution of different regions from the surface to the core of the hollow chilled cast iron roll under different cooling rate conditions by simulating the solidification conditions of the local position of the roll; the method is characterized by:
[0012] The specific process is as follows:
[0013] ⑴Sand material mixing
[0014] Mix floating beads, fine sand and quartz powder in a mass ratio of 2:1:1, wherein the mesh sizes of the floating beads are 10 mesh, 20 mesh, 30 mesh and 40 mesh, wherein the mass ratio of the floating beads of 10 mesh, the floating beads of 20 mesh, the floating beads of 30 mesh and the floating beads of 40 mesh is 1:1:1:1, add water glass accounting for 20% of the total mass of the floating beads, fine sand and quartz powder, mix and stir in a sand mixer for 1 minute to obtain a sand material;
[0015] (2) Sand mold molding
[0016] Before molding, a layer of water glass is first applied to the inside of the sand box, the boss of the cold iron block is inserted into the first positioning groove at the bottom of the sand box, the boss of the wooden mold is inserted into the second positioning groove of the cold iron block, the cold iron block and the wooden mold are arranged in the sand box from bottom to top, and iron rods are inserted into the positions of inserting thermocouple I and thermocouple II, the sand mold material is poured in and compacted, the wooden mold and the iron rod are pulled out, a mold cavity and a thermocouple jack are formed in the sand mold, and CO2 is used to shape the sand mold; the height of the mold cavity is consistent with the wall thickness of the simulated hollow chilled cast iron roll, and the height of the cold iron block is consistent with the wall thickness of the metal mold used for casting the actually produced hollow chilled cast iron roll;
[0017] (3) Sand box drying
[0018] Put the sand box into the drying furnace and dry it in the drying furnace. During drying, heat it to 100℃ and keep it for 1 hour, then continue to heat it to 200℃ and keep it for 1 hour, then continue to heat it to 300℃ and keep it for 1 hour, then continue to heat it to 400℃ and keep it for 1 hour, then continue to heat it to 500℃ and keep it for 2 hours, and finally cool it to room temperature;
[0019] (4) Paint
[0020] After the sand mold is dried, evenly apply refractory paint on the surface of the sand mold, install the insulation cover, riser, thermocouple I and thermocouple II, and seal them with refractory mud, and then dry them at 200℃ for 30 minutes;
[0021] (5) Metal smelting
[0022] Preheat the cold iron block in the sand box to 120℃, heat the metal raw material to 1550℃ through the medium frequency induction furnace to melt it into molten metal, and pour it when the temperature of the molten metal and the temperature of the cold iron block are cooled to the required temperature for simulation;
[0023] (6) Metal solidification
[0024] Under the action of the chilled iron block and the insulating sand mold, the heat of the molten metal is mainly transferred along the direction of the chilled iron block, achieving a one-dimensional heat transfer effect, realizing the simulation of the solidification conditions of the hollow chilled cast iron roll, and obtaining a thermally simulated ingot.
[0025] Furthermore, the material of the cold iron block is gray cast iron.
[0026] Furthermore, the metal materials are pig iron and Q235 steel, and the carbon content in the pig iron is adjusted by adding Q235 steel.
[0027] Furthermore, the cross-sectional area of the cavity is 100 mm×100 mm.
[0028] The beneficial effects of the present invention are:
[0029] (1) The device is ingeniously designed. When the molten metal enters the mold cavity, under the insulation effect of the sand mold and the insulation cover, the central area of the molten metal in the mold transfers heat in one dimension along the direction of the cold iron block, simulating the solidification conditions of the hollow chilled cast iron roll, making the experimental results highly reproducible and reliable.
[0030] (2) By simulating the solidification conditions at a local position of a hollow chilled cast iron roll, the distribution of the solidification structure from the surface to the core can be reproduced, thereby simulating the solidification process of a roll weighing tens of tons on a smaller experimental scale (small kilogram level), greatly improving research efficiency and significantly reducing research costs.
[0031] (3) Thermocouples I and II are used to measure the temperature of the cold iron block and the molten metal, as well as the temperature of the center point of the core of the casting. The temperature change curve over time during the cooling process can be recorded and analyzed in real time, providing accurate data support for the formation of solidification structure.
[0032] (4) The formation process of the white cast iron structure on the surface of the hollow chilled cast iron roll, the pitted structure in the middle transition area, and the gray cast iron structure in the core were successfully simulated, revealing the distribution of the solidification structure under different cooling rates, which has important guiding significance for optimizing the roll material and process.
[0033] (5) By adjusting variables such as the chill temperature and metal pouring temperature, the effects of these factors on the solidification structure and properties of the roll can be systematically studied, providing a scientific basis for the production and quality control of the roll.
[0034] (6) The device has a simple structure and is easy to operate. It is easy to promote and use in laboratories and production sites, which helps to improve the research and development and production level of hollow chilled cast iron rolls. BRIEF DESCRIPTION OF THE DRAWINGS
[0035] Figure 1 It is a schematic structural diagram of a hollow chilled cast iron roll solidification structure thermal simulation device of the present invention;
[0036] Figure 2 yes Figure 1 Side view of
[0037] Figure 3 yes Figure 1 AA section view;
[0038] Figure 4 It is a structural schematic diagram of a wooden mold of the present invention;
[0039] Figure 5 It is a drying process curve diagram of the sand mold in the present invention;
[0040] Figure 6 This is a metallographic structure diagram of the fracture of the central area of a large ingot thermally simulated in an embodiment of the present invention;
[0041] Figure 7 This is a fracture microstructure diagram of a hollow chilled cast iron roll actually cast under the same process parameters as the thermal simulation large ingot in Example 1 of the present invention.
[0042] In the figure, 1-sand box, 101-first positioning groove, 2-insulation cover, 3-sand mold, 4-cold iron block, 401-second positioning groove, 402-cold iron block boss, 5-thermocouple I, 6-thermocouple II, 7-glass protection tube, 8-mold cavity, 9-riser, 10-pouring cup, 11-wooden mold, 1101-wooden mold boss. DETAILED DESCRIPTION
[0043] Example 1
[0044] like Figure 1-4 As shown, the solidification structure thermal simulation device of the hollow chilled cast iron roll comprises a sand box 1, a heat preservation cover 2 is arranged on the top of the sand box 1, a riser 9 is opened in the middle of the heat preservation cover 2, a pouring cup 10 is arranged on the top of the heat preservation cover 2, a sand mold 3 is filled in the sand box 1, the sand mold 3 comprises an upper sand mold and a lower sand mold, a chill block 4 is embedded and installed in the lower sand mold, the material of the chill block 4 is gray cast iron, a first positioning groove 101 is opened at the bottom of the sand box, a chill block boss 402 is arranged at the bottom of the chill block 4, and the chill block boss 4 02 is inserted in the first positioning groove 101 that matches it, a second positioning groove 401 is opened on the top of the cold iron block 4, a cavity 8 is provided in the upper sand mold, a thermocouple Ⅰ5 is inserted horizontally through the sand box 1 body and the lower sand mold at the position of the sand box 1 corresponding to the cold iron block 4 and extends to the center of the cold iron block 4, a thermocouple Ⅱ6 is inserted horizontally through the sand box 1 body and the upper sand mold at the position of the sand box 1 corresponding to the cavity 8 and extends into the cavity 8, and glass protection tubes 7 are provided on the thermocouple Ⅰ5 and the thermocouple Ⅱ6 located in the cavity 8.
[0045] (1) Prepare the cold iron block and wooden mold
[0046] A cold iron block boss 402 with a height of 2.5 mm matching the first positioning groove 101 of the sand box 1 is machined at the bottom of the cold iron block 4 by a machine tool, so that the cold iron block 4 and the sand box 1 are positioned; a second positioning groove 401 with a depth of 5 mm is machined at the top of the cold iron block 4, which is convenient for positioning the cold iron block 4 and the wooden mold 11 during molding; three horizontally arranged circular holes passing through the cold iron core are machined on one side of the cold iron block 4, which are convenient for inserting the thermocouple I5 for temperature measurement during the experiment; a wooden mold boss 1101 with a height of 4 mm matching the second positioning groove 401 is machined at the bottom of the wooden mold 11 corresponding to the second positioning groove 401, and the cross-sectional area of the wooden mold 11 is 100 mm×100 mm;
[0047] (2) Preparation of sand mold materials
[0048] Mix floating beads, fine sand and quartz powder in a mass ratio of 2:1:1, wherein the mesh sizes of the floating beads are 10 mesh, 20 mesh, 30 mesh and 40 mesh, wherein the mass ratio of the floating beads of 10 mesh, the floating beads of 20 mesh, the floating beads of 30 mesh and the floating beads of 40 mesh is 1:1:1:1, add water glass accounting for 20% of the total mass of the floating beads, fine sand and quartz powder, mix and stir in a sand mixer for 1 minute to obtain a sand material;
[0049] (3) Sand mold molding
[0050] Before molding, a layer of water glass is first applied to the inside of the sand box 1, the boss of the cold iron block 4 is inserted into the first positioning groove 101 at the bottom of the sand box, and the boss of the wooden mold 11 is inserted into the second positioning groove 401 of the cold iron block 4. The cold iron block 4 and the wooden mold 11 are arranged from bottom to top in the sand box 1, and iron rods are inserted into the positions of the thermocouple I5 and the thermocouple II6. The sand mold material is poured in and compacted. After the molding is completed, the wooden mold is gently tapped to loosen it slightly, and then the wooden mold and the iron rod are pulled out to form a cavity 8 and a thermocouple jack in the sand mold 3, and the sand mold 3 is fixed using CO2;
[0051] (4) Sand box 1 drying
[0052] Place the sand box 1 in the drying oven. Figure 5 The sand mold drying process shown is to dry the sand mold, that is, heating to 100°C and keeping it for 1 hour, continuing to heat to 200°C and keeping it for 1 hour, continuing to heat to 300°C and keeping it for 1 hour, continuing to heat to 400°C and keeping it for 1 hour, continuing to heat to 500°C and keeping it for 2 hours, and finally cooling to room temperature;
[0053] (5) Paint
[0054] The sand box 1 is cooled to room temperature, refractory coating is evenly applied on the surface of the sand mold 3, and the insulation cover 2, riser 9, thermocouple I 5 and thermocouple II 6 are installed, and sealed with refractory mud, and then dried at 200°C for 30 minutes;
[0055] (6) Metal smelting
[0056] Preheat the cold iron block 4 in the sand box 1 to 120°C, heat the metal raw material to 1550°C through a medium frequency induction furnace to melt it into a metal melt, and pour it when the temperature of the metal melt and the temperature of the cold iron block 4 are cooled to the required temperature during simulation. In this embodiment, the temperature of the metal melt is 1220°C and the temperature of the cold iron block 4 is 100°C for example.
[0057] In this embodiment, pig iron and Q235 steel are used as metal raw materials. The composition of the molten metal formed after heating is 3.8%wt of C, 0.6%wt of Si, and 0.04%wt of Cu;
[0058] (7) Metal solidification
[0059] Under the action of the chilled iron block 4 and the insulating sand mold 3, the heat of the molten metal is mainly transferred along the chilled iron block, achieving a one-dimensional heat transfer effect, realizing the simulation of the solidification conditions of the hollow chilled cast iron roll, and obtaining a thermally simulated ingot.
[0060] Sample preparation: Use wire cutting to cut samples from the core of the hot simulated ingot. The metallographic sample and hardness sample are selected at the core of the ingot, with a size of 10×10×200mm. The friction and wear sample is selected at the end of the heat dissipation direction of the ingot core, with a size of Φ25×5mm. The metallographic structure diagram of this embodiment is shown in Figure 6 described.
[0061] The same metal raw material as in Example 1 is used, and the hollow chilled cast iron roll is actually cast under the same process parameters as the large thermal simulation ingot in Example 1. The height of the thermal simulation ingot in Example 1 is consistent with the wall thickness of the hollow chilled cast iron roll, and the height of the chill block 4 is consistent with the wall thickness of the metal mold used to cast the hollow chilled cast iron roll. The metal raw material is melted to form a metal melt and cast at a temperature of 1220°C. During the casting, the temperature of the metal mold is 100°C. The fracture microstructure of the hollow chilled cast iron roll obtained by casting is shown in FIG. Figure 7 shown.
[0062] Depend on Figure 6 and Figure 7 By comparison, Figure 6 and Figure 7 The left side of the metallographic diagram is all white cast iron structure, the middle is all martensite structure, and the right side is gray cast iron structure. The organizational structure of the thermal simulation ingot is consistent with that of the hollow chilled cast iron roll, and the range of the white cast iron structure of the thermal simulation ingot is highly consistent with that of the hollow chilled cast iron roll, which can provide a scientific basis for studying the hardness and wear resistance of the hollow chilled cast iron roll.
[0063] The temperature of the cold iron during pouring can be measured by a thermocouple II 6. A thermocouple is placed at the center of the core of the mold, and a curve of the temperature change over time during the cooling process of the measured part of the ingot can be obtained, which is convenient for studying the influence of the cooling rate on the solidification structure.
[0064] The present invention realizes thermal simulation under heat preservation conditions, restores the solidification process of the hollow chilled cast iron roll through the solidification process of the ingot core, adjusts the process parameters by changing the preheating temperature and pouring temperature of the chill, and realizes thermal simulation under different cooling rates, which is convenient for studying the influence of the chill temperature (the casting metal mold temperature of the hollow chilled cast iron roll), the pouring temperature (the metal melt temperature) and the alloy elements of the metal melt on the solidification structure.
Claims
1. A hollow chilled cast iron roll solidification structure thermal simulation device, comprising a sand box, a heat preservation cover is provided on the top of the sand box, a riser is provided in the middle of the heat preservation cover, and a pouring cup is provided on the top of the heat preservation cover, wherein: The sand box is filled with sand molds, which include an upper sand mold and a lower sand mold. A cold iron block is embedded in the lower sand mold, and a cavity is provided in the upper sand mold. A thermocouple I is inserted horizontally through the sand box body and the lower sand mold at the position of the cold iron block in the sand box and extends to the center of the cold iron block. A thermocouple II is inserted horizontally through the sand box body and the upper sand mold at the position of the cavity in the sand box and extends into the cavity.
2. The hollow chilled cast iron roll solidification structure thermal simulation device according to claim 1 is characterized in that: A first positioning groove is arranged at the bottom of the sand box, and a boss matching the first positioning groove is arranged at the bottom of the cold iron block.
3. The hollow chilled cast iron roll solidification structure thermal simulation device according to claim 1 is characterized in that: Thermocouple I and thermocouple II located in the cavity are both covered with glass protection tubes.
4. The hollow chilled cast iron roll solidification structure thermal simulation device according to claim 1 is characterized in that: A second positioning groove is provided on the top of the cold iron block.
5. A method for thermal simulation of the solidification structure of a hollow chilled cast iron roll using the hollow chilled cast iron roll solidification structure thermal simulation device as claimed in claim 1, characterized in that: The specific process is as follows: ⑴Sand material mixing Mix floating beads, fine sand and quartz powder in a mass ratio of 2:1:1, wherein the mesh sizes of the floating beads are 10 mesh, 20 mesh, 30 mesh and 40 mesh, wherein the mass ratio of the floating beads of 10 mesh, the floating beads of 20 mesh, the floating beads of 30 mesh and the floating beads of 40 mesh is 1:1:1:1, add water glass accounting for 20% of the total mass of the floating beads, fine sand and quartz powder, mix and stir in a sand mixer for 1 minute to obtain a sand material; (2) Sand mold molding Before molding, a layer of water glass is first applied to the inside of the sand box, the boss of the cold iron block is inserted into the first positioning groove at the bottom of the sand box, the boss of the wooden mold is inserted into the second positioning groove of the cold iron block, the cold iron block and the wooden mold are arranged in the sand box from bottom to top, and iron rods are inserted into the positions of inserting thermocouple I and thermocouple II, the sand mold material is poured in and compacted, the wooden mold and the iron rod are pulled out, a mold cavity and a thermocouple jack are formed in the sand mold, and CO2 is used to shape the sand mold; the height of the mold cavity is consistent with the wall thickness of the simulated hollow chilled cast iron roll, and the height of the cold iron block is consistent with the wall thickness of the metal mold used for casting the actually produced hollow chilled cast iron roll; (3) Sand box drying Put the sand box into the drying furnace and dry it in the drying furnace. During drying, heat it to 100℃ and keep it for 1 hour, then continue to heat it to 200℃ and keep it for 1 hour, then continue to heat it to 300℃ and keep it for 1 hour, then continue to heat it to 400℃ and keep it for 1 hour, then continue to heat it to 500℃ and keep it for 2 hours, and finally cool it to room temperature; (4) Paint After the sand mold is dried, evenly apply refractory paint on the surface of the sand mold, install the insulation cover, riser, thermocouple I and thermocouple II, and seal them with refractory mud, and then dry them at 200℃ for 30 minutes; (5) Metal smelting Preheat the cold iron block in the sand box to 120℃, heat the metal raw material to 1550℃ through the medium frequency induction furnace to melt it into molten metal, and pour it when the temperature of the molten metal and the temperature of the cold iron block are cooled to the required temperature for simulation; (6) Metal solidification Under the action of the chilled iron block and the insulating sand mold, the heat of the molten metal is mainly transferred along the direction of the chilled iron block, achieving a one-dimensional heat transfer effect, realizing the simulation of the solidification conditions of the hollow chilled cast iron roll, and obtaining a thermally simulated ingot.
6. The method for thermal simulation of solidification structure of hollow chilled cast iron roll according to claim 5, characterized in that: The material of the cold iron block is grey cast iron.
7. The method for thermal simulation of solidification structure of hollow chilled cast iron roll according to claim 5, characterized in that: The metal materials are pig iron and Q235 steel, and the carbon content in the pig iron is adjusted by adding Q235 steel.
8. The method for thermal simulation of solidification structure of hollow chilled cast iron roll according to claim 5, characterized in that: The cross-sectional area of the cavity is 100 mm×100 mm.