Casting method of cast iron for high-strength machine tool guide rail and lathe bed casting
By adding alloy elements and using inoculant to cast iron, the pearlite content and tissue structure are optimized, and the problems of uneven hardness and poor wear resistance of cast iron guide rails are solved, and cast iron guide rails with high strength and wear resistance are realized, meeting the requirements of high-end machine tools.
Patent Information
- Application Number
- CN202411887187.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-20
- Publication Date
- 2025-03-14
AI Technical Summary
The prior art is difficult to optimize the pearlite content and structure in cast iron, resulting in uneven hardness and poor wear resistance of cast iron, which cannot meet the high-strength and wear resistance requirements of high-end machine tools for guide rails.
By controlling the chemical composition of cast iron, adding alloy elements such as Cu, Sn and Cr, and using pretreatment agents and incubators during the smelting process, adjusting the size and content of pearlite to achieve high hardness and wear resistance cast iron guides.
It improves the hardness and wear resistance of cast iron guide rails, ensures the machining accuracy of the machine tool, reduces costs, and improves economic benefits.
Smart Images
Figure CN119614990A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of casting, and relates to a method for casting cast iron for high-strength machine tool guide rails and bed castings, and is suitable for manufacturing high-end machine tools that require guide rails with high and uniform hardness, good wear resistance and stable structure. Background Art
[0002] Guide rails are the reference components to ensure the movement accuracy of machine tools. Compared with the steel-lined guide rails or linear guide rails often used in medium and large high-precision machine tools, surface-hardened cast iron guide rails or cast iron guide rails integrated with the bed have obvious advantages in shock absorption, stability, wear resistance and overall rigidity.
[0003] The performance of cast iron materials is mainly determined by the composition of cast iron and its casting process. The chemical composition and casting process of cast iron determine the mechanical properties and phase content of cast iron, especially the pearlite content, size, distribution, etc. The uniformity of the hardness of the guide rail surface after induction quenching is greatly affected by the pearlite content. Low pearlite content in cast iron will lead to high ferrite content in cast iron. When induction quenching is heated for a short time, after the Fe3C type carbide dissolves, the carbon concentration in the matrix is low, and the carbon in graphite dissolves slowly, so it is difficult to achieve uniform matrix composition, resulting in uneven hardness of the guide rail surface after quenching. The pearlite structure with abundant and even distribution can make the carbon content in cast iron high under low heating temperature and short heating conditions, and at the same time achieve uniform composition, improve the hardness of the guide rail surface after quenching, and improve hardness uniformity. In addition, because cast iron contains a small amount of strong carbide-forming elements, its solidification melting point is relatively high, and it has a strong tendency to form carbides. Therefore, fine granular carbides can be formed when the cast iron solidifies, which is earlier than the formation of pearlite structure. It can play a role in improving the nucleation of pearlite. At the same time, the fine carbides formed by strong carbide-forming elements can also play a role in improving the hardness and wear resistance of cast iron.
[0004] At present, the widely used methods for controlling the phase content in cast iron include adding casting inoculants, adjusting the cooling rate, and adding certain rare earth elements or other metal elements. Under the existing technical conditions, due to the large differences in cast iron composition, the cast iron structure is chaotic, and the pearlite content and size of the cast iron are difficult to meet the high-intensity service requirements of machine tools. At the same time, the large differences in structure increase the difficulty of subsequent heat treatment control and reduce the heat treatment pass rate.
[0005] Therefore, it is now necessary to develop a cast iron for machine tools that can promote structural stability and meet the requirements of heat treatment performance, increase the pearlite content of the cast iron, optimize the pearlite structure, and improve its wear resistance and rigidity. Summary of the invention
[0006] In view of the above-mentioned technical problems, the present invention provides a casting method for cast iron for high-strength machine tool guide rails and bed castings. The casting method controls the chemical composition of cast iron, adds different contents of alloy elements to cast iron, and adjusts the size and content of pearlite of cast iron, so that the cast iron guide rails have high hardness and rigidity, improves the wear resistance of the guide rail contact surface, and thus ensures the machining accuracy of the machine tool, improves economic benefits, and reduces costs.
[0007] In order to achieve the above object, the present invention provides the following technical solutions.
[0008] A method for casting cast iron for high-strength machine tool guide rails and bed castings, comprising the following steps: Step 1: Determine the composition of the smelting charge, including pig iron, scrap steel, recycled materials, etc.; Step 2: Determine the content of the required added elements according to the chemical composition range required for smelting cast iron and the target value of pearlite content; Step 3: adding the pig iron, scrap steel and recycled materials from step 1 into a smelting furnace for smelting, adding a pretreatment agent during the smelting process to obtain raw iron liquid; Step 4: After the raw iron liquid in the furnace of step 3 is adjusted to meet the requirements, the inoculant is added into the pouring ladle, and the raw iron liquid is poured into the pouring ladle to produce iron; Step 5: After deslagging, pour the molten iron in the pouring ladle of step 4. The pouring temperature of the molten iron is controlled at 1330°C to 1400°C. During the pouring, inoculation treatment is performed to finally obtain high-strength cast iron for machine tool guide rails and bed castings.
[0009] Furthermore, in step one, the control range of charge composition is C: 3.0~3.1wt%, Si: 1.6~1.8wt%, Mn: 0.8~1.0wt%, P<0.05wt%, S: <0.10wt%; high-quality carbon scrap steel with good smelting level is used, the addition amount is 70~80wt%, the pig iron addition amount is less than 10wt%, and the rest is the same material recycled material with the same cast iron composition.
[0010] Furthermore, in step 2, the added elements are Cu, Sn and Cr; wherein the content of Cu element added to the cast iron is 0.7-0.8wt%, the content of Sn element added to the cast iron is 0.04-0.05wt%, and the content of Cr element added to the cast iron is <0.1wt%.
[0011] Furthermore, in step three, the specific steps of smelting are: adding the pig iron, scrap steel and recycled materials in step one into a medium frequency induction melting furnace to melt the alloy material to form qualified liquid metal; taking samples for chemical composition detection during the smelting process, and adjusting the content of each element until it meets the composition requirements; controlling the temperature of the molten iron out of the furnace to 1510°C ~ 1530°C, and the insulation time to 5 ~ 10 minutes to remove harmful gases and impurity elements in the molten iron.
[0012] Furthermore, in step three, the composition range of the pretreatment agent is Si: 62.00-69.00wt%, Al: 3.00-5.00wt%, Zr: 3.00-5.00wt%, Ca: 0.60-1.90wt%, and Fe as the balance; the amount of the pretreatment agent added is 0.1-0.2wt% of the smelted cast iron.
[0013] Furthermore, in step four, during the iron tapping process, the inoculant is dripped onto the pouring iron flow through the inoculant bucket; the inoculant is a manganese-zirconium inoculant with a particle size of 1 to 3 mm and an addition amount of 0.4 to 0.5 wt% of the smelted cast iron.
[0014] Furthermore, in step five, the inoculation with the flow is as follows: a high manganese zirconium inoculant with a mass of 0.1 to 0.15wt% of cast iron is evenly dropped onto the pouring molten iron flow through a handheld inoculation bucket; the pouring temperature of gray cast iron is controlled at 1360 to 1400°C, and the upper limit temperature is taken for castings with complex structures and large differences in wall thickness, and the lower limit temperature is taken otherwise; the pouring temperature of ductile iron is controlled at 1330 to 1360°C.
[0015] Compared with the prior art, the beneficial effects of the present invention are as follows.
[0016] 1. The utilization of scrap steel has been increased from 50-60wt% to 70-80wt%, which further optimizes the composition of cast iron.
[0017] 2. Add 0.1-0.2wt% pretreatment agent during the smelting process to purify the molten iron, increase the nucleation core of the molten iron, and create favorable conditions for subsequent inoculation treatment.
[0018] 3. In terms of alloying, the amount of copper added is 0.7-0.8wt%, the amount of tin added is 0.04-0.05wt%, and the content of chromium is less than 0.1wt%. The pearlite content is increased and the pearlite is refined through copper and tin composite alloying.
[0019] 4. In terms of inoculation treatment, adding 0.4-0.5wt% manganese-zirconium-containing inoculant can prevent inoculation decay, produce white cast, increase nucleation cores, and further improve the strength of the casting.
[0020] 5. Flow incubation further strengthens incubation and ensures tissue uniformity. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 The microstructure of Example 1.
[0022] Figure 2 The microstructure of Example 2.
[0023] Figure 3 The microstructure of Example 3.
[0024] Figure 4 The microstructure of comparative example 1.
[0025] Figure 5 Comparative Example 2 is a 1000-fold magnified microstructure.
[0026] Figure 6 Comparative Example 2 is a 500-fold magnified microstructure. DETAILED DESCRIPTION
[0027] The following is a description of preferred embodiments of the present invention. The preferred embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.
[0028] A method for casting cast iron for high-strength machine tool guide rails and bed castings, comprising the following steps: Step 1: Determine the composition of the charge for smelting, including pig iron, scrap steel, recycled materials, etc.; the control range of the charge composition is C: 3.0~3.1wt%, Si: 1.6~1.8wt%, Mn: 0.8~1.0wt%, P<0.05wt%, S: <0.10wt%; use high-quality carbon scrap steel with good smelting level, add 70~80wt%, pig iron addition is less than 10wt%, and the rest is recycled materials of the same material as cast iron; Step 2: According to the chemical composition range required for smelting cast iron and the target value of pearlite content, determine the content of the required added elements; the added elements are Cu, Sn and Cr; wherein, the added content of Cu element in cast iron is 0.7-0.8wt%, the added content of Sn element in cast iron is 0.04-0.05wt%, and the added content of Cr element in cast iron is <0.1wt%; Step 3: Add the pig iron, scrap steel and recycled materials in step 1 into a smelting furnace for smelting, and add a pretreatment agent during the smelting process to obtain raw iron liquid; wherein, the specific smelting steps are: add the pig iron, scrap steel and recycled materials in step 1 into a medium frequency induction smelting furnace to melt the alloy material to form qualified liquid metal; during the smelting process, take samples for chemical composition detection, and adjust the content of each element until it meets the composition requirements; the temperature of the molten iron out of the furnace is controlled to be 1510℃~1530℃, and the insulation time is 5~10min to remove harmful gases and impurity elements in the molten iron; the composition range of the pretreatment agent is Si: 62.00~69.00wt%, Al: 3.00~5.00wt%, Zr: 3.00~5.00wt%, Ca: 0.60~1.90wt%, Fe balance; the amount of the pretreatment agent added is 0.1~0.2wt% of the smelted cast iron; Step 4: After the raw iron liquid in the furnace of step 3 is adjusted to meet the requirements, the inoculant is added into the casting ladle, and the raw iron liquid is tapped into the casting ladle at the same time; during the tapping process, the inoculant is dripped onto the pouring iron flow through the inoculant bucket; the inoculant is a manganese zirconium inoculant with a particle size of 1 to 3 mm and an addition amount of 0.4 to 0.5wt% of the smelted cast iron; Step 5: After deslagging, pour the molten iron in the pouring ladle in step 4, and control the pouring temperature of the molten iron to 1330°C to 1400°C. During pouring, perform flow inoculation treatment, and flow inoculation is as follows: through a handheld inoculation bucket, evenly drip a high manganese zirconium inoculant with a total cast iron content of 0.1 to 0.15wt% onto the pouring molten iron flow; the pouring temperature of gray cast iron is controlled at 1360 to 1400°C, and the upper limit temperature is taken for castings with complex structures and large differences in wall thickness, and the lower limit temperature is taken otherwise; the pouring temperature of ductile iron is controlled at 1330 to 1360°C, and finally high-strength cast iron for machine tool guide rails and bed castings is obtained.
[0029] Example 1.
[0030] A method for casting cast iron for high-strength machine tool guide rails and bed castings, comprising the following steps: Step 1: Determine the charge composition: 75wt% of high-quality carbon scrap steel, 10wt% of pig iron, and the rest is recycled materials of the same material as cast iron; the main charge composition is C: 3.0wt%, Si: 1.6wt%, Mn: 0.9wt%, P < 0.05wt%, S: < 0.10%; Step 2: According to the chemical composition range required for smelting cast iron and the target value of pearlite content, the additives are determined to be Cu, Sn and Cr, wherein the addition amount of Cu element is 0.75wt%, the addition amount of Sn element is 0.04wt%, and the addition amount of Cr element is 0.08wt%; Step 3: Add the pig iron, scrap steel and recycled materials in step 1 into a medium frequency induction melting furnace to melt the alloy material, add a pretreatment agent during the smelting process to form a qualified liquid metal, take samples during the smelting process for chemical composition detection, and adjust the content of each element until it meets the composition requirements to obtain raw iron liquid; wherein, the molten iron furnace temperature is controlled to be 1520°C, and the insulation time is 8min; the pretreatment agent is 0.15wt% of a material containing Si, Al, Zr, and Ca, and the composition of the pretreatment agent is Si: 62.00~69.00wt%, Al: 3.00~5.00wt%, Zr: 3.00~5.00wt%, Ca: 0.60~1.90wt%, Fe balance; Step 4: After the raw iron liquid in the furnace of step 3 is adjusted to meet the requirements, the inoculant is added into the casting ladle for inoculation treatment, and the raw iron liquid is tapped into the casting ladle, and the inoculant is dripped onto the pouring iron flow through the inoculation bucket; the inoculant is a manganese zirconium inoculant with a particle size of 1 to 3 mm and an addition amount of 0.45wt%; Step 5: After deslagging, pour the molten iron in the pouring ladle in step 4. The pouring temperature of the molten iron is controlled at 1380°C. During pouring, inoculation is performed along the flow. Through a handheld inoculation bucket, 0.1wt% of the high manganese zirconium inoculant of the total mass of the cast iron is evenly dripped onto the pouring molten iron flow to obtain high-strength cast iron for machine tool guide rails and bed castings.
[0031] Figure 1 This is the microstructure phase diagram of the alloy of Example 1 of the present invention. It can be seen that the pearlite content of this example is relatively high, and a certain amount of graphite is precipitated.
[0032] Example 2.
[0033] A method for casting cast iron for high-strength machine tool guide rails and bed castings, comprising the following steps: Step 1: Determine the charge composition: 70wt% of high-quality carbon scrap steel, 8wt% of pig iron, and the rest is recycled materials of the same material as cast iron; the main charge composition is C: 3.1wt%, Si: 1.7wt%, Mn: 0.8wt%, P < 0.05wt%, S: 0.06 ~ 0.10wt%; Step 2: According to the chemical composition range required for smelting cast iron and the target value of pearlite content, the additives are determined to be Cu, Sn and Cr, wherein the addition amount of Cu element is 0.8wt%, the addition amount of Sn element is 0.05wt%, and the addition amount of Cr element is 0.08wt%; Step 3: Add the pig iron, scrap steel and recycled materials in step 1 into a medium frequency induction melting furnace to melt the alloy material, add a pretreatment agent during the smelting process to form a qualified liquid metal, take samples during the smelting process for chemical composition detection, and adjust the content of each element until it meets the composition requirements to obtain raw iron liquid; wherein, the molten iron furnace temperature is controlled to be 1530°C, and the insulation time is 10min; the pretreatment agent is a material containing Si, Al, Zr, and Ca of 0.15wt% cast iron, and the composition of the pretreatment agent is Si: 62.00~69.00wt%, Al: 3.00~5.00wt%, Zr: 3.00~5.00wt%, Ca: 0.60~1.90wt%, Fe balance; Step 4: After the raw iron liquid in the furnace of step 3 is adjusted to meet the requirements, an inoculant is added into a casting ladle for inoculation treatment, and the raw iron liquid is poured into the casting ladle, and the inoculant is dripped onto the pouring iron flow through the inoculation bucket; the inoculant is a manganese zirconium inoculant with a particle size of 1 to 3 mm and an addition amount of 0.4wt% of the smelted cast iron; Step 5: After deslagging, pour the molten iron in the pouring ladle in step 4. The pouring temperature of the molten iron is controlled at 1370°C. During pouring, inoculation is performed along the flow. Through a handheld inoculation bucket, 0.1wt% high manganese zirconium inoculant is evenly dripped onto the pouring molten iron flow to obtain high-strength cast iron for machine tool guide rails and bed castings.
[0034] Figure 2 This is the microstructure phase diagram of the alloy of Example 2 of the present invention. It can be seen that the pearlite content of this example is relatively high, and a certain amount of graphite is precipitated.
[0035] Example 3.
[0036] A method for casting cast iron for high-strength machine tool guide rails and bed castings, comprising the following steps: Step 1: Determine the charge composition: 80wt% of high-quality carbon scrap steel, 8wt% of pig iron, and the rest is recycled materials of the same material as cast iron; the main charge composition is C: 3.0wt%, Si: 1.8wt%, Mn: 1.0wt%, P < 0.05wt%, S: < 0.10wt%; Step 2: According to the chemical composition range required for smelting cast iron and the target value of pearlite content, the additives are determined to be Cu, Sn and Cr, wherein the addition amount of Cu element is 0.75wt%, the addition amount of Sn element is 0.04wt%, and the addition amount of Cr element is 0.08wt%; Step 3: Add the pig iron, scrap steel and recycled materials in step 1 into a medium frequency induction melting furnace to melt the alloy material, add a pretreatment agent during the smelting process to form a qualified liquid metal, take samples during the smelting process for chemical composition detection, and adjust the content of each element until it meets the composition requirements to obtain raw iron liquid; wherein, the molten iron furnace temperature is controlled to be 1520°C, and the insulation time is 10min; the pretreatment agent is 0.2wt% of a material containing Si, Al, Zr, and Ca, and the composition of the pretreatment agent is Si: 62.00~69.00wt%, Al: 3.00~5.00wt%, Zr: 3.00~5.00wt%, Ca: 0.60~1.90wt%, and Fe balance; Step 4: After the raw iron liquid in the furnace of step 3 is adjusted to meet the requirements, the inoculant is added into the casting ladle for inoculation treatment, and the raw iron liquid is poured into the casting ladle, and the inoculant is dripped onto the pouring iron flow through the inoculation bucket; the inoculant is a manganese zirconium inoculant with a particle size of 1 to 3 mm and an addition amount of 0.4wt%; Step 5: After deslagging, pour the molten iron in the pouring ladle in step 4. The pouring temperature of the molten iron is controlled at 1400°C. During the pouring, inoculation is performed along the flow. Through a handheld inoculation bucket, 0.15wt% high manganese zirconium inoculant is evenly dripped onto the pouring molten iron flow to obtain high-strength cast iron for machine tool guide rails and bed castings.
[0037] Figure 3 This is the microstructure phase diagram of the alloy of Example 3 of the present invention. It can be seen that the pearlite content of this example is relatively high, and a certain amount of graphite is precipitated.
[0038] Comparative example 1.
[0039] A method for casting cast iron for machine tool guide rails and bed castings, comprising the following steps: Step 1: Determine the charge composition: 73wt% of high-quality carbon scrap steel, 8wt% of pig iron, and the rest is recycled materials of the same material as cast iron; the main charge composition is C: 3.0wt%, Si: 1.6wt%, Mn: 0.9wt%, P < 0.05wt%, S: < 0.10%; Step 2: According to the chemical composition range required for smelting cast iron and the target value of pearlite content, the additives are determined to be Cu, Sn and Cr, wherein the addition amount of Cu element is 0.4wt%, the addition amount of Sn element is 0.02wt%, and the addition amount of Cr element is 0.08wt%; Step 3: Add the pig iron, scrap steel and recycled materials in step 1 into a medium frequency induction melting furnace to melt the alloy material, add a pretreatment agent during the smelting process to form a qualified liquid metal, take samples during the smelting process for chemical composition detection, and adjust the content of each element until it meets the composition requirements to obtain raw iron liquid; wherein, the molten iron furnace temperature is controlled to be 1520°C, and the insulation time is 8min; the pretreatment agent is 0.15wt% of a material containing Si, Al, Zr, and Ca, and the composition of the pretreatment agent is Si: 62.00~69.00wt%, Al: 3.00~5.00wt%, Zr: 3.00~5.00wt%, Ca: 0.60~1.90wt%, Fe balance; Step 4: After the raw iron liquid in the furnace of step 3 is adjusted to meet the requirements, the inoculant is added into the casting ladle for inoculation treatment, and the raw iron liquid is poured into the casting ladle, and the inoculant is dripped onto the pouring iron flow through the inoculation bucket; the inoculant is a manganese zirconium inoculant with a particle size of 1 to 3 mm and an addition amount of 0.45wt%; Step 5: After deslagging, pour the molten iron in the ladle of step 4. The pouring temperature of the molten iron is controlled at 1380°C. During pouring, inoculation is performed along the flow. Through a handheld inoculation bucket, 0.1wt% high manganese zirconium inoculant is evenly dripped onto the pouring molten iron flow to obtain cast iron for machine tool guide rails and bed castings.
[0040] Figure 4 This is the alloy structure phase diagram of comparative example 1 of the present invention. It can be seen that the pearlite content of this comparative example is reduced compared with that of the alloy of comparative example 1.
[0041] Comparative example 2.
[0042] A method for casting cast iron for high-strength machine tool guide rails and bed castings, comprising the following steps: Step 1: Determine the charge composition: 73wt% of high-quality carbon scrap steel, 8wt% of pig iron, and the rest is recycled materials of the same material as cast iron; the main charge composition is C: 3.0wt%, Si: 1.6wt%, Mn: 0.9wt%, P=0.4wt%, S: <0.10%; Step 2: According to the chemical composition range required for smelting cast iron and the target value of pearlite content, the additives are determined to be Cu, Sn and Cr, wherein the addition amount of Cu element is 0.75wt%, the addition amount of Sn element is 0.04wt%, and the addition amount of Cr element is 0.08wt%; Step 3: Add the pig iron, scrap steel and recycled materials in step 1 into a medium frequency induction melting furnace to melt the alloy material, add a pretreatment agent during the smelting process to form a qualified liquid metal, take samples during the smelting process for chemical composition detection, and adjust the content of each element until it meets the composition requirements to obtain raw iron liquid; wherein, the molten iron furnace temperature is controlled to be 1520°C, and the insulation time is 8min; the pretreatment agent is 0.15wt% of a material containing Si, Al, Zr, and Ca, and the composition of the pretreatment agent is Si: 62.00~69.00wt%, Al: 3.00~5.00wt%, Zr: 3.00~5.00wt%, Ca: 0.60~1.90wt%, Fe balance; Step 4: After the raw iron liquid in the furnace of step 3 is adjusted to meet the requirements, the inoculant is added into the casting ladle for inoculation treatment, and the raw iron liquid is poured into the casting ladle, and the inoculant is dripped onto the pouring iron flow through the inoculation bucket; the inoculant is a manganese zirconium inoculant with a particle size of 1 to 3 mm and an addition amount of 0.45wt%; Step 5: After deslagging, pour the molten iron in the pouring ladle in step 4. The pouring temperature of the molten iron is controlled at 1380°C. During pouring, inoculation is performed along the flow. Through a handheld inoculation bucket, 0.1wt% high manganese zirconium inoculant is evenly dripped onto the pouring molten iron flow to obtain high-strength cast iron for machine tool guide rails and bed castings.
[0043] Figure 5 and Figure 6 The alloy microstructure phase diagrams of comparative example 2 of the present invention at different magnifications show that the matrix microstructure of comparative example 2 is broken, and the pearlite content is no different from that of embodiment 1; due to the high P content, a large amount of phosphorus eutectic is precipitated in the cast alloy.
Claims
1. A method for casting cast iron for high-strength machine tool guide rails and bed castings, characterized in that: The following steps are involved: Step 1: Determine the composition of the smelting charge, including pig iron, scrap steel, recycled materials, etc.; Step 2: Determine the content of the required added elements according to the chemical composition range required for smelting cast iron and the target value of pearlite content; Step 3: adding the pig iron, scrap steel and recycled materials from step 1 into a smelting furnace for smelting, adding a pretreatment agent during the smelting process to obtain raw iron liquid; Step 4: After the raw iron liquid in the furnace of step 3 is adjusted to meet the requirements, the inoculant is added into the pouring ladle, and the raw iron liquid is poured into the pouring ladle to produce iron; Step 5: After deslagging, pour the molten iron in the pouring ladle of step 4. The pouring temperature of the molten iron is controlled at 1330°C to 1400°C. During pouring, inoculation treatment is performed to finally obtain high-strength cast iron for machine tool guide rails and bed castings.
2. The casting method of high-strength cast iron for machine tool guide rails and bed castings according to claim 1, characterized in that: In the step 1, the control range of the charge composition is C: 3.0wt%~3.1wt%, Si: 1.6wt%~1.8wt%, Mn: 0.8wt%~1.0wt%, P<0.05wt%, S:<0.10wt%; high-quality carbon scrap steel with good smelting level is used, the addition amount is 70wt%~80wt%, the pig iron addition amount is less than 10wt%, and the rest is the same material recycled material with the same cast iron composition.
3. The casting method of high-strength cast iron for machine tool guide rails and bed castings according to claim 1, characterized in that: In the step 2, the added elements are Cu, Sn and Cr; wherein the content of Cu element added to the cast iron is 0.7wt% to 0.8wt%, the content of Sn element added to the cast iron is 0.04wt% to 0.05wt%, and the content of Cr element added to the cast iron is <0.1wt%.
4. The casting method of high-strength cast iron for machine tool guide rails and bed castings according to claim 1, characterized in that: In the step three, the specific smelting steps are: adding the pig iron, scrap steel and recycled materials in step one into a medium frequency induction melting furnace to melt the alloy material to form qualified liquid metal; taking samples for chemical composition detection during the smelting process, and adjusting the content of each element until it meets the composition requirements; controlling the temperature of the molten iron out of the furnace to 1510°C ~ 1530°C, and the insulation time to 5min ~ 10min, to remove harmful gases and impurity elements in the molten iron.
5. The casting method of high-strength cast iron for machine tool guide rails and bed castings according to claim 1, characterized in that: In the step three, the composition range of the pretreatment agent is Si: 62.00wt%~69.00wt%, Al: 3.00wt%~5.00wt%, Zr: 3.00wt%~5.00wt%, Ca: 0.60wt%~1.90wt%, Fe balance; the amount of the pretreatment agent added is 0.1wt%~0.2wt% of the smelted cast iron.
6. The casting method of high-strength cast iron for machine tool guide rails and bed castings according to claim 1, characterized in that: In the step 4, during the iron tapping process, the inoculant is dripped onto the pouring iron flow through the inoculant bucket; the inoculant is a manganese-zirconium inoculant with a particle size of 1 mm to 3 mm and an addition amount of 0.4wt% to 0.5wt% of the smelted cast iron.
7. The casting method of high-strength cast iron for machine tool guide rails and bed castings according to claim 1, characterized in that: In the step 5, the inoculation with the flow is: using a handheld inoculation bucket, a high manganese zirconium inoculant with a mass of 0.1wt% to 0.15wt% of the cast iron is evenly dropped onto the pouring molten iron flow.