A method for preparing gray cast iron with high damping and good processing performance for machine tool castings

Abstract

The present invention relates to a method for preparing gray cast iron with high damping and good processing performance for machine tool castings, and belongs to the technical field of gray cast iron. The present invention creatively uses pure nickel, pure titanium, Ca31Si60 silicon-calcium alloy and FeSi90Al1.5 silicon-iron alloy with a certain mass ratio as raw materials, so that they are mixed and smelted in sequence, air-cooled to room temperature, and crushed to prepare a first inoculant, and then the molten iron obtained in the preparation process of the gray cast iron is subjected to an in-package inoculation treatment by the first inoculant, thereby completing the first inoculation of the molten iron, and then a silicon-barium inoculant is used as a second inoculant and 75FeSi is used as a third inoculant, and the two are synergistically compounded to form a composite inoculant, and the composite inoculant is used to perform in-stream inoculation on the molten iron that has completed the first inoculation during pouring, and then a conventional cooling treatment is performed to obtain a gray cast iron that not only has the characteristics of high damping, but also has excellent processing performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of gray cast iron, and particularly relates to a preparation method of gray cast iron with high damping and good machining performance for machine tool castings. Background Art

[0002] As a metal material, gray cast iron is widely used in various industrial fields due to its good casting properties, thermal conductivity and other properties. Among them, in the manufacturing of machine tools, gray cast iron has always been the mainstream material for making core components such as bed bodies and columns. However, with the continuous development of precision machining technology, higher performance requirements are also put forward for gray cast iron, that is, it is necessary to ensure the stability and machining accuracy under high-intensity cutting conditions, and at the same time, it can effectively absorb vibration and reduce noise. Based on this, the limitations of traditional gray cast iron gradually appear. How to prepare a gray cast iron with high damping and good machining performance is an urgent problem to be solved. Summary of the Invention

[0003] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a preparation method of gray cast iron with high damping and good machining performance for machine tool castings. The present invention creatively uses pure nickel, pure titanium, Ca31Si60 calcium silicate alloy and FeSi90Al1.5 ferrosilicon alloy with a certain mass ratio as raw materials, and after they are mixed and melted, air-cooled to room temperature, and crushed in sequence, a first inoculant is prepared. Then, the first inoculant is used for in-package inoculation treatment of the molten iron obtained in the preparation process of gray cast iron, so as to complete the first inoculation of the molten iron. Then, a silicon-barium inoculant is used as the second inoculant and 75FeSi is used as the third inoculant, and the two are synergistically compounded to form a composite inoculant. The composite inoculant is used for in-stream inoculation when pouring the molten iron that has completed the first inoculation. After subsequent conventional cooling treatment, a kind of gray cast iron is obtained, which not only has the characteristics of high damping, but also has excellent machining performance.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] A preparation method of gray cast iron with high damping and good machining performance for machine tool castings, the preparation method comprising the following steps:

[0006] (1) Weigh materials according to chemical components, add high-purity pig iron, ferrosilicon, ferromanganese, ferrochromium, ferromolybdenum, pure copper, pure tin, ferrous sulfide and a carbon additive into an intermediate frequency induction furnace, and then heat up to 1470 - 1520 °C and keep the temperature constant for 3 - 5 min to obtain molten iron;

[0007] (2) Add the first inoculant to the bottom of the ladle, preheat it, and pour the molten iron for inoculation treatment to obtain component A;

[0008] (3) Pour the component A and simultaneously add a composite inoculant for in-stream inoculation, then air-cool to room temperature to complete the preparation.

[0009] As a preferred technical solution of the present invention, the chemical composition in step (1) is composed of, by weight percentage: 1.6 - 1.8% of Si, 3.4 - 3.5% of C, 0.1 - 0.3% of Mn, 0.06 - 0.1% of S, 0.015 - 0.05% of Cu, 0.2 - 0.3% of Cr, 0.1% of Sn, 0.15 - 0.2% of Mo, and the balance of Fe.

[0010] As a preferred technical solution of the present invention, the recarburizer in step (1) is a graphite recarburizer.

[0011] As a preferred technical solution of the present invention, the heating rate in step (1) is controlled at 15 - 20 °C / min.

[0012] As a preferred technical solution of the present invention, the first inoculant in step (2) is prepared by the following steps:

[0013] Step A: Add 3 - 4 parts by weight of pure nickel, 6 parts by weight of pure titanium, 8 - 10 parts by weight of Ca31Si60, and 10 - 12 parts by weight of FeSi90Al1.5 into an intermediate frequency induction furnace, then heat up to 1700 - 1750 °C, keep the temperature constant for 15 - 20 min, air-cool to room temperature, and crush to complete the preparation.

[0014] Further, the heating rate in step A is controlled at 15 - 20 °C / min.

[0015] Further, the crushing in step A means crushing into particles with a particle size of 1 - 2 mm.

[0016] As a preferred technical solution of the present invention, the dosage of the first inoculant in step (2) is 0.3 - 0.4% of the mass of the molten iron.

[0017] As a preferred technical solution of the present invention, the preheating in step (2) means preheating to 650 - 700 °C.

[0018] As a preferred technical solution of the present invention, the pouring temperature in step (3) is 1380 - 1400 °C.

[0019] As a preferred technical solution of the present invention, the dosage of the composite inoculant in step (3) is 0.1 - 0.15% of the mass of the component A; the composite inoculant is composed of a second inoculant and a third inoculant mixed in a mass ratio of 1:1 - 1.5; the second inoculant is a silicon-barium inoculant; the third inoculant is 75FeSi with a particle size of 1 - 2 mm.

[0020] Advantages of the present invention:

[0021] (1) The present invention creatively uses pure nickel, pure titanium, Ca31Si60 calcium silicate alloy and FeSi90Al1.5 ferrosilicon alloy with a certain mass ratio as raw materials. After they are mixed and melted, air-cooled to room temperature, and crushed in sequence, a first inoculant is prepared. Then, the first inoculant is used for in-package inoculation treatment of the molten iron obtained during the preparation of gray cast iron, thus completing the first inoculation of the molten iron. Then, a silicon-barium inoculant is used as the second inoculant and 75FeSi is used as the third inoculant. The two are synergistically compounded to form a composite inoculant. The composite inoculant is used for in-stream inoculation when pouring the molten iron that has completed the first inoculation. After subsequent conventional cooling treatment, a kind of gray cast iron is obtained, which not only has the characteristics of high damping but also has excellent machining performance.

[0022] (2) The present invention creatively first uses conventional raw materials for mixed melting to prepare molten iron, and then in-package inoculation with the first inoculant, in-stream inoculation with the composite inoculant, and air-cooling to room temperature are carried out in sequence, thus preparing a kind of gray cast iron that not only has the characteristics of high damping but also has excellent machining performance; an appropriate amount of nickel can not only play a role in solution strengthening during inoculation, occupying the lattice positions of the matrix metal, but also reduce the segregation of each element composition during subsequent crystallization, promote the uniform distribution of components, and thus improve the various properties of the obtained gray cast iron; the introduction of titanium can refine the grains, provide more crystal nuclei, and play an excellent strengthening effect; Ca31Si60, as a calcium silicate alloy, itself has a good inoculation effect. It can promote the growth of graphite, and thus obtain more flake graphite. Both FeSi90Al1.5 and 75FeSi are ferrosilicon alloys, which can effectively reduce the white mouth tendency and improve the morphology of graphite. As for the silicon-barium inoculant, it can refine graphite to a certain extent and obtain a more uniform graphite structure.

[0023] (3) The present invention creatively makes technical improvements from the inoculation treatment of molten iron, so that the finally obtained gray cast iron can obtain more excellent machining performance and damping performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] For the convenience of those skilled in the art to understand, the present invention will be further described below with reference to the accompanying drawings.

[0025] Figure 1 It is a graph of the graphite morphology of the gray cast iron prepared in Example 3 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] To further elaborate on the technical means and effects adopted by the present invention to achieve the intended invention purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation manners, structures, features and their effects of the present invention as follows.

[0027] The silicon-barium inoculants in all examples and comparative examples of the present invention were directly purchased from the market, purchased from Yangzhou Xinlong Ferroalloy Manufacturing Co., Ltd., and the model was BaII-1.

[0028] Example 1

[0029] A preparation method of gray cast iron with high damping and good machining performance for machine tool castings, the preparation method comprising the following steps:

[0030] (1) Charge according to the chemical composition, add high-purity pig iron, ferrosilicon, ferromanganese, ferrochromium, ferromolybdenum, pure copper, pure tin, ferrous sulfide and a carbon additive into an intermediate frequency induction furnace, and then heat up to 1470 °C and keep the temperature constant for 3 min to obtain molten iron;

[0031] (2) Add a first inoculant to the bottom of the ladle, preheat it, and pour the molten iron for inoculation treatment to obtain component A;

[0032] (3) Pour the component A and simultaneously add a composite inoculant for in-stream inoculation, and air-cool to room temperature to complete the preparation.

[0033] The chemical composition in step (1) comprises, by weight percentage: 1.6% of Si, 3.4% of C, 0.1% of Mn, 0.06% of S, 0.015% of Cu, 0.2% of Cr, 0.1% of Sn, 0.15% of Mo and the balance of Fe.

[0034] The carbon additive in step (1) is a graphite carbon additive.

[0035] The heating rate in step (1) is controlled at 15 °C / min.

[0036] The first inoculant in step (2) is prepared by the following steps:

[0037] Step A: Add 3 parts by weight of pure nickel, 6 parts by weight of pure titanium, 8 parts by weight of Ca31Si60 and 10 parts by weight of FeSi90Al1.5 into an intermediate frequency induction furnace, then heat up to 1700 °C, keep the temperature constant for 15 min, air-cool to room temperature, and crush to complete the preparation.

[0038] The heating rate in step A is controlled at 15 °C / min.

[0039] The crushing in step A means crushing to particles with a particle size of 1 mm.

[0040] The dosage of the first inoculant described in step (2) is 0.3% of the mass of the molten iron.

[0041] The preheating described in step (2) means preheating to 650 °C.

[0042] The pouring temperature described in step (3) is 1380 °C.

[0043] The dosage of the composite inoculant described in step (3) is 0.1% of the mass of component A; the composite inoculant is formed by mixing a second inoculant and a third inoculant in a mass ratio of 1:1; the second inoculant is a silicon-barium inoculant; the third inoculant is 75FeSi with a particle size of 1 mm.

[0044] Example 2

[0045] A preparation method of gray iron for machine tool castings with high damping and good machining performance, the preparation method includes the following steps:

[0046] (1) Charge according to the chemical composition, add high-purity pig iron, ferrosilicon, ferromanganese, ferrochromium, ferromolybdenum, pure copper, pure tin, ferrous sulfide and a carbon additive into an intermediate frequency induction furnace, then heat up to 1520 °C and keep it at a constant temperature for 5 min to obtain molten iron.

[0047] (2) Add the first inoculant to the bottom of the ladle, preheat, pour the molten iron for inoculation treatment to obtain component A.

[0048] (3) Pour the component A and simultaneously add a composite inoculant for in-stream inoculation, and air-cool to room temperature to complete the preparation.

[0049] The chemical composition described in step (1) includes, by weight percentage: 1.8% Si, 3.5% C, 0.3% Mn, 0.1% S, 0.05% Cu, 0.3% Cr, 0.1% Sn, 0.2% Mo and the balance Fe.

[0050] The carbon additive described in step (1) is a graphite carbon additive.

[0051] The heating rate described in step (1) is controlled at 20 °C / min.

[0052] The first inoculant described in step (2) is prepared through the following steps:

[0053] Step A: Add 4 parts by weight of pure nickel, 6 parts by weight of pure titanium, 10 parts by weight of Ca31Si60 and 12 parts by weight of FeSi90Al1.5 into an intermediate frequency induction furnace, then heat up to 1750 °C, keep it at a constant temperature for 20 min, air-cool to room temperature, and crush to complete the preparation.

[0054] The heating rate in Step A is controlled at 20 °C / min.

[0055] The crushing in Step A means crushing into particles with a particle size of 2 mm.

[0056] The dosage of the first inoculant in Step (2) is 0.4% of the mass of the molten iron.

[0057] The preheating in Step (2) means preheating to 700 °C.

[0058] The pouring temperature in Step (3) is 1400 °C.

[0059] The dosage of the composite inoculant in Step (3) is 0.15% of the mass of Component A; the composite inoculant is composed of a second inoculant and a third inoculant mixed in a mass ratio of 1:1.5; the second inoculant is a silicon-barium inoculant; the third inoculant is 75FeSi with a particle size of 2 mm.

[0060] Example 3

[0061] A preparation method of gray iron for machine tool castings with high damping and good machinability, the preparation method includes the following steps:

[0062] (1) Charge according to the chemical composition, add high-purity pig iron, ferrosilicon, ferromanganese, ferrochromium, ferromolybdenum, pure copper, pure tin, ferrous sulfide and a carbonizing agent into an intermediate frequency induction furnace, then heat up to 1500 °C and keep it at a constant temperature for 4 min to obtain molten iron;

[0063] (2) Add the first inoculant to the bottom of the ladle, preheat, pour the molten iron for inoculation treatment to obtain Component A;

[0064] (3) Pour the Component A and simultaneously add a composite inoculant for in-stream inoculation, and air-cool to room temperature to complete the preparation.

[0065] The chemical composition in Step (1) includes, by weight percentage: 1.7% Si, 3.45% C, 0.2% Mn, 0.08% S, 0.03% Cu, 0.25% Cr, 0.1% Sn, 0.18% Mo and the balance Fe.

[0066] The carbonizing agent in Step (1) is a graphite carbonizing agent.

[0067] The heating rate in Step (1) is controlled at 18 °C / min.

[0068] The first inoculant in Step (2) is prepared through the following steps:

[0069] Step A: Add 3.5 parts by weight of pure nickel, 6 parts by weight of pure titanium, 9 parts by weight of Ca31Si60, and 11 parts by weight of FeSi90Al1.5 into an intermediate frequency induction furnace, then heat up to 1730 °C, keep the temperature constant for 18 min, air-cool to room temperature, and crush to complete the preparation.

[0070] The heating rate in Step A is controlled at 18 °C / min.

[0071] The crushing in Step A means crushing to particles with a particle size of 1.5 mm.

[0072] The dosage of the first inoculant in Step (2) is 0.35% of the mass of the molten iron.

[0073] The preheating in Step (2) means preheating to 680 °C.

[0074] The pouring temperature in Step (3) is 1390 °C.

[0075] The dosage of the composite inoculant in Step (3) is 0.13% of the mass of Component A; the composite inoculant is composed of a second inoculant and a third inoculant mixed in a mass ratio of 1:1.2; the second inoculant is a silicon-barium inoculant; the third inoculant is 75FeSi with a particle size of 1.5 mm.

[0076] Comparative Example 1

[0077] Based on Example 3, the pure nickel is changed to an equal weight of pure titanium, and the rest remains unchanged.

[0078] Comparative Example 2

[0079] Based on Example 3, the pure titanium is changed to an equal weight of Ca31Si60, and the rest remains unchanged.

[0080] Comparative Example 3

[0081] Based on Example 3, the Ca31Si60 is changed to an equal weight of FeSi90Al1.5, and the rest remains unchanged.

[0082] Comparative Example 4

[0083] Based on Example 3, the FeSi90Al1.5 is changed to an equal weight of pure nickel, and the rest remains unchanged.

[0084] Comparative Example 5

[0085] Based on Example 3, the second inoculant is changed to an equal weight of the third inoculant, and the rest remains unchanged.

[0086] Comparative Example 6

[0087] Based on Example 3, the third inoculant is changed to the second inoculant of equal weight, and the rest remains unchanged.

[0088] Comparative Example 7

[0089] Based on Example 3, the first inoculant is changed to a composite inoculant of equal weight, and the rest remains unchanged.

[0090] Comparative Example 8

[0091] Based on Example 3, the composite inoculant is changed to the first inoculant of equal weight, and the rest remains unchanged.

[0092] Test Example 1

[0093] Performance test:

[0094] The gray cast irons prepared in Example 3 and Comparative Examples 1-8 were respectively subjected to performance tests.

[0095] Table 1. Performance test results

[0096]

[0097]

[0098] From Test Example 1, by comparing Example 3 with Comparative Examples 1-8, it can be seen that the gray cast iron prepared by the present invention can obtain more excellent machining performance and damping performance.

[0099] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content within the scope of the technical solution of the present invention to make equivalent embodiments with equivalent changes. However, as long as it does not depart from the content of the technical solution of the present invention, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing gray cast iron with high damping and good processing performance for machine tool castings, characterized in that: The preparation method comprises the following steps: (1) According to the chemical composition, high-purity pig iron, ferrosilicon, ferromanganese, ferrochrome, ferromolybdenum, pure copper, pure tin, ferrous sulfide and carburizer are added to the medium frequency induction furnace, and then the temperature is raised to 1470-1520°C and kept at a constant temperature for 3-5 minutes to obtain molten iron; (2) adding a first inoculant to the bottom of the ladle, preheating it, and pouring the molten iron into it for inoculation treatment to obtain component A; (3) pouring the component A and adding a composite inoculant to inoculate the component, and air cooling the component to room temperature to complete the preparation; Step (2) The first inoculant is prepared by the following steps: Step A: add 3-4 parts by weight of pure nickel, 6 parts by weight of pure titanium, 8-10 parts by weight of Ca31Si60 and 10-12 parts by weight of FeSi90Al1.5 into a medium frequency induction furnace, then heat to 1700-1750°C, keep constant temperature for 15-20 minutes, air cool to room temperature, and crush, and the preparation is completed; the heating rate in step A is controlled at 15-20°C / min; the crushing refers to crushing into particles with a particle size of 1-2 mm.

2. The method for preparing a gray cast iron with high damping and good processing performance for machine tool castings according to claim 1, characterized in that: The chemical composition of step (1) comprises, by weight percentage, 1.6-1.8% Si, 3.4-3.5% C, 0.1-0.3% Mn, 0.06-0.1% S, 0.015-0.05% Cu, 0.2-0.3% Cr, 0.1% Sn, 0.15-0.2% Mo and the balance Fe.

3. The method for preparing a gray cast iron with high damping and good processing performance for machine tool castings according to claim 1, characterized in that: The recarburizer in step (1) is a graphite recarburizer.

4. The method for preparing a gray cast iron with high damping and good processing performance for machine tool castings according to claim 1, characterized in that: In step (2), the dosage of the first inoculant is 0.3-0.4% of the mass of the molten iron.

5. The method for preparing a gray cast iron with high damping and good processing performance for machine tool castings according to claim 1, characterized in that: The preheating in step (2) refers to preheating to 650-700°C.

6. The method for preparing gray cast iron with high damping and good processing performance for machine tool castings according to claim 1, characterized in that: The pouring temperature in step (3) is 1380-1400°C.

7. The method for preparing gray cast iron with high damping and good processing performance for machine tool castings according to claim 1, characterized in that: The amount of the composite inoculant in step (3) is 0.1-0.15% of the mass of component A; the composite inoculant is formed by mixing the second inoculant and the third inoculant in a mass ratio of 1:1-1.5; the second inoculant is a silicon-barium inoculant; and the third inoculant is 75FeSi with a particle size of 1-2 mm.

Images