High-carbon-equivalent gray cast iron brake disc and casting method thereof

Abstract

The invention discloses a high-carbon-equivalent gray cast iron brake disc and a casting method thereof, and relates to the technical field of cast iron. In the casting process of the high-carbon-equivalent gray cast iron brake disc, a specific amount of the inoculant with proper components and proper granularity is added in a proper adding mode, so that the structure defects of blocky graphite, graphite floating, coarse graphite and the like are avoided, the brake disc has a fine and bent A-type graphite form, and the service life of the brake disc is prolonged. The high thermal conductivity requirement of the brake disc is met, and the thermal fatigue performance of the brake disc is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cast iron, in particular to a high-carbon-equivalent gray cast iron brake disc and a casting method thereof. BACKGROUND

[0002] Gray cast iron has good thermal conductivity and wear resistance and is inexpensive, so gray cast iron has always been the first choice for automobile brake discs, but gray cast iron brake discs have a problem of thermal fatigue failure. In order to solve the problem of brake disc thermal fatigue failure, the brake disc material should first have high thermal conductivity, because using a material with high thermal conductivity can significantly reduce the temperature difference between the surface and the interior of the brake disc during braking. Graphite has excellent thermal conductivity, so high-carbon-equivalent gray cast iron can be used to produce brake discs. However, when the carbon equivalent exceeds the eutectic composition, it is easy to appear blocky graphite, coarse graphite and graphite floating and other organizational defects, which makes the thermal fatigue performance of the brake disc deteriorate. Therefore, it is necessary to develop a high-carbon-equivalent gray cast iron brake disc with good graphite morphology. SUMMARY

[0003] Based on the technical problems existing in the background art, the present application proposes a high-carbon-equivalent gray cast iron brake disc and a casting method thereof.

[0004] The casting method of the high-carbon-equivalent gray cast iron brake disc proposed by the present application comprises the following steps:

[0005] S1, add the chemical composition into the electric furnace, melt to obtain molten iron, the molten iron comprises the following components: C: 3.80~3.95wt%, Si: 1.80~2.30wt%, Mn: 0.50~0.80wt%, P: 0~0.10wt%, S: 0~0.10wt%, and the balance is Fe;

[0006] S2, the molten iron is discharged into a transfer ladle, and a first inoculation treatment is carried out by adding a silicon-rare earth complex inoculant and a silicon-zirconium complex inoculant along with the flow when discharging the molten iron; the amount of the silicon-rare earth complex inoculant is 0.25% of the weight of the molten iron, and the composition of the silicon-rare earth complex inoculant is as follows: Si: 65~75wt%, rare earth Ce: 0.5~1.5wt%, and the balance is Fe; the amount of the silicon-zirconium complex inoculant is 0.25% of the weight of the molten iron, and the composition of the silicon-zirconium complex inoculant is as follows: Si: 65~75wt%, Zr: 4.5~5.5wt%, and the balance is Fe;

[0007] S3, the molten iron after the first inoculation treatment is transported to a pouring ladle, then poured into a cavity of a brake disc pouring mold, and a silicon-rare earth compound inoculant is added during pouring to perform a second inoculation treatment, and a high-carbon equivalent gray cast iron brake disc is obtained after cooling; wherein the amount of the silicon-rare earth compound inoculant is 0.1% of the weight of the molten iron, and the composition of the silicon-rare earth compound inoculant is as follows: Si: 65-75 wt%, rare earth Ce: 0.5-1.5 wt%, and the balance is Fe.

[0008] In the present application, the rare earth Ce combines with sulfur (S) and oxygen (O) in the molten iron to form a non-homogeneous nucleation core, promote the graphite to be small and uniform, and form more small and curved A-type graphite, and the high Re content can inhibit the growth of graphite to produce E-type graphite; the zirconium (Zr) combines with nitrogen (N) in the molten iron to form a non-homogeneous nucleation core, promote the graphite to be small and uniform, and form more small and curved A-type graphite, and can also reduce the nitrogen pore defects; the large particle inoculant with a particle size of 3-8 mm is used with the molten iron, and the addition amount of the silicon-rare earth compound inoculant and the silicon-zirconium compound inoculant is controlled, and the large particle large amount principle is adopted to prolong the inoculant decay time and ensure the inoculation effect; the fine particle silicon-rare earth compound inoculant with a particle size of 0.1-0.8 mm is used with the molten iron during pouring, and the addition amount of the silicon-rare earth compound inoculant is controlled, and the fine particle small amount principle is adopted to accelerate the melting speed of the inoculant, avoid the occurrence of slag gas hole defects, and achieve the purpose of instantaneous inoculation. In summary, in the process of tapping the molten iron and pouring the molten iron, the inoculant with the appropriate composition and particle size is added with the molten iron respectively, the blocky graphite, floating graphite, coarse graphite and other organizational defects are avoided, the graphite is refined, and the brake disc has small and curved A-type graphite morphology.

[0009] Preferably, in S2, the particle size of the silicon-rare earth compound inoculant and the silicon-zirconium compound inoculant is 3-8 mm.

[0010] Preferably, in S3, the particle size of the silicon-rare earth compound inoculant is 0.1-0.8 mm.

[0011] Preferably, in S2 and S3, the composition of the silicon-rare earth compound inoculant is the same.

[0012] Preferably, in S1, the temperature of smelting is 1510-1530°C.

[0013] In S1, the raw materials used for batching adopt conventional raw materials in the art, which can include pig iron, scrap steel, carburizing agent and manganese iron alloy.

[0014] The present application also proposes a high-carbon equivalent gray cast iron brake disc prepared by the preparation method.

[0015] The beneficial effects of the present application are as follows:

[0016] The present invention avoids the occurrence of structural defects such as blocky graphite, floating graphite, and coarse graphite by adding a specific amount of an inoculant of suitable composition and particle size in a suitable manner during the casting process of a high-carbon equivalent gray cast iron brake disc, so that the brake disc has a small, curved A-type graphite morphology, which not only meets the high thermal conductivity requirement of the brake disc, but also helps to improve the thermal fatigue performance of the brake disc. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Fig. 1 This is a metallographic image of the high carbon equivalent gray cast iron brake disc prepared in Example 1.

[0018] Figs. 2-6 They are metallographic images of high carbon equivalent gray cast iron brake discs prepared in Comparative Examples 1 to 5, respectively. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is described in detail below through specific embodiments.

[0020] In the following embodiments and comparative examples, the silicon-zirconium composite inoculant adopts the Jiangsu Debang ZS-2 model, and the composition is as follows: Si: 65~75wt%, Zr: 4.5~5.5wt%, and the balance is Fe; the silicon-rare earth composite inoculant adopts the Jiangsu Debang S40 model, and the composition is as follows: Si: 65~75wt%, rare earth Ce: 0.5~1.5wt%, and the balance is Fe.

[0021] Example 1

[0022] A method for casting a high carbon equivalent gray cast iron brake disc comprises the following steps:

[0023] S1. Add materials according to chemical composition into an electric furnace and smelt at 1510-1530° C. to obtain molten iron. The molten iron has the following composition: C: 3.88wt%, Si: 2.15wt%, Mn: 0.67wt%, P: 0.02wt%, S: 0.03wt%, and the balance is Fe;

[0024] S2, discharging the molten iron into a transfer ladle, and adding a silicon rare earth composite inoculant with a particle size of 3 to 8 mm and a silicon zirconium composite inoculant with a particle size of 3 to 8 mm to perform an inoculation treatment as the molten iron is discharged; wherein the amount of the silicon rare earth composite inoculant is 0.25% by weight of the molten iron, and the amount of the silicon zirconium composite inoculant is 0.25% by weight of the molten iron;

[0025] S3, the molten iron after the first inoculation treatment is transported to a pouring ladle, then poured into the cavity of the brake disc pouring mold, and a silicon-rare earth compound inoculant with a particle size of 0.1-0.8 mm is added during pouring for secondary inoculation treatment, and a high-carbon equivalent gray cast iron brake disc is obtained after cooling; wherein the amount of the silicon-rare earth compound inoculant is 0.1% of the weight of the molten iron.

[0026] Comparative Example 1

[0027] A casting method of a high-carbon equivalent gray cast iron brake disc, comprising the following steps:

[0028] S1, the chemical composition is added to an electric furnace, and the molten iron is obtained by smelting at 1510-1530℃, and the composition of the molten iron is as follows: C: 3.88wt%, Si: 2.15wt%, Mn: 0.67wt%, P: 0.02wt%, S: 0.03wt%, and the balance is Fe;

[0029] S2, the molten iron is discharged into a transfer ladle, and a silicon-rare earth compound inoculant with a particle size of 3-8 mm and a silicon-zirconium compound inoculant with a particle size of 3-8 mm are added during the discharge of the molten iron for primary inoculation treatment; wherein the amount of the silicon-rare earth compound inoculant is 0.35% of the weight of the molten iron, and the amount of the silicon-zirconium compound inoculant is 0.15% of the weight of the molten iron;

[0030] S3, the molten iron after the first inoculation treatment is transported to a pouring ladle, then poured into the cavity of the brake disc pouring mold, and a silicon-rare earth compound inoculant with a particle size of 0.1-0.8 mm is added during pouring for secondary inoculation treatment, and a high-carbon equivalent gray cast iron brake disc is obtained after cooling; wherein the amount of the silicon-rare earth compound inoculant is 0.1% of the weight of the molten iron.

[0031] Comparative Example 2

[0032] A casting method of a high-carbon equivalent gray cast iron brake disc, comprising the following steps:

[0033] S1, the chemical composition is added to an electric furnace, and the molten iron is obtained by smelting at 1510-1530℃, and the composition of the molten iron is as follows: C: 3.88wt%, Si: 2.15wt%, Mn: 0.67wt%, P: 0.02wt%, S: 0.03wt%, and the balance is Fe;

[0034] S2, the molten iron is discharged into a transfer ladle, and a silicon-rare earth compound inoculant with a particle size of 3-8 mm and a silicon-zirconium compound inoculant with a particle size of 3-8 mm are added during the discharge of the molten iron for primary inoculation treatment; wherein the amount of the silicon-rare earth compound inoculant is 0.35% of the weight of the molten iron, and the amount of the silicon-zirconium compound inoculant is 0.15% of the weight of the molten iron;

[0035] S3. The molten iron after the primary inoculation treatment is transferred to a casting ladle, and then poured into the cavity of the brake disc casting mold. During the pouring, a silicon rare earth composite inoculant with a particle size of 0.1-0.8 mm is added to the flow for secondary inoculation. After cooling, a high carbon equivalent gray cast iron brake disc is obtained; wherein the amount of the silicon rare earth composite inoculant is 0.1% by weight of the molten iron.

[0036] Comparative Example 3

[0037] A method for casting a high carbon equivalent gray cast iron brake disc comprises the following steps:

[0038] S1. Add materials according to chemical composition into an electric furnace and smelt at 1510-1530° C. to obtain molten iron. The molten iron has the following composition: C: 3.88wt%, Si: 2.15wt%, Mn: 0.67wt%, P: 0.02wt%, S: 0.03wt%, and the balance is Fe;

[0039] S2, discharging the molten iron into a transfer ladle, and adding a silicon rare earth composite inoculant with a particle size of 3 to 8 mm and a silicon zirconium composite inoculant with a particle size of 3 to 8 mm to perform an inoculation treatment as the molten iron is discharged; wherein the amount of the silicon rare earth composite inoculant is 0.2% by weight of the molten iron, and the amount of the silicon zirconium composite inoculant is 0.3% by weight of the molten iron;

[0040] S3. The molten iron after the primary inoculation treatment is transferred to a casting ladle, and then poured into the cavity of the brake disc casting mold. During the pouring, a silicon rare earth composite inoculant with a particle size of 0.1-0.8 mm is added to the flow for secondary inoculation. After cooling, a high carbon equivalent gray cast iron brake disc is obtained; wherein the amount of the silicon rare earth composite inoculant is 0.1% by weight of the molten iron.

[0041] Comparative Example 4

[0042] A method for casting a high carbon equivalent gray cast iron brake disc comprises the following steps:

[0043] S1. Add materials according to chemical composition into an electric furnace and smelt at 1510-1530° C. to obtain molten iron. The molten iron has the following composition: C: 3.88wt%, Si: 2.15wt%, Mn: 0.67wt%, P: 0.02wt%, S: 0.03wt%, and the balance is Fe;

[0044] S2, discharging the molten iron into a transfer ladle, and adding a silicon rare earth composite inoculant with a particle size of 3 to 8 mm and a silicon zirconium composite inoculant with a particle size of 3 to 8 mm to perform an inoculation treatment when the molten iron is discharged; wherein the amount of the silicon rare earth composite inoculant is 0.15% by weight of the molten iron, and the amount of the silicon zirconium composite inoculant is 0.35% by weight of the molten iron;

[0045] S3, the molten iron after the first inoculation treatment is transported to a pouring ladle, then poured into a cavity of a brake disc pouring mold, and a silicon-rare earth compound inoculant with a particle size of 0.1-0.8 mm is added during pouring for secondary inoculation treatment, and a high-carbon-equivalent gray cast iron brake disc is obtained after cooling; wherein the amount of the silicon-rare earth compound inoculant is 0.1% of the weight of the molten iron.

[0046] Comparative Example 5

[0047] A casting method of a high-carbon-equivalent gray cast iron brake disc, comprising the following steps:

[0048] S1, ingredients are proportioned and added to an electric furnace to obtain molten iron at 1510-1530℃, and the composition of the molten iron is as follows: C: 3.88wt%, Si: 2.15wt%, Mn: 0.67wt%, P: 0.02wt%, S: 0.03wt%, and the balance is Fe;

[0049] S2, the molten iron is discharged into a transfer ladle, and a 75 silicon-iron inoculant with a particle size of 3-8 mm is added during the discharge of the molten iron; wherein the amount of the 75 silicon-iron compound inoculant is 0.5% of the weight of the molten iron;

[0050] S3, the molten iron after the first inoculation treatment is transported to a pouring ladle, then poured into a cavity of a brake disc pouring mold, and a silicon-rare earth compound inoculant with a particle size of 0.1-0.8 mm is added during pouring for secondary inoculation treatment, and a high-carbon-equivalent gray cast iron brake disc is obtained after cooling; wherein the amount of the silicon-rare earth compound inoculant is 0.1% of the weight of the molten iron.

[0051] The brake discs prepared in Example 1 and Comparative Examples 1-5 are respectively detected, and the results are shown in Table 1 and Figs. 1-6

[0052] Table 1

[0053]

[0054] As shown in Table 1 and Figs. 1-6 It can be seen from the table that, by adding an inoculant with a specific amount and a suitable particle size in a suitable adding manner during the casting process of the high-carbon-equivalent gray cast iron brake disc, the present application avoids the occurrence of organizational defects such as blocky graphite, graphite floating, and coarse graphite, so that the brake disc has fine and curved A-type graphite morphology, which can meet the product performance requirements, while the microstructure of Comparative Examples 1-5 is not good, and there are obvious organizational defects such as blocky graphite, which does not meet the product performance requirements.

[0055] ​The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art, according to the technical solution and inventive concept of the present application, makes equivalent replacement or change within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for casting a high carbon equivalent gray cast iron brake disc, characterized in that: The following steps are involved: S1. Add materials according to chemical composition into an electric furnace and smelt to obtain molten iron, wherein the molten iron includes the following components: C: 3.80-3.95wt%, Si: 1.80-2.30wt%, Mn: 0.50-0.80wt%, P: 0-0.10wt%, S: 0-0.10wt%, and the balance is Fe; S2. Discharging the molten iron into a transfer ladle, and adding a silicon-rare earth composite inoculant and a silicon-zirconium composite inoculant to the molten iron during the discharge of the molten iron for a first inoculation treatment; wherein the amount of the silicon-rare earth composite inoculant is 0.25% by weight of the molten iron, and the composition of the silicon-rare earth composite inoculant is as follows: Si: 65-75wt%, rare earth Ce: 0.5-1.5wt%, and the balance is Fe; the amount of the silicon-zirconium composite inoculant is 0.25% by weight of the molten iron, and the composition of the silicon-zirconium composite inoculant is as follows: Si: 65-75wt%, Zr: 4.5-5.5wt%, and the balance is Fe; S3. Transferring the molten iron after the primary inoculation treatment to a casting ladle, and then pouring it into the cavity of a brake disc casting mold, and adding a silicon-rare earth composite inoculant during the pouring process for secondary inoculation, to obtain a high carbon equivalent gray cast iron brake disc after cooling; wherein the silicon-rare earth composite inoculant is used in an amount of 0.1% by weight of the molten iron, and the composition of the silicon-rare earth composite inoculant is as follows: Si: 65-75wt%, rare earth Ce: 0.5-1.5wt%, and the balance Fe.

2. The casting method of high carbon equivalent gray cast iron brake disc according to claim 1, characterized in that: In S2, the particle size of the silicon rare earth composite inoculant and the silicon zirconium composite inoculant is 3-8 mm.

3. The casting method of high carbon equivalent gray cast iron brake disc according to claim 1, characterized in that: In S3, the particle size of the silicon-rare earth composite inoculant is 0.1-0.8 mm.

4. The casting method of high carbon equivalent gray cast iron brake disc according to claim 1, characterized in that: In S2 and S3, the components of the silicon-rare earth composite inoculant are the same.

5. The casting method of high carbon equivalent gray cast iron brake disc according to claim 1, characterized in that: In S1, the melting temperature is 1510~1530℃.

6. A high carbon equivalent grey cast iron brake disc, characterized in that: Prepared by the preparation method according to any one of claims 1 to 5.

Images