Inoculant material for grey cast iron and method of production

Abstract

The present application belongs to the technical field of cast iron material, and particularly relates to an inoculant material for gray cast iron; graphite material is used as a furnace core body, silicon carbide is generated by electric heating of a mixture of quartz SiO2 and graphite, then the silicon carbide is crushed to a required particle size range, the crushed silicon carbide is put into a furnace, then nitrogen gas and ammonia gas are introduced, carbon-nitrogen replacement is carried out at 1400 DEG C, and sintering time is 6-8 hours, part of the SiC is replaced into SiN, after preparation, crushing is carried out to 1-5mm particle size, and the inoculant is obtained; only ordinary carbon products raw materials are used for sintering, production cost is effectively reduced, and the purpose of cost reduction can be greatly achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of cast iron materials, and particularly relates to an inoculant material for gray cast iron and a preparation method thereof. BACKGROUND

[0002] Gray cast iron materials are widely used, such as cylinder blocks and cylinder heads of commercial vehicle diesel engines, brake discs (drums), machine tool bed bodies and the like. With the development of metallurgical technology and the progress of material science, a gray cast iron production mode with higher strength and lower cost is widely needed in the market.

[0003] At present, there are various inoculants for gray cast iron in the market, such as 75SiFe inoculant, that is, an ordinary inoculant containing 75% of Si and the rest of Fe; SiBa inoculant, that is, a series of inoculants containing 75% of Si, 3% of Ba and 2% of Ca, and the rest of Fe. There are also CrMnSi inoculants for improving the performance of gray cast iron, that is, inoculants containing 40% of Cr, 13% of Mn, 13% of Si and the rest of Fe.

[0004] The inoculants of these types are added to provide nucleation cores for gray cast iron, and to precipitate high-quality A-type graphite, so that the gray cast iron material has higher strength and better comprehensive performance. SUMMARY

[0005] The application provides an inoculant material for gray cast iron and a preparation method thereof; only ordinary carbon-based product raw materials are sintered, the production cost is effectively reduced, and the cost reduction purpose can be achieved to a large extent.

[0006] A production method of an inoculant material for gray cast iron comprises the following contents.

[0007] Step one, preparation of silicon carbide:

[0008] Graphite material is used as a furnace core body, quartz SiO2 and graphite mixture are heated by electricity to generate silicon carbide, and then are crushed to a required particle size range;

[0009] Step two, preparation of silicon nitride:

[0010] The crushed silicon carbide is placed into a furnace, nitrogen and ammonia gases are then introduced, carbon-nitrogen replacement is carried out at 1400 DEG C, and the sintering time is 6-8 hours, so that part of the SiC is replaced into SiN;

[0011] Step three, the obtained product is high-pressure washed to remove surface floating ash;

[0012] Step four, after the preparation is completed, crushing is carried out to 1-5 mm particle size, and the prepared product is an inoculant, which is named as SiCN-A gray cast iron inoculant, and is hereinafter referred to as SiCN-A.

[0013] The prepared inoculant SiCN-A comprises the following components, respectively, in terms of mass fraction: 75% of silicon carbide, 20% of silicon nitride, 1% of free carbon, 1% of free silicon, 1% of silicon dioxide, 1% of aluminum oxide, 0.5% of moisture, and 0.5% of other impurities.

[0014] In the process of preparing silicon nitride in the second step, the sintering time is shortened to 4-6 hours, and finally the SiCN-B inoculant is obtained.

[0015] The SiCN-B comprises the following components, respectively, in terms of mass fraction: 80% of silicon carbide, 15% of silicon nitride, 1% of free carbon, 1% of free silicon, 1% of silicon dioxide, 1% of aluminum oxide, 0.5% of moisture, and 0.5% of other impurities.

[0016] The silicon carbide is prepared by using an Acheson furnace in the first step.

[0017] The silicon nitride is prepared by using an electric resistance furnace in the second step.

[0018] The beneficial effects of the present application are as follows:

[0019] The present application increases N in ordinary gray cast iron by containing N element itself, so that the gray cast iron has higher strength, has the advantages of low cost, easy operation, and further improved strength of the gray cast iron; the inoculant of the present application can effectively replace the dependence on ferromolybdenum in the production process of gray cast iron, effectively reduces or replaces ferromolybdenum. The present inoculant only uses ordinary carbon-based product raw materials for sintering, effectively reduces the dependence on precious metals, and greatly reduces the cost. DETAILED DESCRIPTION

[0020] The present application will be further described in conjunction with the embodiments. It can be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application.

[0021] In the description of the present application, unless otherwise explicitly specified and limited, the terms "connected", "connected", "fixed" should be understood in a broad sense, for example, can be fixedly connected, or can be detachably connected, or can be integrated; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium; can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0022] In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the first feature "on", "above" and "over" the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the first feature is higher in horizontal height than the second feature. The first feature "under", "below" and "under" the second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the first feature is lower in horizontal height than the second feature.

[0023] In the description of the present embodiment, the terms "upper", "lower", "left", "right", and other orientation or position relationships are only for the convenience of description and simplification of operation, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0024] Embodiment 1

[0025] A method for preparing an inoculant material for gray cast iron, comprising the following contents:

[0026] Step one, preparing silicon carbide:

[0027] Using a graphite material as a furnace core body, the quartz SiO2 and graphite mixture is heated by electricity to generate silicon carbide; then it is crushed to the required particle size range;

[0028] Step two, preparing silicon nitride:

[0029] The crushed silicon carbide is placed in a furnace, then nitrogen and ammonia gases are introduced, carbon-nitrogen replacement is carried out at 1400℃, and the sintering time is 6-8 hours, part of the SiC is replaced by SiN;

[0030] Step three, high-pressure cleaning the obtained product to remove surface dust;

[0031] Step four, after preparation, crushing to 1-5mm particle size, the prepared product is an inoculant, named SiCN-A gray cast iron inoculant, hereinafter referred to as SiCN-A.

[0032] The prepared inoculant SiCN-A includes the following components, respectively, in terms of mass fraction: 75% silicon carbide, 20% silicon nitride, 1% free carbon, 1% free silicon, 1% silicon dioxide, 1% aluminum trioxide, 0.5% moisture, and 0.5% other impurities.

[0033] The sintering time in the second step of preparing silicon nitride is shortened to 4-6 hours, and finally the SiCN-B inoculant is obtained.

[0034] The SiCN-B comprises the following components in mass fraction: 80% of silicon carbide, 15% of silicon nitride, 1% of free carbon, 1% of free silicon, 1% of silicon dioxide, 1% of aluminum trioxide, 0.5% of moisture, and 0.5% of other impurities.

[0035] The silicon carbide is prepared by using an Acheson furnace in the first step.

[0036] The silicon nitride is prepared by using an electric resistance furnace in the second step.

[0037] Gray cast iron smelting process

[0038] 1. Material production process: using pig iron, scrap steel, and recycled material as main materials to melt in a medium-frequency furnace (the N element content of the cupola itself is relatively high, which is not suitable for this product)

[0039] 2. After the molten iron is melted, spectral detection is performed, and the gray cast iron composition is adjusted according to the user's requirements;

[0040] 3. Before tapping, the inoculant (SiCN-A or SiCN-B) is added to the ladle at 0.5-1.0%, and then the molten iron is tapped and poured.

[0041] After material detection, the inoculant completely meets the user's usage requirements. According to the product structure of the cylinder head, different combustion chamber structures are set with different flow rates of circulating water during pouring, so that the cylinder head blank has different combustion chamber sizes before heat treatment, and the deformation occurs during heat treatment is offset.

[0042] Taking the production of HT250 brake disc in a certain factory as an example, the factory smelts molten iron by adding pig iron, scrap steel, and recycled material in a proportion of 10:70:20 as required. The adjusted composition before the furnace is: C: 3.20±0.05; Si: 1.75-1.85; Mn: 0.5-0.6; P<0.03; S: 0.10±0.02; Cr: 0.22±0.02; Cu: 0.60±0.05; Mo: 0.1-0.2 (unit wt%), when tapping the molten iron, 0.4% 75SiFe inoculant is added to the ladle bottom for inoculation, and then pouring is performed.

[0043] The process is a traditional production process, characterized by simple operation, good material performance and large-scale stable production. However, molybdenum iron belongs to a precious metal alloy, and the cost is extremely high. The application is improved on the basis of the traditional process, and the addition of molybdenum iron is cancelled. After changing the specific components, the components are C: 3.20±0.05; Si: 1.55-1.65; Mn: 0.5-0.6; P<0.03; S: 0.10±0.02; Cr: 0.22±0.02; Cu: 0.60±0.05 (unit wt%). When the molten iron is discharged, 0.3% of the product and 0.2% of 75SiFe inoculant are added to the ladle bottom for inoculation, and then pouring is carried out. Experiments prove that the same performance effect can be achieved, and the cost reduction effect is realized.

[0044] The above describes the preferred embodiments of the application in detail, but the protection scope of the application is not limited to the specific details in the above embodiments. Within the technical concept range of the application, any person skilled in the art can make equivalent replacement or change according to the technical scheme and the inventive concept of the application within the technical range disclosed by the application, and these simple modifications all belong to the protection scope of the application.

[0045] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the application will not further describe various possible combinations.

[0046] In addition, various different embodiments of the application can also be combined in any manner, as long as they do not deviate from the idea of the application, and they should also be considered as disclosed by the application.

Claims

1. A method of producing an inoculant material for gray cast iron, characterized by, The application relates to a method for preparing a SiCN-A or SiCN-B inoculant. Step one, preparing silicon carbide: A graphite material is used as a furnace core body, a quartz SiO2 and graphite mixture is heated by electricity to generate silicon carbide; and then the silicon carbide is crushed to a required particle size range; Step two, preparing silicon nitride: The crushed silicon carbide is put into a furnace, nitrogen and ammonia gases are introduced, carbon-nitrogen replacement is carried out at 1400 DEG C, and the sintering time is 6-8 hours, so that part of the SiC is replaced into SiN; Step three, the obtained product is high-pressure cleaned to remove surface floating dust; Step four, after the preparation is completed, the product is crushed to a particle size of 1-5 mm, and the prepared product is an inoculant, which is named as SiCN-A gray cast iron inoculant, and is hereinafter referred to as SiCN-A. The prepared inoculant SiCN-A comprises the following components, and the mass fractions are respectively: 75% of silicon carbide, 20% of silicon nitride, 1% of free carbon, 1% of free silicon, 1% of silicon dioxide, 1% of aluminum trioxide, 0.5% of moisture, and 0.5% of other impurities.

2. The method of producing an inoculant material for gray cast iron according to claim 1, characterized by, In the process of preparing the silicon nitride in the step two, the sintering time is shortened to 4-6 hours, and finally the SiCN-B inoculant is obtained. The SiCN-B comprises the following components, and the mass fractions are respectively: 80% of silicon carbide, 15% of silicon nitride, 1% of free carbon, 1% of free silicon, 1% of silicon dioxide, 1% of aluminum trioxide, 0.5% of moisture, and 0.5% of other impurities.

3. The method of producing an inoculant material for gray cast iron according to claim 1, characterized by, The step one adopts an Acheson furnace to prepare the silicon carbide.

4. The method of producing an inoculant material for gray cast iron according to claim 1, characterized by, The step two adopts an electric resistance furnace to prepare the silicon nitride.