Inoculation method for disa line grey cast iron, grey cast iron

Abstract

The application belongs to the technical field of gray cast iron smelting, and particularly relates to a DISA line gray cast iron inoculation method and gray cast iron, which comprises the following steps: S1, taking not more than 60% of main materials and not less than 40% of return materials by mass percentage and placing them in an electric furnace to obtain materials; S2, tapping inoculation, adding 0.1% of GB-10 silicon barium in the total material mass of S1, with a particle size of 3-8 mm, and controlling the temperature at 1550+ / -10 DEG C; S3, transfer inoculation, adding 0.3% of GB-10 silicon barium in the total material mass of S2, with a particle size of 3-8 mm, and controlling the temperature at 1500+ / -10 DEG C; and S4, stream inoculation, adding 0.1% of SiSr silicon strontium in the total material mass of S3, with a particle size of 0.2-0.8 mm, and controlling the temperature at 1420-1470 DEG C, to obtain the gray cast iron.

Description

Technical Field

[0001] This invention belongs to the field of gray cast iron smelting technology, specifically relating to a method for inoculating DISA line gray cast iron and gray cast iron. Background Technology

[0002] Gray cast iron is a type of cast iron, primarily composed of iron, carbon, silicon, manganese, sulfur, and phosphorus. Carbon exists in the form of flake graphite within the cast iron, serving as its "core." The fracture surface is gray. It possesses good casting and machining properties, and excellent wear resistance. It is used to manufacture machine frames, housings, etc. Because the graphite in gray cast iron is flake-shaped, the effective load-bearing area is relatively small, and stress concentration easily occurs at the graphite tips. Therefore, gray cast iron has lower strength, plasticity, and toughness than other cast irons. However, it possesses excellent vibration damping properties, low notch sensitivity, and high wear resistance.

[0003] Thinning gray cast iron is a long-standing problem in the industry. It has high requirements for graphite morphology, and when the wall thickness is ≤5mm, D / E type supercooled graphite is very likely to occur, resulting in insufficient flake graphite, which is also known in the industry as "lack of core".

[0004] Therefore, overcoming the deficiency of flake graphite cores in thin-walled gray cast iron is a technical problem that urgently needs to be solved in this field.

[0005] It should be noted that the information disclosed in this background section is only for understanding the background technology of the present application concept, and therefore, the above description is not considered to constitute prior art information. Summary of the Invention

[0006] This disclosure provides at least one method for inoculating DISA line gray cast iron, and gray cast iron.

[0007] In a first aspect, embodiments of this disclosure provide a method for inoculating gray cast iron for DISA lines, comprising the following steps: S1, taking no more than 60% of the main material and no less than 40% of the recycled material by mass percentage and placing them in an electric furnace to obtain the material; S2, inoculating by slag removal, adding 0.1% of GB-10 barium silicon by mass of the total material in S1, with a particle size of 3-8 mm, and controlling the temperature at 1550±10℃; S3, inoculating by subcontracting, adding 0.3% of GB-10 barium silicon by mass of the total material in S2, with a particle size of 3-8 mm, and controlling the temperature at 1500±10℃; S4, in-flow inoculation, adding 0.1% of SiSr silicon by mass of the total material in S3, with a particle size of 0.2-0.8 mm, and controlling the temperature at 1420~1470℃ to obtain gray cast iron.

[0008] In one alternative implementation, the main materials include pig iron and scrap steel.

[0009] In one optional embodiment, the components in the pig iron, by mass ratio, satisfy the following: C≥3.4%, Si 0.5~1.0%, Mn≤0.2%, P≤0.06%, S≤0.035%.

[0010] In one alternative embodiment, the emissivity of the pig iron is ≤0.46 μSv / h.

[0011] In one optional embodiment, the components in the scrap steel, by mass ratio, satisfy the following: C≤1.5%, Si≤0.6%, Mn≤1.2%, P≤0.06%, S≤0.04%, Cr≤0.1%, Pb≤0.01%, V≤0.05%, Sb≤0.015%, Ti≤0.06%, Sn≤0.06%, Al≤0.08%.

[0012] In one alternative embodiment, the recycled material is HT250 gray cast iron.

[0013] Secondly, embodiments of this disclosure also provide a gray cast iron obtained by the method described above, wherein the components in the gray cast iron, by mass ratio, satisfy the following: C 3.0~3.5%, Si 1.6~2.4%, Mn 0.6~1.2%, P≤0.15%, S≤0.15%; the gray cast iron contains ≥90% pearlite and does not contain cementite and carbides.

[0014] In one alternative embodiment, the gray cast iron has a wall thickness >5 mm, wherein graphite type A >80%, and graphite type B and graphite type C ≤20%.

[0015] In one optional embodiment, the wall thickness of the gray cast iron is ≤5mm, wherein graphite type A is >80%, and graphite type B, graphite type C, graphite type D and graphite type E are ≤20%.

[0016] In one optional embodiment, the gray cast iron has a tensile strength of 250–350 MPa and a hardness of 170–230 HBW.

[0017] The beneficial effects of this invention are that the inoculation method for gray cast iron in the DISA line, and the targeted "core replenishment" at each step of the gray cast iron in the tapping, transfer, and pouring process, are used. The advantages of barium silicon are high density, long-lasting effect, strong anti-fading ability, and significant elimination of white iron. It is used in the early ladle and transfer process. The advantages of strontium silicon are instantaneous strong effect, almost no increase in the number of eutectic clusters, extremely strong suppression of DE type graphite, and avoidance of shrinkage porosity. It is suitable for the final flow. The two complement each other and the effect is better than a single variety or a single method. It ensures that there are enough flake graphite cores when the molten iron enters the thin-walled area. In the case of long process and multiple molds, it can ensure that there are still enough cores in the thin-walled area when the last batch is poured.

[0018] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained through the structures particularly pointed out in the description and the drawings.

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 A top view of a casting provided in an embodiment of this disclosure; Figure 2 A cross-sectional view of a casting provided in an embodiment of this disclosure; Figure 3 Metallographic image of cross-sectional region 1 of a casting provided in an embodiment of this disclosure; Figure 4 A corrosion diagram of a cross-sectional region 1 of a casting provided in an embodiment of this disclosure; Figure 5 Metallographic image of cross-sectional region 2 of a casting provided in an embodiment of this disclosure; Figure 6 A corrosion diagram of cross-sectional region 2 of a casting provided for an embodiment of this disclosure; Figure 7 Metallographic image of cross-sectional region 3 of a casting provided for an embodiment of this disclosure; Figure 8 A corrosion diagram of cross-sectional region 3 of a casting provided for an embodiment of this disclosure; Figure 9 Metallographic image of cross-sectional region 4 of a casting provided in an embodiment of this disclosure; Figure 10 A corrosion diagram of cross-sectional region 4 of a casting provided for an embodiment of this disclosure; Figure 11 Metallographic image of cross-sectional region 5 of a casting provided in an embodiment of this disclosure; Figure 12 Corrosion diagram of cross-sectional region 5 of a casting provided in an embodiment of this disclosure. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] As used herein, the phrases “in one embodiment,” “according to one embodiment,” “in some embodiments,” etc., generally refer to the fact that a particular feature, structure, or characteristic following the phrase can be included in at least one embodiment of this disclosure. Therefore, a particular feature, structure, or characteristic can be included in more than one embodiment of this disclosure, such that these phrases do not necessarily refer to the same embodiment. As used herein, the terms “example,” “exemplary,” etc., are used to “serve as an example, instance, or illustration.” Any implementation, aspect, or design described herein as “example” or “exemplary” is not necessarily to be construed as preferred or superior to other implementations, aspects, or designs. Rather, the use of the terms “example,” “exemplary,” etc., is intended to present concepts in a specific manner.

[0024] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0025] This disclosure provides a method for inoculating gray cast iron for DISA production, comprising the following steps: S1, taking no more than 60% of the main material and no less than 40% of the recycled material by mass percentage and placing them in an electric furnace to obtain the material; S2, inoculating by slag removal, adding 0.1% of GB-10 barium silicon by mass of the total material in S1, with a particle size of 3-8 mm, and controlling the temperature at 1550±10℃; S3, inoculating by subcontracting, adding 0.3% of GB-10 barium silicon by mass of the total material in S2, with a particle size of 3-8 mm, and controlling the temperature at 1500±10℃; S4, in-flow inoculation, adding 0.1% of SiSr silicon by mass of the total material in S3, with a particle size of 0.2-0.8 mm, and controlling the temperature at 1420~1470℃ to obtain gray cast iron.

[0026] In some embodiments, specifically, the main material includes pig iron and scrap steel.

[0027] In some embodiments, specifically, the components in the pig iron, by mass ratio, satisfy the following: C≥3.4%, Si 0.5~1.0%, Mn≤0.2%, P≤0.06%, S≤0.035%.

[0028] In some embodiments, specifically, the emissivity of the pig iron is ≤0.46 μSv / h.

[0029] In some embodiments, specifically, the components in the scrap steel, by mass ratio, satisfy the following: C≤1.5%, Si≤0.6%, Mn≤1.2%, P≤0.06%, S≤0.04%, Cr≤0.1%, Pb≤0.01%, V≤0.05%, Sb≤0.015%, Ti≤0.06%, Sn≤0.06%, Al≤0.08%.

[0030] In some embodiments, specifically, the recycled material is HT250 gray cast iron.

[0031] This disclosure also provides a gray cast iron obtained by the method described above, wherein the components in the gray cast iron, by mass ratio, satisfy the following: C 3.0~3.5%, Si 1.6~2.4%, Mn 0.6~1.2%, P≤0.15%, S≤0.15%; the gray cast iron contains ≥90% pearlite and does not contain cementite and carbides.

[0032] In some embodiments, specifically, the wall thickness of the gray cast iron is >5mm, wherein graphite type A is >80%, and graphite type B and graphite type C are ≤20%.

[0033] In some embodiments, specifically, the wall thickness of the gray cast iron is ≤5mm, wherein graphite type A is >80%, and graphite type B, graphite type C, graphite type D and graphite type E are ≤20%.

[0034] In some embodiments, specifically, the gray cast iron has a tensile strength of 250–350 MPa and a hardness of 170–230 HBW 10 / 3000 KGF.

[0035] Example 1, a method for inoculating gray cast iron, includes the following steps: S1, by mass percentage, 60% of the main material and 40% of the recycled material are placed in an electric furnace to obtain the material; the main material includes pig iron and scrap steel. The pig iron, in addition to meeting the acceptance conditions of composition and radiance, must also meet the following requirements: the shape is accepted as block shape, the surface is clean and free of residual sand and slag, and a small amount of graphite is allowed; it is not allowed to be damp or contain moisture, and it is not allowed to be severely rusted, but a small amount of water rust is allowed; the scrap steel must meet the composition acceptance conditions; the recycled material is HT250 gray cast iron. S2, incubation, with 0.1% of GB-10 barium silicon (DRBa-2 grade) added to the total material mass of S1, with a particle size of 3-8mm, and the temperature controlled at 1550±10℃; S3, subcontracted inoculation, with 0.3% of GB-10 barium silicon (DRBa-2) added to the total material mass of S2, with a particle size of 3-8mm, and the temperature controlled at 1500±10℃; S4 is inoculated with a flow, and SiSr silicon strontium (DRSr-3) with a particle size of 0.2-0.8 mm is added at a total material mass ratio of 0.1% to S3. The temperature is controlled at 1420-1470℃ to obtain gray cast iron.

[0036] The resulting gray cast iron is as follows Figure 1 As shown, along Figure 1 The cross-section at the middle red line divides the resulting structure into: Figure 2 The specific parameters for regions 1-5 are shown in Table 1 below.

[0037] Table 1 Parameters for Regions 1-5 Area 1 Figure 3 Graphite Type A 99% Level 4-5 Figure 4 99% Area 2 Figure 5 Graphite Type A 99% Level 4-5 Figure 6 99% Area 3 Figure 7 Graphite Type A 97% Level 4-5 Figure 8 99% Area 4 Figure 9 Graphite Type A 98% Level 4 Figure 10 98% Area 5 Figure 11 Graphite Type A 99% Level 4-5 Figure 12 99% In region 2, the left wall thickness is 3.5 mm, making it the thinnest region. Due to the rapid cooling rate, the primary austenite dendrite arm spacing (SDAS) of the hypoeutectic gray cast iron thin-walled part is significantly refined, and the remaining liquid phase is divided into highly confined isolated molten pools. When inoculation is insufficient, the eutectic austenite, due to its low nucleation energy barrier, preferentially nucleates and displaces carbon in the dendrites, resulting in strong compositional supercooling between the dendrites. Graphite is forced to undergo explosive nucleation in the eutectic austenite dendrites under extremely high effective supercooling, and its growth mode switches from steady-state spiral dislocation curling to high-frequency twinning branching, ultimately forming DE-type supercooled graphite. When fully inoculated, a large number of heterogeneous nuclei significantly reduce the heterogeneous nucleation energy barrier of graphite, allowing it to nucleate first under extremely low supercooling and achieve coupled symbiotic growth with eutectic austenite, thereby inhibiting the premature growth of eutectic austenite. Therefore, even with limited physical space between primary austenite dendrites, graphite can still grow using a low-undercooling spiral mechanism to form type A graphite, effectively overcoming the defect of increased tendency for precipitation of type DE graphite in thin-walled parts.

[0038] In summary, the inoculation method for gray cast iron in this DISA line involves targeted "core replenishment" at each step of the process, including pouring, sub-pouring, and casting. Barium silicon is advantageous due to its high density, long-lasting effect, strong resistance to fading, and significant elimination of white cast iron. It is used in the early stages of pouring and sub-pouring. Strontium silicon is advantageous due to its instantaneous high efficiency, minimal increase in eutectic clusters, strong suppression of DE-type graphite, and prevention of shrinkage porosity. It is suitable for final flow-following. The two complement each other, resulting in a superior effect compared to a single product or method. This ensures a sufficient number of flake graphite cores when the molten iron enters the thin-walled zone. In long-process, multi-mold scenarios, it guarantees that there are still enough cores in the thin-walled area during the final pour.

[0039] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for inoculating DISA line gray cast iron, characterized in that, Includes the following steps: S1, by mass percentage, take no more than 60% of the main material and no less than 40% of the recycled material and place them in an electric furnace to obtain the material; S2, broth preparation, with 0.1% GB-10 barium silicon added as part of the total S1 material mass ratio, particle size 3-8mm, temperature controlled at 1550±10℃; S3, subcontracted incubation, added to the total material mass ratio of S2 0.3% GB-10 barium silicon, particle size 3-8mm, temperature controlled at 1500±10℃; S4 is inoculated with the flow, and SiSr silicon strontium with a particle size of 0.1% of the total material mass of S3 is added. The temperature is controlled at 1420~1470℃ to obtain gray cast iron.

2. The inoculation method for DISA line gray cast iron as described in claim 1, characterized in that, The main materials include pig iron and scrap steel.

3. The inoculation method for DISA line gray cast iron as described in claim 2, characterized in that, The components in the pig iron, by mass ratio, satisfy the following: C≥3.4%, Si 0.5~1.0%, Mn≤0.2%, P≤0.06%, S≤0.035%.

4. The inoculation method for DISA line gray cast iron as described in claim 2, characterized in that, The emissivity of the pig iron is ≤0.46 μSv / h.

5. The inoculation method for DISA line gray cast iron as described in claim 2, characterized in that, The components in the scrap steel, by mass ratio, satisfy the following: C≤1.5%, Si≤0.6%, Mn≤1.2%, P≤0.06%, S≤0.04%, Cr≤0.1%, Pb≤0.01%, V≤0.05%, Sb≤0.015%, Ti≤0.06%, Sn≤0.06%, Al≤0.08%.

6. The inoculation method for DISA line gray cast iron as described in claim 1, characterized in that, The recycled material is HT250 gray cast iron.

7. A type of gray cast iron obtained by inoculation using the method described in any one of claims 1-6, characterized in that, The components in the gray cast iron, by mass ratio, satisfy the following: C 3.0~3.5%, Si 1.6~2.4%, Mn 0.6~1.2%, P≤0.15%, S≤0.15%; the gray cast iron contains ≥90% pearlite and does not contain cementite or carbides.

8. The gray cast iron as described in claim 7, characterized in that, The gray cast iron has a wall thickness >5mm, of which graphite type A >80%, and graphite type B and graphite type C ≤20%.

9. The gray cast iron as described in claim 7, characterized in that, The wall thickness of the gray cast iron is ≤5mm, of which graphite type A is >80%, and graphite type B, graphite type C, graphite type D and graphite type E are ≤20%.

10. The gray cast iron as described in claim 7, characterized in that, The gray cast iron has a tensile strength of 250–350 MPa and a hardness of 170–230 HBW.

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