Method for preparing silicon oxide passive film around gray cast iron flake graphite
By heating the gray cast iron in an oxidizing atmosphere with high oxygen partial pressure, the oxygen element reacts with the silicon around the graphite to form a continuous SiO2 passivation film, the problem of oxidation of gray cast iron at high temperature is solved and its oxidation resistance and strength are improved.
Patent Information
- Application Number
- CN202510333270.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-20
- Publication Date
- 2025-06-13
AI Technical Summary
Gray cast iron is prone to oxidation at high temperatures, resulting in internal expansion stress and weakening its strength. It is difficult for the prior art to form a continuous SiO2 passivation film around the cast iron sheet graphite to improve oxidation resistance.
The gray cast iron is heated in an oxidizing atmosphere with high oxygen partial pressure. The oxygen element enters through the interface between the graphite and the substrate, reacts with the silicon around the graphite to form a SiO2 passivation film. The continuous SiO2 passivation film is gradually formed around the graphite by using the polarization phenomenon of silicon.
It effectively improves the anti-oxidation and growth ability of gray cast iron, forms a continuous SiO2 passivation film around graphite, and enhances the strength and heat resistance of cast iron.
Smart Images
Figure CN120138545A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of passivation film preparation, and particularly to a method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron. Background Art
[0002] When ordinary gray cast iron works at high temperature, oxygen in the air enters the interior of the cast iron through the boundary between the flake graphite and the matrix, and chemically reacts with the iron in the matrix to form iron oxide. Since the iron oxide is not dense, oxygen passes through the iron oxide and causes the iron in the matrix to oxidize gradually from the graphite edge into the matrix. Since the specific volume of iron oxide is greater than that of iron, the iron oxidation process is accompanied by irreversible volume expansion. Since this expansion occurs inside the cast iron, while reducing the effective load-bearing area of the cast iron, internal expansion stress is generated, seriously weakening the strength of the cast iron.
[0003] Currently, the effective way to prevent the oxidation and growth of gray cast iron is usually to improve the oxidation resistance of gray cast iron by increasing or adding elements such as silicon, chromium, and aluminum.
[0004] When the silicon content of gray cast iron is increased to more than 5%, a dense SiO 2 oxide film is formed on the surface of the cast iron, which has a protective effect on gray cast iron. Due to the too high silicon content, the brittleness of ferrite increases. At the same time, due to the large thermal expansion coefficient of the cast iron, it is easy to crack under the conditions of fast heating and cooling. If the silicon content is low, a continuous SiO 2 passivation film cannot be formed on the surface of the cast iron, and the oxidation resistance of gray cast iron is insufficient.
[0005] Therefore, aiming at the deficiencies of the prior art, it is very necessary to provide a method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron to solve the deficiencies of the prior art. Summary of the Invention
[0006] The purpose of the present invention is to avoid the deficiencies of the prior art and provide a method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron. Gray cast iron with a carbon content of 2.9 - 3.8%, a silicon content of 1.6 - 4.0%, a manganese content of 0.6 - 0.8%, a phosphorus content ≤ 0.03%, and a sulfur content ≤ 0.03% is heated to 600°C - 900°C in an oxidizing atmosphere heating furnace with an oxygen partial pressure P O2 greater than 10 -37 -10 -24 Pa and held for 10 - 14 hours. Under this condition, oxygen elements enter the interior through the gap at the graphite-matrix interface, and react with the silicon in the matrix around the graphite to form SiO 2 , and by utilizing the phenomenon that silicon can segregate towards the matrix around the graphite, a continuous SiO 2 passivation film is gradually formed around the graphite. At the same time, a continuous SiO can also be formed on the surface of the cast iron2 The passivation film can achieve the purpose of improving the oxidation resistance and growth ability of gray cast iron. The process is simple, the operation is convenient, and it is easy to realize industrialization. There is a continuous SiO around the flake graphite of the prepared gray cast iron 2 passivation film
[0007] The above object of the present invention is achieved by the following technical means
[0008] A method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron is provided, including the following steps
[0009] S1: Preparation of gray cast iron
[0010] S2: Adding the prepared gray cast iron into an oxidizing atmosphere heating furnace for heat treatment
[0011] S3: Air-cooling treatment of the gray cast iron after heat treatment
[0012] S4: Conducting electron microscope scanning on the gray cast iron
[0013] S5: Obtaining the detection data of the SiO 2 passivation film of gray cast iron
[0014] Specifically, in step S1, gray cast iron with a carbon content of 2.9-3.8%, a silicon content of 1.6-4.0%, a manganese content of 0.6-0.8%, a phosphorus content ≤ 0.03%, and a sulfur content ≤ 0.03% is prepared
[0015] Preferably, in step S2, the oxygen partial pressure P in the oxidizing atmosphere heating furnace O2 is greater than 10 -37 -10 -24 Pa
[0016] Preferably, in step S2, it is heated to 600°C-900°C in the oxidizing atmosphere heating furnace in step S2
[0017] Preferably, in step S3, the air-cooling holding time is 10-14 hours
[0018] Specifically, in step S4, the surface distribution states of carbon, oxygen, and silicon are determined by a scanning electron microscope, and the continuity and thickness of the SiO 2 passivation film around the flake graphite are calibrated
[0019] The present invention uses gray cast iron with a carbon content of 2.9-3.8%, a silicon content of 1.6-4.0%, a manganese content of 0.6-0.8%, a phosphorus content ≤ 0.03%, and a sulfur content ≤ 0.03% under an oxygen partial pressure P O2 greater than 10 -37 -10 -24Heat it in an oxidizing atmosphere furnace at 600 °C - 900 °C for 10 - 14 hours. Under this condition, oxygen elements enter the interior through the interface gap between graphite and the matrix, and react with silicon in the matrix around the graphite to form SiO 2 , taking advantage of the phenomenon that silicon can segregate towards the matrix around graphite, and gradually form continuous SiO 2 passivation film around the graphite. Meanwhile, a continuous SiO 2 passivation film can also be formed on the surface of the cast iron, achieving the purpose of improving the oxidation resistance and growth ability of gray cast iron. The process is simple, easy to operate, and easy to industrialize. The prepared gray cast iron has continuous SiO 2 passivation film around the flake graphite. Description of the Drawings
[0020] The present invention is further described with reference to the accompanying drawings, but the content in the drawings does not constitute any limitation to the present invention.
[0021] Figure 1 It is a scanning electron microscope image of the passivation film formed on gray cast iron with 3.42 wt%, Si: 2.50 wt% in a method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron according to the present invention.
[0022] Figure 2 It is a scanning electron microscope image of the passivation film formed on gray cast iron with 3.25 wt%, Si: 3.00 wt% in a method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron according to the present invention.
[0023] Figure 3 It is a scanning electron microscope image of the passivation film formed on gray cast iron with 3.08 wt%, Si: 3.50 wt% in a method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron according to the present invention.
[0024] Figure 4 It is a scanning electron microscope image of the passivation film formed on gray cast iron with 2.92 wt%, Si: 4.00 wt% in a method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron according to the present invention.
[0025] Figure 5 It is a scanning electron microscope image of the passivation film formed on gray cast iron heated to 700 °C and held for 12 hours in a method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron according to the present invention.
[0026] Figure 6 It is a scanning electron microscope image of the passivation film formed on gray cast iron heated to 750 °C and held for 10 hours in a method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron according to the present invention.
[0027] Figure 7SEM image of the passivation film formed on gray cast iron heated to 750 °C and held for 12 hours, which is a method of preparing a silicon oxide passivation film around the flake graphite of gray cast iron according to the present invention.
[0028] Figure 8 SEM image of the passivation film formed on gray cast iron heated to 750 °C and held for 14 hours, which is a method of preparing a silicon oxide passivation film around the flake graphite of gray cast iron according to the present invention.
[0029] Figure 9 SEM image of the passivation film formed on gray cast iron heated to 800 °C and held for 12 hours, which is a method of preparing a silicon oxide passivation film around the flake graphite of gray cast iron according to the present invention.
[0030] Figure 10 Flow chart of a method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron according to the present invention. Detailed implementation manners
[0031] The present invention will be further described in conjunction with the following embodiments.
[0032] Embodiment 1:
[0033] A method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron, comprising the following steps:
[0034] S1: Preparation of gray cast iron, preparing gray cast iron with a carbon content of 3.42%, a silicon content of 2.5%, a manganese content of 0.6 - 0.8%, a phosphorus content ≤ 0.03%, and a sulfur content ≤ 0.03%;
[0035] S2: Adding the prepared gray cast iron to an oxidizing atmosphere heating furnace with an oxygen partial pressure P O2 greater than 10 -28 and heating to 800 °C;
[0036] S3: Holding the heat-treated gray cast iron for 12 hours and then air-cooling;
[0037] S4: Conducting SEM scanning on the gray cast iron to determine the surface distribution states of carbon, oxygen, and silicon, and calibrating the continuity and thickness of the SiO 2 passivation film around the flake graphite;
[0038] S5: Obtaining the detection data of the SiO 2 passivation film of gray cast iron. The SiO 2 passivation film of gray cast iron around the flake graphite is as Figure 1 shown.
[0039] Embodiment 2:
[0040] A method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron, comprising the following steps:
[0041] S1: Preparation of gray cast iron, preparing gray cast iron with a carbon content of 3.25%, a silicon content of 3.0%, a manganese content of 0.6 - 0.8%, a phosphorus content ≤ 0.03%, and a sulfur content ≤ 0.03%;
[0042] S2: Adding the prepared gray cast iron to an oxidizing atmosphere heating furnace with an oxygen partial pressure P O2 greater than 10 -28 and heating to 800 °C;
[0043] S3: Keeping the heat-treated gray cast iron for 12 hours and then air-cooling;
[0044] S4: Conducting electron microscopy scanning on the gray cast iron, determining the surface distribution states of carbon, oxygen, and silicon by scanning electron microscopy, and calibrating the continuity and thickness of the SiO 2 passivation film around the flake graphite;
[0045] S5: Obtaining the detection data of the SiO 2 passivation film of the gray cast iron. The SiO 2 passivation film of the gray cast iron around the flake graphite is as Figure 2 shown
[0046] Example 3:
[0047] A method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron, comprising the following steps:
[0048] S1: Preparation of gray cast iron, preparing gray cast iron with a carbon content of 3.08%, a silicon content of 3.5%, a manganese content of 0.6 - 0.8%, a phosphorus content ≤ 0.03%, and a sulfur content ≤ 0.03%;
[0049] S2: Adding the prepared gray cast iron to an oxidizing atmosphere heating furnace with an oxygen partial pressure P O2 greater than 10 -28 and heating to 800 °C;
[0050] S3: Keeping the heat-treated gray cast iron for 12 hours and then air-cooling;
[0051] S4: Conducting electron microscopy scanning on the gray cast iron, determining the surface distribution states of carbon, oxygen, and silicon by scanning electron microscopy, and calibrating the continuity and thickness of the SiO 2 passivation film around the flake graphite;
[0052] S5: Obtaining the detection data of the SiO 2 passivation film of the gray cast iron. The SiO 2 passivation film of the gray cast iron around the flake graphite is as Figure 3 shown.
[0053] Example 4:
[0054] A method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron, comprising the following steps:
[0055] S1: Preparation of gray cast iron, preparing gray cast iron with a carbon content of 2.92%, a silicon content of 4.0%, a manganese content of 0.6 - 0.8%, a phosphorus content ≤ 0.03%, and a sulfur content ≤ 0.03%;
[0056] S2: Adding the prepared gray cast iron to an oxidizing atmosphere heating furnace with an oxygen partial pressure P O2 greater than 10 -28 and heating to 800 °C;
[0057] S3: Keeping the heat-treated gray cast iron for 12 hours and then air-cooling;
[0058] S4: Conducting an electron microscope scan on the gray cast iron to determine the surface distribution states of carbon, oxygen, and silicon, and calibrating the continuity and thickness of the SiO 2 passivation film around the flake graphite;
[0059] S5: Obtaining the detection data of the SiO 2 passivation film of the gray cast iron. The SiO 2 passivation film around the flake graphite of the gray cast iron is as Figure 4 shown.
[0060] Example 5:
[0061] A method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron, comprising the following steps:
[0062] S1: Preparation of gray cast iron, preparing gray cast iron with a carbon content of 3.7%, a silicon content of 1.75%, a manganese content of 0.6 - 0.8%, a phosphorus content ≤ 0.03%, and a sulfur content ≤ 0.03%;
[0063] S2: Adding the prepared gray cast iron to an oxidizing atmosphere heating furnace with an oxygen partial pressure P O2 greater than 10 -32 Pa and heating to 700 °C; 10 -32 Pa
[0064] S3: Keeping the heat-treated gray cast iron for 12 hours and then air-cooling;
[0065] S4: Conducting an electron microscope scan on the gray cast iron to determine the surface distribution states of carbon, oxygen, and silicon, and calibrating the continuity and thickness of the SiO 2 passivation film around the flake graphite;
[0066] S5: Obtain the detection data of the SiO passivation film on gray cast iron. The SiO passivation film on gray cast iron around flake graphite is as follows. 2 The SiO passivation film on gray cast iron around flake graphite is as follows. 2 The SiO passivation film is as Figure 5 shown.
[0067] Example 6:
[0068] A method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron, comprising the following steps:
[0069] S1: Prepare gray cast iron with a carbon content of 3.7%, a silicon content of 1.75%, a manganese content of 0.6 - 0.8%, a phosphorus content ≤ 0.03%, and a sulfur content ≤ 0.03%.
[0070] S2: Add the prepared gray cast iron to an oxidizing atmosphere heating furnace with an oxygen partial pressure P O2 greater than 10 -30 Pa and heat it to 750 °C.
[0071] S3: Keep the heat-treated gray cast iron for 10 hours and then perform air cooling treatment.
[0072] S4: Perform electron microscopy scanning on the gray cast iron to determine the surface distribution states of carbon, oxygen, and silicon, and calibrate the continuity and thickness of the SiO passivation film around the flake graphite. 2 The continuity and thickness of the SiO passivation film around the flake graphite.
[0073] S5: Obtain the detection data of the SiO passivation film on gray cast iron. The SiO passivation film on gray cast iron around flake graphite is as follows. 2 The SiO passivation film on gray cast iron around flake graphite is as follows. 2 The SiO passivation film is as Figure 6 shown.
[0074] Example 7:
[0075] A method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron, comprising the following steps:
[0076] S1: Prepare gray cast iron with a carbon content of 3.7%, a silicon content of 1.75%, a manganese content of 0.6 - 0.8%, a phosphorus content ≤ 0.03%, and a sulfur content ≤ 0.03%.
[0077] S2: Add the prepared gray cast iron to an oxidizing atmosphere heating furnace with an oxygen partial pressure P O2 greater than 10 -30 Pa and heat it to 750 °C.
[0078] S3: Keep the heat-treated gray cast iron for 12 hours and then perform air cooling treatment.
[0079] S4: Conduct electron microscopy scanning on gray cast iron. The scanning electron microscope determines the surface distribution states of carbon, oxygen, and silicon, and calibrates the continuity and thickness of the SiO passivation film around the flake graphite; 2 Continuity and thickness of the passivation film;
[0080] S5: Obtain the SiO passivation film detection data of gray cast iron. The SiO passivation film of gray cast iron is as shown around the flake graphite; 2 The SiO passivation film of gray cast iron is as shown around the flake graphite; 2 The SiO passivation film is as Figure 7 shown.
[0081] Example 8:
[0082] A method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron, comprising the following steps:
[0083] S1: Prepare gray cast iron with a carbon content of 3.7%, a silicon content of 1.75%, a manganese content of 0.6 - 0.8%, a phosphorus content ≤ 0.03%, and a sulfur content ≤ 0.03%;
[0084] S2: Add the prepared gray cast iron to an oxidizing atmosphere heating furnace with an oxygen partial pressure P O2 greater than 10 -30 Pa and heat it to 750 °C;
[0085] S3: Carry out air cooling treatment on the heat-treated gray cast iron for 14 hours;
[0086] S4: Conduct electron microscopy scanning on gray cast iron. The scanning electron microscope determines the surface distribution states of carbon, oxygen, and silicon, and calibrates the continuity and thickness of the SiO passivation film around the flake graphite; 2 Continuity and thickness of the passivation film;
[0087] S5: Obtain the SiO passivation film detection data of gray cast iron. The SiO passivation film of gray cast iron is as shown around the flake graphite; 2 The SiO passivation film of gray cast iron is as shown around the flake graphite; 2 The SiO passivation film is as Figure 8 shown.
[0088] Example 9:
[0089] A method for preparing a silicon oxide passivation film around the flake graphite of gray cast iron, comprising the following steps:
[0090] S1: Prepare gray cast iron with a carbon content of 3.7%, a silicon content of 1.75%, a manganese content of 0.6 - 0.8%, a phosphorus content ≤ 0.03%, and a sulfur content ≤ 0.03%;
[0091] S2: Add the prepared gray cast iron to an oxidizing atmosphere heating furnace with an oxygen partial pressure P O2 greater than 10 -28 and heat it to 800 °C;
[0092] S3: Insulate the heat-treated gray cast iron for 12 hours and then air cool it;
[0093] S4: Conduct an electron microscopy scan on the gray cast iron. The scanning electron microscope determines the surface distribution states of carbon, oxygen, and silicon, and calibrates the continuity and thickness of the SiO passivation film around the flake graphite; 2 Continuity and thickness of the passivation film;
[0094] S5: Obtain the SiO passivation film detection data of the gray cast iron. The SiO passivation film of the gray cast iron is as shown around the flake graphite; 2 The SiO passivation film of the gray cast iron around the flake graphite; 2 The SiO passivation film is as Figure 9 shown.
[0095] During the preparation process, gray cast iron with a carbon content of 2.9 - 3.8%, a silicon content of 1.6 - 4.0%, a manganese content of 0.6 - 0.8%, a phosphorus content ≤ 0.03%, and a sulfur content ≤ 0.03% is heated to 600°C - 900°C in an oxidizing atmosphere heating furnace with an oxygen partial pressure P greater than 10 - 10 Pa, and insulated for 10 - 14 hours. Under this condition, oxygen elements enter the interior through the interface gap between the graphite and the matrix, react with the silicon in the matrix around the graphite to form SiO, and utilize the phenomenon that silicon can segregate towards the matrix around the graphite to gradually form a continuous SiO passivation film around the graphite. At the same time, a continuous SiO passivation film can also be formed on the surface of the cast iron, achieving the purpose of improving the oxidation resistance and growth ability of the gray cast iron. The process is simple, easy to operate, and easy to industrialize. The gray cast iron prepared has a continuous SiO passivation film around the flake graphite. O2 greater than 10 -37 -10 -24 Pa, and insulated for 10 - 14 hours. Under this condition, oxygen elements enter the interior through the interface gap between the graphite and the matrix, react with the silicon in the matrix around the graphite to form SiO, and utilize the phenomenon that silicon can segregate towards the matrix around the graphite to gradually form a continuous SiO passivation film around the graphite. At the same time, a continuous SiO passivation film can also be formed on the surface of the cast iron, achieving the purpose of improving the oxidation resistance and growth ability of the gray cast iron. The process is simple, easy to operate, and easy to industrialize. The gray cast iron prepared has a continuous SiO passivation film around the flake graphite. 2 passivation film, and at the same time, a continuous SiO passivation film can also be formed on the surface of the cast iron, achieving the purpose of improving the oxidation resistance and growth ability of the gray cast iron. The process is simple, easy to operate, and easy to industrialize. The gray cast iron prepared has a continuous SiO passivation film around the flake graphite. 2 passivation film, and at the same time, a continuous SiO passivation film can also be formed on the surface of the cast iron, achieving the purpose of improving the oxidation resistance and growth ability of the gray cast iron. The process is simple, easy to operate, and easy to industrialize. The gray cast iron prepared has a continuous SiO passivation film around the flake graphite. 2 passivation film, achieving the purpose of improving the oxidation resistance and growth ability of the gray cast iron. The process is simple, easy to operate, and easy to industrialize. The gray cast iron prepared has a continuous SiO passivation film around the flake graphite. 2 passivation film.
[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.
Claims
1. A method for preparing a silicon oxide passivation film around gray cast iron flake graphite, characterized in that: The following steps are involved: S1: Grey cast iron preparation; S2: adding the prepared grey cast iron into an oxidizing atmosphere heating furnace for heating treatment; S3: air cooling the grey cast iron after heating; S4: SEM scanning of grey cast iron; S5: Obtaining the detection data of SiO2 passivation film of grey cast iron.
2. A method for preparing a silicon oxide passivation film around gray cast iron flake graphite according to claim 1, characterized in that: In step S1, gray cast iron having a carbon content of 2.9-3.8%, a silicon content of 1.6-4.0%, a manganese content of 0.6-0.8%, a phosphorus content of ≤0.03%, and a sulfur content of ≤0.03% is prepared.
3. A method for preparing a silicon oxide passivation film around gray cast iron flake graphite according to claim 1, characterized in that: In step S2, the oxygen partial pressure P in the oxidizing atmosphere heating furnace is O2 Greater than 10 -37 -10 -24 Pa.
4. A method for preparing a silicon oxide passivation film around gray cast iron flake graphite according to claim 1, characterized in that: In step S2, the material is heated to 600°C-900°C in the oxidizing atmosphere heating furnace in step S2.
5. A method for preparing a silicon oxide passivation film around gray cast iron flake graphite according to claim 1, characterized in that: In step S3, the air cooling and heat preservation time is 10-14 hours.
6. A method for preparing a silicon oxide passivation film around gray cast iron flake graphite according to claim 1, characterized in that: In step S4, a scanning electron microscope is used to determine the surface distribution of carbon, oxygen, and silicon, and to calibrate the continuity and thickness of the SiO2 passivation film around the flake graphite.