Preparation method of alpha / beta-silicon carbide mixed particle nodular cast iron inoculant

Abstract

The invention discloses a preparation method of an alpha / beta-silicon carbide mixed particle nodular cast iron inoculant, and belongs to the field of preparation of silicon carbide composite inoculants. The problem that an existing nodular cast iron inoculant is poor in inoculation effect is solved. The method comprises: 1, preparing a dispersant solution; 2, preparing silicon carbide slurry; 3, uniformly stirring the nodular cast iron inoculant and the silicon carbide slurry; and 4, carrying out microwave drying on the mixed slurry, and finally grinding, crushing and sieving. The method is used for preparing the alpha / beta-silicon carbide mixed particle nodular cast iron nucleating agent.

Description

Technical Field

[0001] The invention belongs to the field of preparation of silicon carbide composite inoculant. Background Art

[0002] Ductile iron is widely used in the fields of automobiles, machinery, pipelines and energy due to its excellent comprehensive properties (high strength, high toughness, wear resistance and good casting properties). In recent years, with the progress of materials science and preparation technology, the research on ductile iron has achieved remarkable results. However, there are still some defects that cannot be ignored in actual production and use, such as poor graphite spheroidization, uneven matrix structure, the presence of pores and cracks, and the significant decrease in the toughness of ductile iron in low temperature environments (such as below -20°C). This is due to insufficient inoculation or spheroidization treatment, reduced graphite spheroidization, and decreased material strength and toughness. Compared with traditional inoculants, silicon carbide composite inoculants are widely used in the inoculation treatment of cast iron, cast steel and other alloys to improve the structure and properties of castings because of their unique composition advantages and inoculation effects. However, silicon carbide composite inoculants have the problem of particle agglomeration, which affects their uniform distribution and inoculation effect. Therefore, it is urgent to provide a new silicon carbide composite inoculant. Summary of the invention

[0003] The present invention aims to solve the problem that the existing ductile iron inoculant has a poor inoculation effect, and further provides a method for preparing α / β-silicon carbide mixed particles@ductile iron inoculant.

[0004] A method for preparing α / β-silicon carbide mixed particles@ductile iron inoculant is carried out according to the following steps:

[0005] 1. Add the dispersant into deionized water and stir evenly to obtain a dispersant solution;

[0006] 2. Add α-silicon carbide powder and β-silicon carbide powder to the dispersant solution and grind them, then add a defoamer and stir evenly to obtain silicon carbide slurry;

[0007] The particle size of the α-silicon carbide powder is 50nm to 200nm; the particle size of the β-silicon carbide powder is 1μm to 5μm;

[0008] 3. Evenly stirring the ductile iron inoculant and the silicon carbide slurry to obtain a mixed slurry;

[0009] Fourth, the mixed slurry is microwave dried, and finally ground, crushed and sieved to complete the preparation method of α / β-silicon carbide mixed particles @ ductile iron inoculant.

[0010] The beneficial effects of the present invention are:

[0011] The present invention adopts a composite method of two silicon carbide with different crystal phases to prepare a new type of silicon carbide composite inoculant. The silicon carbide uniformly coated on the surface of the inoculant can effectively improve the agglomeration problem of the inoculant, increase the use efficiency of the inoculant, and delay the reaction time of the inoculant and molten iron at high temperature, increase the inoculation time, thereby further optimizing the uniformity and sphericity of the graphite ball and enhancing the mechanical properties of ductile iron. In addition, silicon carbide can also be used as a deoxidizer to reduce the oxygen content in ductile iron, reduce the defects in ductile iron, and extend its use time. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The microscopic morphology of the α / β-silicon carbide mixed particles@ductile iron inoculant prepared in step 4 of Example 1;

[0013] Figure 2 The microscopic morphology of the ductile iron surface prepared by using the α / β-silicon carbide mixed particles@ductile iron inoculant in Example 1;

[0014] Figure 3 The mechanical properties of ductile iron prepared by using the α / β-silicon carbide mixed particles@ductile iron inoculant of Examples 1 to 3;

[0015] Figure 4 The low temperature impact resistance of ductile iron prepared by using the α / β-silicon carbide mixed particles@ductile iron inoculant of Examples 1 to 3. DETAILED DESCRIPTION

[0016] Specific implementation method 1: This implementation method is a method for preparing α / β-silicon carbide mixed particles @ ductile iron inoculant, which is carried out according to the following steps:

[0017] 1. Add the dispersant into deionized water and stir evenly to obtain a dispersant solution;

[0018] 2. Add α-silicon carbide powder and β-silicon carbide powder to the dispersant solution and grind them, then add a defoamer and stir evenly to obtain silicon carbide slurry;

[0019] The particle size of the α-silicon carbide powder is 50nm to 200nm; the particle size of the β-silicon carbide powder is 1μm to 5μm;

[0020] 3. Evenly stirring the ductile iron inoculant and the silicon carbide slurry to obtain a mixed slurry;

[0021] Fourth, the mixed slurry is microwave dried, and finally ground, crushed and sieved to complete the preparation method of α / β-silicon carbide mixed particles @ ductile iron inoculant.

[0022] The beneficial effects of this embodiment are:

[0023] This embodiment adopts a composite method of two silicon carbide with different crystal phases to prepare a new type of silicon carbide composite inoculant. The silicon carbide uniformly coated on the surface of the inoculant can effectively improve the agglomeration problem of the inoculant, increase the use efficiency of the inoculant, and delay the reaction time of the inoculant and molten iron at high temperature, increase the inoculation time, thereby further optimizing the uniformity and sphericity of the graphite ball and enhancing the mechanical properties of ductile iron. In addition, silicon carbide can also be used as a deoxidizer to reduce the oxygen content in ductile iron, reduce defects in ductile iron, and extend its use time.

[0024] Specific implementation method 2: This implementation method is different from specific implementation method 1 in that: the dispersant in step 1 is kv5088; the concentration of the dispersant in the dispersant solution in step 1 is 1g / L to 5g / L; the stirring in step 1 is stirring at a stirring rate of 10Hz to 20Hz. The rest is the same as specific implementation method 1.

[0025] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that the mass ratio of α-silicon carbide powder to β-silicon carbide powder in step 2 is 1:(0.5-2). Other aspects are the same as specific implementation method 1 or 2.

[0026] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the volume ratio of the total mass of the α-silicon carbide powder and the β-silicon carbide powder to the dispersant solution in step 2 is 1 g: (5-20) mL. The rest is the same as specific embodiment 3.

[0027] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the defoaming agent in step 2 is n-octanol and the volume ratio of the defoaming agent in step 2 to the dispersant solution is 1 g: (1 to 10) L. Others are the same as specific embodiments 1 to 4.

[0028] Specific embodiment 6: This embodiment is different from specific embodiments 1 to 5 in that the sand grinding in step 2 is performed for 5 hours to 10 hours at a rotation speed of 300 r / min to 1000 r / min and a ball-to-material mass ratio of (2 to 5):1. The rest is the same as specific embodiments 1 to 5.

[0029] Specific embodiment 7: This embodiment is different from specific embodiments 1 to 6 in that: the stirring in step 2 is specifically stirring for 0.5h to 5h at a rotation speed of 600rpm to 1200rpm; the stirring in step 3 is specifically stirring for 2h to 5h at a rotation speed of 300rpm to 800rpm. The rest is the same as specific embodiments 1 to 6.

[0030] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the mass ratio of the silicon carbide slurry to the ductile iron inoculant in step 3 is 1:(5-20). Other aspects are the same as specific embodiments 1 to 7.

[0031] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that the microwave drying described in step 4 is carried out at a drying frequency of 2400 MHz to 2500 MHz for 2 hours to 10 hours. The rest is the same as specific embodiments 1 to 8.

[0032] Specific embodiment 10: This embodiment differs from Specific embodiments 1 to 9 in that the sieving in step 4 is through a 5-15 mesh sieve. The rest is the same as Specific embodiments 1 to 9.

[0033] The following examples are used to verify the beneficial effects of the present invention:

[0034] Embodiment 1:

[0035] A method for preparing α / β-silicon carbide mixed particles@ductile iron inoculant is carried out according to the following steps:

[0036] 1. Add the dispersant into deionized water and stir for 0.5 h at a stirring rate of 15 Hz to obtain a dispersant solution;

[0037] The dispersant is kv5088; the concentration of the dispersant in the dispersant solution is 1g / L;

[0038] 2. Add α-silicon carbide powder and β-silicon carbide powder to the dispersant solution, sand mill for 10 hours at a speed of 800 r / min and a ball-to-material mass ratio of 5:1, then add a defoamer, stir for 0.5 hours at a speed of 900 rpm to obtain silicon carbide slurry;

[0039] The average particle size of the α-silicon carbide powder is 50 nm; the average particle size of the β-silicon carbide powder is 3.5 μm; the mass ratio of the α-silicon carbide powder to the β-silicon carbide powder is 1:0.5; the volume ratio of the total mass of the α-silicon carbide powder and the β-silicon carbide powder to the dispersant solution is 1 g:9 mL; the defoaming agent is n-octanol; the mass ratio of the defoaming agent to the dispersant solution is 1 g:2 L;

[0040] 3. Stirring the ductile iron inoculant and silicon carbide slurry at a rotation speed of 500 rpm for 5 hours to obtain a mixed slurry;

[0041] The mass ratio of the silicon carbide slurry to the ductile iron inoculant is 1:5; the ductile iron inoculant is from Inner Mongolia Haite Huacai Technology Co., Ltd., and its composition by mass percentage is: silicon: 40% to 75%, calcium: 0.5% to 2.5%, aluminum: 0.5% to 2.0%, manganese: 0.2% to 1.0%, iron: balance; the average particle size of the ductile iron inoculant is 1.5 mm;

[0042] 4. Under the condition of a drying frequency of 2400 MHz, the mixed slurry was microwave dried for 5 hours, and finally ground and crushed for 30 minutes, and sieved through a 10-mesh sieve to obtain α / β-silicon carbide mixed particles @ ductile iron inoculant.

[0043] Embodiment 2: This embodiment is different from Embodiment 1 in that the mass ratio of the α-silicon carbide powder to the β-silicon carbide powder in step 2 is 1:1. The rest is the same as Embodiment 1.

[0044] Embodiment 3: This embodiment is different from Embodiment 1 in that the mass ratio of the α-silicon carbide powder to the β-silicon carbide powder in step 2 is 1:2. The rest is the same as Embodiment 1.

[0045] Figure 1 This is a microscopic morphology spectrum of the α / β-silicon carbide mixed particles @ ductile iron inoculant prepared in step 4 of Example 1; as can be seen from the figure, a layer of silicon carbide particles is evenly coated on the surface of the inoculant, indicating that the α / β-silicon carbide mixed particles @ ductile iron inoculant is successfully prepared by the method in the embodiment.

[0046] Ductile iron experimental castings were cast using industrial raw iron liquid, and the α / β-silicon carbide mixed particles @ ductile iron inoculant prepared in Examples 1 to 3 were added during the inoculation process to obtain ductile iron, and the test was performed as follows: the grade of the cast iron was QT-400, and the test block size was 500mm×500mm×500mm. First, the pig iron, scrap steel and QT-400 recycled materials were smelted in a 12T medium frequency induction furnace, and then desulfurized, quenched and tempered to make the composition of the molten iron meet the requirements for casting QT-400 castings, and the molten iron was kept warm at the tapping temperature. The pouring process adopted the method of inoculation with the flow, and the addition amount of the α / β-silicon carbide mixed particles @ ductile iron inoculant prepared in Examples 1 to 3 was 0.2% of the total mass of the pig iron, scrap steel and QT-400 recycled materials.

[0047] Figure 2 This is a microscopic morphology spectrum of the ductile iron surface prepared using the α / β-silicon carbide mixed particles @ ductile iron inoculant in Example 1; as can be seen from the figure, the graphite nodules are evenly distributed, well bonded to the matrix, have no obvious pore defects, and have good sphericity, indicating that the modified reinforcing agent has a very good effect.

[0048] Tested according to GB / T 228.1-2010 standard; Figure 3 The mechanical properties of ductile iron prepared by using the α / β-silicon carbide mixed particles@ductile iron inoculant of Examples 1 to 3; as can be seen from the figure, the tensile strength of the ductile iron in Example 2 reaches 445MPa, which has excellent tensile strength.

[0049] Tested according to GB / T 228.1-2010 standard; Figure 4 The low temperature impact resistance of ductile iron prepared by using α / β-silicon carbide mixed particles @ ductile iron inoculant in Examples 1 to 3. As can be seen from the figure, the low temperature impact energy of the ductile iron in Example 2 reached 12.7J and 9.9J at -20℃ and -40℃, respectively, and has excellent low temperature toughness. This shows that the high-performance ductile iron inoculant was successfully prepared by the method in the example.

Claims

1. A method for preparing α / β-silicon carbide mixed particles @ ductile iron inoculant, characterized in that It is carried out in the following steps:

1. Add the dispersant into deionized water and stir evenly to obtain a dispersant solution; 2. Add α-silicon carbide powder and β-silicon carbide powder to the dispersant solution and grind them, then add a defoamer and stir evenly to obtain silicon carbide slurry; The particle size of the α-silicon carbide powder is 50nm to 200nm; the particle size of the β-silicon carbide powder is 1μm to 5μm; 3. Evenly stirring the ductile iron inoculant and the silicon carbide slurry to obtain a mixed slurry; Fourth, the mixed slurry is microwave dried, and finally ground, crushed and sieved to complete the preparation method of α / β-silicon carbide mixed particles @ ductile iron inoculant.

2. The method for preparing an α / β-silicon carbide mixed particle@ductile iron inoculant according to claim 1, characterized in that The dispersant described in step one is kv5088; the concentration of the dispersant in the dispersant solution described in step one is 1g / L to 5g / L; the stirring described in step one is specifically stirring at a stirring rate of 10Hz to 20Hz.

3. The method for preparing an α / β-silicon carbide mixed particle@ductile iron inoculant according to claim 1, characterized in that The mass ratio of the α-silicon carbide powder to the β-silicon carbide powder in step 2 is 1:(0.5-2).

4. The method for preparing an α / β-silicon carbide mixed particle@ductile iron inoculant according to claim 1, characterized in that The volume ratio of the total mass of the α-silicon carbide powder and the β-silicon carbide powder to the dispersant solution described in step 2 is 1 g: (5-20) mL.

5. The method for preparing an α / β-silicon carbide mixed particle@ductile iron inoculant according to claim 1, characterized in that The defoaming agent described in step 2 is n-octanol; the volume ratio of the mass of the defoaming agent described in step 2 to the dispersant solution is 1g:(1-10)L.

6. The method for preparing an α / β-silicon carbide mixed particle@ductile iron inoculant according to claim 1, characterized in that The sand grinding described in step 2 is specifically performed for 5h to 10h at a rotation speed of 300r / min to 1000r / min and a ball-to-material mass ratio of (2 to 5):

1.

7. The method for preparing an α / β-silicon carbide mixed particle@ductile iron inoculant according to claim 1, characterized in that The stirring uniformly described in step 2 specifically refers to stirring for 0.5h to 5h at a rotation speed of 600rpm to 1200rpm; the stirring uniformly described in step 3 specifically refers to stirring for 2h to 5h at a rotation speed of 300rpm to 800rpm.

8. The method for preparing the α / β-silicon carbide mixed particles@ductile iron inoculant according to claim 1, characterized in that The mass ratio of the silicon carbide slurry to the ductile iron inoculant described in step three is 1:(5-20).

9. The method for preparing an α / β-silicon carbide mixed particle@ductile iron inoculant according to claim 1, characterized in that The microwave drying described in step 4 is specifically carried out under the condition of a drying frequency of 2400 MHz to 2500 MHz for 2 h to 10 h.

10. The method for preparing the α / β-silicon carbide mixed particles@ductile iron inoculant according to claim 1, characterized in that The sieving described in step 4 is through a 5-mesh to 15-mesh sieve.

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