A high-molybdenum and high-chromium wear-resistant cast iron material and preparation method thereof

Abstract

The invention belongs to the technical field of alloy materials and their preparation, and specifically relates to a high-molybdenum high-chromium wear-resistant cast iron material and a preparation method thereof. By weight percentage, the composition of the high-molybdenum high-chromium wear-resistant cast iron material is: 1.8-3% C, 15-20% Cr, 13-18% Mo, 0.5-2% V, 0.1-1% Si, 0.1-1% Mn, and the balance is Fe. The master alloy is melted in a vacuum induction furnace, and the operation process is: pre-burning and heat preservation at 800-1000°C for 1-6 hours, heating the alloy element raw material to 1300-1450°C for refining for 1-10 minutes, and pouring at a temperature of 1250-1450°C, taking out of the furnace after 2-10 minutes of casting, transferring to a 300-800°C muffle furnace for cooling with the furnace, and obtaining a high-molybdenum high-chromium wear-resistant cast iron master alloy ingot. The alloy of the invention has good uniformity of structure, high hardness and good processing performance, and can be applied to wear-resistant parts in aircraft engines.

Description

Technical Field

[0001] The invention belongs to the technical field of alloy materials and preparation thereof, and particularly relates to a high-molybdenum and high-chromium wear-resistant cast iron material and a preparation method thereof. Background Art

[0002] High chromium cast iron is the abbreviation of high chromium white wear-resistant cast iron. It is an anti-wear material with excellent performance and is particularly valued. It has much higher wear resistance than alloy steel, much higher toughness and strength than ordinary white cast iron, and it also has good high temperature resistance and corrosion resistance. In addition, it is easy to produce and has moderate cost, so it is known as one of the best anti-abrasive wear materials in contemporary times.

[0003] The chromium in high chromium cast iron can not only effectively improve the corrosion resistance of the material in the slurry, but also has isolated hexagonal rods or lath-shaped M 7 C 3 Type carbides are intermittently distributed in the matrix, which greatly weakens the impact on the matrix splitting, resulting in high chromium cast iron with excellent wear resistance and good toughness. However, when the number of carbides increases to a certain extent, coarse primary carbides will appear in the high chromium cast iron. Although the hardness is improved to a certain extent, the toughness of the high chromium cast iron is sharply reduced, and the scrap rate is extremely high due to crack defects during casting production.

[0004] High chromium cast iron has excellent wear resistance due to the presence of more hard phases in its structure, and is widely used in the fields of petrochemical, aerospace, power and mining. However, due to the poor impact toughness of high chromium cast iron, in order to obtain wear resistance and use effect, workers engaged in high chromium cast iron casting production constantly change its matrix structure and refine the grains by adjusting the chemical composition, microalloying, inoculation treatment, etc., thus significantly improving the performance and use effect of high chromium cast iron. Summary of the invention

[0005] The purpose of the present invention is to provide a high-molybdenum and high-chromium wear-resistant cast iron material and a preparation method thereof. The prepared alloy has high hardness and excellent wear resistance. At the same time, the alloy structure is highly uniform, the carbides are uniform and fine, and it has better processing performance, and can be used in wear-resistant parts of aircraft engines.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A high-molybdenum and high-chromium wear-resistant cast iron material has the following components by weight: C 1.8-3%, Cr 15-20%, Mo 13-18%, V 0.5-2%, Si 0.1-1%, Mn 0.1-1%; the rest is Fe.

[0008] The high-molybdenum and high-chromium wear-resistant cast iron material preferably has the following chemical compositions by weight: C1.8-3%, Cr 15-20%, Mo 13.5-16.5%, V 0.5-2%, Si 0.3-1%, Mn 0.2-0.8%, and the remainder Fe.

[0009] The preparation method of the high-molybdenum and high-chromium wear-resistant cast iron material adopts a vacuum induction furnace to smelt the master alloy, and the smelting crucible is made of MgO, Al 2 O 3 Or CaO ceramic crucible, the operation process is:

[0010] (1) weighing the raw materials of various alloy elements according to weight percentage, and pre-burning at 800-1000° C. for 1-6 hours;

[0011] (2) placing raw materials C, Cr, Mo, V and Fe into a crucible according to the composition, evacuating the crucible until the pressure reaches 50 Pa to 0.1 Pa, and then melting the alloy;

[0012] (3) After the alloy raw materials are purified, high temperature refining is carried out;

[0013] (4) After power failure and conjunctiva, stop vacuuming and fill with high-purity argon gas;

[0014] (5) Sending electricity, punching the film and adding raw materials Si and Mn to it for low-temperature refining;

[0015] (6) The alloy liquid is poured into a mold tube to form a master alloy ingot.

[0016] In the preparation method of the high-molybdenum and high-chromium wear-resistant cast iron material, in step (1), the raw material V added is a ferrovanadium alloy, and the ferrovanadium alloy is used to provide all the vanadium elements and part of the iron elements.

[0017] In the preparation method of the high-molybdenum and high-chromium wear-resistant cast iron material, in step (3), the temperature of high-temperature refining is 1450-1600° C., and the refining time is 1-20 minutes.

[0018] In the method for preparing the high-molybdenum and high-chromium wear-resistant cast iron material, in step (4), the pressure in the furnace is 0.1-0.01 MPa after argon is filled.

[0019] In the preparation method of the high-molybdenum and high-chromium wear-resistant cast iron material, in step (5), the temperature of low-temperature refining is 1300° C. to 1450° C., and the refining time is 1 to 30 minutes.

[0020] In the preparation method of the high-molybdenum and high-chromium wear-resistant cast iron material, in step (6), the casting temperature is 1250°C to 1450°C, the casting is completed 2 to 10 minutes after the furnace is taken out, and transferred to a 300 to 800°C muffle furnace for cooling, to obtain a high-molybdenum and high-chromium wear-resistant cast iron master alloy ingot.

[0021] According to the preparation method of the high-molybdenum and high-chromium wear-resistant cast iron material, the Rockwell hardness of the cast high-molybdenum and high-chromium wear-resistant cast iron material is not less than 58HRC.

[0022] The alloy composition design concept of the high-molybdenum and high-chromium wear-resistant cast iron material of the present invention is as follows:

[0023] The composition design of high chromium cast iron materials should consider increasing the proportion of hard phase and optimizing the hard phase morphology on the one hand, and on the other hand, it is necessary to consider increasing the matrix hardness and optimizing the uniformity of the structure to ensure higher comprehensive hardness and wear resistance; at the same time, in order to ensure the processing performance, the refinement of the hard phase should be considered.

[0024] Usually, the chromium content of high chromium cast iron should be between 12% and 30%. The increase in chromium content can increase the content of carbides to a certain extent. At the same time, the chromium dissolved in the matrix can also improve the matrix hardness and hardenability of cast iron. The amount of carbon is the most direct factor affecting the carbide content. Increasing carbon can increase the number of carbides, thereby improving the wear resistance of cast iron. However, the addition of too much carbon will reduce toughness and easily cause problems such as cracking. The carbon content is controlled at 1.8% to 3%, hoping that the alloy will have higher wear resistance while ensuring better processing performance.

[0025] Molybdenum element exists in high chromium cast iron mainly in three parts, one part is M 2 C-type carbide, part of which enters M 7 C 3 In the molybdenum-type carbide, a part is dissolved in the matrix. The molybdenum dissolved in the matrix can improve the hardness of the matrix and the hardenability of the alloy. At the same time, molybdenum improves the uniformity of the organization and can reduce the formation tendency of blocky carbides, which has a certain improvement on the processing performance. In addition, the addition of molybdenum has little effect on the Ms temperature. The high-molybdenum-high-chromium wear-resistant cast iron described in the present invention is specially and massively added with molybdenum elements, and the purpose is to obtain a wear-resistant material with overall high hardness and uniform organization.

[0026] Manganese has a good effect on stabilizing austenite, and the combination of manganese and molybdenum has a better effect on improving hardenability. At the same time, manganese sharply reduces the Ms point, which will cause a large amount of residual austenite and affect wear resistance. The Mn content in high chromium cast iron should be controlled below 1%.

[0027] Silicon is an indispensable element for deoxidation, but since silicon is an element that reduces hardenability, the addition of silicon to the material is usually less than 1%.

[0028] The vanadium element can combine with carbon to form primary carbides and promote the formation of secondary carbides, which can be used to stabilize cementite and prevent graphitization. In particular, in chromium-molybdenum cast iron, adding a certain amount of vanadium can improve its strength and wear resistance.

[0029] The advantages and beneficial effects of the present invention are:

[0030] 1. Wear-resistant high chromium cast iron is used in some precision wear-resistant parts in the aviation field. The two most concerned issues are wear resistance and processing performance. The key point to improve the wear resistance of high chromium cast iron is to improve the overall hardness of the alloy. The alloy of the present invention adds a large amount of Mo. On the one hand, the Mo element can form a large amount of M 2 C and M 7 C 3 On the other hand, Mo improves the hardness of the matrix by dissolving in the matrix. From the perspective of alloy processing performance, the coarse hard phase in the structure is the key point that will cause processing difficulties. The alloy of the present invention has good uniformity in the cast structure, and the carbides are mainly fine particles with a carbide particle size of 0.1 to 5 μm. The volume fraction of carbide particles is more than 60%, which has high wear resistance and hardness, and good processing performance. At the same time, the alloy contains more Mo elements, and the alloy hardenability is also very excellent.

[0031] 2. The present invention provides a wear-resistant alloy with good hardenability, excellent wear resistance and high hardness. It has good structural uniformity, high hardness and good processing performance, and can be stably used in specific wear-resistant parts of aerospace professional equipment (such as aircraft engines, etc.). BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a low-magnification microstructure diagram of the alloy of the present invention.

[0033] Figure 2 This is a microstructure morphology diagram of the alloy of the present invention. DETAILED DESCRIPTION

[0034] In the specific implementation process, the present invention provides a high-molybdenum and high-chromium wear-resistant cast iron, whose chemical composition and content are as follows: 1.8-3% C, 15-20% Cr, 13-18% Mo, 0.5-2% V, 0.1-1% Si, 0.1-1% Mn, and the balance is Fe. The master alloy is melted in a vacuum induction furnace, and the operation process is as follows: pre-sintering and heat preservation at 800-1000°C for 1-6h, heating the above-mentioned component alloy element raw materials to 1300-1450°C for refining for 1-30min, and pouring at a temperature of 1250-1450°C, taking out of the furnace after 2-10min of casting completion, transferring to a 300-800°C muffle furnace for cooling along with the furnace, and obtaining a high-molybdenum and high-chromium wear-resistant cast iron master alloy ingot.

[0035] Below, the present invention is further described in detail by examples.

[0036] Example 1

[0037] In this embodiment, according to the chemical composition and weight percentage: C 2.0%, Cr 17.6%, Mo 14.8%, V1.25%, Si 0.64%, Mn 0.46%, and the rest is Fe, the weight of the ingredients is calculated and the ingredients are mixed, and the pre-sintering is carried out at 900°C for 5 hours; the smelting mass is 50kg, and the smelting equipment used is a 50kg vacuum induction melting furnace.

[0038] Put C, Cr, Mo, V-Fe and Fe into a crucible, and melt the alloy when the vacuum is evacuated to a pressure of 5Pa. After the alloy raw materials are purified, high-temperature refining is performed. The high-temperature refining time is 15 minutes and the high-temperature refining temperature is 1600°C. Its function is to remove O and N in the metal raw materials and volatilize and remove low-melting-point slag.

[0039] After high-temperature refining is completed, the power is turned off and the temperature is lowered to the liquid surface, and vacuuming is stopped and high-purity argon gas (volume purity 99.999%) is filled in. When the gas pressure reaches 0.03MPa, the blowing of argon gas is stopped.

[0040] Power is supplied, the film is punched, and Si and Mn are added to the crucible. After the liquid level stabilizes, it is allowed to stand for 5 minutes. This is to reduce the generation of splashing and improve the precise control of the alloy composition. In addition, the standing process is conducive to the floating of non-metallic inclusions and improves the purity of the melt.

[0041] Low-temperature refining is carried out at 1430°C for 30 minutes, which is used to further degas and float inclusions to improve the purity of the melt.

[0042] The temperature is raised to 1450℃ for casting. Choosing the appropriate casting temperature can improve the metallurgical quality of the ingot.

[0043] The ingot is taken out of the furnace 5 minutes after casting is completed and transferred to a 600℃ muffle furnace to cool along with the furnace. After the alloy ingot is cooled, the riser part is cut off and the surface is polished to a bright finish.

[0044] After testing, the cast hardness and wear-resistant phase volume fraction of the alloy are shown in Table 1.

[0045] Table 1 Cast hardness and wear-resistant phase volume fraction of alloy

[0046]

[0047] like Figure 1-Figure 2As shown in Table 1, the alloy prepared in this embodiment has excellent hardening performance, and the average hardness of the cast state can reach more than 64HRC, which is much higher than ordinary high chromium cast iron. In particular, the hard wear-resistant phase carbide in its structure is in the form of fine and uniform particles, with a volume fraction of up to 63%, which makes the alloy have excellent processing performance and wear resistance.

[0048] Example 2

[0049] In this embodiment, according to the chemical composition and weight percentage: C 1.8%, Cr 16.4%, Mo 15.2%, V1.31%, Si 0.66%, Mn 0.39%, and the rest is Fe, the weight of the ingredients is calculated and the ingredients are mixed, and the pre-sintering is carried out at 850°C for 4 hours; the smelting mass is 50kg, and the smelting equipment used is a 50kg vacuum induction melting furnace.

[0050] Put C, Cr, Mo, V-Fe and Fe into a crucible, and melt the alloy when the vacuum is evacuated to a pressure of 0.5 Pa. After the alloy raw materials are purified, high-temperature refining is performed. The high-temperature refining time is 10 minutes and the high-temperature refining temperature is 1560°C. Its function is to remove O and N in the metal raw materials and volatilize and remove low-melting-point slag.

[0051] After high-temperature refining, the power is turned off and the temperature is lowered to the liquid surface, and vacuuming is stopped and high-purity argon gas (volume purity 99.999%) is filled in. When the gas pressure reaches 0.06MPa, the blowing of argon gas is stopped.

[0052] Power is supplied, the film is punched, and Si and Mn are added to the crucible. After the liquid level stabilizes, it is allowed to stand for 5 minutes. This is to reduce the generation of splashing and improve the precise control of the alloy composition. In addition, the standing process is conducive to the floating of non-metallic inclusions and improves the purity of the melt.

[0053] Low-temperature refining is carried out at 1400°C for 20 minutes, which is used to further degas and float inclusions to improve the purity of the melt.

[0054] The temperature is raised to 1420℃ for casting. Choosing the appropriate casting temperature can improve the metallurgical quality of the ingot.

[0055] The ingot was taken out of the furnace 8 minutes after casting was completed and transferred into a 500°C muffle furnace to cool along with the furnace. After the alloy ingot was cooled, the riser part was cut off and the surface was polished to a bright finish.

[0056] After testing, the cast hardness and wear-resistant phase volume fraction of the alloy are shown in Table 2.

[0057] Table 2 Cast hardness and wear-resistant phase volume fraction of alloy

[0058]

[0059] Example 3

[0060] In this embodiment, according to the chemical composition and weight percentage: C 2.1%, Cr15.0%, Mo 13.9%, V1.46%, Si 0.55%, Mn0.48%, and the rest is Fe, the weight of the ingredients is calculated and the ingredients are mixed, and the pre-sintering is carried out at 900°C for 3 hours; the smelting mass is 50kg, and the smelting equipment used is a 50kg vacuum induction melting furnace.

[0061] Put C, Cr, Mo, V-Fe and Fe into a crucible, and melt the alloy when the vacuum is evacuated to a pressure of 12Pa. After the alloy raw materials are purified, high-temperature refining is performed. The high-temperature refining time is 20 minutes and the high-temperature refining temperature is 1520°C. Its function is to remove O and N in the metal raw materials and volatilize and remove low-melting-point slag.

[0062] After high-temperature refining, the power is turned off and the temperature is lowered to the liquid surface, and vacuuming is stopped and high-purity argon gas (volume purity 99.999%) is filled in. When the gas pressure reaches 0.04MPa, the blowing of argon gas is stopped.

[0063] Power is supplied, the film is punched, and Si and Mn are added to the crucible. After the liquid level stabilizes, it is allowed to stand for 5 minutes. This is to reduce the generation of splashing and improve the precise control of the alloy composition. In addition, the standing process is conducive to the floating of non-metallic inclusions and improves the purity of the melt.

[0064] Low-temperature refining is carried out at 1350°C for 25 minutes, which is used to further degas and float inclusions to improve the purity of the melt.

[0065] The temperature is raised to 1380°C for casting. Choosing the appropriate casting temperature can improve the metallurgical quality of the ingot.

[0066] The ingot was taken out of the furnace 6 minutes after casting was completed and transferred into a 700℃ muffle furnace to cool along with the furnace. After the alloy ingot was cooled, the riser part was cut off and the surface was polished to a bright finish.

[0067] After testing, the alloy casting hardness and wear-resistant phase volume fraction are shown in Table 3.

[0068] Table 3 Cast hardness and wear-resistant phase volume fraction of alloy

[0069]

[0070] The implementation results show that the high-molybdenum and high-chromium wear-resistant cast iron of the present invention has excellent hardenability, high cast hardness, excellent wear resistance, especially the volume fraction of the wear-resistant phase in the structure is very high, and the wear resistance is greatly improved compared with ordinary high-chromium cast iron. In addition, the alloy structure of the present invention is better in uniformity, and the carbides are uniform and fine particles, which is conducive to preventing collapse during processing.

Claims

1. A high-molybdenum and high-chromium wear-resistant cast iron material, characterized in that: The material composition is as follows by weight percentage: C 1.8~3%, Cr 15~20%, Mo 13~18%, V 0.5~2%, Si 0.1~1%, Mn 0.1~1%; the rest is Fe; The preparation method of the high-molybdenum and high-chromium wear-resistant cast iron material adopts a vacuum induction furnace to smelt the master alloy, and the smelting crucible is a crucible made of MgO, Al2O3 or CaO ceramic material. The operation process is as follows: (1) Weigh the raw materials of each alloy element according to the weight percentage, and pre-sinter at 800-1000℃ for 1-6 hours; (2) Put the raw materials C, Cr, Mo, V and Fe into the crucible according to the weight percentage of the components, and melt the alloy when the vacuum is evacuated to the pressure of 50Pa ~ 0.1Pa; (3) After the alloy raw materials are purified, high temperature refining is carried out; (4) After power failure and conjunctiva formation, stop vacuuming and fill with high-purity argon gas; (5) Power is supplied, the film is punched and raw materials Si and Mn are added thereto for low-temperature refining; (6) pouring the alloy liquid into the mold tube to form a master alloy ingot; In step (3), the high temperature refining temperature is 1450-1600°C, and the refining time is 1-20 min; In step (5), the temperature of low temperature refining is 1300°C to 1450°C, and the refining time is 1 to 30 minutes; In step (6), the casting temperature is 1250° C. to 1450° C., and the cast iron is taken out of the furnace 2 to 10 minutes after the casting is completed, and transferred into a muffle furnace at 300 to 800° C. to cool along with the furnace, thereby obtaining a high-molybdenum and high-chromium wear-resistant cast iron master alloy ingot; The Rockwell hardness of the as-cast high-molybdenum and high-chromium wear-resistant cast iron material is not less than 58HRC.

2. The high-molybdenum and high-chromium wear-resistant cast iron material according to claim 1, characterized in that: The chemical composition of the material is, by weight percentage, C 1.8~3%, Cr 15~20%, Mo 13.5~16.5%, V 0.5~2%, Si 0.3~1%, Mn 0.2~0.8%, and the rest is Fe.

3. A method for preparing the high-molybdenum and high-chromium wear-resistant cast iron material according to claim 1 or 2, characterized in that: The master alloy is smelted in a vacuum induction furnace. The smelting crucible is made of MgO, Al2O3 or CaO ceramic material. The operation process is as follows: (1) Weigh the raw materials of each alloy element according to the weight percentage, and pre-sinter at 800-1000℃ for 1-6 hours; (2) Put the raw materials C, Cr, Mo, V and Fe into the crucible according to the weight percentage of the components, and melt the alloy when the vacuum is evacuated to the pressure of 50Pa ~ 0.1Pa; (3) After the alloy raw materials are purified, high temperature refining is carried out; (4) After power failure and conjunctiva formation, stop vacuuming and fill with high-purity argon gas; (5) Power is supplied, the film is punched and raw materials Si and Mn are added thereto for low-temperature refining; (6) pouring the alloy liquid into the mold tube to form a master alloy ingot; In step (3), the high temperature refining temperature is 1450-1600°C, and the refining time is 1-20 min; In step (5), the temperature of low temperature refining is 1300°C to 1450°C, and the refining time is 1 to 30 minutes; In step (6), the casting temperature is 1250°C to 1450°C. The casting is completed 2 to 10 minutes after the furnace is removed from the furnace and transferred into a muffle furnace at 300 to 800°C for cooling, thereby obtaining a high-molybdenum and high-chromium wear-resistant cast iron master alloy ingot.

4. The method for preparing high-molybdenum and high-chromium wear-resistant cast iron material according to claim 3, characterized in that: In step (1), the raw material V added is a ferrovanadium alloy, which is used to provide all the vanadium elements and part of the iron element.

5. The method for preparing high-molybdenum and high-chromium wear-resistant cast iron material according to claim 3, characterized in that: In step (4), after the argon gas is filled, the pressure in the furnace is 0.1~0.01MPa.

6. The method for preparing high-molybdenum and high-chromium wear-resistant cast iron material according to claim 3, characterized in that: The Rockwell hardness of the as-cast high-molybdenum and high-chromium wear-resistant cast iron material is not less than 58HRC.

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