Heat treatment method for oil-liquid secondary quenching of high-chromium grinding balls

Abstract

The invention discloses a heat treatment method for oil-liquid secondary quenching of a high-chromium grinding ball, which comprises the following steps: austenitizing a high-chromium grinding ball blank, carrying out primary oil quenching to cool the grinding ball to 100-140 DEG C, carrying out secondary quenching to cool the grinding ball to 0-40 DEG C, and tempering to obtain the high-chromium grinding ball. By selecting a proper heat treatment process and combining mutual cooperation of all elements, the martensite content and the contents of C and Cr in martensite can be increased, grains are refined, growth of eutectic carbides is inhibited, the eutectic carbides are uniformly distributed, and the grinding ball still keeps good toughness while having high wear resistance.

Description

Technical Field

[0001] The invention relates to the technical field of wear-resistant balls, in particular to a heat treatment method for oil-liquid secondary quenching of high-chromium grinding balls. Background Art

[0002] The chromium content in high chromium grinding balls is higher than 10%, and they have good wear resistance and corrosion resistance. The heat treatment process is a key step to improve the performance of high chromium grinding balls. Heat treatment makes the grinding balls austenitized and quenches them through a certain cooling medium to complete the martensitic transformation. The transformation amount of martensite is the key. The larger the martensite transformation amount, the higher the matrix hardness, and to a certain extent, the better the wear resistance of the grinding balls. The transformation amount of martensite depends on the final temperature of the transformation process. The martensite transformation temperature of the traditional quenching process using mineral oil for cooling is high, the martensite transformation amount is limited, and there is a large amount of residual austenite in the matrix. During use, the residual austenite is prone to transformation to martensite, causing volume changes and then causing the surface of the grinding balls to peel off and lose roundness. In addition, the existing high chromium grinding balls also have the problem that wear resistance and toughness cannot be taken into account at the same time. High-wear-resistant high chromium grinding balls often crack during use due to their low toughness. Summary of the invention

[0003] Based on the technical problems existing in the background technology, the present invention proposes a heat treatment method for oil-liquid secondary quenching of high chromium grinding balls. The present invention can increase the martensite content and the C and Cr contents in the martensite by selecting a suitable heat treatment process and combining the mutual coordination of various elements, and refine the grains, inhibit the growth of eutectic carbides, and make them evenly distributed, so that the grinding balls have higher wear resistance while still maintaining good toughness.

[0004] The invention provides a heat treatment method for oil-liquid two-stage quenching of high-chromium grinding balls, comprising the following steps: taking a high-chromium grinding ball blank for austenitization, then performing a primary oil quenching to cool the grinding ball to 100-140°C, performing a secondary quenching to cool the grinding ball to 0-40°C, and then tempering to obtain the high-chromium grinding ball.

[0005] Preferably, the raw materials of the high chromium grinding ball blank include, by weight percentage: C 2.1-3.6%, Si 0.3-1.2%, Mn 0.4-1.5%, Cr 10-20%, V 0.04-0.06%, W 0.8-1.0%, Nb 0.08-0.1%, and the balance is Fe and unavoidable impurities.

[0006] Preferably, the quenching oil is KR4188 quenching oil.

[0007] Preferably, the secondary quenching is performed with an aqueous solution of polyvinyl pyrrolidone.

[0008] Preferably, the mass fraction of the polyvinyl pyrrolidone aqueous solution is 5-25wt%.

[0009] Preferably, the temperature of the polyvinyl pyrrolidone aqueous solution is 0-40°C.

[0010] Preferably, the austenitizing temperature is 920-960° C., and the time is 1-6 h.

[0011] Preferably, the tempering procedure is: keeping at 200-450° C. for 5-7 hours, and then air cooling to room temperature.

[0012] The invention selects a suitable austenitizing temperature so that austenite is kept in an unstable state, then selects KR4188 quenching oil for primary quenching, adjusts the cooling rate, increases the martensite transformation amount and increases the content of C and Cr elements in the martensite, and increases the hardness of the martensite, and then selects a polyvinyl pyrrolidone aqueous solution for secondary quenching, controls the concentration and temperature of the polyvinyl pyrrolidone aqueous solution, reduces the cooling rate, makes the final martensite transformation end temperature at 0-40 DEG C, further increases the martensite transformation amount, and reduces the content of residual austenite. The hardness and wear resistance of the grinding balls are improved; in addition, a suitable tempering temperature is selected to convert the quenched martensite into tempered martensite, stabilize the structure, relieve stress, stabilize the size of the grinding balls, and avoid the problem of uneven stress and easy cracking of the grinding balls; in addition, the present invention selects V, W, and Nb to cooperate with each other in a suitable proportion, which can improve the hardenability, thereby further increasing the content of martensite during the primary quenching and the secondary quenching; and the three cooperate with each other to refine the grains, inhibit the growth of eutectic carbides, make them evenly distributed, and transform the carbides from strips to nets, so that the grinding balls maintain good toughness. DETAILED DESCRIPTION

[0013] The technical solution of the present invention is described in detail below through specific embodiments.

[0014] Example 1

[0015] A heat treatment method for oil-liquid two-stage quenching of high-chromium grinding balls comprises the following steps:

[0016] A high chromium grinding ball blank with a diameter of 100 mm, wherein the raw materials include, by weight percentage, C 2.1%, Si 1.2%, Mn 0.4%, Cr 20%, V 0.04%, W 1.0%, Nb 0.08%, and the balance is Fe and unavoidable impurities;

[0017] Take the high chromium grinding ball blank, heat it to 960℃ and keep it for 1h for austenitization, then add it into KR4188 quenching oil for quenching to cool the grinding ball to 140℃, then add it into a polyvinyl pyrrolidone aqueous solution with a temperature of 40℃ and a mass fraction of 25wt%, perform secondary quenching to cool the grinding ball to 40℃, then take the grinding ball and keep it at 450℃ for 5h, then air cool it to room temperature for tempering to obtain high chromium grinding ball.

[0018] Example 2

[0019] A heat treatment method for oil-liquid two-stage quenching of high-chromium grinding balls comprises the following steps:

[0020] A high chromium grinding ball blank with a diameter of 100 mm, wherein the raw materials include, by weight percentage, 3.6% C, 0.3% Si, 1.5% Mn, 10% Cr, 0.06% V, 0.8% W, 0.1% Nb, and the balance is Fe and unavoidable impurities;

[0021] Take the high chromium grinding ball blank, heat it to 920℃ and keep it for 6 hours to austenitize, then add it into KR4188 quenching oil for quenching to cool the grinding ball to 100℃, then add it into a polyvinyl pyrrolidone aqueous solution with a temperature of 0℃ and a mass fraction of 5wt%, perform secondary quenching to cool the grinding ball to 0℃, then take the grinding ball and keep it at 200℃ for 7 hours, and then air cool it to room temperature for tempering to obtain high chromium grinding ball.

[0022] Example 3

[0023] A heat treatment method for oil-liquid two-stage quenching of high-chromium grinding balls comprises the following steps:

[0024] A high chromium grinding ball blank with a diameter of 100 mm, wherein the raw materials thereof include, by weight percentage, C 2.8%, Si 0.7%, Mn 0.7%, Cr 12.0%, V 0.05%, W 0.9%, Nb 0.09%, and the balance being Fe and unavoidable impurities;

[0025] Take the high chromium grinding ball blank, heat it to 940℃ and keep it for 3h for austenitization, then add it into KR4188 quenching oil for quenching to cool the grinding ball to 120℃, then add it into a polyvinyl pyrrolidone aqueous solution with a temperature of 20℃ and a mass fraction of 10wt%, perform secondary quenching to cool the grinding ball to 20℃, then take the grinding ball and keep it at 300℃ for 6h, and then air cool it to room temperature for tempering to obtain high chromium grinding ball.

[0026] Comparative Example 1

[0027] A heat treatment method for high chromium grinding balls comprises the following steps:

[0028] The composition of the high chromium grinding ball blank is the same as that of the high chromium grinding ball blank in Example 3;

[0029] Take the high chromium grinding ball blank, heat it to 940℃ and keep it for 3 hours to austenitize, then add it into KR4188 quenching oil for quenching to cool the grinding ball to 120℃, then take the grinding ball and keep it at 300℃ for 6 hours, then air cool it to room temperature for tempering to obtain high chromium grinding ball.

[0030] Comparative Example 2

[0031] A heat treatment method for high chromium grinding balls comprises the following steps:

[0032] The composition of the high chromium grinding ball blank is the same as that of the high chromium grinding ball blank in Example 3;

[0033] Take the high chromium grinding ball blank, heat it to 940℃ and keep it for 3 hours to austenitize, then add it into a 20℃, 10wt% polyvinyl pyrrolidone aqueous solution to quench the grinding ball to 20℃, then take the grinding ball and keep it at 300℃ for 6 hours, and then air cool it to room temperature for tempering to obtain a high chromium grinding ball.

[0034] Comparative Example 3

[0035] The temperature was raised to 970°C and kept for 3 hours for austenitization, and the rest was the same as in Example 3.

[0036] Comparative Example 4

[0037] The temperature was raised to 910°C and kept for 3 hours for austenitization, and the rest was the same as in Example 3.

[0038] Comparative Example 5

[0039] V is not included, and the rest is the same as in Example 3.

[0040] Comparative Example 6

[0041] W is not included, and the rest is the same as in Example 3.

[0042] Comparative Example 7

[0043] It does not contain Nb, and the rest is the same as in Example 3.

[0044] The mechanical properties of the grinding balls obtained in Examples 1-3 and Comparative Examples 1-7 were tested, and the results are shown in Table 1.

[0045] Table 1 Test results

[0046] Test items Hardness(HRC) Impact energy (J) Example 1 65.8 4.0 Example 2 66.5 3.8 Example 3 66.1 4.3 Comparative Example 1 59.8 4.3 Comparative Example 2 57.7 3.9 Comparative Example 3 61.4 4.1 Comparative Example 4 61.0 4.0 Comparative Example 5 63.2 3.9 Comparative Example 6 63.5 3.9 Comparative Example 7 63.0 3.8

[0047] It can be seen from the above table that the high chromium grinding balls produced by the process of the present invention have higher hardness and wear resistance and maintain better toughness.

[0048] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A heat treatment method for oil-liquid two-stage quenching of high-chromium grinding balls, characterized in that: The method comprises the following steps: taking a high chromium grinding ball blank and austenitizing it, then performing a primary oil quenching to cool the grinding ball to 100-140 DEG C, performing a secondary quenching to cool the grinding ball to 0-40 DEG C, and then performing tempering to obtain the high chromium grinding ball.

2. The heat treatment method for oil-liquid two-stage quenching of high chrome grinding balls according to claim 1, characterized in that: The raw materials of the high chromium grinding ball blank include, by weight percentage, C 2.1-3.6%, Si 0.3-1.2%, Mn 0.4-1.5%, Cr 10-20%, V 0.04-0.06%, W 0.8-1.0%, Nb 0.08-0.1%, and the balance is Fe and unavoidable impurities.

3. The heat treatment method for oil-liquid two-stage quenching of high chrome grinding balls according to claim 1 or 2, characterized in that: The quenching oil is KR4188 quenching oil.

4. The heat treatment method for oil-liquid two-stage quenching of high chrome grinding balls according to any one of claims 1 to 3, characterized in that: A second quenching was performed with polyvinyl pyrrolidone aqueous solution.

5. The heat treatment method for oil-liquid two-stage quenching of high chrome grinding balls according to claim 4, characterized in that: The mass fraction of the polyvinyl pyrrolidone aqueous solution is 5-25wt%.

6. The heat treatment method for oil-liquid two-stage quenching of high chrome grinding balls according to claim 4, characterized in that: The temperature of the polyvinyl pyrrolidone aqueous solution is 0-40°C.

7. The heat treatment method for oil-liquid two-stage quenching of high chrome grinding balls according to any one of claims 1 to 6, characterized in that: The austenitizing temperature is 920-960°C and the time is 1-6h.

8. The heat treatment method for oil-liquid two-stage quenching of high chrome grinding balls according to any one of claims 1 to 7, characterized in that: The tempering procedure is: keep at 200-450℃ for 5-7h, then air cool to room temperature.