BTMCr26 cast iron material and heat treatment process thereof

Abstract

The invention discloses a BTMCr26 cast iron material and a heat treatment process thereof, and relates to the technical field of cast iron materials. The BTMCr26 cast iron material comprises 2.8%-3.2% of C, 0.4%-0.9% of Si, 0.7%-1.2% of Mn, 25.0%-28.0% of Cr, 0.3%-0.6% of Ni, 0.1%-0.4% of Mo, 0.2%-0.6% of Cu, smaller than or equal to 0.035% of S, smaller than or equal to 0.035% of P and the balance Fe. The BTMCr26 cast iron material is treated by the following heat treatment process: heating a cast iron blank to 180-220 DEG C, preserving heat, then heating to 660-700 DEG C, and cooling in air; raising the temperature of the material to 340-360 DEG C, then raising the temperature to 590-610 DEG C, continuing raising the temperature to 980-1020 DEG C, keeping the temperature, and carrying out air cooling or air cooling; and heating the material to 140-160 DEG C, then heating to 400-500 DEG C, and carrying out air cooling. According to the BTMCr26 cast iron material, the specific alloy component proportion is adopted, meanwhile, the specific heat treatment technology is adopted in a matched mode, and the technological parameters of the heating temperature and the heat preservation time are optimized, so that the BTMCr26 cast iron material can have the high HRC hardness, the excellent wear resistance and the low production cost.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of cast iron materials, in particular to a BTMCr26 cast iron material and a heat treatment process thereof. BACKGROUND

[0002] BTMCr26 is a high-chromium wear-resistant cast iron, which has extremely high hardness and excellent wear resistance, is applied to the mining, power, construction and other industries, and is widely applied to wear-resistant parts such as plate hammers and hammer heads, and has a broad market prospect.

[0003] According to the requirements of the standard GB / T8263-2010 'Abrasion-resistant white cast iron parts', the main index requirements of the BTMCr26 material are as follows:

[0004] Table 1 Chemical composition (%)

[0005] Grade C Si Mn Cr Mo Ni Cu S P BTMCr26 2.0-3.3 ≤1.2 ≤2.0 23.0-30.0 ≤3.0 ≤2.5 ≤1.2 ≤0.06 ≤0.06

[0006] The performance requirements are as follows: the surface hardness (HRC) of the hardened state is greater than or equal to 58.

[0007] In order to meet the hardness requirements of high-chromium wear-resistant castings, the castings in the prior art usually adopt a formula with high Ni, Mo and Cu contents, and the production cost of noble metals is high; or a complex modification treatment is adopted, which not only has a complex process, but also is easy to cause composition segregation, and affects the uniformity of the structure and the performance. For example, the patent CN107475599A discloses a composite modification treatment technology for BTMCr26, in which 0.5% of rare earth, 0.12% of boron and 1% of vanadium are added as additives in the BTMCr26 composite modification process according to the weight percentage of the iron liquid, so that the Rockwell hardness of the material reaches 61-63HRC. However, the process depends on the complex modification additives, and the production conditions are harsh, and the production cost is high. SUMMARY

[0008] The application aims to overcome the defects and deficiencies of the existing high-chromium cast iron material, and provides a BTMCr26 cast iron material, which has high surface hardness and impact toughness, good wear resistance, and can reduce the addition amount of noble metals and has low production cost.

[0009] Another object of the application is to provide a heat treatment process for the BTMCr26 cast iron material.

[0010] The above objects of the application are achieved by the following technical solutions.

[0011] The application protects a BTMCr26 cast iron material, which comprises the following chemical components in mass percentage:

[0012] C 2.8-3.2%, Si 0.4-0.9%, Mn 0.7-1.2%, Cr 25.0-28.0%, Ni 0.3-0.6%, Mo 0.1-0.4%, Cu 0.2-0.6%, S≤0.035%, P≤0.035%, the balance being Fe and inevitable impurities;

[0013] The BTMCr26 cast iron material is treated by the following heat treatment process:

[0014] S1, softening annealing: the cast iron material is heated to 180-220 DEG C and kept for 0.8-1.2h, then heated to 660-700 DEG C and kept for 4-6h, air cooling;

[0015] S2, hardening: the material after step S1 is heated to 340-360 DEG C and kept for 0.8-1.2h, then heated to 590-610 DEG C and kept for 1-2h, continuously heated to 980-1020 DEG C and kept for 7-8h, air cooling or air blast cooling;

[0016] S3, tempering: the material after step S2 is heated to 140-160 DEG C and kept for 1-2h, then heated to 400-500 DEG C and kept for 9-10h, air cooling.

[0017] The BTMCr26 cast iron material of the application adopts specific alloy component proportioning, and cooperates with the heat treatment process of softening annealing, hardening treatment and tempering, and optimizes the process parameters of heating temperature and holding time, so that the BTMCr26 cast iron material can meet the requirements of standard GB / T8263-2010, has higher HRC hardness, excellent wear resistance, and low production cost.

[0018] During the cooling process after pouring, the matrix of high-chromium cast iron castings will be supersaturated with carbon and alloy elements, so during the heat treatment process, the carbon and other alloy elements will be precipitated and dissolved from the matrix, and the precipitated carbon and alloy elements will form secondary carbides dispersed in the matrix. Due to the precipitation of secondary carbides, the content of carbon and alloy elements dissolved in the matrix decreases, and different properties are obtained with different heat treatment process parameters such as heating temperature and holding time. Through the heat treatment process, the matrix structure can be improved, and the carbon and alloy elements in the matrix structure can be precipitated and dissolved to redistribute them, thereby obtaining the required properties.

[0019] On one hand, the present application optimizes the chemical composition of the material, especially adopts a specific C and Cr ratio, which can reduce the content of Ni, Mo and Cu elements as much as possible on the basis of ensuring performance, and at the same time makes the matrix structure obtain more M7C3 type carbide to improve the wear resistance of the material. On the other hand, the high chromium cast iron casting with specific eutectic carbide is treated by a specific heat treatment process and the process parameters are optimized to improve the morphology distribution of eutectic carbide in the matrix structure, thereby enhancing the wear resistance and impact toughness of the casting.

[0020] In some embodiments, the mass ratio of Cr and C atoms in the chemical composition is (8-10):1.

[0021] In some embodiments, the chemical composition includes the following mass percentages:

[0022] C 2.8-3.2%, Si 0.5-0.85%, Mn 0.8-1.1%, Cr 25.0-26.5%, Ni 0.4-0.55%, Mo 0.2-0.3%, Cu 0.2-0.3%, S≤0.035%, P≤0.03%, the balance being Fe and unavoidable impurities.

[0023] In some embodiments, the BTMCr26 cast iron material further contains yttrium-based heavy rare earth alloy with a mass fraction of 0.1-0.3%.

[0024] In some embodiments, the heating rate in step S1 or step S1 of the heat treatment process is ≤100℃ / h.

[0025] In some embodiments, the heating rate in step S2 of the heat treatment process is ≤80℃ / h.

[0026] In some embodiments, step S3 of the heat treatment process includes: heating the material after step S2 to 140-160℃ for 1-2h, then heating to 430-450℃ for 9-10h, and air cooling.

[0027] In some embodiments, the microstructure in the hardened state is a structure of carbide, martensite and residual austenite.

[0028] In some embodiments, the hardness value in the hardened state is 60-64HRC, and the impact toughness at room temperature is 4-6.5J / cm 2 .

[0029] A heat treatment process for a BTMCr26 cast iron material, comprising the following steps:

[0030] S1, the BTMCr26 cast iron material is heated to 180-220 DEG C and kept for 0.8-1.2 h, then heated to 660-700 DEG C and kept for 4-6 h, and air-cooled;

[0031] The BTMCr26 cast iron material comprises the following chemical components in percentage by mass:

[0032] C 2.8-3.2%, Si 0.4-0.9%, Mn 0.7-1.2%, Cr 25.0-28.0%, Ni 0.3-0.6%, Mo 0.1-0.4%, Cu 0.2-0.6%, S≤0.035%, P≤0.035%, and the balance of Fe and inevitable impurities;

[0033] S2, the material after step S1 is heated to 340-360 DEG C and kept for 0.8-1.2 h, then heated to 590-610 DEG C and kept for 1-2 h, and heated to 980-1020 DEG C and kept for 7-8 h, and air-cooled or air-cooled;

[0034] S3, the material after step S2 is heated to 140-160 DEG C and kept for 1-2 h, then heated to 430-450 DEG C and kept for 9-10 h, and air-cooled.

[0035] Compared with the prior art, the beneficial effects of the present application are:

[0036] The present application provides a BTMCr26 cast iron material, which adopts specific alloy component ratio, and cooperates with specific heat treatment process and optimizes the process parameters of heating temperature and holding time, so that the BTMCr26 cast iron material has high HRC hardness and excellent wear resistance, and can reduce the addition amount of noble metal on the basis of ensuring mechanical properties, and reduce production cost. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 It is the softening annealing process curve diagram of the BTMCr26 cast iron material of the embodiment 1 of the present application.

[0038] Figure 2 It is the hardening treatment and tempering treatment process curve diagram of the BTMCr26 cast iron material of the embodiment 1 of the present application.

[0039] Figure 3 It is the microstructure metallographic diagram of the BTMCr26 cast iron material after softening annealing treatment of the embodiment 1 of the present application.

[0040] Figure 4 It is the microstructure metallographic diagram of the BTMCr26 cast iron material after hardening treatment and tempering treatment of the embodiment 1 of the present application. DETAILED DESCRIPTION

[0041] The application will be further described in conjunction with the specific embodiments below, but the embodiments do not limit the application in any form.

[0042] A high-chromium cast iron material was heated to a melting temperature, 0.2% yttrium grade heavy rare earth ferrosilicon alloy (Y 20%, Si 40%, the balance being Fe and unavoidable impurities) was added to refine the grains and improve the carbide morphology, and then was poured into a mold to obtain a BTMCr26 casting; and the BTMCr26 casting was treated by the following heat treatment process. The chemical composition of the high-chromium cast iron material according to the mass percentage is shown in Table 2.

[0043] Table 2

[0044]

[0045] Examples 1-5

[0046] This example provides a series of BTMCr26 castings, the chemical composition of which according to the mass percentage is the high-chromium cast iron material of A1 to A5 shown in Table 2.

[0047] The BTMCr26 castings are treated by the following heat treatment process, the process curve is shown in Figures 1-2 and includes the following steps:

[0048] S1, softening annealing treatment: the heating rate in the furnace is ≤100℃ / h, the cast iron blank is heated to 200℃ for 1h, then heated to 680℃ for 5h, and air-cooled to room temperature;

[0049] S2, hardening treatment: the heating rate in the furnace is ≤80℃ / h, the material after step S1 is heated to 350℃ for 1h, then heated to 600℃ for 1.5h, continuously heated to 1000℃ for 7.5h, and air-cooled to room temperature;

[0050] S3, tempering treatment: the material after step S2 is heated to 120℃ for 1.5h, then heated to 440℃ for 9.5h, and air-cooled.

[0051] Example 6

[0052] A BTMCr26 casting, different from Example 1, is a high-chromium cast iron material of A6 in terms of chemical composition, and the heat treatment process thereof includes the following steps:

[0053] S1, softening annealing treatment: the heating rate in the furnace is ≤100℃ / h, the cast iron blank is heated to 200℃ for 1h, then heated to 660℃ for 5h, and air-cooled to room temperature;

[0054] S2, hardening treatment: the heating rate in the furnace is less than or equal to 80℃ / h, the material after step S1 is heated to 350℃ and kept for 1h, then heated to 600℃ and kept for 1.5h, continuously heated to 1000℃ and kept for 7.5h, and then air-cooled to room temperature after taken out of the furnace;

[0055] S3, tempering treatment: the material after step S2 is heated to 120℃ and kept for 1.5h, then heated to 440℃ and kept for 9.5h, and then air-cooled.

[0056] Example 7

[0057] A BTMCr26 casting, different from example 1, is a high-chromium cast iron material with the chemical composition of A7, and its heat treatment process includes the following steps:

[0058] S1, softening annealing treatment: the heating rate in the furnace is less than or equal to 100℃ / h, the cast iron blank is heated to 200℃ and kept for 1h, then heated to 700℃ and kept for 5h, and then air-cooled to room temperature;

[0059] S2, hardening treatment: the heating rate in the furnace is less than or equal to 80℃ / h, the material after step S1 is heated to 350℃ and kept for 1h, then heated to 600℃ and kept for 1.5h, continuously heated to 1000℃ and kept for 7.5h, and then air-cooled to room temperature after taken out of the furnace;

[0060] S3, tempering treatment: the material after step S2 is heated to 120℃ and kept for 1.5h, then heated to 440℃ and kept for 9.5h, and then air-cooled.

[0061] Example 8

[0062] A BTMCr26 casting, different from example 1, is a high-chromium cast iron material with the chemical composition of A8, and its heat treatment process includes the following steps:

[0063] S1, softening annealing treatment: the heating rate in the furnace is less than or equal to 100℃ / h, the cast iron blank is heated to 200℃ and kept for 1h, then heated to 680℃ and kept for 5h, and then air-cooled to room temperature;

[0064] S2, hardening treatment: the heating rate in the furnace is less than or equal to 80℃ / h, the material after step S1 is heated to 350℃ and kept for 1h, then heated to 600℃ and kept for 1.5h, continuously heated to 980℃ and kept for 7.5h, and then air-cooled to room temperature after taken out of the furnace;

[0065] S3, tempering treatment: the material after step S2 is heated to 120℃ and kept for 1.5h, then heated to 400℃ and kept for 9.5h, and then air-cooled.

[0066] Example 9

[0067] A BTMCr26 casting, different from Example 1 in that the chemical composition of the high-chromium cast iron material of this example is A9, and the heat treatment process thereof comprises the following steps:

[0068] S1, softening annealing treatment: the heating rate in the furnace is ≤100℃ / h, the cast iron blank is heated to 200℃ and kept for 1h, then heated to 680℃ and kept for 5h, and air-cooled to room temperature;

[0069] S2, hardening treatment: the heating rate in the furnace is ≤80℃ / h, the material after step S1 is heated to 350℃ and kept for 1h, then heated to 600℃ and kept for 1.5h, continuously heated to 1020℃ and kept for 7.5h, and air-cooled to room temperature;

[0070] S3, tempering treatment: the material after step S2 is heated to 120℃ and kept for 1.5h, then heated to 440℃ and kept for 9.5h, and air-cooled.

[0071] Example 10

[0072] A BTMCr26 casting, different from Example 1 in that the chemical composition of the high-chromium cast iron material of this example is A10, and the heat treatment process thereof comprises the following steps:

[0073] S1, softening annealing treatment: the heating rate in the furnace is ≤100℃ / h, the cast iron blank is heated to 200℃ and kept for 1h, then heated to 680℃ and kept for 5h, and air-cooled to room temperature;

[0074] S2, hardening treatment: the heating rate in the furnace is ≤80℃ / h, the material after step S1 is heated to 350℃ and kept for 1h, then heated to 600℃ and kept for 1.5h, continuously heated to 1000℃ and kept for 7.5h, and air-cooled to room temperature;

[0075] S3, tempering treatment: the material after step S2 is heated to 120℃ and kept for 1.5h, then heated to 500℃ and kept for 9.5h, and air-cooled.

[0076] Comparative Example 1

[0077] A BTMCr26 casting, different from Example 1 in that the chemical composition of the high-chromium cast iron material of this example is B1.

[0078] Comparative Example 2

[0079] A BTMCr26 casting, different from Example 1 in that the heat treatment process of this comparative example comprises the following steps:

[0080] S1, softening annealing treatment: the heating rate in the furnace is less than or equal to 100 ℃ / h, the cast iron blank is heated to 200 ℃ and kept for 1 h, then heated to 680 ℃ and kept for 5 h, and air-cooled to room temperature;

[0081] S2, hardening treatment: the heating rate in the furnace is less than or equal to 80 ℃ / h, the material after step S1 is heated to 350 ℃ and kept for 1 h, then heated to 600 ℃ and kept for 1.5 h, continuously heated to 1060 ℃ and kept for 7.5 h, and air-cooled to room temperature;

[0082] S3, tempering treatment: the material after step S1 is heated to 120 ℃ and kept for 1.5 h, then heated to 440 ℃ and kept for 9.5 h, and air-cooled.

[0083] Comparative Example 3

[0084] A BTMCr26 casting, which is different from Example 1 in that the heat treatment process of the present comparative example comprises the following steps:

[0085] S1, softening annealing treatment: the heating rate in the furnace is less than or equal to 100 ℃ / h, the cast iron blank is heated to 1000 ℃ and kept for 1 h, then heated to 720 ℃ and kept for 5 h, and air-cooled to room temperature;

[0086] S2, hardening treatment: the heating rate in the furnace is less than or equal to 80 ℃ / h, the material after step S1 is heated to 350 ℃ and kept for 1 h, then heated to 600 ℃ and kept for 1.5 h, continuously heated to 1000 ℃ and kept for 7.5 h, and air-cooled to room temperature;

[0087] S3, tempering treatment: the material after step S2 is heated to 120 ℃ and kept for 1.5 h, then heated to 440 ℃ and kept for 9.5 h, and air-cooled.

[0088] Performance test

[0089] The BTMCr26 castings of the above examples and comparative examples are subjected to surface hardness, impact toughness and metallographic structure analysis tests, and the results are shown in Figures 3-4 and Table 3.

[0090] The test method of surface hardness: tested according to the method of GB / T 230.1-2018 “Metallic Materials Rockwell Hardness Test Part 1: Test Method”.

[0091] The test method of impact toughness: tested according to the method of GB / T 229-2020 “Metallic Materials Charpy Pendulum Impact Test Method”.

[0092] Table 3

[0093]

[0094] The results show that the cast HRC hardness of the BTMCr26 cast iron material reaches more than 57, the softening state HRC hardness is less than 40.8, the processability is excellent, the hardened state HRC hardness reaches more than 60, the impact toughness is 4J / cm 2 The above meets the requirements of the standard GB / T8263-2010, and has higher wear resistance and toughness.

[0095] Compared with example 1, the C content in comparative example 1 is higher, and the Cr content is lower, after heat treatment, the surface hardness of the hardened state decreases, and the wear resistance is poor. The hardening treatment temperature in comparative example 2 is too high, which leads to the decrease of the HRC hardness of the hardened state. In comparative example 3, high temperature treatment of 1000 DEG C is adopted, although it can better reduce the hardness of the softening state, but the energy consumption is too high, which increases the cost burden, and the HRC hardness of the hardened state is equivalent to that of the application, which proves that the specific formula of the cast iron material of the application can realize the softening treatment at a lower temperature on the basis of ensuring the hardness performance, and reduce the production cost.

[0096] The above examples of the application are only examples for clearly illustrating the application, and are not the limitation to the embodiments of the application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments are not required to be exhausted. Any modification, equivalent replacement and improvement within the spirit and principle of the application should be included in the protection scope of the claims of the application.

Claims

1. A BTMCr26 cast iron material, characterized in that: The chemical composition includes the following percentages by mass: C 2.8-3.2%, Si 0.4-0.9%, Mn 0.7-1.2%, Cr 25.0-28.0%, Ni 0.3-0.6%, Mo 0.1-0.4%, Cu 0.2-0.6%, S≤0.035%, P≤0.035%, the balance is Fe and unavoidable impurities; The BTMCr26 cast iron material is subjected to the following heat treatment processes: S1, soft annealing: heat the cast iron material to 180-220℃ and keep it for 0.8-1.2h, then heat it to 660-700℃ and keep it for 4-6h, then air cool; S2, hardening: the material treated in step S1 is heated to 340-360℃ and kept warm for 0.8-1.2h, then heated to 590-610℃ and kept warm for 1-2h, and then heated to 980-1020℃ and kept warm for 7-8h, and then cooled in air or by wind; S3, tempering: the material treated in step S2 is heated to 140-160°C and kept warm for 1-2 hours, then heated to 400-500°C and kept warm for 9-10 hours, and then air-cooled.

2. The BTMCr26 cast iron material according to claim 1, characterized in that In its chemical composition, the mass ratio of Cr and C atoms is (8-10):

1.

3. The BTMCr26 cast iron material according to claim 1, characterized in that The chemical composition includes the following percentages by mass: C 2.8-3.2%, Si 0.5-0.85%, Mn 0.8-1.1%, Cr 25.0-26.5%, Ni 0.4-0.55%, Mo0.2-0.3%, Cu 0.2-0.3%, S≤0.035%, P≤0.03%, the balance is Fe and unavoidable impurities.

4. The BTMCr26 cast iron material according to claim 1, characterized in that The BTMCr26 cast iron material further contains yttrium-based heavy rare earth alloy with a mass fraction of 0.1-0.3%.

5. The BTMCr26 cast iron material according to claim 1, characterized in that: In step S1 or step S1 of the heat treatment process, the heating rate is ≤100°C / h.

6. The BTMCr26 cast iron material according to claim 1, characterized in that: In step S2 of the heat treatment process, the heating rate is ≤80°C / h.

7. The BTMCr26 cast iron material according to claim 1, characterized in that: Step S3 of the heat treatment process comprises: heating the material treated in step S2 to 140-160° C. and keeping the temperature for 1-2 hours, then heating the material to 430-450° C. and keeping the temperature for 9-10 hours, and then air cooling.

8. The BTMCr26 cast iron material according to claim 1, characterized in that: Its metallographic structure in the hardened state is carbide, martensite and retained austenite structure.

9. The BTMCr26 cast iron material according to claim 1, characterized in that: Its hardness in the hardened state is 60-64HRC and its impact toughness is 4-6.5J / cm 2 .

10. A heat treatment process for BTMCr26 cast iron material, characterized in that: The following steps are involved: S1, heating the BTMCr26 cast iron material to 180-220℃ and keeping it at that temperature for 0.8-1.2h, then heating it to 660-700℃ and keeping it at that temperature for 4-6h, and then air cooling; The BTMCr26 cast iron material comprises the following chemical compositions in percentage by mass: C 2.8-3.2%, Si 0.4-0.9%, Mn 0.7-1.2%, Cr 25.0-28.0%, Ni 0.3-0.6%, Mo 0.1-0.4%, Cu 0.2-0.6%, S≤0.035%, P≤0.035%, the balance is Fe and unavoidable impurities; S2, heating the material after the treatment in step S1 to 340-360°C and keeping it warm for 0.8-1.2h, then heating it to 590-610°C and keeping it warm for 1-2h, and then heating it to 980-1020°C and keeping it warm for 7-8h, and then cooling it in air or by wind; S3, heating the material treated in step S2 to 140-160°C and keeping it warm for 1-2 hours, then heating it to 430-450°C and keeping it warm for 9-10 hours, and air cooling it.

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