A heat treatment method of a high-organization-uniformity boron steel

Abstract

The application relates to the field of boron steel materials, and particularly discloses a heat treatment method of high-organization-uniformity boron steel. The heat treatment method of normalizing + quenching + tempering + secondary quenching + secondary tempering is used to successfully prepare a boron steel material with high organization uniformity, high mechanical performance, high hardness and long service life. The hydraulic shear blade prepared from the boron steel material effectively solves the problems of limited hardness and mechanical performance of the hydraulic shear blade in the prior art, short service life, and limited service life of the hydraulic shear, thereby providing a new idea for the development of the boron steel material.

Description

Technical Field

[0001] This invention relates to the field of boron steel materials, and specifically discloses a heat treatment method for boron steel with high microstructure uniformity. Background Technology

[0002] Hydraulic shears are one of the main attachments used in demolition and cutting operations, primarily for building demolition, partial renovation work, vehicle dismantling, and emergency rescue. Compared to traditional manual dismantling operations, they offer advantages such as greater safety, speed, and efficiency, while also being quiet and dust-free, minimizing impact on surrounding buildings. Depending on the specific working conditions, hydraulic shears can be designed with different hydraulic cylinder drive systems, jaw blades, and the shape and distribution of the steel teeth. Currently, common types of hydraulic shears on the market include heavy-duty shears, vehicle dismantling shears, beak shears, rebar shears, and building demolition shears.

[0003] With the increasing number of scrapped vehicles in my country, traditional, extensive dismantling methods are energy-intensive and result in significant metal loss, leading to low material recycling rates, low work efficiency, and a limited range of recyclable materials. To improve efficiency, hydraulic shears and car clamps are typically used together. The clamps compress the scrapped vehicles before the shears cut and dismantle them. However, it has been found that current hydraulic shear blades are not durable, with limited hardness and mechanical properties, resulting in a service life of only 300-400 hours and very limited workload. Therefore, developing a hydraulic shear blade with high hardness and good mechanical properties is crucial for extending the service life of hydraulic shears. Summary of the Invention

[0004] To address the limitations of existing hydraulic shear blades in terms of blade hardness and mechanical properties, resulting in short service life and consequently limited lifespan, this invention provides a boron steel with high microstructure uniformity. This invention utilizes a heat treatment process to further enhance the microstructure uniformity of the boron steel, thereby improving its hardness and mechanical properties.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution.

[0006] The first aspect of this invention provides a heat treatment method for boron steel with high microstructure uniformity, comprising the following steps:

[0007] Step 1: Normalize the hot-rolled boron steel at 780℃-840℃, cool it once, and then heat it up again to 780℃-840℃ for quenching once to obtain the first-treated steel.

[0008] Step 2: Temper the first-treated steel at 470℃-530℃ to obtain the second-treated steel;

[0009] Step 3: The secondary-treated steel is quenched again at 780℃-840℃, then heated to 270℃-330℃ for secondary tempering, and finally cooled to obtain boron steel with high microstructure uniformity.

[0010] The primary and secondary quenching processes are both carried out using an organic quenching fluid, which comprises the following raw material components in parts by mass: 5-10 parts of polyalkylene glycol, 5-10 parts of polyvinyl alcohol, 1-3 parts of sodium benzoate, 1-3 parts of antioxidant, 1-3 parts of scale inhibitor, and the balance being water.

[0011] Compared to existing technologies, this invention provides a heat treatment method for improving the uniformity of boron steel's microstructure and mechanical properties. The inventors discovered that the uniformity of the microstructure of boron steel determines whether its mechanical properties meet requirements. Therefore, this invention provides a boron steel material with high microstructure uniformity. First, the hot-rolled boron steel is normalized to further refine its microstructure, modifying its original structure towards greater uniformity. Then, the normalized boron steel undergoes a first quenching treatment, which increases its hardness and further refines the microstructure, resulting in a first-stage treated steel. However, the hardness and mechanical properties of this first-stage treated steel are insufficient to meet the target requirements. Therefore, the inventors perform a tempering treatment to remove the quenching stress generated during the first quenching process, preventing the boron steel from becoming brittle and unsuitable for use. The tempered second-stage treated steel then undergoes a second quenching and a second tempering treatment to further refine the microstructure, resulting in a boron steel material with high microstructure uniformity and high hardness. The heat treatment process for boron steel provided by this invention is simple to operate, and the resulting boron steel material has excellent mechanical properties and a long service life.

[0012] The organic quenching fluid selected in this invention can assist steel in developing towards a more regular crystal structure and finer microstructure at high temperatures. Compared to using water as a quenching fluid, the quenching fluid provided by this invention has a faster cooling rate, and the cooling rate is not affected at medium temperatures. Furthermore, the quenching fluid provided by this invention does not increase the brittleness of steel parts or cause cracks, and it is particularly helpful for the rapid quenching and cooling of boron steel.

[0013] Preferably, in step one, the metallographic structure of the normalized boron steel is ferrite + pearlite.

[0014] Preferably, in step one, the metallographic structure of the steel processed in the first step is quenched martensite.

[0015] Preferably, in step two, the metallographic structure of the secondary treated steel is tempered sorbite.

[0016] Preferably, in step three, the metallographic structure of the boron steel after secondary quenching is quenched martensite.

[0017] Preferably, in step three, the metallographic structure of the high-uniformity boron steel is tempered martensite.

[0018] Preferably, in step one, the hot-rolled boron steel comprises the following chemical composition by mass percentage: C: 0.40%-0.44%, Si: 0.15%-0.35%, Mn: 0.6%-1.0%, B: 0.0003%-0.005%, with the balance being Fe and unavoidable impurities.

[0019] Preferably, in step one, the heat preservation time for normalizing is 1-2 hours.

[0020] Preferably, in step one, the holding time for the first quenching is 1-2 hours.

[0021] Preferably, in step two, the holding time for the first tempering is 1.5h-2.5h.

[0022] Preferably, in step three, the holding time for the secondary quenching is 1-2 hours.

[0023] Preferably, in step three, the holding time for the secondary tempering is 1.5h-2.5h.

[0024] Preferably, the primary cooling is air cooling, cooling to 320℃-350℃.

[0025] Preferably, the antioxidant is any one or both of phenothiazine or tert-butylhydroquinone.

[0026] Preferably, the scale inhibitor is any one or both of hydroxyethylidene phosphoric acid or aminomethylphosphoric acid.

[0027] A second aspect of the present invention provides a boron steel with high microstructure uniformity, which is obtained by heat treatment using the heat treatment method for the boron steel with high microstructure uniformity.

[0028] The third aspect of this invention provides the application of high-uniformity boron steel in the preparation of hydraulic shears.

[0029] In summary, this invention provides a heat treatment method for boron steel with high microstructure uniformity. Utilizing a process of normalizing + quenching + tempering + secondary quenching + secondary tempering, a boron steel material with high hardness and long service life is effectively obtained. Hydraulic shear blades made from this boron steel material effectively solve the problem of limited blade hardness and mechanical properties, resulting in short service life for hydraulic shears in existing technologies. Testing shows that the hydraulic shear blades made from the boron steel material provided by this invention have a service life of up to 850 hours. Attached Figure Description

[0030] Figure 1 Metallographic diagram of the untreated boron steel material in Example 1;

[0031] Figure 2 The image shows the metallographic structure of the boron steel material after normalizing treatment in Example 1.

[0032] Figure 3 The image shows the metallographic structure of the boron steel material after the second tempering heat treatment in Example 1. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] Example 1

[0035] This embodiment provides a heat treatment process for boron steel with high microstructure uniformity, specifically including the following steps:

[0036] Step 1: The hot-rolled boron steel is sent into a heating furnace and normalized at 820°C for 1.5 hours. The resulting boron steel is then cooled to 330°C and heated again to 820°C for 1.5 hours. The boron steel is then quickly immersed in an organic quenching liquid for a first quenching to obtain a first-treatment steel.

[0037] Step 2: Place the first-treated steel in a heating furnace, heat it to 510°C for a first tempering treatment, and hold it at that temperature for 2 hours to obtain the second-treated steel.

[0038] Step 3: Place the secondary treated steel in a heating furnace and heat it to 800°C. Hold it at that temperature for 1.5 hours. Then, quickly immerse the boron steel in an organic quenching liquid for secondary quenching. Heat it again to 290°C for secondary tempering and hold it at that temperature for 2 hours. Allow the boron steel to cool naturally to room temperature to obtain the high-uniformity boron steel.

[0039] The organic quenching fluid comprises the following raw material components in parts by weight per 1L: 80mL of polyalkylene glycol, 50mL of polyvinyl alcohol, 30mL of sodium benzoate, 20mL of antioxidant, 10mL of scale inhibitor, and the balance being water.

[0040] Example 2

[0041] This embodiment provides a heat treatment process for boron steel with high microstructure uniformity, specifically including the following steps:

[0042] Step 1: The hot-rolled boron steel is sent into a heating furnace and normalized at 830°C for 2 hours. The resulting boron steel is cooled to 330°C and then heated to 830°C again for 1 hour. The boron steel is then quickly immersed in an organic quenching liquid for a first quenching to obtain the first-treated steel.

[0043] Step 2: Place the first-treated steel in a heating furnace, heat it to 510°C for a first tempering treatment, and hold it at that temperature for 1.5 hours to obtain the second-treated steel.

[0044] Step 3: Place the secondary treated steel in a heating furnace and heat it to 800°C. Hold it at that temperature for 2 hours. Then, quickly immerse the boron steel in an organic quenching liquid for secondary quenching. Heat it again to 290°C for secondary tempering and hold it at that temperature for 2.5 hours. Allow the boron steel to cool naturally to room temperature to obtain the high-uniformity boron steel.

[0045] The organic quenching fluid comprises the following raw material components in parts by weight per 1L: 100mL of polyalkylene glycol, 60mL of polyvinyl alcohol, 20mL of sodium benzoate, 10mL of antioxidant, 20mL of scale inhibitor, and the balance being water.

[0046] Example 3

[0047] This embodiment provides a heat treatment process for boron steel with high microstructure uniformity, specifically including the following steps:

[0048] Step 1: The hot-rolled boron steel is sent into a heating furnace and normalized at 780°C for 1 hour. The resulting boron steel is then cooled to 330°C and heated to 780°C again for 1.5 hours. The boron steel is then quickly immersed in an organic quenching liquid for a first quenching to obtain a first-treatment steel.

[0049] Step 2: Place the first-treated steel in a heating furnace, heat it to 510°C for a first tempering treatment, and hold it at that temperature for 2 hours to obtain the second-treated steel.

[0050] Step 3: Place the secondary treated steel in a heating furnace and heat it to 820°C. Hold it at that temperature for 1.5 hours. Then, quickly immerse the boron steel in an organic quenching liquid for secondary quenching. Heat it again to 290°C for secondary tempering and hold it at that temperature for 1.5 hours. Allow the boron steel to cool naturally to room temperature to obtain the high-uniformity boron steel.

[0051] The organic quenching fluid comprises the following raw material components in parts by weight per 1L: 50mL of polyalkylene glycol, 100mL of polyvinyl alcohol, 30mL of sodium benzoate, 20mL of antioxidant, 10mL of scale inhibitor, and the balance being water.

[0052] Example 4

[0053] This embodiment provides a heat treatment process for boron steel with high microstructure uniformity, specifically including the following steps:

[0054] Step 1: The hot-rolled boron steel is sent into a heating furnace and normalized at 830°C for 1.5 hours. The resulting boron steel is then cooled to 330°C and heated again to 820°C for 1.5 hours. The boron steel is then quickly immersed in an organic quenching liquid for a first quenching to obtain a first-treatment steel.

[0055] Step 2: Place the first-treated steel in a heating furnace, heat it to 510°C for a first tempering treatment, and hold it at that temperature for 2 hours to obtain the second-treated steel.

[0056] Step 3: Place the secondary treated steel in a heating furnace and heat it to 780°C. Hold it at that temperature for 1.5 hours. Then, quickly immerse the boron steel in an organic quenching liquid for secondary quenching. Heat it again to 270°C for secondary tempering and hold it at that temperature for 2 hours. Allow the boron steel to cool naturally to room temperature to obtain the high-uniformity boron steel.

[0057] The organic quenching fluid comprises the following raw material components in parts by weight per 1L: 95mL of polyalkylene glycol, 95mL of polyvinyl alcohol, 10mL of sodium benzoate, 30mL of antioxidant, 20mL of scale inhibitor, and the balance being water.

[0058] Example 5

[0059] This embodiment provides a heat treatment process for boron steel with high microstructure uniformity, specifically including the following steps:

[0060] Step 1: The hot-rolled boron steel is sent into a heating furnace and normalized at 780°C for 2 hours. The resulting boron steel is cooled to 350°C and then heated to 780°C again for 1 hour. The boron steel is then quickly immersed in an organic quenching liquid for a first quenching to obtain the first-treated steel.

[0061] Step 2: Place the first-treated steel in a heating furnace, heat it to 530°C for a first tempering treatment, and hold it at that temperature for 2 hours to obtain the second-treated steel.

[0062] Step 3: Place the secondary treated steel in a heating furnace and heat it to 840°C. Hold it at that temperature for 1.5 hours. Then, quickly immerse the boron steel in an organic quenching liquid for secondary quenching. Heat it again to 330°C for secondary tempering and hold it at that temperature for 2 hours. Allow the boron steel to cool naturally to room temperature to obtain the high-uniformity boron steel.

[0063] The organic quenching fluid comprises the following raw material components in parts by weight per 1L: 95mL of polyalkylene glycol, 65mL of polyvinyl alcohol, 15mL of sodium benzoate, 25mL of antioxidant, 30mL of scale inhibitor, and the balance being water.

[0064] Comparative Example 1

[0065] This comparative example provides a heat treatment method for boron steel, which differs from Example 1 in that the quenching liquid used is water, while the other steps and compositions remain unchanged. Specifically, it includes the following steps.

[0066] Step 1: The hot-rolled boron steel is sent into a heating furnace and normalized at 820°C for 1.5 hours. The resulting boron steel is then cooled to 330°C and heated to 820°C again for 1.5 hours. The boron steel is then quickly immersed in water for quenching to obtain the first-treatment steel.

[0067] Step 2: Place the first-treated steel in a heating furnace, heat it to 510°C for a first tempering treatment, and hold it at that temperature for 2 hours to obtain the second-treated steel.

[0068] Step 3: Place the secondary treated steel in a heating furnace and heat it to 800°C. Hold it at that temperature for 1.5 hours. Then, quickly immerse the boron steel in water for secondary quenching. Heat it again to 290°C for secondary tempering and hold it at that temperature for 2 hours. Allow the boron steel to cool naturally to room temperature to obtain the high-uniformity boron steel.

[0069] Comparative Example 2

[0070] This comparative example provides a commercially available boron steel material, model 40MnB.

[0071] To further demonstrate the technical effects of the present invention, the boron steel materials obtained in Examples 1-5 and Comparative Examples 1-2 were subjected to the following performance tests. The yield strength, tensile strength, and hardness of each boron steel material were determined according to GB / T3077-2015 standard. Each boron steel material was prepared into a hydraulic shear blade, and its service life was tested. The blade was hydraulically sheared at a speed of V = 300 times / min for 12 hours. Based on the comparison of blade wear before and after shearing, the blade service life was calculated, and the results are shown in Table 1.

[0072] Table 1 Performance test results of various boron steel materials

[0073]

[0074] As can be seen from Table 1, the high-uniformity boron steel material provided in this embodiment of the invention has superior mechanical properties and hardness compared to the boron steel material provided in the comparative example, and also has a longer service life.

[0075] To further demonstrate the performance of the boron steel material provided by this invention, metallographic structure testing was also performed on the boron steel material obtained in Example 1, and the results are as follows: Figure 1-3 As shown. According to Figure 1 It can be seen that before heat treatment, the boron steel material has poor microstructure uniformity and is mostly blocky, while after normalizing treatment ( Figure 2 It is evident that the metallographic structure of the boron steel becomes finer, mainly consisting of ferrite and pearlite, with a significant reduction in massive structures and coarse grains. The metallographic structure of the boron steel material after heat treatment is shown in the image below. Figure 3 As shown, according to Figure 3 It can be seen that the obtained boron steel material has a higher degree of structural uniformity, and the metallographic structure is tempered martensite.

[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A heat treatment method for boron steel with high microstructure uniformity, characterized in that: Includes the following steps: Step 1: Normalize the hot-rolled boron steel at 780℃-840℃, cool it once, and then heat it up again to 780℃-840℃ for quenching once to obtain the first-treated steel. Step 2: Temper the first-treated steel at 470℃-530℃ to obtain the second-treated steel; Step 3: The secondary-treated steel is quenched at 780℃-840℃, then heated to 270℃-330℃ for secondary tempering, and finally cooled to obtain boron steel with high microstructure uniformity. The hot-rolled boron steel comprises the following chemical composition by mass percentage: C: 0.40%-0.44%, Si: 0.15%-0.35%, Mn: 0.6%-1.0%, B: 0.0003%-0.005%, with the balance being Fe and unavoidable impurities; Both the primary and secondary quenching processes are performed using an organic quenching fluid, which comprises the following raw material components in parts by mass: 5-10 parts of polyalkylene glycol, 5-10 parts of polyvinyl alcohol, 1-3 parts of sodium benzoate, 1-3 parts of antioxidant, 1-3 parts of scale inhibitor, and the balance being water.

2. The heat treatment method for high-uniformity boron steel as described in claim 1, characterized in that: In step one, the metallographic structure of the normalized boron steel is ferrite + pearlite; and / or In step three, the metallographic structure of the high-uniformity boron steel is tempered martensite.

3. The heat treatment method for high-uniformity boron steel as described in claim 1, characterized in that: In step one, the holding time for normalizing is 1-2 hours; and / or In step one, the holding time for the first quenching is 1-2 hours.

4. The heat treatment method for high-uniformity boron steel as described in claim 1, characterized in that: In step two, the holding time for the first tempering is 1.5h-2.5h; and / or In step three, the holding time for the secondary quenching is 1-2 hours; and / or In step three, the holding time for the secondary tempering is 1.5h-2.5h.

5. The heat treatment method for high-uniformity boron steel as described in claim 1, characterized in that: The primary cooling is air cooling, cooling to 320℃-350℃.

6. The heat treatment method for high-uniformity boron steel as described in claim 1, characterized in that: The antioxidant is any one or both of phenothiazine or tert-butylhydroquinone.

7. The heat treatment method for high-uniformity boron steel as described in claim 1, characterized in that: The scale inhibitor is any one or both of hydroxyethylidene phosphoric acid or aminomethylphosphoryl.

8. A boron steel with high microstructure uniformity, characterized in that: It is prepared by heat treatment using the heat treatment method for high microstructure uniformity boron steel according to any one of claims 1-7.

9. The application of the high-uniformity boron steel according to claim 8 in the preparation of hydraulic shear blades.

Images