TWI767815B - Wear resistant steel plate and method of fabricating the same - Google Patents

Abstract

A wear resistant steel plate and a method of fabricating the same are provided. A microalloying treatment is applied to control type and shape morphology of inclusions in a steel plate. Moreover, by specific condition of quenching process, microscopic structure of the steel plate contains most self-tempered martensite. In this way, the wear resistant steel plate with high strength, high elongation, high flexibility and great formability can be obtained.

Description

Wear-resistant steel plate and method of making the same

The present invention relates to a steel plate and a manufacturing method thereof, in particular to a wear-resistant steel plate and a manufacturing method thereof.

Wear-resistant steel plate is a kind of plate commonly used in heavy industries such as mining, transportation and steelmaking. Since such plates usually have appropriate hardness and good low temperature toughness, the steel plate can resist abrasion and impact during use.

The manufacturing process of the conventional wear-resistant steel plate is through alloy control, quenching process and tempering treatment, so that the obtained steel plate has high hardness. However, the strength of the steel sheet obtained by this process is too high, so the elongation and bendability are often inferior to ordinary steel sheets. Therefore, when the wear-resistant steel plate is used to process and manufacture mechanical equipment, the steel plate is prone to surface cracks due to poor bendability, which in turn affects the processing and manufacture of the equipment.

In view of this, there is an urgent need to provide a wear-resistant steel plate and a method for manufacturing the same, so as to improve the elongation and bending properties of the wear-resistant steel plate, thereby improving the formability of the wear-resistant steel plate.

One aspect of the present invention is to provide a wear-resistant steel plate, which is a wear-resistant steel plate with good elongation, bendability and formability by including a specific intervening substance and a high proportion of self-tempered loose iron.

Another aspect of the present invention is to provide a method for manufacturing a wear-resistant steel plate, which is processed by microalloying and controlling the subsequent quenching process, so as to obtain a wear-resistant steel plate with good elongation, bendability and formability. steel plate.

According to an aspect of the present invention, a wear-resistant steel sheet is provided, which comprises 0.12 wt% to 0.18 wt% carbon, 0.001 wt% to 0.005 wt% calcium, 0.4 wt% or less silicon, 1.0 wt% to 1.5 wt% % manganese, 0.01 wt% or less phosphorus, 0.005 wt% or less sulfur, 1.0 wt% or less chromium, 0.5 wt% or less molybdenum, 1.0 wt% or less nickel, 0.01 to 0.05 wt% aluminum, 0.01 Nitrogen below wt%, and the rest are iron and inevitable impurities. The wear-resistant steel plate contains calcium sulfide intervening substances, and the wear-resistant steel plate contains more than 95% by volume of self-tempered loose iron.

According to an embodiment of the present invention, the above-mentioned calcium sulfide interposer is a spherical interposer.

According to an embodiment of the present invention, a particle size of the calcium sulfide intercalator is 0.5 μm to 5.0 μm.

According to an embodiment of the present invention, the above-mentioned wear-resistant steel plate further comprises less than 5% by volume of Worcester iron.

According to an embodiment of the present invention, the above-mentioned wear-resistant steel plate further comprises titanium, vanadium and niobium in a total amount of 0.02 wt % to 0.07 wt %.

According to another aspect of the present invention, a method for manufacturing a wear-resistant steel plate is provided. The method includes microalloying the molten steel, casting the molten steel into a steel billet, performing a hot rolling process on the billet to obtain a finished rolled steel plate, and performing a quenching process on the finished rolled steel plate to obtain a wear-resistant steel plate. The molten steel contains 0.12 wt% to 0.18 wt% carbon, 0.001 wt% to 0.005 wt% calcium, 0.4 wt% or less silicon, 1.0 wt% to 1.5 wt% manganese, 0.01 wt% or less phosphorus, 0.005 wt% Sulfur below 1.0 wt%, Molybdenum below 0.5 wt%, Nickel below 1.0 wt%, Al 0.01 wt% to 0.05 wt%, Nitrogen below 0.01 wt%, and the rest are iron and inevitable impurities . The cooling rate of the quenching process is 5°C/s to 30°C/s and the complete cooling temperature is less than 250°C.

According to an embodiment of the present invention, before performing the hot rolling process, the above-mentioned method further includes performing a heating process on the steel billet, wherein the temperature of the heating process is 1050°C to 1150°C.

According to an embodiment of the present invention, the above-mentioned hot rolling process includes performing a first hot rolling step on the steel billet to obtain a first steel sheet; and performing a second hot rolling step on the first steel sheet to obtain a finished steel sheet. The temperature of the first hot rolling step is 900°C to 1150°C. The starting temperature of the second hot rolling step is 850°C to 900°C, and the finishing temperature is (Ar ₃ +50)°C or higher.

According to an embodiment of the present invention, the initial cooling temperature of the quenching process is above (Ar ₃ +20)°C.

According to an embodiment of the present invention, after the quenching process is performed, the tempering treatment is not performed.

Applying the wear-resistant steel plate of the present invention and its manufacturing method, the micro-alloying process is used to control the type and type of the intervening substances in the steel plate, and by specifying the conditions of the quenching process, most of the microstructure is The self-tempered loose iron can obtain a wear-resistant steel plate with high strength, high elongation, high bendability and good formability.

Based on the above, the present invention provides a wear-resistant steel plate and a method for manufacturing the same. By introducing a micro-alloy treatment technology in the manufacturing process, the type and shape of the contents in the steel plate are controlled, so as to improve the elongation and bendability of the wear-resistant steel plate. and strength, thereby improving its formability.

Please refer to FIG. 1 , which is a schematic flowchart of a manufacturing method 100 of a wear-resistant steel plate according to some embodiments of the present invention. First, operation 110 is performed to microalloy the molten steel. The molten steel is produced by conventional methods of steelmaking or electric furnaces. In some embodiments, the molten steel comprises 0.12 wt% to 0.18 wt% carbon, 0.001 wt% to 0.005 wt% calcium, 0.4 wt% or less silicon, 1.0 wt% to 1.5 wt% manganese, 0.01 wt% or less 0.005 wt% or less of sulfur, 1.0 wt% or less of chromium, 0.5 wt% or less of molybdenum, 1.0 wt% or less of nickel, 0.01 to 0.05 wt% of aluminum, 0.01 wt% or less of nitrogen, and the rest are Iron and inevitable impurities. Compared with the conventional molten steel used for wear-resistant steel plates, the molten steel after the microalloying treatment of the present invention has a lower carbon content, and by adjusting the content of other alloying elements, the intervening substances in the molten steel are further controlled. type. In some embodiments, the intervening substance in the molten steel is calcium sulfide (CaS), so the content of calcium must be about 0.001 wt % to 0.005 wt % (preferably about 0.002 wt % to about 0.005 wt %), and calcium The affinity for sulfur is higher than that of other metals, which ensures that calcium sulfide intercalators are produced in molten steel, rather than manganese sulfide (MnS) intercalators that are easily generated in conventional processes.

In some embodiments, the molten steel may optionally contain titanium, vanadium, and niobium in a total amount of 0.02 wt % to 0.07 wt %. The addition of titanium, vanadium and niobium helps to refine the grains produced in subsequent processes.

Next, operation 120 is performed to provide a steel billet cast from the above-mentioned molten steel. Those skilled in the art should understand that the steel billet has the same composition as the molten steel described above.

Then, proceed to operation 130 to perform a hot rolling process on the steel billet to obtain a finished rolled steel sheet. In some embodiments, the hot rolling process includes a first hot rolling step and a second hot rolling step. In some embodiments, the first hot rolling step (rough rolling stage) is rolling at a temperature of 900°C to 1150°C. Carrying out the first rolling step in this temperature range can effectively cause a large amount of the above-mentioned intervening substances to precipitate out of the grain boundary, thereby preventing the growth of the grains. In some embodiments, the reduction ratio of the first hot rolling step is above 60%. Following the first hot rolling step, a second hot rolling step (finishing rolling stage) is performed. In some embodiments, the starting rolling temperature of the second hot rolling step may be 850°C to 900°C. When the starting rolling temperature of the second hot rolling step is within this range, the grains can be further reduced and the grains will not be recrystallized, so the microstructure of the steel sheet will become finer, thereby optimizing the low-temperature impact properties. In some embodiments, the reduction ratio of the second hot rolling step is above 30%.

In some embodiments, the finish rolling temperature of the second hot rolling step is above (Ar ₃ +50)°C. It is supplemented that the Ar ₃ temperature refers to the critical temperature at which ferrite iron begins to precipitate from the Voss field iron when the iron-carbon alloy is cooled. In some specific examples, Ar ₃ can be, for example, 912°C. In some embodiments, the hot rolling process is carried out at conditions above the recrystallization temperature of the Worcester iron. In the present invention, the finished rolling temperature is controlled to be above (Ar ₃ +50)° C. in order to prevent the finished rolled steel sheet from having a fertile iron phase.

After the above-mentioned hot rolling process, spherical calcium sulfide intercalated substances will be produced inside the obtained finished rolled steel sheet. In the conventional process, there are many spindle-shaped manganese sulfide interlayers inside the steel plate. However, the manganese sulfide interlayers are inherently softer and larger in size. Therefore, after subsequent rolling, the manganese sulfide interlayers tend to become smaller. It is slender and easy to crack in subsequent processes or applications, resulting in poor elongation and bending properties of the resulting steel sheet. In this case, by controlling the composition of the steel billet, calcium sulfide interlayers are produced inside the steel plate. Due to the high melting point of the calcium sulfide interlayer, it will not be affected by the subsequent process, and it is not easy to break, so the obtained steel plate has better elongation, bendability and formability. In some embodiments, the particle size of the calcium sulfide intercalator is 0.5 microns to 5.0 microns.

In some embodiments, the steel billet may optionally be subjected to a heating process to be heated to 1050°C to 1150°C prior to operation 130 . In some embodiments, after operation 130 is performed, the method 100 of the present invention does not perform a cold rolling process.

Next, in operation 140, a quenching process is performed on the finished rolled steel sheet to obtain a wear-resistant steel sheet. In some embodiments, the initial cooling temperature of the quenching process is above (Ar ₃ +20)° C., to ensure that the finished rolled steel sheet is quenched in a fully Worcesterian iron phase. It is supplemented that, because the ferrite iron structure is relatively soft, in order to avoid the decrease of the hardness of the wear-resistant steel plate obtained later, the aforementioned finished rolling steel plate does not have the ferrite granule structure, and the cooling temperature of the quenching process is (Ar _{3 )} . +20) ℃ above. In some embodiments, the cooling rate of the quenching process is 5°C/s to 30°C/s. If the cooling rate of the quenching process is less than 5°C/s, the obtained wear-resistant steel plate is likely to have fertilized iron and toughened iron phases, which will reduce its hardness. If the cooling rate of the quenching process is greater than 30℃/s, although the faster cooling rate can more effectively avoid the formation of fertilized iron and toughened iron phases, the equipment cost and the required cooling water cost will be reduced. Substantial Increase. Preferably, the cooling rate of the quenching process may be 10°C/s to 20°C/s. In some embodiments, the cooling temperature of the quenching process is less than 250° C. to obtain a structure composed of self-tempered loose iron. If the cooling temperature is not less than 250°C, the obtained wear-resistant steel plate has less self-tempering loose iron phase, and easily contains fertilized iron or toughened iron phase, which reduces the hardness of the wear-resistant steel plate. In some embodiments, after operation 140 is performed, the tempering process is not performed. It should be understood that, in operation 140, the steel plate will start to produce loose iron at about 350°C. The microstructures are all tempered to become Matian loose iron, so that the obtained steel plate has better hardness and elongation.

In other words, the present invention does not perform a tempering process to obtain a loose iron structure, but controls the temperature of the quenching process to generate self-tempered loose iron. In some embodiments, the wear resistant steel sheet comprises greater than 95% by volume of self-tempered loose iron. The higher content of self-tempered loose iron can provide better low temperature toughness of the wear-resistant steel plate. When the self-tempering loose iron of the wear-resistant steel plate is less than 95% by volume, the hardness of the wear-resistant steel plate will be too low. In some embodiments, the wear resistant steel sheet may optionally contain less than 5 vol % Wasserite, preferably 0 vol %. Because of the low hardness of Wostian iron, it is easy to cause the impact resistance of the steel plate to decrease.

Several embodiments are used below to illustrate the application of the present invention, but they are not intended to limit the present invention. Those with ordinary knowledge in the technical field of the present invention can make various changes and modifications without departing from the spirit and scope of the present invention. retouch. Example

Examples are made to include 0.12 wt% to 0.18 wt% carbon, 0.001 wt% to 0.005 wt% calcium, 0.4 wt% or less silicon, 1.0 wt% to 1.5 wt% manganese, 0.01 wt% or less phosphorus, 0.005 wt% or less sulfur, 1.0 wt% or less chromium, 0.5 wt% or less molybdenum, 1.0 wt% or less nickel, 0.01 wt% to 0.05 wt% aluminum, 0.01 wt% or less nitrogen, the rest is iron and inevitable The impurity of the molten steel is microalloyed. Next, the steel billet cast by the above molten steel is heated at 1050°C to 1150°C and hot rolled. The hot rolling operation includes rolling at a temperature of 900°C to 1150°C, then finishing rolling, and controlling the start rolling temperature to be 850°C to 900°C and the finish rolling temperature to be above (Ar ₃ +50)°C. Next, the cooling temperature is controlled to be above (Ar ₃ +50)° C., and the quenching process of the steel plate is carried out with direct quenching equipment. The cooling rate of the quenching process is 5°C/s to 30°C/s, and the cooling temperature is less than 250°C. After cooling, the wear-resistant steel plates of the examples were obtained. Comparative example

The comparative example is a wear-resistant steel plate obtained according to the process of the above-mentioned embodiment, but without microalloying treatment. Evaluation method Hardness test

After grinding the surfaces of the wear-resistant steel plates of the Examples and Comparative Examples to a thickness of 1 mm, respectively, a Brinell hardness tester was used to test with a tungsten carbide indenter with a load of 3000 kgf. The results are shown in Table 1 below. Low temperature impact test

The wear-resistant steel plates of the examples and comparative examples were processed into standard Charpy impact test pieces with V-shaped grooves (10mm×10mm×55mm), and then the test pieces were cooled to -40°C and then subjected to an impact test. Longitudinal (L-direction) impact absorption energy, and the results are shown in Table 1 below. Stretching test

The wear-resistant steel plates of the examples and comparative examples were subjected to a tensile test with a universal testing machine to measure the yield strength, tensile strength and elongation of the wear-resistant steel plates, and the results are shown in Table 1 below. Bending test

The wear-resistant steel plates of the examples and comparative examples were subjected to bending tests. Under different (bending radius/steel plate thickness) ratios, they were bent at 90 degrees to observe the minimum (bending radius/steel plate thickness) ratio when cracks occurred in the steel plates. The results are shown in Table 1 below. Microstructure observation

After grinding and polishing the wear-resistant steel plates of the examples and comparative examples, they were etched with a nitric acid alcohol solution, and then the intervening state of the wear-resistant steel plates was observed by an optical microscope.

Table 1

According to Table 1, the hardness of the wear-resistant steel plates of the examples can reach more than 400 HBW, and the yield strength and tensile strength are also greater than 1200 MPa and 1310 MPa, respectively. Obviously, the mechanical properties of the examples are better than those of the comparative examples. Moreover, the wear-resistant steel plate of Example 1 has an elongation of more than 13% and the low-temperature impact absorption energy is also better than that of the comparative example, and its (bending radius/plate thickness) ratio can reach 2 without cracks, so the implementation The wear-resistant steel plate of the example has good formability.

FIG. 2A and FIG. 2B are optical metallographic microstructure photographs of the wear-resistant steel sheets of the example and the comparative example, respectively. It can be seen in FIG. 2A that the microstructure of the embodiment is composed of flat self-tempered loose iron, and the shape of the intervening objects is spherical (as indicated by the arrow). However, the microstructure of the comparative example shown in FIG. 2B is also composed of flat self-tempered loose iron, but the shape of the intervening objects is spindle-shaped (as indicated by the arrow).

According to the above embodiments, the wear-resistant steel plate and its manufacturing method provided by the present invention are processed by microalloying to control the types and types of intervening substances, and by specifying the conditions of the quenching process, so that most of the microstructures are In order to self-tempering loose iron, the wear-resistant steel plate with high strength, high elongation and good formability can be obtained.

Although the present invention has been disclosed above with several embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field to which the present invention belongs, without departing from the spirit and scope of the present invention, can make various Therefore, the scope of protection of the present invention should be determined by the scope of the appended patent application.

100: Method 110, 120, 130, 140: Operation

Aspects of the present disclosure will be better understood from the following detailed description read in conjunction with the accompanying drawings. It should be noted that, as is standard practice in the industry, many features are not drawn to scale. In fact, the dimensions of many features can be arbitrarily scaled for clarity of discussion. [FIG. 1] is a schematic flow chart illustrating a method 100 for manufacturing a wear-resistant steel plate according to some embodiments of the present invention. [ FIG. 2A ] and [ FIG. 2B ] are photos of optical metallographic microstructures of the wear-resistant steel sheets of Examples and Comparative Examples, respectively.

Domestic storage information (please note in the order of storage institution, date and number) none Foreign deposit information (please note in the order of deposit country, institution, date and number) none

100: Method

110, 120, 130, 140: Operation

Claims (9)

A wear-resistant steel plate, comprising: 0.12wt% to 0.18wt% carbon; 0.001wt% to 0.005wt% calcium; 0.4wt% or less silicon; 1.0wt% to 1.5wt% manganese; and 0.01wt% or less phosphorus 0.005wt% or less sulfur; 1.0wt% or less chromium; 0.5wt% or less molybdenum; 1.0wt% or less nickel; 0.01wt% to 0.05wt% aluminum; 0.01wt% or less nitrogen; Inevitable impurities, wherein the wear-resistant steel plate contains calcium sulfide intervening matter, the wear-resistant steel plate contains more than 95% by volume of self-tempered loose iron and less than 5% by volume of Vostian iron, and the self-tempered iron is The iron series is not produced by the tempering process. The wear-resistant steel plate according to claim 1, wherein the calcium sulfide interlayer is a spherical interlayer. The wear-resistant steel plate according to claim 1, wherein a particle size of the calcium sulfide intercalator is 0.5 to 5.0 microns. The wear-resistant steel plate according to claim 1 further comprises a total amount of 0.02wt% to 0.07wt% of titanium, vanadium and niobium. A method for manufacturing a wear-resistant steel plate, comprising: performing a microalloying treatment on a molten steel, wherein the molten steel comprises: 0.12wt% to 0.18wt% of carbon; 0.001wt% to 0.005wt% of calcium; 0.4wt% or less 1.0wt% to 1.5wt% manganese; 0.01wt% or less phosphorus; 0.005wt% or less sulfur; 1.0wt% or less chromium; 0.5wt% or less molybdenum; 1.0wt% or less nickel; 0.01wt% % to 0.05 wt % of aluminum; 0.01 wt % or less of nitrogen; the rest are iron and inevitable impurities; cast the molten steel into a steel billet; perform a hot rolling process on the steel billet to obtain a finished rolled steel plate; and performing a quenching process on the finished rolled steel plate to obtain the wear-resistant steel plate, wherein a cooling rate of the quenching process is 5°C/s to 30°C/s and a complete cooling temperature is less than 250°C. The method for manufacturing a wear-resistant steel plate according to claim 5, further comprising performing a heating process on the steel billet before the hot rolling process, wherein a temperature of the heating process is 1050°C to 1150°C. The method for manufacturing a wear-resistant steel sheet according to claim 5, wherein the hot rolling process comprises: performing a first hot rolling step on the steel billet to obtain a first steel sheet, wherein a temperature of the first hot rolling step is and performing a second hot rolling step on the first steel sheet to obtain the finished rolled steel sheet, wherein a starting temperature of the second hot rolling step is 850°C to 900°C, and a finished rolling The temperature is (Ar ₃ +50)°C or higher. The method for manufacturing a wear-resistant steel plate according to claim 5, wherein a quenching temperature in the quenching process is (Ar ₃ +20)° C. or higher. The method for manufacturing a wear-resistant steel plate according to claim 5, wherein after the quenching process is performed, a tempering treatment is not performed.

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