Hot-rolled round steel for forging bucket tooth, production method of hot-rolled round steel, bucket tooth and production method of bucket tooth

Abstract

The invention provides hot-rolled round steel for forging bucket teeth, a production method of the hot-rolled round steel, the bucket teeth and the production method of the bucket teeth. The hot-rolled round steel comprises the following components: 0.28%-0.36% of C, 1.10%-1.35% of Si, 1.60%-1.90% of Cr, 1.20%-1.60% of Mn, 0.10%-0.40% of Mo, 0.06%-0.15% of V, 0.04%-0.10% of Ti, 0.018%-0.030% of Al, less than or equal to 0.020% of P, less than or equal to 0.020% of S and the balance of Fe and inevitable impurities. Compared with the prior art, the components of the bucket tooth steel are controlled, so that the steel has better hardenability and hardenability, and the bucket tooth can obtain ideal strength, hardness and impact toughness through heat treatment.

Description

Technical Field

[0001] The invention belongs to the field of steel production, and in particular relates to a hot-rolled round steel for forging bucket teeth and a production method thereof, a bucket tooth and a production method thereof. Background Art

[0002] Bucket teeth are important components of construction machinery such as excavators and bulldozers. They are in direct contact with ore, sand, gravel, concrete, etc. during work, and are subjected to strong impact, bending and grinding. They are one of the components with the most serious wear and tear.

[0003] Commonly used bucket teeth are mainly made of cast manganese steel, which can also be modified by adding Cr, V, Ti, Mo, Nb or RE elements. Its advantages are simple production process, and its disadvantages are unstable product quality, low production efficiency and prominent production environment problems.

[0004] Compared with the casting production method, the raw materials used in forged bucket teeth are stable, the structure after forging is more uniform and delicate, the product quality is stable, the production efficiency is high, and the environmental pollution is small. Therefore, bucket tooth products have gradually improved from cast bucket teeth to forged bucket teeth.

[0005] The patent with publication number CN 114182179 A published on March 15, 2022, discloses a high-strength bucket tooth steel for engineering machinery, its production method and heat treatment process, and its disclosed composition is: C: 0.31%-0.36%; Si: 1.10%-1.35%; Cr: 1.00%-1.35%; Mn: 0.90%-1.10%, Al0.015-0.045%; the balance is Fe and unavoidable impurities. After the steel is forged into bucket teeth, it needs to be quenched and tempered, and the heat treatment cost is high. Summary of the invention

[0006] The purpose of the present invention is to provide a hot-rolled round steel for forging bucket teeth and a production method thereof. By controlling the composition of bucket tooth steel, the steel has good hardenability and hardenability, so that after hot rolling, the bucket tooth manufacturer only needs to air cool or wind cool after forging the bucket teeth, and then temper the bucket teeth to obtain ideal strength, hardness and impact toughness, eliminating the quenching heating and cooling process, and effectively reducing the heat treatment cost.

[0007] The present invention provides a bucket tooth and a production method thereof, which is produced by using the hot-rolled round steel for forging bucket teeth, and after the forging bucket teeth are finished, they are air-cooled or wind-cooled, and then tempered. The heat treatment process does not require quenching, and the cost is low.

[0008] The specific technical solutions of the present invention are as follows:

[0009] A hot-rolled round steel for forging bucket teeth, comprising the following components in percentage by mass:

[0010] C: 0.28% - 0.36%, Si: 1.10% - 1.35%, Cr: 1.60 - 1.90%, Mn: 1.20% - 1.60%, Mo: 0.10% - 0.40%, V: 0.06% - 0.15%, Ti: 0.04% - 0.10%, Al: 0.018% - 0.030%, P ≤ 0.020%, S ≤ 0.020%, and the balance is Fe and inevitable impurities.

[0011] A production method of hot-rolled round steel for forging bucket teeth provided by the present invention includes the following technological processes:

[0012] Converter smelting - LF refining - RH refining - continuous casting - hot rolling - slow cooling.

[0013] For the said converter smelting, the C content in the converter tapping is ≥ 0.08%, P ≤ 0.015%, the tapping temperature is ≥ 1630 °C, and slag materials and alloys are added during the tapping process;

[0014] For the said LF refining, the LF refining time is ≥ 40 min, 300 - 500 Kg of quicklime and slag melting agent are added to ensure the foaming property and fluidity of the refining slag, and the white slag refining time is ≥ 20 min;

[0015] For the said RH refining, the RH deep vacuum time is ≥ 15 min, and the soft blowing time is ≥ 15 min;

[0016] For the said continuous casting, protective casting is adopted, and the secondary cooling water ratio is 0.2 - 0.3 L / Kg.

[0017] For the said hot rolling, since the Si content of this steel is relatively high, the scale after heating is dense and firm, and not easy to remove. The heating time in the furnace for hot rolling is ≥ 240 min to ensure the rolling start temperature is 1080 - 1120 °C.

[0018] For the said slow cooling, it is cooled at a cooling rate not exceeding 0.5 °C / s to 500 °C and then air-cooled. If the cooling rate is too fast, there will be more fast-cooled structures and the hardness of the rolled material will be high, resulting in difficulties in sawing or shearing for blanking.

[0019] A production method of bucket teeth provided by the present invention is obtained by using the hot-rolled round steel for forging bucket teeth produced by the above method. Specifically:

[0020] Heat and forge the above hot-rolled round steel for forging bucket teeth into shape, then cool it; and then perform tempering.

[0021] The said hot forging and forming means forging and forming after heating to 1050-1150°C; the temperature after heating and forging is 900-950°C; the structure of the sample at this temperature is austenite. Different from the martensite obtained by conventional quenching treatment, during the air cooling process of the sample, a large amount of bainite structure and a small amount of martensite structure can be obtained when the sample is cooled in air or air blast. Then, through tempering, the phase transformation internal stress generated by cooling can be eliminated and the toughness of the sample can be improved.

[0022] The said cooling is air cooling or air blast;

[0023] For the said tempering, the temperature is 230-270°C.

[0024] A kind of bucket tooth provided by the present invention is produced by using the above production method of the bucket tooth.

[0025] The metallographic structure of the produced bucket tooth is bainite + martensite, and the hardness of the bucket tooth steel with this kind of structure can reach 50-52HRC.

[0026] The yield strength of the produced bucket tooth is ≥1600 Mpa, the tensile strength is ≥1700 MPa, the elongation is ≥11%, the reduction of area is ≥45%, the room temperature Akv2 is ≥30 J, and the hardness is 50-52HRC.

[0027] In the composition of the bucket tooth steel provided by the present invention, the control and functions of each element are as follows:

[0028] C is one of the main elements to ensure the strength and hardness of the finished bucket tooth. If the C content is too low, the strength and hardness will be low; if the content is too high, the impact performance will be reduced. Controlling the C content at 0.28%-0.36% can make the bucket tooth have good comprehensive mechanical properties, have good strength and hardness while having better impact toughness, and keep the bucket tooth with an ideal service life.

[0029] Si: It can significantly improve the elastic limit of the bucket tooth steel, increase the strength, and at the same time can also play a role in deoxidation during the smelting process, improving the cleanliness of the steel.

[0030] Cr: It can improve the hardenability of the bucket tooth steel, play a role in refining grains with carbides, and increase the strength of the bucket tooth.

[0031] Mn: It can significantly improve the hardenability of the steel, has a good effect on increasing the strength and hardness, and at the same time can also play a role in deoxidation and desulfurization during the smelting process, improving the cleanliness of the steel.

[0032] Mo: It can refine the grains of the steel, can significantly improve the hardenability of the steel, reduce the temper brittleness, and improve the mechanical properties of the steel. Mo delays the transformation and promotes the formation of bainite. At the same time, Mo acts together with V and Ti to refine the grains.

[0033] V: It has a strong solution strengthening effect, refines the grain size, and can improve the strength and toughness of steel. The carbide formed with carbon has high wear resistance.

[0034] Ti: It can refine the grain structure of steel, thereby improving the strength and toughness of steel. The TiC formed with carbon has relatively high hardness, which can improve the hardness and wear resistance of the bucket teeth.

[0035] Low P and S reduce grain boundary embrittlement and improve toughness.

[0036] The above elements are the main components of the bucket teeth. Among them, C is the basic element to ensure the strength and hardness of the bucket teeth, and elements such as Cr, Mn, Mo, V, and Ti ensure excellent hardenability of the steel. After the forging of the bucket teeth is completed, it does not require secondary heating and does not need to be cooled with quenching agents such as oil or PAG. By using air cooling or air blast cooling methods, the desired phase transformation can be obtained. This saves the investment in tooling, medium, and energy during the quenching heating and cooling processes, achieving the purpose of reducing costs and emissions.

[0037] In the present invention, Al is used for deoxidation to form AlN, which inhibits grain growth. The carbonitrides of Ti are stable at high temperatures and prevent the growth of austenite grains, refining the final structure. The carbonitrides of V precipitate at lower temperatures, resulting in precipitation strengthening. In this way, during the cooling process after hot rolling, by controlling the cooling rate, the corresponding structure can be obtained, so as to obtain a good combination of strength and toughness without the need for quenching. Cr and Mn improve hardenability. Under air cooling or air blast cooling conditions, bainite is mainly obtained, which has both relatively high strength and good toughness. Moreover, the combined action of Cr, Mo, and V enhances the surface hardness and anti-wear performance.

[0038] Compared with the prior art, the present invention controls the composition of the bucket tooth steel to make the steel have good hardenability and hardenability. After heat treatment, the bucket teeth can obtain ideal strength, hardness, and impact toughness. Description of the Drawings

[0039] Figure 1 It is the metallographic structure diagram of the bucket teeth in Embodiment 1 of the present invention, and the structure is bainite + martensite. Detailed Embodiment

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, rather than all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] The test materials, reagents, etc. used in the following examples can be obtained from commercial sources without special instructions.

[0042] For those without specific technical or conditions noted in the examples, they can all be carried out according to the techniques or conditions described in the literature in this field or according to the product specifications.

[0043] Examples 1 - 4

[0044] A hot-rolled round steel for forging bucket teeth includes the following components by mass percentage: As shown in Table 1, the balance not shown in Table 1 is Fe and unavoidable impurities.

[0045] Table 1 Composition of hot-rolled round steel for forging bucket teeth in each example (wt%)

[0046]

[0047] The production method of the hot-rolled round steel for forging bucket teeth in the above examples includes the following technological processes:

[0048] Converter smelting - LF refining - RH refining - continuous casting - hot rolling - slow cooling.

[0049] Among them, in the converter smelting step, the C content in the converter tapping is ≥0.08%, P ≤0.015%, the tapping temperature is ≥1630°C, and slag materials and alloys are added during the tapping process;

[0050] In the LF refining step, the LF refining time is ≥40 min, 300 - 500 Kg of quicklime and slag melting agent are added to ensure the foaming property and fluidity of the refining slag, and the white slag refining time is ≥20 min;

[0051] In the RH refining step, the RH deep vacuum time is ≥15 min, and the soft blowing time is ≥15 min;

[0052] In the continuous casting step; continuous casting with protective casting, and the secondary cooling water ratio is 0.2 - 0.3 L / Kg;

[0053] In the hot rolling step, the heating time of the rolled steel in the furnace is ≥240 min, and it is advisable to ensure the starting rolling temperature is 1080 - 1120°C;

[0054] In the slow cooling step, it is cooled at a cooling rate not exceeding 0.5°C / s to 500°C and then air-cooled.

[0055] The main parameters of the production in each example are shown in Table 2.

[0056] Table 2 Main production parameters of each example

[0057]

[0058] The round steel produced in the above embodiments is heated to 1050 - 1150 °C for forging, and the temperature after heating and forging is 900 - 950 °C; then it is air-cooled or air-blown; and then tempered at 230 - 270 °C to obtain the bucket teeth. The production parameters of each specific embodiment are shown in Table 2.

[0059] The bucket teeth produced in each embodiment are subjected to performance testing, and the results are shown in Table 3.

[0060] Table 3 Performance of the bucket teeth produced in each embodiment

[0061]

[0062] The description of the above embodiments is to enable those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A hot-rolled round steel for forging bucket teeth, characterized in that: The hot-rolled round steel for forging bucket teeth comprises the following components in percentage by mass: C: 0.28% ~ 0.36%, Si: 1.10% ~ 1.35%, Cr: 1.60 ~ 1.90%, Mn: 1.20% ~ 1.60%, Mo: 0.10% ~ 0.40%, V: 0.06% ~ 0.15%, Ti: 0.04% ~ 0.10%, Al: 0.018% ~ 0.030%, P ≤ 0.020%, S ≤ 0.020%, the balance is Fe and unavoidable impurities.

2. A method for producing hot-rolled round steel for forged bucket teeth according to claim 1, characterized in that: The production method comprises the following process flow: Converter smelting—LF refining—RH refining—continuous casting—hot rolling—slow cooling.

3. The production method according to claim 2, characterized in that: The continuous casting adopts protective casting, and the secondary cooling water volume is 0.2-0.3L / Kg.

4. The production method according to claim 2, characterized in that: In the hot rolling, the steel is heated in the furnace for ≥240 min, and the starting rolling temperature is ensured to be 1080-1120°C.

5. The production method according to claim 2 or 4, characterized in that: The slow cooling is performed by cooling to 500° C. at a cooling rate not exceeding 0.5° C. / s and then air cooling.

6. A method for producing bucket teeth, characterized in that: The forged bucket teeth are produced by using the hot-rolled round steel as claimed in claim 1. The production method of the bucket teeth is as follows: the hot-rolled round steel is heated and forged into shape, then cooled; and then tempered.

7. The production method according to claim 6, characterized in that: The heating forging process refers to heating to 1050-1150° C. forging process.

8. The production method according to claim 6 or 7, characterized in that: The cooling is air cooling or wind cooling.

9. The production method according to claim 6, characterized in that: The tempering temperature is 230-270°C.

10. A bucket tooth, characterized in that: The bucket tooth is produced by the production method according to any one of claims 6 to 9, wherein the metallographic structure of the bucket tooth is bainite + martensite, the yield strength of the bucket tooth is ≥1600Mpa, the tensile strength is ≥1700MPa, the elongation is ≥11%, the cross-sectional shrinkage is ≥45%, the room temperature Akv2 is ≥30J, and the hardness is 50-52HRC.

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