Alloy steel rod for manufacturing large-diameter drill rod for breaking hammer and method for manufacturing the same

Abstract

The present application relates to a kind of alloy steel bar for manufacturing breaking hammer large specification drill rod and its manufacturing method, with Fe as base element, further comprising the following mass percentage chemical composition: C:0.35~0.41%, Si:0.90~1.40%, Mn:1.00~1.50%, P:0~0.025%, S:0~0.025%, Cr:1.00~1.40%, W:0.30~0.70%, B:0.0005~0.0050%, Ni:0~0.30%, Cu:0~0.25%, Mo:0~0.25%, Al:0.008~0.035%, Ti:0.010~0.050%.Production specification is 150-260mm.According to chemical composition, molten steel is smelted, and molten steel is poured into billet, and billet is heated to 1150~1250 ℃, and after heat preservation, it is discharged and rolled or forged into steel bar, and the compression ratio of rolling or forging is ≥5, and after rolling or forging, it is air-cooled.Circular steel is sawn according to the design length, and one end is processed into the tip of drill rod, and then quenching and tempering heat treatment is carried out, and after heat treatment, it is finished to obtain drill rod.The surface hardness of drill rod is ≥51HRC, the core hardness is ≥46HRC, and the tensile strength at 500 ℃ temperature reaches 900MPa or more.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of special steel, and particularly relates to an alloy steel rod for manufacturing a large-specification drill rod of a breaking hammer and a manufacturing method thereof. BACKGROUND

[0002] The breaking hammer is widely applied to the fields of metallurgy, mine, road and building, and is used for mining, breaking and demolishing hard objects such as rock, concrete, ladle, frozen earth, cement pavement, bridge pier and building. The drill rod is a consumable part of the breaking hammer. The breaking hammer is generally composed of three main parts, i.e. the drill rod, the piston and the piston cylinder. The drill rod is directly contacted with the broken object, and is a consumable part. When the object is broken, the drill rod not only bears complex periodic external force, but also bears high temperature because the continuous and intense friction between the drill rod and the broken object (such as rock, concrete and cement pavement) will definitely cause the drill rod to heat, and the local temperature of the drill rod often reaches 500 DEG C or above. Therefore, the drill rod not only needs to have high hardness and strength at normal temperature, but also needs to have certain high-temperature hardness and strength.

[0003] At present, the material for manufacturing the drill rod is mostly 42CrMo steel. However, when the drill rod with large specification (diameter ≥ 175 mm) is manufactured by using the 42CrMo steel, the hardening layer depth of the drill rod after quenching is difficult to meet the service requirement because the hardenability of the steel is relatively low, and the service life of the manufactured drill rod is relatively short. On the other hand, the high-temperature hardness and high-temperature strength of the drill rod manufactured by using the 42CrMo steel are also relatively low, and it is difficult to meet the requirement of heat resistance of the drill rod in the long-time rock drilling process.

[0004] After checking some currently published technologies for manufacturing the drill rod, it is found that either the performance cannot meet the requirement of rock mining, the service life of the drill rod is relatively short, or the production cost is very high. Some drill rods are manufactured by using some alloy steels with low carbon content after carburizing and quenching. The alloy raw material is relatively high in price, the manufacturing process of the drill rod is complex, the manufacturing cost is very high, the performance is not resistant to high temperature, and the performance-price ratio of the manufactured drill rod is not high. Therefore, it is of great significance to develop a large-specification drill rod steel with high hardenability and long service life. SUMMARY

[0005] The present application provides an alloy steel rod for manufacturing a large-specification drill rod of a breaking hammer and a manufacturing method thereof. The production diameter of the steel rod is 150-260 mm.

[0006] The alloy steel rod for manufacturing the large-diameter drill rod of the breaking hammer is characterized in that the steel rod is based on Fe and further comprises the following chemical components in percentage by mass: C: 0.35-0.41%, Si: 0.90-1.40%, Mn: 1.00-1.50%, P: 0-0.025%, S: 0-0.025%, Cr: 1.00-1.40%, W: 0.30-0.70%, B: 0.0005-0.0050%, Ni: 0-0.30%, Cu: 0-0.25%, Mo: 0-0.25%, Al: 0.008-0.035%, and Ti: 0.010-0.050%.

[0007] The raw material is prepared according to the chemical components, and then sequentially subjected to melting, refining, vacuum degassing and continuous casting to produce high-purity molten steel and cast into a continuous casting billet or an ingot, and then the continuous casting billet or the ingot is heated to 1150-1250 DEG C in a heating furnace, taken out and rolled or forged into a steel rod with a required diameter, the rolling or forging ratio of the steel rod is greater than or equal to 5, and the steel rod is air-cooled after rolling or forging.

[0008] The steel rod is sawed into a certain length, heated at one end and forged into a pointed part with different shapes (quadrilateral, octagonal or circular) and then air-cooled, and then machined or cut into a pointed part at one end, and then subjected to quenching and tempering heat treatment (quenching temperature: 850-920 DEG C, and tempering temperature: 200-430 DEG C), and then subjected to subsequent finishing and other processes to obtain the breaking hammer drill rod, the surface hardness of the drill rod is greater than or equal to 51 HRC, the core hardness is greater than or equal to 46 HRC, and the tensile strength at 500 DEG C is greater than 900 MPa, while the tensile strength of 42CrMo at 500 DEG C is only 550 MPa. The drill rod manufactured by using the alloy steel rod has high thermal strength, and the service life is significantly improved, and the needs of the drill rod service are greatly met. The service life of the drill rod manufactured by using the round steel is significantly improved, and is more than 2.8 times of the service life of the drill rod manufactured by using the existing 42CrMo steel.

[0009] The functions and amounts of the elements contained in the alloy steel rod are described as follows.

[0010] C: Carbon is the most basic, the most economical, the most effective strengthening element in steel, carbon can significantly improve the strength of steel through solid solution strengthening and precipitation strengthening. In order to ensure the strength, hardness and wear resistance of the drill rod, it must have sufficient carbon content. When the carbon content in the martensite is less than 0.4%, the hardness increases sharply with the increase of the carbon content; when the carbon content in the martensite is greater than 0.4%, the hardness increases slowly with the increase of the carbon content. The higher the C content, the higher the hardness, and the relative toughness is poor, the lower the C content, the more the lath martensite formed after quenching, and the relative toughness is high, therefore, under the premise of ensuring the hardness, according to the test results in the early stage on other medium carbon steel, when C is 0.35%-0.41%, it can not only ensure high strength and hardness, but also make the material have good toughness, and the C content is controlled to be 0.35-0.41% in the application.

[0011] Si: Si is a non-carbide forming element, which can improve the hardness and strength of the steel in the form of solid solution strengthening, especially it can obviously improve the yield strength and yield ratio of the steel, and can improve the hardenability of the steel. In addition, Si reduces the diffusion speed of C in ferrite, so that the carbides precipitated during tempering are not easy to gather, which can obviously increase the tempering stability of the steel, so that the drill rod can fully reduce the internal stress after tempering and can also maintain high hardness to increase wear resistance. However, high Si content will increase the decarburization tendency of the steel, and also graphite tendency. The Si content in the application is controlled to be 0.90-1.40%.

[0012] Mn: Mn is a weak carbide forming element, Mn is a very effective element for improving the hardenability of the steel in the steel. However, high Mn can easily cause center segregation and cracks in the casting blank, and high Mn can also cause the grains to grow easily, thereby adversely affecting the toughness. The Mn content in the application is controlled to be Mn: 1.00-1.50%.

[0013] Cr: Cr is a strong carbide forming element, which is an important alloying element for improving hardenability, strength and wear resistance. Cr can also improve the oxidation resistance and corrosion resistance of the steel, reduce the corrosion of the drill rod in the working environment, prolong the service life, and appropriately improve the hot strength; but if the element is added in excess, the impact toughness will be reduced. The content of the application is controlled to be Cr: 1.00-1.40%.

[0014] W: W is a strong carbide forming element, which can form refractory carbides in the steel, the main role of W in the steel is to improve the high temperature strength and hardness, increase the tempering stability, W can also inhibit the temper brittleness, W can also reduce the overheating sensitivity of the steel, and can improve the creep strength of the steel; but too high W content will increase the cost of the steel. The W content in the application is controlled to be 0.30-0.70%.

[0015] B: the role of B in steel is to improve hardenability, it can very effectively improve the hardenability of steel, adding trace B in steel, can replace more expensive molybdenum, nickel, chromium and other elements, in almost no increase in the cost of steel can significantly improve the hardenability of steel, according to relevant research shows that in the role of improving hardenability, B element is equivalent to several hundred times, even several thousand times of general alloying elements. The mechanism of B improving the hardenability of steel is that B can effectively inhibit the nucleation of ferrite at the grain boundary during austenite transformation. Because B is adsorbed on the grain boundary, the grain boundary energy is reduced, the nucleation of new phase is difficult, the stability of austenite is increased, and the hardenability is effectively improved. The content of B in the application is controlled to be 0.0005-0.0050%.

[0016] S, P: S, P elements are harmful impurity elements in steel. As harmful impurity elements, they can reduce the strength and toughness of steel, therefore, the content of these elements should be reduced as much as possible. However, excessively reducing the content of these elements will inevitably increase the cost of steelmaking. Therefore, considering comprehensively, the content of P is controlled to be 0-0.025%, and the content of S is controlled to be 0-0.025%.

[0017] Al: Al is added as a deoxidizing element in steel. In addition to reducing the dissolved oxygen in molten steel, Al and N form dispersed fine AlN particles, which can refine the grains, improve the plasticity, toughness and strength, and improve the comprehensive performance of the steel. However, when the content of Al is too high, brittle inclusions such as Al2O3 are easily formed during the smelting process of molten steel, which reduces the purity of the molten steel. Therefore, the content of Al in the application is controlled to be 0.008-0.035%.

[0018] Ni, Cu, Mo content: during the smelting process of molten steel, Ni, Cu, Mo and other elements will inevitably exist in the raw materials. When the content of Ni, Cu and Mo is high, the strength will be improved, which is the favorable aspect. However, at the same time, the plasticity of the steel will be deteriorated, which is the unfavorable aspect. In addition, when the content of these elements is high, the hardenability of the steel will be significantly increased, which will lead to a high risk of quenching cracking. Therefore, the content of these elements should be stably controlled within a certain range. The content of Ni, Cu and Mo in the application is required to be 0-0.30% for Ni, 0-0.25% for Cu, and 0-0.25% for Mo.

[0019] Ti: Ti is a strong nitride and carbide forming element. In steel, Ti first combines with N to form a compound, avoiding the opportunity of N combining with B, so that solid-solution B exists in the steel, playing a role in protecting B to improve the hardenability. On the other hand, the compound formed by Ti combining with N or C also plays a role in refining the grains. The content of Ti is closely related to the content of N in the molten steel. According to the existing production process and equipment, the content of Ti in the application is controlled to be 0.010-0.050%.

[0020] Compared with the prior art, the application has the advantages that in order to improve the strength, especially the high-temperature strength of the large-diameter drill rod, the service life is prolonged. The application innovatively designs the element composition of the drill rod steel, and the drill rod obtained by quenching and tempering the round steel smelted by using the composition has high hardenability, high core and surface hardness, high-temperature strength, and the service life of the drill rod is significantly prolonged. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A comparison chart of the hardenability of the steel material of the embodiment 1 of the application and the 37CrMnMo steel and the 42CrMo steel produced according to the GB / T 3077 standard;

[0022] Figure 2 The round steel with a diameter of 205 mm produced in batches according to the application;

[0023] Figure 3 The round steel with a diameter of 260 mm produced in batches according to the application;

[0024] Figure 4 The drill rod (the tip is an octahedron) produced by the round steel with a diameter of 205 mm according to the application;

[0025] Figure 5 The drill rod (the tip is a tetrahedron) produced by the round steel with a diameter of 260 mm according to the application. DETAILED DESCRIPTION

[0026] The application will be further described in detail below in combination with the drawings and the embodiments, which are exemplary and intended to explain the application, and cannot be understood as a limitation to the application.

[0027] Embodiment 1

[0028] This embodiment relates to the steel rod with a diameter of 205 mm and the drill rod produced thereby, and the components and mass percentages contained are as follows: C: 0.37%, Si: 1.12%, Mn: 1.20%, P: 0.013%, S: 0.005%, Cr: 1.20%, Ni: 0.05%, Cu: 0.02%, Mo: 0.01%, B: 0.0020%, W: 0.39%, Al: 0.031%, Ti: 0.035%, and the balance is iron and inevitable impurity elements.

[0029] The manufacturing method of the round rod with a diameter of 205 mm: smelt the raw material according to the chemical composition as described above, and sequentially perform:

[0030] smelting - refining - vacuum degassing - continuous casting (the continuous casting billet specification: 390mm*510mm) - heating the continuous casting billet to 1150-1250℃ and keeping the temperature to burn through - high-pressure water descaling - rolling into a round rod with a diameter of 205mm - cutting - air cooling - finishing

[0031] The manufacturing method of the 205mm breaking hammer large size drill rod is as follows:

[0032] The 205mm round bar is cut into segments, one end is heated and forged into an octagonal tip, air cooled, machined, quenched (heating temperature 880°C), tempered (heating temperature 260°C), and finished. The total length of the drill rod is 1700mm.

[0033] The surface hardness of the drill rod manufactured according to the above method is 51-53.5HRC, and the core hardness of the cross section 300mm from the tip is 46-50HRC. The tensile strength of the drill rod tip is measured at 933MPa at 500°C. The drill rod of the present embodiment is used in the same mine as the drill rod made of 42CrMo steel, and the service life of the drill rod made of 42CrMo steel is 27 hours when the contrast drill rod is worn to a total length of 1300mm, and the service life of the drill rod of the present embodiment is 82 hours, which is 3.037 times the service life of the drill rod made of 42CrMo steel.

[0034] Figure 1 The hardenability curve of the steel material of Example 1 is measured and compared with the hardenability of 37CrMnMo steel and 42CrMo steel produced according to GB / T 3077 standard, and the material of Example 1 has higher hardenability, and Table 1 is the chemical composition of the three steel materials of Example 1, 37CrMnMo, and 42CrMo.

[0035] Table 1

[0036]

[0037] Example 2

[0038] This embodiment relates to a steel bar with a diameter of 260mm and a drill rod made of the same, and the components and mass percentages contained are: C: 0.38%, Si: 1.29%, Mn: 1.37%, P: 0.008%, S: 0.010%, Cr: 1.32%, Ni: 0.03%, Cu: 0.02%, Mo: 0.02%, B: 0.0017%, W: 0.50%, Al: 0.021%, Ti: 0.038%, and the balance is iron and unavoidable impurities.

[0039] The manufacturing method of the 260mm round bar is as follows: the raw materials are prepared according to the above-mentioned chemical composition, and the following steps are performed in sequence:

[0040] Melting - Refining - Vacuum degassing - Continuous casting (700 mm diameter round billet) - Heating the continuous casting billet to 1150-1250 °C and keeping it for solidification - High pressure water descaling - Rolling into a 260 mm diameter round bar - Cutting - Air cooling - Finishing

[0041] 260 round breaking hammer large diameter drill rod is manufactured as follows:

[0042] The 260 mm round bar is cut into segments, one end is heated and forged into a tetrahedral tip, air cooled, machined, quenched (heating temperature 870 °C), tempered (heating and holding temperature 260 °C), and finished. The total length of the manufactured drill rod is about 1950 mm.

[0043] The surface hardness of the drill rod manufactured by the above method is measured to be 51-53 HRC, and the core hardness of the cross section at a distance of about 380 mm from the tip is 47-49 HRC. A sample is taken from the tip of the drill rod, and the tensile strength is measured at a temperature of 500 °C to be 950 MPa. The drill rod of the present application is used in the same mine as the drill rod made of 40CrNiMo steel, and the service time of the comparative drill rod is compared when the drill rod is worn to a total length of 1500 mm. The service life of the drill rod made of 40CrNiMo steel is an average of 38 hours, and the service life of the drill rod of the present application is 85 hours. The service life of the drill rod of the present application is 2.237 times that of the drill rod made of 40CrNiMo steel. The large drill rod manufactured by the present application has a high service life, greatly meeting the needs of drill rod service.

[0044] In addition to the above embodiments, the present application also includes other embodiments, and any technical solutions formed by equivalent transformation or equivalent replacement shall fall within the protection scope of the claims of the present application.

Claims

1. A hydraulic breaker chisel rod, characterized in that: Based on Fe, it also contains the following chemical composition by mass percentage: C: 0.35–0.41%, Si: 0.90–1.40%, Mn: 1.00–1.50%, P: 0–0.025%, S: 0–0.025%, Cr: 1.00–1.40%, W: 0.30–0.70%, B: 0.0005–0.0050%, Ni: 0.03–0.30%, Cu: 0.02–0.25%, Mo:

0. 0.01~0.25%, Al: 0.008~0.035%, Ti: 0.010~0.050%; round steel is cut to the designed length, one end is machined into the tip of the drill rod, and then quenched and tempered for heat treatment. After heat treatment, the drill rod is finished. The quenching temperature is 850℃-920℃, the tempering temperature is 200℃-430℃, the surface hardness of the drill rod is ≥51HRC, the core hardness is ≥46HRC, and the tensile strength at 500℃ reaches ≥900MPa.

2. The hydraulic breaker chisel rod according to claim 1, characterized in that: The production specifications for the round steel are 150-260mm.

3. The hydraulic breaker rod according to claim 1, characterized in that: The manufacturing method involves smelting steel according to its chemical composition, casting the molten steel into steel billets, heating the steel billets to 1150-1250℃ and holding them at that temperature until fully heated, then rolling or forging them into steel bars. The compression ratio of the rolling or forging process is ≥5, and the steel bars are air-cooled after rolling or forging.

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