An M2 high-speed steel and a preparation method thereof

Abstract

The present invention relates to the technical field of continuous casting and rolling of high-speed steel, and particularly relates to an M2 high-speed steel and a preparation method thereof. The present invention provides a preparation method of M2 high-speed steel, comprising the following steps: providing molten steel; the chemical composition of the molten steel is the same as that of M2 high-speed steel; subjecting the molten steel to arc continuous casting to obtain a continuous casting billet; subjecting the continuous casting billet to first annealing, continuous rolling and second annealing in sequence to obtain the M2 high-speed steel. The central porosity level of the M2 high-speed steel prepared by the present invention can reach the production level of the traditional process (ingot casting), and there are no shrinkage cavities, no cracks and no network carbides, and the carbide size is finer.

Description

Technical Field

[0001] The present invention relates to the technical field of continuous casting and rolling of high-speed steel, and specifically relates to an M2 high-speed steel and a preparation method thereof. Background Art

[0002] High-speed steel has good machining performance and comprehensive performance, and it has a wide range of applications in the field of tool materials. In recent years, with the continuous development of technology and the increasing international demand, high-speed steel has entered a comprehensive development stage.

[0003] Currently, the preparation method of domestic M2 high-speed steel is as follows: alloy raw materials are smelted, and the obtained molten steel is produced by die casting process to obtain M2 high-speed steel. However, the quality of the finished product of M2 high-speed steel prepared by the above preparation method is poor. For example, there are small cracks in the finished product and the size of intragranular carbides in M2 high-speed steel is large. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide an M2 high-speed steel and a preparation method thereof. The preparation method of the M2 high-speed steel provided by the present invention has good quality of the prepared M2 high-speed steel finished product, no cracks in the finished product, and finer carbide size.

[0005] In order to achieve the above purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a preparation method of M2 high-speed steel, including the following steps:

[0007] Provide molten steel according to the composition of the M2 high-speed steel;

[0008] Perform arc continuous casting on the molten steel to obtain a continuous casting billet;

[0009] Perform first annealing, continuous rolling and second annealing on the continuous casting billet in sequence to obtain the M2 high-speed steel.

[0010] Preferably, the arc continuous casting includes steel liquid transfer, refrigeration forming and straightening in sequence.

[0011] Preferably, when transferring the steel liquid, the tapping temperature of the steel liquid is 1500 - 1600 °C;

[0012] The refrigeration forming includes cooling water cooling and secondary cooling zone cooling in sequence; the temperature difference between the inlet and outlet of the cooling water is 6 - 8 °C; the specific water volume of the secondary cooling zone is 6 - 8 L / kg;

[0013] The speed of the straightening is 0.80 - 1.40 m / min.

[0014] Preferably, the temperature of the first annealing is 860 - 880 °C, and the holding time is 4 - 8 h.

[0015] Preferably, the tandem rolling includes rough rolling and finish rolling which are carried out successively.

[0016] Preferably, the initial rolling temperature of the rough rolling is 1090 - 1110 °C; the final rolling temperature is 970 - 990 °C;

[0017] The final rolling temperature of the finish rolling is 890 - 910 °C.

[0018] Preferably, during the tandem rolling, the single - pass deformation amount is 10% - 15%.

[0019] Preferably, the temperature of the second annealing is 860 - 880 °C, and the heat - preservation time is 1 - 4 h.

[0020] Preferably, the obtaining of the molten steel includes the following steps:

[0021] Smelt the alloy raw materials corresponding to the chemical element composition of the M2 high - speed steel to obtain molten steel.

[0022] The present invention also provides the M2 high - speed steel prepared by the above - mentioned preparation method, and the carbide size in the M2 high - speed steel is 5 - 15 μm.

[0023] The present invention provides a preparation method of M2 high - speed steel, including the following steps: providing molten steel; the chemical composition of the molten steel is the same as that of the M2 high - speed steel; subjecting the molten steel to arc continuous casting to obtain a continuous casting billet; successively carrying out first annealing, tandem rolling and second annealing on the continuous casting billet to obtain the M2 high - speed steel. The preparation method of the present invention can effectively improve the quality of the M2 high - speed steel (without cracks and with finer carbide size).

[0024] The data of the examples show that: the central porosity level of the M2 high - speed steel prepared by the present invention can reach the production level of the traditional process (ingot casting), and there are no shrinkage cavities, cracks and network carbides, and the carbide size is finer. Description of the Drawings

[0025] Figure 1 It is the OM diagram of the carbide of the M2 high - speed steel bar and wire rod prepared in Example 1;

[0026] Figure 2 It is the SEM diagram of the carbide of the M2 high - speed steel bar and wire rod prepared in Example 1;

[0027] Figure 3 It is the OM diagram of the carbide of the M2 high - speed steel bar and wire rod prepared in Comparative Example 1;

[0028] Figure 4 It is the SEM diagram of the carbide of the M2 high - speed steel bar and wire rod prepared in Comparative Example 2. Detailed Description of the Invention

[0029] The present invention provides a method for preparing M2 high-speed steel, comprising the following steps:

[0030] Provide molten steel according to the composition of the M2 high-speed steel;

[0031] Perform arc continuous casting on the molten steel to obtain a continuous casting billet;

[0032] Perform first annealing, continuous rolling and second annealing on the continuous casting billet in sequence to obtain the M2 high-speed steel.

[0033] In the present invention, by mass percentage, the chemical composition of the M2 high-speed steel preferably includes:

[0034] C 0.80 - 0.90%; Si 0.15 - 0.40%; Mn 0.20 - 0.45%; Cr 3.80 - 4.40%;

[0035] W 5.50 - 6.75%; Mo 4.50 - 5.50%; V 1.75 - 2.20%; Nb 0.01 - 0.03%;

[0036] The balance is Fe and inevitable impurities.

[0037] In the present invention, the molten steel after smelting is subjected to arc continuous casting to obtain a continuous casting billet; the composition of the molten steel is the component composition of the M2 high-speed steel as described above.

[0038] In the present invention, the obtaining of the molten steel preferably includes the following steps:

[0039] Smelt alloy raw materials corresponding to the chemical element composition of the M2 high-speed steel to obtain molten steel.

[0040] In the present invention, the smelting preferably includes primary smelting and secondary refining carried out in sequence.

[0041] In the present invention, the form of the alloy raw materials is preferably powder or block. In the present invention, the purity of the alloy raw materials is preferably greater than or equal to 99 wt.%, more preferably greater than or equal to 99.9 wt.%. In the present invention, the alloy raw materials preferably include graphite electrodes, ferrosilicon, pure manganese, pure chromium, pure tungsten, pure molybdenum, pure vanadium, pure niobium and pure iron.

[0042] In the present invention, vacuum degassing is preferably further included during the secondary refining. In the present invention, the operation of the vacuum degassing is not specifically limited, and the operations well-known to those skilled in the art can be adopted.

[0043] After obtaining the molten steel, the present invention performs arc continuous casting on the molten steel to obtain a continuous casting billet.

[0044] In the present invention, the arc continuous casting includes ladle steel transfer, refrigeration forming, and straightening in sequence to obtain a continuous casting billet.

[0045] In the present invention, during the ladle steel transfer, the tapping temperature of the molten steel is preferably 1500 - 1600 °C, more preferably 1550 °C. In the present invention, the ladle steel transfer is preferably carried out in the continuous casting tundish. In the present invention, before the ladle steel transfer, it is preferably included to preheat the continuous casting tundish, and the preheating temperature is preferably 1485 °C - 1495 °C, more preferably 1490 °C. In the present invention, the ladle steel transfer is preferably carried out under the condition of tundish covering flux.

[0046] In the present invention, the refrigeration forming includes cooling water cooling and secondary cooling zone cooling in sequence; the temperature difference between the inlet and outlet water of the cooling water is preferably 6 - 8 °C, more preferably 7 °C; the specific water consumption in the secondary cooling zone is preferably 6 - 8 L / kg, more preferably 7 L / kg. In the present invention, the straightening speed is preferably 0.80 - 1.40 m / min, more preferably 1.0 - 1.2 m / min. In the present invention, the refrigeration forming is preferably carried out in the mold, and the refrigeration forming is preferably carried out under the condition of mold powder.

[0047] In the present invention, the straightening is preferably carried out under the action of a straightening machine and a mold vibrator. In the present invention, during the straightening, the vibration frequency of the mold vibrator is preferably 90 - 100 Hz, more preferably 95 Hz; the amplitude is preferably 2 mm. In the present invention, the straightening speed is preferably 0.80 - 1.40 m / min, more preferably 1.00 - 1.20 m / min.

[0048] In the present invention, after straightening, it preferably further includes sizing and cutting. In the embodiment of the present invention, the size of the continuous casting billet after sizing and cutting is preferably 180 mm × 180 mm.

[0049] After obtaining the continuous casting billet, the present invention anneals the continuous casting billet in sequence for the first annealing, continuous rolling, and the second annealing to obtain the M2 high-speed steel.

[0050] In the present invention, the temperature of the first annealing is preferably 860 - 880 °C, more preferably 860 °C, and the holding time is preferably 4 - 8 h, more preferably 6 h. In the present invention, the first annealing is preferably carried out under a protective gas, and the protective gas preferably includes nitrogen.

[0051] In the present invention, after the first annealing, it preferably further includes cooling. In the present invention, the target temperature of the cooling is preferably < 400 °C, more preferably 200 - 350 °C. In the present invention, the cooling is preferably furnace cooling.

[0052] In the present invention, the continuous rolling includes rough rolling and finish rolling which are carried out successively. In the present invention, the initial rolling temperature of the rough rolling is preferably 1090 - 1110 °C, more preferably 1100 °C; the finish rolling temperature is 970 - 990 °C. In the present invention, the initial rolling temperature of the finish rolling is 950 - 970 °C; the finish rolling temperature is 890 - 910 °C. In the present invention, during the continuous rolling, the single-pass deformation amount is preferably 10% - 15%, more preferably 12 - 14%.

[0053] In the present invention, the temperature of the second annealing is preferably 860 - 880 °C, more preferably 860 °C, and the holding time is preferably 1 - 4 h, more preferably 2 h. In the present invention, the second annealing is preferably carried out under a protective gas, and the protective gas preferably includes nitrogen.

[0054] In the present invention, after the second annealing, cooling is preferably further included. In the present invention, the target temperature of the cooling is preferably 200 °C. In the present invention, the cooling is preferably furnace cooling.

[0055] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0056] Example 1

[0057] By mass percentage, the composition of the M2 high-speed steel bar wire is: C = 0.89%, Si = 0.30%, Mn = 0.30%, Cr = 4.05%, W = 5.95%, Mo = 4.93%, V = 1.97%, Nb = 0.02%, and the balance is Fe and unavoidable impurities.

[0058] After the alloy raw materials are initially melted in an electric arc furnace, secondary refining is carried out, and vacuum degassing is carried out during the secondary refining to obtain molten steel.

[0059] The continuous casting tundish is baked for 5 h. After the temperature of the continuous casting tundish reaches 1490 °C, the molten steel is transferred into the continuous casting tundish, and a tundish covering agent is added to the molten steel. Then, the molten steel in the continuous casting tundish is flowed into the continuous casting mold through an immersion nozzle. The temperature difference between the inlet and outlet water of the mold is 7 °C, the water flow rate is 95 t / h, the secondary cooling water adopts an automatic control mode, the specific water volume is 7 L / kg, and a mold powder is added for control. After solidification, a continuous casting bloom with a size of 180 mm × 180 mm is continuously drawn and straightened at a speed of 1.15 - 1.20 m / min by an R9m arc continuous casting machine. At the same time, the vibration amplitude of the mold is turned on to be 2 mm, and the vibration frequency is 95 Hz.

[0060] The continuously cast square billet cut to a fixed length is directly hot-transported to an annealing furnace for annealing process treatment. The annealing temperature is 860 °C, and after holding for 6 h, it is cooled in the furnace and taken out of the furnace when the temperature drops below 400 °C. Then, the continuously cast square billet is sent into a continuous rolling mill. The starting rolling temperature is 1100 °C, the finishing rolling temperature of rough rolling is 980 °C, the finishing rolling temperature of finish rolling is 900 °C, the single-pass deformation is 10%, and it is rolled to a finished size of steel bar wire. The M2 steel bar wire after continuous rolling is directly hot-transported to a bell-type protective atmosphere annealing furnace for annealing process treatment. The annealing temperature is 860 °C, and after holding for 2 h, it is cooled in the furnace and taken out of the furnace when the temperature drops to 200 °C.

[0061] Comparative Example 1

[0062] By mass percentage, the composition of the M2 high-speed steel bar wire is: C = 0.86%, Si = 0.30%, Mn = 0.30%, Cr = 4.20%, W = 6.05%, Mo = 4.95%, V = 2.00%, and the balance is Fe and unavoidable impurities.

[0063] The M2 high-speed steel is prepared by the process route of electric arc furnace → ladle furnace refining → vacuum degassing → ingot casting → annealing → hot rolling → annealing.

[0064] Figure 1 It is the OM diagram of the carbide of the M2 high-speed steel bar wire prepared in Example 1; Figure 2 It is the SEM diagram of the carbide of the M2 high-speed steel bar wire prepared in Example 1; Figure 3 It is the OM diagram of the carbide of the M2 high-speed steel bar wire prepared in Comparative Example 1; Figure 4 It is the SEM diagram of the carbide of the M2 high-speed steel bar wire prepared in Comparative Example 2. It can be seen from Figures 1 to 4 that: the carbide size of the M2 high-speed steel prepared by the present invention is finer.

[0065] Test Example

[0066] The present invention conducts performance tests on the M2 high-speed steel bar wires prepared in Example 1 and Comparative Example 1, and the test results are shown in Table 1.

[0067] Table 1 Performance of the M2 high-speed steel bar wires prepared in Example 1 and Comparative Example 1

[0068]

[0069] In summary: The central porosity level of the M2 high-speed steel prepared in Example 1 is the same as that of ingot casting, the central segregation is slightly higher, there are no shrinkage cavities, no cracks, no network carbides, and the carbide size is finer.

[0070] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements can be made, and these improvements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of M2 high-speed steel, characterized in that, The steps are as follows: Provide molten steel according to the composition of the M2 high-speed steel; Perform arc continuous casting on the molten steel to obtain a continuous casting billet; Subject the continuous casting billet to first annealing, continuous rolling, and second annealing in sequence to obtain the M2 high-speed steel; The arc continuous casting includes molten steel transfer, refrigeration forming, and straightening in sequence; When the molten steel is transferred, the tapping temperature of the molten steel is 1500 - 1600 °C; The refrigeration forming includes cooling water cooling and secondary cooling zone cooling in sequence; The temperature difference between the inlet and outlet of the cooling water is 6 - 8 °C; the specific water volume in the secondary cooling zone is 6 - 8 L / kg; The speed of the straightening is 0.80 - 1.40 m / min; The temperature of the first annealing is 860 - 880 °C, and the holding time is 4 - 8 h; the continuous rolling includes rough rolling and finish rolling in sequence; The initial rolling temperature of the rough rolling is 1090 - 1110 °C; the final rolling temperature is 970 - 990 °C; The final rolling temperature of the finish rolling is 890 - 910 °C; During the continuous rolling, the single-pass deformation amount is 10% - 15%; The temperature of the second annealing is 860 - 880 °C, and the holding time is 1 - 4 h.

2. The preparation method according to claim 1, wherein The obtaining of the molten steel includes the following steps: Smelt alloy raw materials corresponding to the chemical element composition of the M2 high-speed steel to obtain molten steel. M2 high-speed steel prepared by the preparation method according to any one of claims 1 to 2, characterized in that, The carbide size in the M2 high-speed steel is 5 - 15 μm.

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