Method for improving toughness of wear-resistant medium plate

Abstract

The invention provides a method for improving the toughness of a wear-resistant medium plate, and belongs to the technical field of steel smelting. The preparation method of the wear-resistant medium-thickness plate comprises the following steps: firstly, obtaining molten iron meeting the following requirements: less than or equal to 0.030 wt% of C, 0.5 wt%-0.7 wt% of Si, 12 wt%-14 wt% of Cr, 0.01 wt%-0.03 wt% of Ti, less than or equal to 0.030 wt% of P, less than or equal to 0.002 wt% of S, less than or equal to 0.6 wt% of Ni, 0.1 wt%-0.3 wt% of Mo, 0.1 wt%-0.3 wt% of Cu, 0.01 wt%-0.03 wt% of Nb, 0.05 wt%-0.10 wt% of V, 0.20 wt%-0.215 wt% of N and the balance of iron; then aluminum wires are added, a casting blank is obtained through casting, and the casting blank is subjected to heating treatment and descaling; and then carrying out hot rolling, rapid tempering and two times of tempering to obtain the wear-resistant medium-thickness plate. According to the method for improving the toughness of the wear-resistant medium-thickness plate, the toughness of the wear-resistant steel medium-thickness plate is remarkably improved by adjusting the element proportion in the alloy and optimizing the heat treatment process, and meanwhile the hardness and wear resistance of the wear-resistant steel medium-thickness plate are kept.

Description

Technical Field

[0001] The present invention relates to the technical field of steel smelting, and particularly relates to a method for improving the toughness of wear-resistant medium and heavy plates. Background Art

[0002] Wear-resistant steel medium and heavy plates are widely used in fields such as engineering machinery and mining equipment, and are required to have high hardness, high wear resistance and good toughness. However, traditional wear-resistant steel medium and heavy plates often lead to a decrease in toughness while increasing hardness and wear resistance, affecting their service life and safety performance. In the prior art, alloying elements such as niobium and vanadium are usually added to increase the strength of steel, but excessive addition will result in a decrease in toughness. In addition, a high content of inclusions in steel will also affect its purity, thereby reducing toughness. Therefore, how to improve the toughness of wear-resistant steel medium and heavy plates without significantly reducing hardness and wear resistance has become an urgent technical problem in this field.

[0003] For example, Patent CN105385835B discloses a heat treatment method for improving the strength and toughness of medium and heavy plate high-strength steel parts: including the following steps: 1) homogenizing the steel parts; 2) quickly quenching the steel parts treated in step 1) into an oil bath for oil quenching, and then performing austenitizing treatment; 3) quickly quenching the steel parts treated in step 2) into a salt bath for quenching, and then cooling; 4) performing cryogenic treatment on the steel parts treated in step 3), and then performing heat preservation treatment. For medium and heavy plate steel parts, on the premise of ensuring high strength, carbon distribution and cryogenic tempering treatment are adopted, and the tempering temperature and time are reasonably designed, greatly improving the impact toughness of the steel parts, thereby improving the strength and toughness of medium and heavy plate high-strength steel parts.

[0004] Patent CN115261744B discloses a high-toughness low-chromium ferritic stainless steel medium and heavy plate and its manufacturing method, and the mass percentages of component elements satisfy: C: ≤0.08%; N: ≤0.08%; Si: ≤0.5%; Cr: 12% - 14%; P: ≤0.04%; S: ≤0.005%; Al: 0.10% - 0.20%; Mn: 0.6% - 1.0%; Ni ≤0.6%; where C + N ≤0.08%; the chromium equivalent Creq satisfies: 10 ≤ Creq ≤ 12, Creq = Cr% + 2Si% - 2Ni% - Mn% - 15N% - 30C%.

[0005] However, the low-temperature toughness of the above alloys is still poor and cannot meet the use requirements. Summary of the Invention

[0006] In view of this, the present invention provides a method for improving the toughness of wear-resistant medium and heavy plates, adjusting the content of elements to improve the purity of steel, and optimizing the heat treatment process, significantly improving the toughness of wear-resistant steel medium and heavy plates while maintaining their hardness and wear resistance.

[0007] The method for improving the toughness of wear-resistant medium-thick plates according to the present invention comprises the following steps:

[0008] (1) Add alloys to the molten iron, charge it into a converter for smelting, and then charge the molten steel into a vacuum VD furnace for refining and degassing, so that the mass percentages of various elements in the molten iron meet the following requirements:

[0009] C ≤ 0.030 wt%, Si 0.5 wt% - 0.7 wt%, Cr 12 wt% - 14 wt%, Ti 0.01% - 0.03%, P ≤ 0.030 wt%, S ≤ 0.002 wt%, Ni ≤ 0.6 wt%, Mo 0.1 wt% - 0.3 wt%, Cu 0.1 wt% - 0.3 wt%, Nb 0.01 wt% - 0.03 wt%, V 0.05 wt% - 0.10 wt%, N 0.20 wt% - 0.215 wt%, and the balance is iron;

[0010] (2) Add aluminum wire to the molten steel in step (1), continue heating, and cast to obtain a billet;

[0011] (3) Heat-treat the billet in a heating furnace, and then perform descaling;

[0012] (4) Hot-roll the heat-treated billet, and then quickly cool it to room temperature;

[0013] (5) Temper the hot-rolled steel plate for the first time, air-cool it to room temperature, then perform the second tempering, and air-cool it to room temperature to obtain a wear-resistant medium-thick plate.

[0014] Preferably, the smelting temperature in step (1) is 1350°C - 1450°C.

[0015] Preferably, the addition amount of the aluminum wire in step (2) is 0.1 wt% - 0.3 wt% of the molten steel.

[0016] Preferably, the heating temperature in step (2) is 1350°C - 1400°C, and the heating time is 0.5 - 1 h.

[0017] Preferably, the heating temperature in step (3) is 1100°C - 1150°C, and the heating time is 30 min - 120 min.

[0018] Preferably, the descaling pressure in step (3) is 20 MPa.

[0019] Preferably, the starting rolling temperature of the hot rolling in step (4) is 1020°C - 1100°C, the finishing rolling temperature is 850°C - 900°C; and the cooling rate is 10°C / min.

[0020] Preferably, the hot rolling in step (4) is carried out for 4 - 5 passes, and the reduction ratio per pass is less than 20%.

[0021] Preferably, the temperature of the first tempering in step (5) is 500°C - 550°C, and the holding time is 1.5 h - 2 h.

[0022] Preferably, the temperature of the second tempering in step (5) is 480°C - 500°C, and the holding time is 1.5 h - 2 h.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention provides a method for improving the toughness of wear-resistant medium and heavy plates. By adjusting the element ratio in the alloy and optimizing the heat treatment process, the toughness of the wear-resistant medium and heavy plates is significantly improved, while maintaining their hardness and wear resistance.

[0025] The wear-resistant medium and heavy plates of the present application include the following elements:

[0026] Niobium is a strong carbide-forming element and can also dissolve in the steel matrix in small amounts. It forms stable NbC or Nb4C3 in the steel and is finely dispersed on the matrix, playing a role in precipitation strengthening. At the same time, it can prevent the overheating of the steel, reduce the aging sensitivity of the steel, and improve the welding performance of the steel. Vanadium is a strong carbide-forming element and can also dissolve in the steel matrix in small amounts. It forms stable V4C3 or VC in the steel and is finely dispersed on the matrix, playing a role in precipitation strengthening. However, the addition of Nb and V will have an adverse effect on the toughness of the alloy. The present application limits the amounts of Nb and V and adds a small amount of Ti to improve the low-temperature toughness of the steel plate while ensuring hardness and wear resistance. In addition, the present application limits the cooling rate and adopts a two-step tempering process to further improve the toughness of the alloy. Specific Embodiments

[0027] The present invention provides a method for improving the toughness of wear-resistant medium and heavy plates, and the steps are as follows:

[0028] (1) Add alloys to the molten iron, charge into a converter for smelting, and obtain molten steel, which is charged into a vacuum VD furnace for refining and degassing to make the mass percentages of each element in the molten iron meet the following requirements:

[0029] C ≤ 0.030 wt%, Si 0.5 wt% - 0.7 wt%, Cr 12 wt% - 14 wt%, Ti 0.01% - 0.03%, P ≤ 0.030 wt%, S ≤ 0.002 wt%, Ni ≤ 0.6 wt%, Mo 0.1 wt% - 0.3 wt%, Cu 0.1 wt% - 0.3 wt%, Nb 0.01 wt% - 0.03 wt%, V 0.05 wt% - 0.10 wt%, N 0.20 wt% - 0.215 wt%, and the balance is iron;

[0030] (2) Add 0.2 wt% aluminum wire to the molten steel in step (1), continue heating at 1360 °C for 1 h, and cast to obtain a slab with a thickness of 100 mm.

[0031] (3) Heat the slab in a heating furnace at 1130 °C for 40 min, and then descale it under 20 MPa.

[0032] (4) Hot-roll the heat-treated slab, and then rapidly cool it to room temperature at a rate of 10 °C / min; the starting rolling temperature of the hot rolling is 1100 °C, and the finishing rolling temperature is 890 °C; the hot rolling is carried out for 4 - 5 passes, and the reduction ratio per pass is less than 25%.

[0033] (5) Temper the hot-rolled steel plate for the first time and air-cool it to room temperature, and then carry out the second tempering and air-cool it to room temperature; the temperature of the first tempering is 520 °C and the holding time is 1.5 h; the temperature of the second tempering is 480 °C and the holding time is 1.5 h to obtain a wear-resistant medium-thick plate.

[0034] The present invention will be further described below in conjunction with embodiments.

[0035] In Examples 1 - 3, the elemental mass contents of the molten iron in step (1) are shown in Table 1.

[0036] Table 1

[0037]

[0038]

[0039] Comparative Example 1

[0040] A method for improving the toughness of a wear-resistant medium-thick plate, the raw material composition and preparation method are the same as those in Example 1, the difference is that Comparative Example 1 does not contain Ti.

[0041] Comparative Example 2

[0042] A method for improving the toughness of a wear-resistant medium-thick plate, the raw material composition and preparation method are the same as those in Example 1, the difference is that Comparative Example 2 does not contain Nb.

[0043] Comparative Example 3

[0044] A method for improving the toughness of a wear-resistant medium-thick plate, the raw material composition and preparation method are the same as those in Example 1, the difference is that the Nb content in Comparative Example 3 is 0.037 wt%.

[0045] Comparative Example 4

[0046] A method for improving the toughness of a wear-resistant medium-thick plate, the raw material composition and preparation method are the same as those in Example 1, the difference is that Comparative Example 4 does not contain V.

[0047] Comparative Example 5

[0048] A method for improving the toughness of wear-resistant medium-thick plates, with the raw material composition and preparation method being the same as those in Example 1, except that in Comparative Example 5, the V content is 0.15 wt%.

[0049] Comparative Example 6

[0050] A method for improving the toughness of wear-resistant medium-thick plates, with the raw material composition and preparation method being the same as those in Example 1, except that in step (4) of Comparative Example 6, the cooling rate is 5 °C / min.

[0051] Comparative Example 7

[0052] A method for improving the toughness of wear-resistant medium-thick plates, with the raw material composition and preparation method being the same as those in Example 1, except that in Comparative Example 7, the temperature of the first tempering is 580 °C.

[0053] Comparative Example 8

[0054] A method for improving the toughness of wear-resistant medium-thick plates, with the raw material composition and preparation method being the same as those in Example 1, except that the rolling method in Comparative Example 8 is different from that in Example 1.

[0055] The thickness (mm) of the steel plates after each pass of rolling in Examples 1 - 3 and Comparative Example 8 is shown in Table 2, and the rolling process of the remaining comparative examples is the same as that in Example 1.

[0056] Table 2

[0057] Example 1 Example 2 Example 3 Comparative Example 8 Slab thickness 100 100 100 100 The first pass 82 85 81 78 The second pass 75 73 63 50 The third pass 64 62 50 40 The fourth pass 51 50 40 - The fifth pass 40 40 - -

[0058] According to the national standards of GB / T228, GB / T231, and GB / T229, the performance of the medium-thick plates prepared in Examples 1 - 3 and Comparative Examples 1 - 8 was tested, and the results are shown in Table 3.

[0059] Table 3

[0060] Thickness Tensile strength / MPa Hardness / HBW Impact energy at -20°C / J Example 1 40mm 1127 467 147 Example 2 40mm 1109 459 137 Example 3 40mm 1122 462 141 Comparative Example 1 40mm 1085 421 103 Comparative Example 2 40mm 1118 418 120 Comparative Example 3 40mm 1121 434 121 Comparative Example 4 40mm 1119 432 115 Comparative Example 5 40mm 1124 457 109 Comparative Example 6 40mm 1117 435 125 Comparative Example 7 40mm 1109 427 131 Comparative Example 8 40mm 1120 441 112

[0061] 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 and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for improving the toughness of wear-resistant medium and thick plates, characterized in that: The following steps are involved: (1) Add alloy to molten iron, put it into converter for smelting, and put the obtained molten steel into vacuum VD furnace for refining and degassing, so that the mass percentage of each element in the molten iron meets the following requirements: C≤0.030wt%, Si 0.5wt%-0.7wt%, Cr 12wt%-14wt%, Ti 0.01%-0.03%, P≤0.030wt%, S≤0.002wt%, Ni≤0.6wt%, Mo 0.1wt%-0.3wt%, Cu 0.1wt%-0.3wt%, Nb0.01wt%-0.03wt%, V 0.05wt%-0.10wt%, N 0.20wt%-0.215wt%, and the balance is iron; (2) adding aluminum wire to the molten steel in step (1), continuing heating, and casting to obtain a cast ingot; (3) heating the ingot in a heating furnace and then descaling it; (4) hot rolling the heated ingot and then rapidly cooling it to room temperature; (5) After hot rolling, the steel plate is tempered for the first time and air-cooled to room temperature, and then tempered for the second time and air-cooled to room temperature to obtain a wear-resistant medium and thick plate.

2. The method for improving the toughness of wear-resistant medium and thick plates according to claim 1, characterized in that: The smelting temperature in step (1) is 1350°C-1450°C.

3. The method for improving the toughness of wear-resistant medium and thick plates according to claim 1, characterized in that: The amount of aluminum wire added in step (2) is 0.1wt% to 0.3wt% of the molten steel.

4. The method for improving the toughness of wear-resistant medium and thick plates according to claim 1, characterized in that: The heating temperature in step (2) is 1350° C.-1400° C., and the heating time is 0.5-1 h.

5. The method for improving the toughness of wear-resistant medium and thick plates according to claim 1, characterized in that: The heating temperature in step (3) is 1100° C.-1150° C., and the heating time is 30 min-120 min.

6. The method for improving the toughness of wear-resistant medium and thick plates according to claim 1, characterized in that: The descaling pressure in step (3) is 20 MPa.

7. The method for improving the toughness of wear-resistant medium and thick plates according to claim 1, characterized in that: In step (4), the starting temperature of the hot rolling is 1020°C-1100°C, and the final rolling temperature is 850°C-900°C; the cooling rate is 10°C / min.

8. The method for improving the toughness of wear-resistant medium and thick plates according to claim 1, characterized in that: The hot rolling in step (4) is performed in 4-5 passes, with the reduction rate of each pass being less than 20%.

9. The method for improving the toughness of wear-resistant medium and thick plates according to claim 1, characterized in that: The temperature of the first tempering in step (5) is 500°C-550°C, and the temperature is kept for 1.5h-2h.

10. The method for improving the toughness of wear-resistant medium and thick plates according to claim 1, characterized in that: The temperature of the second tempering in step (5) is 480°C-500°C, and the heat preservation time is 1.5h-2h.

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