Wear-resistant alloy for roller and preparation method of wear-resistant alloy

Abstract

The invention provides a wear-resistant alloy for a roller and a preparation method thereof, and relates to the technical field of metal material preparation, and the wear-resistant alloy for the roller comprises the following components in percentage by weight: 3-3.5 wt% of C, 8.5-9 wt% of V, 3-3.5 wt% of Cr, 0.5-1 wt% of Mn, 0.5-1 wt% of Si, 0.5-1 wt% of Al, 0.5-1 wt% of Ni, 0-0.5 wt% of Cu, 1-1.5 wt% of Co, 0.5-1 wt% of Nb, 0-0.5 wt% of B, 0-0.1 wt% of N, less than or equal to 0.03 wt% of P, less than or equal to 0.03 wt% of S and the balance of Fe. By adding C and V and controlling the content of C and V, a micron-scale and nano-scale multi-scale VC structure is formed in the alloy; wherein the micron-sized VC phase improves the strength and hardness of the alloy by refining grains; the nanoscale VC phase remarkably improves the hardness, the wear resistance and the thermal stability of the alloy, meanwhile, the V element is introduced by adding ferrovanadium to strengthen the alloy, the strengthening effect of traditional rare and precious metals W and Mo is replaced, and formation of brittle intermetallic compounds can be reduced, so that the toughness and the impact resistance of the alloy are ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material preparation, and in particular relates to a wear-resistant alloy for a rolling roller and a preparation method thereof. Background Art

[0002] At present, two major types of wear-resistant alloy materials are mainly used in the field of roller manufacturing: traditional cast steel / forged steel materials (such as 60CrNiMo series) and high-speed steel / high-boron alloy centrifugal casting materials. Although traditional materials have mature technology and low cost, they cannot meet the dual requirements of high wear resistance of the roller working surface and high toughness of the core due to their completely consistent internal and external components. Although the high-speed steel / high-boron alloy rollers prepared by centrifugal casting have a high surface hardness, during the production process, the hard phase will be segregated due to density differences, resulting in insufficient material interface bonding strength. At the same time, the diffusion of alloy elements to the core will cause the core material to become brittle, which not only increases the risk of roller breakage, but also makes it difficult to effectively recycle waste rollers.

[0003] From a materials science perspective, improving wear resistance requires the presence of a large amount of high-hardness carbides / borides, but these hard phases will destroy the continuity of the metal matrix and significantly reduce the impact toughness of the material; and to ensure sufficient toughness it is necessary to maintain the integrity of the matrix, which will inevitably limit the content of the hard phase, thereby restricting the improvement of wear resistance.

[0004] In summary, the problem with the prior art in preparing wear-resistant alloys for rolling mill rolls is that they cannot have both high wear resistance and toughness. Summary of the invention

[0005] Therefore, the present invention provides a wear-resistant alloy for a rolling mill and a preparation method thereof, which can solve the technical problem in the prior art that the wear-resistant alloy is difficult to have both high wear resistance and high toughness.

[0006] In order to solve the above problems, the present invention provides a wear-resistant alloy for a rolling mill roll. The components of the wear-resistant alloy for a rolling mill roll are, in weight percentage, C3-3.5wt%, V8.5-9wt%, Cr3-3.5wt%, Mn0.5-1wt%, Si0.5-1wt%, Al0.5-1wt%, Ni0.5-1wt%, Cu0-0.5wt%, Co1-1.5wt%, Nb0.5-1wt%, B0-0.5wt%, N0-0.1wt%, P≤0.03wt%, S≤0.03wt%, and the balance is Fe.

[0007] Furthermore, the microstructure of the wear-resistant alloy for rolling mill rolls includes martensite, austenite and VC;

[0008] Among them, the VC includes micron-scale VC and nano-scale VC; the nano-scale VC has a coherent relationship with the austenite; among them, the micron-scale VC is spherical, with a diameter of 0.5 - 5 μm; the nano-scale VC is spherical, with a diameter of 10 - 200 nm.

[0009] Furthermore, in the microstructure of the wear-resistant alloy for rolls: the volume fraction of the VC is 5 - 15%; and / or

[0010] In the VC: the volume fraction of the martensite is 65 - 75%; the volume fraction of the micron-scale VC is 60 - 80%; the volume fraction of the nano-scale VC is 20 - 40%.

[0011] Furthermore, the hardness of the wear-resistant alloy for rolls is 68 - 70 HRC, the compressive strength is 2700 - 3000 MPa, and the impact toughness Aku is 8 - 12 J / cm 2 , and the wear rate is lower than 4.5×10 -6 mm 3 ·N -1 ·m -1 .

[0012] On the other hand, the present invention also provides a preparation method for the wear-resistant alloy for rolls described in any one of the above, including the following steps:

[0013] Step 1): The alloy raw materials are successively subjected to melting treatment and remelting treatment to obtain an ingot;

[0014] Step 2): The ingot is successively subjected to quenching treatment and tempering treatment to obtain the wear-resistant alloy for rolls.

[0015] Furthermore, in the step 1), the melting treatment is carried out by vacuum electric frequency induction melting; and / or

[0016] The raw material for providing the V element is selected as ferroniobium.

[0017] Furthermore, in the step 1), the remelting treatment is carried out by vacuum electroslag remelting;

[0018] Preferably, the current density of the vacuum electroslag remelting is 10 - 15 A / cm 2 ; the voltage of the vacuum electroslag remelting is 40 - 45 V; the current of the vacuum electroslag remelting is 6500 - 7500 A; the remelting speed of the vacuum electroslag remelting is 40 - 80 kg / h.

[0019] Furthermore, in the step 2), the steps of the quenching treatment include:

[0020] The ingot is subjected to tube sealing treatment, then heated to 800 - 850 °C, held for 1 - 1.5 h, then heated to 1050 - 1100 °C, held for 1 - 1.5 h, and then subjected to cryogenic treatment to obtain the alloy after quenching treatment;

[0021] The cryogenic treatment uses liquid nitrogen cryogenic treatment.

[0022] Preferably, the heating rate when heating to 1050 - 1100 °C is 2 - 3 times that when heating to 800 - 850 °C; Further preferably, the heating rate when heating to 800 - 850 °C is 30 - 50 °C / h; The heating rate when heating to 1050 - 1100 °C is 100 - 150 °C / h.

[0023] Further, in the step 2), the steps of the tempering treatment include:

[0024] The alloy after quenching treatment is subjected to tube sealing treatment, then heated to 250 - 270 °C, held for 2 - 2.5 h to obtain the alloy after tempering treatment;

[0025] Preferably, the heating rate is 30 - 50 °C / h; and / or

[0026] Further, in the step 2), before the step of quenching the ingot, it further includes: rough machining the ingot; and / or

[0027] After the step of tempering the ingot, it further includes: finishing the alloy after tempering treatment.

[0028] A wear-resistant alloy for rolls and its preparation method provided by the present invention have the following beneficial effects:

[0029] 1. On the one hand, the present invention provides a wear-resistant alloy for rolls. By adding C and V and controlling their contents, a multi-scale VC structure with micron and nano scales is formed in the alloy; Among them, the micron-scale VC phase improves the strength and hardness of the alloy by refining grains; The nano-scale VC phase significantly improves the hardness, wear resistance and thermal stability of the alloy. At the same time, in this application, V element is introduced by adding ferroniobium to strengthen the alloy, replacing the strengthening effect of traditional rare and precious metals W and Mo, which can reduce the formation of brittle intermetallic compounds, thereby ensuring the toughness and impact resistance of the alloy.

[0030] 2. On the other hand, the present invention provides a method for preparing the wear-resistant alloy for rolls, comprising the following steps: successively performing smelting treatment and remelting treatment on alloy raw materials to obtain an ingot; successively performing quenching treatment, cryogenic treatment and tempering treatment on the ingot to obtain the wear-resistant alloy for rolls; it should be noted that micron-sized VC is formed in-situ in the ingot to ensure obtaining a martensite structure with high hardness and high solid solubility through quenching + cryogenic treatment; the tempering treatment causes a small amount of martensite to transform into tempered austenite, and nano-sized coherent VC phases are precipitated after the tempering treatment, while ensuring the high hardness of the alloy, improving the toughness and stability of the material; at the same time, the tempering treatment further promotes the transformation of retained austenite into martensite, thereby improving the hardness and dimensional stability of the material; based on the above method, a microstructure with tempered martensite as the matrix and fine carbides dispersed therein is obtained, thereby significantly improving the comprehensive mechanical properties of the alloy while avoiding the hazards of thermal stress and brittleness.

[0031] 3. Further, after the alloy raw materials are subjected to smelting treatment, remelting treatment is carried out to reduce defects such as holes and cracks in the ingot, thereby improving the uniformity of the structure and properties of the alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. The drawings in the following description are only exemplary, and for those of ordinary skill in the art, without creative efforts, other implementation drawings can be obtained by extending according to the provided drawings.

[0033] Figure 1 It is a cross-sectional optical microscope image of the ingot in Embodiment 1 of the present invention;

[0034] Figure 2 It is the SEM and TEM microstructure morphology diagrams of the wear-resistant alloy for rolls obtained in Embodiment 2 of the present invention;

[0035] Figure 3 It is a cost comparison diagram of the wear-resistant alloy for rolls obtained in Embodiment 3 of the present invention and the traditional alloy for rolls;

[0036] Figure 4 A comparison diagram of the surface microstructure morphology of the wear-resistant alloy for rolls obtained in Embodiment 1 and Comparative Example 1 of the present invention;

[0037] Figure 5 It is a hardness and compressive strength comparison diagram of the wear-resistant alloy for rolls obtained in Embodiment 1 and Comparative Example 1 of the present invention;

[0038] Figure 6 It is a wear rate and wear loss weight comparison diagram of the wear-resistant alloy for rolls obtained in Embodiment 1 and Comparative Example 2 of the present invention;

[0039] Figure 7 It is a comparison chart of the impact toughness of the wear-resistant alloy for rolls obtained in Example 1 of the present invention and Comparative Example 3;

[0040] Figure 8 It is a comparison chart of the microstructures of the wear-resistant alloy for rolls obtained in Example 1 of the present invention and Comparative Example 3;

[0041] Figure 9 It is a comparison chart of the as-cast structures of the wear-resistant alloy for rolls obtained in Example 1 of the present invention and Comparative Example 4. Detailed implementation manners

[0042] In order to more clearly illustrate the implementation manners of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the implementation manners or the prior art. The drawings in the following description are merely exemplary. For those of ordinary skill in the art, without creative efforts, other implementation drawings can also be obtained based on the provided drawings.

[0043] The wear-resistant alloy material for rolls has great application potential. The present invention constructs a multi-scale coherent VC wear-resistant phase to replace the solid solution effect of W and Mo, and synergistically improves the strength, toughness and wear resistance of the alloy. At the same time, in order to ensure the controllable cost of the alloy, alloy V is added by ferroniobium, and the alloy does not contain precious metal strengthening elements such as W and Mo, and solely relies on the coherent VC / matrix interface to improve the comprehensive performance of the alloy. In addition, it should be noted that: there are mainly three reasons why the solution of the present invention can retain good strength, toughness and wear resistance: (1) The nano-scale coherent VC increases the precipitation phase combination strength and its anti-wear and anti-shedding ability; (2) The micron-scale VC refines the grains and improves the toughness; (3) Vacuum electric frequency induction heating and vacuum electroslag remelting reduce defects such as holes and cracks. The specific solutions are as follows:

[0044] The present invention provides a wear-resistant alloy for rolls. By weight percentage, the components of the wear-resistant alloy for rolls are: C 3-3.5 wt%, V 8.5-9 wt%, Cr 3-3.5 wt%, Mn 0.5-1 wt%, Si 0.5-1 wt%, Al 0.5-1 wt%, Ni 0.5-1 wt%, Cu 0-0.5 wt%, Co 1-1.5 wt%, Nb 0.5-1 wt%, B 0-0.5 wt%, N 0-0.1 wt%, P ≤ 0.03 wt%, S ≤ 0.03 wt%, and the balance is Fe.

[0045] The microstructure of the wear-resistant alloy for rolls includes martensite, austenite and VC; VC includes micron-scale VC and nano-scale VC; the nano-scale VC has a coherent relationship with austenite; among them, the micron-scale VC is spherical, and its diameter is 0.5-5 μm.

[0046] In the microstructure of the wear-resistant alloy for rolls: the volume fraction of martensite is 65 - 75%; the volume fraction of VC is 5 - 15%; in VC: the volume fraction of micron-sized VC is 60 - 80%; the volume fraction of nano-sized VC is 20 - 40%.

[0047] The hardness of the wear-resistant alloy for rolls is 68 - 70 HRC, the compressive strength is 2700 - 3000 MPa, and the impact toughness Aku is 8 - 12 J / cm 2 , and the wear rate is lower than 4.5×10 -6 mm 3 ·N -1 ·m -1 .

[0048] On the other hand, the present invention also provides a preparation method of the wear-resistant alloy for rolls according to any one of the above, comprising the following steps:

[0049] Step 1): successively carry out smelting treatment and remelting treatment on the alloy raw materials to obtain an ingot;

[0050] Specifically, this step is: using vacuum electric frequency induction to smelt the alloy raw materials, obtaining an alloy ingot after casting, and then carrying out vacuum electroslag remelting on the alloy ingot, obtaining an ingot after casting; wherein, the current density of the vacuum electroslag remelting is 10 - 15 A / cm 2 , the voltage is 40 - 45 V, the current is 6500 - 7500 A, and the remelting speed is 40 - 80 kg / h;

[0051] Among them, when using vacuum electric frequency induction to smelt the alloy raw materials, the temperature is 1500 - 1600 °C (exceeding the VC dissolution temperature (about 1300 °C)), and the time is 20 - 60 min (including: the melting stage of 10 - 30 min,, the refining stage of 10 - 20 min).

[0052] Step 2): successively carry out quenching treatment, tempering treatment and cryogenic treatment on the ingot to obtain a wear-resistant alloy;

[0053] Specifically, this step is: carrying out encapsulation treatment on the ingot, then heating it to 800 - 850 °C at a heating rate of 30 - 50 °C / h, holding for 1 - 1.5 h, and then heating it to 1050 - 1100 °C at a heating rate of 100 - 150 °C / h, holding for 1 - 1.5 h, and obtaining the alloy after quenching treatment after cryogenic treatment; carrying out encapsulation treatment on the alloy after quenching treatment, then heating it to 250 - 270 °C at a heating rate of 30 - 50 °C / h, and obtaining the alloy after tempering treatment after holding for 2 - 2.5 h; then carrying out air cooling on the alloy after tempering treatment to obtain a wear-resistant alloy.

[0054] Based on the above method, micron-sized VC is formed in-situ in the ingot, and a high-hardness martensite structure is obtained through quenching treatment; tempering treatment causes a small amount of martensite to transform into tempered austenite, and nano-sized coherent VC is precipitated, which improves the toughness and stability of the material while ensuring the high hardness of the alloy; cryogenic treatment is to further promote the transformation of retained austenite into martensite, thereby improving the hardness and dimensional stability of the material.

[0055] Among them, the micron-sized VC phase improves the strength and hardness of the alloy by refining the grains; the nano-sized VC phase significantly improves the hardness, wear resistance and thermal stability of the alloy. At the same time, in this application, V element is introduced by adding ferroniobium to strengthen the alloy, replacing the strengthening effect of traditional rare and precious metals W and Mo, which can reduce the formation of brittle intermetallic compounds, thereby ensuring the toughness and impact resistance of the alloy. Therefore, through the above method, the application obtains a microstructure with tempered martensite as the matrix and fine carbides dispersed therein, thereby significantly improving the comprehensive mechanical properties of the alloy while avoiding the hazards of thermal stress and brittleness.

[0056] During the quenching treatment, a segmented heating method is adopted (that is, the sealed ingot is heated to 800 - 850 °C, held for 1 - 1.5 h and then heated to 1050 - 1100 °C, held for 1 - 1.5 h). Among them, during the heating and holding process at 800 - 850 °C, pre-dissolution and homogenization of the ingot are carried out. In this temperature range (below the complete formation temperature of austenite), eutectic carbides (such as M 7 C 3 、M 6 C) are partially dissolved, but high-melting-point carbides (such as VC, WC) remain stable; the dissolution of eutectic carbides can improve the stability of the matrix phase austenite and increase the martensite transformation temperature. The remaining VC / WC can still pin the grain boundaries and inhibit grain growth; at the same time, it reduces the agglomeration tendency of carbides in the subsequent high-temperature stage, forming fine transitional carbides (such as M 23 C 6 ), providing nucleation sites for subsequent austenitization; during the heating and holding process at 1050 - 1100 °C, the matrix can be completely austenitized. At the same time, the pre-dissolved carbides are further evenly distributed, inhibiting coarsening; and by controlling the solubility of carbon and alloying elements (such as V, Cr) in austenite, an appropriate amount of retained austenite can be retained after quenching, improving toughness. Direct high-temperature heating (such as directly rising to 1100 °C) easily leads to local over-dissolution or coarsening of carbides; abnormal growth of austenite grains; and aggravated segregation of elements at grain boundaries.

[0057] Among them, the heating rate when heating to 1050 - 1100 °C is 2 - 3 times that when heating to 800 - 850 °C; at the low - temperature stage (800 - 850 °C), the atomic diffusion rate is low, and slow heating is required to ensure the dissolution of carbides and the homogenization of composition (such as the diffusion activation energies of C and V are relatively high); meanwhile, the temperature gradient inside the ingot is large, and rapid heating is likely to cause cracking. Rapidly passing through the medium - temperature range (850 - 1000 °C) can avoid the precipitation of harmful carbides such as Cr 23 C 6 at the grain boundaries; and at high temperatures (1050 - 1100 °C), the diffusion rate increases significantly (following the Arrhenius equation), and rapid heating can reduce energy consumption and prevent excessive grain growth.

[0058] When melting and processing the alloy raw materials, pig iron and ferrovanadium are used as the sources of iron and vanadium. First, the pig iron is added to the furnace and melted, then desulfurization, deoxidation, primary refining, alloying by adding alloying components are carried out in sequence, and then ferrovanadium is added for secondary refining; among them, the batch order of adding alloying elements into the furnace during the alloying process is: Cr, Mn, Co, and other remaining components; the time interval between adding each batch of elements is 3 - 10 min, and after feeding, it is stirred evenly. An appropriate time interval ensures the full dissolution and uniform distribution of alloying elements, avoids segregation; adding in batches reduces element oxidation and improves utilization rate; at the same time, it avoids violent reactions and ensures the smoothness of the melting process.

[0059] Among them, ferrovanadium is an alloy of vanadium and iron. Compared with pure vanadium or other vanadium compounds (such as vanadium oxides), it is more easily and uniformly dissolved and distributed in the molten steel, reducing the risk of segregation; and the vanadium element in ferrovanadium has less loss during the smelting process, with a higher recovery rate, and can play the role of vanadium more effectively; in addition, ferrovanadium has a low price.

[0060] In some embodiments, the above - mentioned wear - resistant alloy is a wear - resistant alloy for rolls; after remelting treatment, the obtained ingot is subjected to rough machining to obtain a blank part in the shape of a roll; then the blank part is subjected to quenching treatment, tempering treatment, and cryogenic treatment in sequence, and finally, finish machining is carried out to obtain the wear - resistant alloy for rolls.

[0061] The present invention will be further described below with specific examples and comparative examples.

[0062] Among them, the alloying components are shown in Table 1.

[0063] Table 1 Chemical compositions (wt%) of the alloys in the examples and comparative examples of the present invention

[0064] C V Cr Mn Si Al Ni Cu Co Nb B N Fe Example 1 3.0 8.6 3.2 0.6 0.8 0.6 0.7 0.3 1.3 0.7 0.3 0.05 remainder Example 2 3.3 8.8 3 0.7 0.7 0.8 0.6 0.2 1.5 0.8 0.2 0.08 remainder Example 3 3.2 9.0 3.5 0.6 0.7 0.8 0.7 0.3 1.3 0.8 0.3 0.06 remainder Comparative Example 1 3.0 5.0 5.5 0.6 0.8 0.6 0.7 0.3 1.3 0.7 0.3 0.05 remainder Comparative Example 2 3.0 10 3.2 0.6 0.8 0.6 0.7 0.3 1.3 0.7 0.3 0.05 remainder Comparative Example 3 3.0 8.6 3.2 0.6 0.8 0.6 0.7 0.3 1.3 0.7 0.3 0.05 remainder Comparative Example 4 3.0 8.6 3.2 0.6 0.8 0.6 0.7 0.3 1.3 0.7 0.3 0.05 remainder

[0065] Example 1

[0066] This embodiment provides a preparation method of wear-resistant alloy for rolls, including the following steps:

[0067] Step 1): Prepare raw materials according to the alloy composition of Example 1 in Table 1; melt an alloy ingot by vacuum medium-frequency induction, and then perform vacuum electroslag remelting on the alloy ingot. After casting, an ingot is obtained; wherein, the current density of vacuum electroslag remelting is 12 A / cm 2 , the voltage is 45 V, the current is 7000 A, and the remelting speed is 60 kg / h;

[0068] Step 2): Perform rough machining on the ingot obtained in Step 1) to obtain a blank part in the shape of a roll; then perform sealing tube treatment on the blank part, and then heat it to 820 °C at a heating rate of 45 °C / h, hold for 1.2 h, and then heat it to 1050 °C at a heating rate of 120 °C / h, hold for 1.3 h, and perform liquid nitrogen cryogenic treatment to obtain the alloy after quenching treatment; perform sealing tube treatment on the alloy after quenching treatment, and then heat it to 260 °C at a heating rate of 50 °C / h, hold for 2.5 h to obtain the alloy after tempering treatment; then perform air cooling on the alloy after tempering treatment, and then perform finish machining to obtain the wear-resistant alloy for rolls.

[0069] The optical microscope morphology of the cross-section of the ingot in this embodiment is as Figure 1 shown. It can be found that the defect content is less than 1%, which is better than that of traditional cast alloy ingots. In the wear-resistant alloy obtained in this embodiment, the size of micron-level VC is 5 - 10 μm, the size of nano-level VC is 50 - 200 nm, it is in a dispersed spherical shape, and the volume fraction is 15 - 20%.

[0070] Example 2

[0071] This embodiment provides a preparation method of wear-resistant alloy for rolls, including the following steps:

[0072] Step 1): Prepare raw materials according to the alloy composition of Example 2 in Table 1; melt an alloy ingot by vacuum medium-frequency induction, and then perform vacuum electroslag remelting on the alloy ingot. After casting, an ingot is obtained; wherein, the current density of vacuum electroslag remelting is 10 A / cm 2 , the voltage is 43 V, the current is 7500 A, and the remelting speed is 80 kg / h;

[0073] Step 2): Rough process the ingot obtained in Step 1) to obtain a blank in the shape of a roll; then perform a pipe sealing treatment on the blank, and then heat it to 800 °C at a heating rate of 50 °C / h, hold for 1.2 h, then heat it to 1050 °C at a heating rate of 100 °C / h, hold for 1.5 h, and obtain the alloy after quenching treatment after cryogenic cooling with liquid nitrogen; perform a pipe sealing treatment on the alloy after quenching treatment, and then heat it to 265 °C at a heating rate of 50 °C / h, hold for 2.2 h to obtain the alloy after tempering treatment; then air-cool the alloy after tempering treatment, and then perform a finish machining treatment to obtain the wear-resistant alloy for rolls.

[0074] In this embodiment, the SEM and TEM microstructural morphologies of the heat-treated alloy are as Figure 2 shown. It can be found that the microstructure of the alloy is composed of micron-scale VC, nano-scale VC, martensite, and austenite matrix, and the multi-scale VC and the surrounding austenite matrix are in a coherent relationship, significantly improving the stability of the wear-resistant phase.

[0075] Example 3

[0076] This embodiment provides a preparation method for a wear-resistant alloy for rolls, including the following steps:

[0077] Step 1): Prepare raw materials according to the alloy composition in Example 3 of Table 1; melt an alloy ingot by vacuum intermediate frequency induction, and then perform vacuum electroslag remelting on the alloy ingot, and obtain an ingot after casting; wherein, the current density of the vacuum electroslag remelting is 10 A / cm 2 , the voltage is 45 V, the current is 7000 A, and the remelting speed is 70 kg / h;

[0078] Step 2): Rough process the ingot obtained in Step 1) to obtain a blank in the shape of a roll; then perform a pipe sealing treatment on the blank, and then heat it to 820 °C at a heating rate of 45 °C / h, hold for 1.5 h, then heat it to 1050 °C at a heating rate of 120 °C / h, hold for 1.2 h, and obtain the alloy after quenching treatment after cryogenic cooling with liquid nitrogen; perform a pipe sealing treatment on the alloy after quenching treatment, and then heat it to 260 °C at a heating rate of 35 °C / h, hold for 2.4 h to obtain the alloy after tempering treatment; then air-cool the alloy after tempering treatment, and then perform a finish machining treatment to obtain the wear-resistant alloy for rolls.

[0079] The cost comparison between the wear-resistant alloy obtained in this embodiment and the cost of the traditional alloy for rolls is as Figure 3 shown. It can be found that the alloy of this application does not contain rare precious metals W and Mo, and the main strengthening element V is added through ferroniobium, greatly reducing the cost of the alloy.

[0080] Comparative Example 1

[0081] This comparative example provides a method for preparing a wear-resistant alloy for rolls, comprising the following steps:

[0082] Step 1): Prepare raw materials according to the alloy composition of Comparative Example 1 in Table 1; melt an alloy ingot by vacuum medium-frequency induction, and then perform vacuum electroslag remelting on the alloy ingot, and obtain an ingot after casting; wherein, the current density of the vacuum electroslag remelting is 12 A / cm 2 , the voltage is 45 V, the current is 7000 A, and the remelting speed is 60 kg / h;

[0083] Step 2): Rough-process the ingot obtained in Step 1) to obtain a blank in the shape of a roll; then perform a sealing tube treatment on the blank, and then heat it to 820 °C at a heating rate of 45 °C / h, hold for 1.2 h, and then heat it to 1050 °C at a heating rate of 120 °C / h, hold for 1.3 h, and obtain an alloy after quenching treatment after cryogenic cooling with liquid nitrogen; perform a sealing tube treatment on the alloy after quenching treatment, and then heat it to 260 °C at a heating rate of 50 °C / h, and obtain an alloy after tempering treatment after holding for 2.5 h; then air-cool the alloy after tempering treatment, and then perform a finishing process to obtain a wear-resistant alloy for rolls.

[0084] The comparison of the surface microstructural morphologies of the wear-resistant alloys obtained in Example 1 and this comparative example is as Figure 4 shown. It can be found that since the V content in the alloy of this comparative example is lower than that in Example 1, the formed VC content is relatively low, only about 15%, and at the same time, due to the decrease in the V content, the Cr carbide content increases, forming a network-like brittle Cr 7 C 3 carbide. Therefore, the compressive strength and hardness of the alloy obtained in Comparative Example 1 are both lower than those in Example 1, as Figure 5 shown.

[0085] Comparative Example 2

[0086] This comparative example provides a method for preparing a wear-resistant alloy for rolls, comprising the following steps:

[0087] Step 1): Prepare raw materials according to the alloy composition of Comparative Example 2 in Table 1; melt an alloy ingot by vacuum medium-frequency induction, and then perform vacuum electroslag remelting on the alloy ingot, and obtain an ingot after casting; wherein, the current density of the vacuum electroslag remelting is 12 A / cm 2 , the voltage is 45 V, the current is 7000 A, and the remelting speed is 60 kg / h;

[0088] Step 2): The ingot obtained in Step 1) is subjected to rough machining to obtain a blank in the shape of a roll; then the blank is subjected to tube sealing treatment, and then heated to 820 °C at a heating rate of 45 °C / h, held for 1.2 h, and then heated to 1050 °C at a heating rate of 120 °C / h, held for 1.3 h, and deep cryogenically cooled with liquid nitrogen to obtain the alloy after quenching treatment; the alloy after quenching treatment is subjected to tube sealing treatment, and then heated to 260 °C at a heating rate of 50 °C / h, held for 2.5 h to obtain the alloy after tempering treatment; then the alloy after tempering treatment is air-cooled, and then subjected to finish machining to obtain the wear-resistant alloy for rolls.

[0089] In the wear-resistant alloy obtained in this comparative example, the diameter of VC is 15 - 30 μm, it is in the shape of a polygon block, and the volume fraction is 20 - 25%. The comparison of the wear rate and wear loss weight of the wear-resistant alloys obtained in Example 1 and this comparative example is as Figure 6 shown. It can be found that since the V content in the alloy of this comparative example is higher than that in Example 1, during high-temperature austenitization, part of VC dissolves, but the high V content will cause undissolved VC to remain (as a nucleation core), promoting the continued growth of VC on the original particles during subsequent cooling, thus forming aggregates of large-diameter VC, which are prone to forming cracks and increasing the wear and shedding of the alloy surface. Therefore, the wear resistance of Comparative Example 2 is lower than that of Example 1.

[0090] Comparative Example 3

[0091] This comparative example provides a preparation method of a wear-resistant alloy for rolls, including the following steps:

[0092] Step 1): Prepare raw materials according to the alloy composition of Comparative Example 2 in Table 1; melt an alloy ingot by vacuum intermediate frequency induction, and then perform vacuum electroslag remelting on the alloy ingot, and obtain an ingot after casting; wherein, the current density of vacuum electroslag remelting is 12 A / cm 2 , the voltage is 45 V, the current is 7000 A, and the remelting speed is 60 kg / h;

[0093] Step 2): The ingot obtained in Step 1) is subjected to rough machining to obtain a blank in the shape of a roll; then the blank is subjected to tube sealing treatment, and then heated to 820 °C at a heating rate of 45 °C / h, held for 1.2 h, and then heated to 1050 °C at a heating rate of 120 °C / h, air-cooled to obtain the alloy after quenching treatment; the alloy after quenching treatment is subjected to tube sealing treatment, and then heated to 260 °C at a heating rate of 50 °C / h, held for 2.5 h to obtain the alloy after tempering treatment; then the alloy after tempering treatment is air-cooled, and then subjected to finish machining to obtain the wear-resistant alloy for rolls.

[0094] The comparison of the impact toughness and microstructure of the wear-resistant alloys obtained in Example 1 and this comparative example are respectively as Figure 7 and8 As shown, it can be found that in this comparative example, since the alloy after normalizing treatment is air-cooled, during air-cooling (room-temperature cooling), atoms still have a certain diffusion ability (especially at higher tempering temperatures), and carbides will slowly precipitate and grow, resulting in a larger diameter; during cryogenic treatment, atomic diffusion is almost completely inhibited, and the supersaturated solid solution is "frozen" and cannot precipitate. After cryogenic treatment, the material still maintains a very high supersaturation. When subsequent tempering occurs, the chemical potential gradient of carbon and alloying elements is much higher than that of the air-cooled sample, thus promoting denser nucleation and forming nano-scale precipitates. At the same time, during quenching, the martensitic transformation causes volume expansion, generating a high density of dislocations and micro-stresses. During air-cooling, part of the stress will be released through dislocation movement or recovery processes, and the defect density decreases. During cryogenic treatment, the extremely low temperature freezes dislocations and vacancies, making it impossible for them to annihilate through thermal activation, thus retaining more high-energy defects and providing nucleation sites for subsequent precipitation. When the cryogenic sample is tempered, carbides tend to nucleate at defects such as dislocations, vacancy clusters, and sub-grain boundaries, forming finer and more dispersed precipitates.

[0095] Therefore, normalizing and air-cooling cannot ensure the nano-scale VC dispersion precipitation during the tempering process, so the effect of nano-phase-induced grain refinement is not obvious. Therefore, the impact toughness of Comparative Example 3 is lower than that of Example 1.

[0096] Comparative Example 4

[0097] This comparative example provides a preparation method for a wear-resistant alloy for rolls, including the following steps:

[0098] Step 1): Prepare raw materials according to the alloy composition of Comparative Example 2 in Table 1; melt an alloy ingot by vacuum medium-frequency induction, and then perform vacuum electroslag remelting on the alloy ingot. After casting, an ingot is obtained; among them, the current density of vacuum electroslag remelting is 3 A / cm 2 , the voltage is 30 V, the current is 5500 A, and the remelting speed is 150 kg / h;

[0099] Step 2) Rough-process the ingot obtained in Step 1) to obtain a blank part in the shape of a roll; then perform a sealing tube treatment on the blank part, and then heat it to 820 °C at a heating rate of 45 °C / h, hold for 1.2 h, and then heat it to 1050 °C at a heating rate of 120 °C / h, hold for 1.3 h, and obtain an alloy after quenching treatment after cryogenic treatment with liquid nitrogen; perform a sealing tube treatment on the alloy after quenching treatment, and then heat it to 260 °C at a heating rate of 50 °C / h, hold for 2.5 h to obtain an alloy after tempering treatment; then air-cool the alloy after tempering treatment, and then perform a finishing process to obtain a wear-resistant alloy for rolls.

[0100] The comparison of the structures of the ingots in Example 1 and this comparative example is as Figure 9As shown, it can be found that since the electroslag remelting process parameters of this comparative example are not within the protection scope of the present invention, obvious segregation of VC occurs in the alloy and there are many micropore defects. Among them, when the current density is too low, the molten pool becomes shallower (, resulting in a decrease in the temperature gradient (G) at the solidification front and a relatively high solidification rate (R), causing the G / R ratio to decrease, and the solidification mode changes from a planar interface → cellular → coarse dendrite; a solute enrichment region (C and V enrichment) is formed between the coarse dendrites. Due to insufficient solidification rate, VC cannot nucleate uniformly but precipitates laggingly between the dendrites, forming macroscopic segregation. The electroslag remelting parameters are low, and the current density and voltage are too low, resulting in a shallow molten pool and a low temperature gradient at the solidification front, causing dendrite coarsening and forming macroscopic solute enrichment of VC.

[0101] It is easy for those skilled in the art to understand that on the premise of no conflict, the advantageous technical features of the above various methods can be freely combined and superimposed.

[0102] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. The above is only the preferred implementation manner of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can still be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A wear-resistant alloy for a rolling mill, characterized in that: Measured in weight percentage, the components of the wear-resistant alloy for rolling rollers are: C3-3.5wt%, V8.5-9wt%, Cr3-3.5wt%, Mn0.5-1wt%, Si0.5-1wt%, Al0.5-1wt%, Ni0.5-1wt%, Cu0-0.5wt%, Co1-1.5wt%, Nb0.5-1wt%, B0-0.5wt%, N0-0.1wt%, P≤0.03wt%, S≤0.03wt%, and the balance is Fe.

2. The wear-resistant alloy for rolling mill roll according to claim 1, characterized in that: The microstructure of the wear-resistant alloy for rolling rolls includes martensite, austenite and VC; Wherein, the VC includes micron-scale VC and nano-scale VC; the nano-scale VC is in a coherent relationship with the austenite; wherein the micron-scale VC is spherical with a diameter of 0.5-5 μm; the nano-scale VC is spherical with a diameter of 10-200 nm.

3. The wear-resistant alloy for rolling mill roll according to claim 2, characterized in that: In the microstructure of the wear-resistant alloy for rolling mill rolls: the volume fraction of martensite is 65-75%; the volume fraction of VC is 5-15%; and / or In the VC, the volume fraction of the micron-scale VC is 60-80%; the volume fraction of the nano-scale VC is 20-40%.

4. The wear-resistant alloy for rolling mill roll according to claim 1, characterized in that: The wear-resistant alloy for the roll has a hardness of 68-70HRC, a compressive strength of 2700-3000MPa, and an impact toughness Aku of 8-12J / cm 2 , the wear rate is less than 4.5×10 - 6 mm 3 ·N -1 ·m -1 .

5. The method for preparing the wear-resistant alloy for a rolling mill roll according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1): performing smelting and remelting on the alloy raw materials in sequence to obtain an ingot; Step 2): sequentially subjecting the ingot to quenching treatment and tempering treatment to obtain the wear-resistant alloy for the rolling roll.

6. The method for preparing the wear-resistant alloy for rolling mill roll according to claim 5, characterized in that: In the step 1), the smelting process adopts vacuum electric frequency induction smelting; and / or The raw material for providing the V element is ferrovanadium; and / or The remelting treatment adopts vacuum electroslag remelting; preferably, the current density of vacuum electroslag remelting is 10-15A / cm2; the voltage of vacuum electroslag remelting is 40-45V; the current of vacuum electroslag remelting is 6500-7500A; the remelting speed of vacuum electroslag remelting is 40-80kg / h.

7. The method for preparing the wear-resistant alloy for rolling mill according to claim 5, characterized in that: In the step 2), the quenching step includes: The ingot is sealed, then heated to 800-850° C., kept warm for 1-1.5 hours, then heated to 1050-1100° C., kept warm for 1-1.5 hours, then cryogenically treated to obtain a quenched alloy; Preferably, the heating rate when heated to 1050-1100°C is 2-3 times that when heated to 800-850°C; further preferably, the heating rate when heated to 800-850°C is 30-50°C / h; the heating rate when heated to 1050-1100°C is 100-150°C / h.

8. The method for preparing the wear-resistant alloy for rolling mill according to claim 7, characterized in that: The cryogenic treatment adopts liquid nitrogen cryogenic treatment.

9. The method for preparing the wear-resistant alloy for roller according to claim 5, characterized in that: In step 2), the tempering step includes: The quenched alloy is sealed, then heated to 250-270° C., and kept warm for 2-2.5 hours to obtain a tempered alloy; preferably, the heating rate is 30-50° C. / h.

10. The method for preparing the wear-resistant alloy for rolling mill according to claim 5, characterized in that: In the step 2), before the step of quenching the ingot, it also includes: performing rough machining on the ingot; and / or After the step of tempering the ingot, the method further includes: performing a finishing process on the tempered alloy.

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