阅读说明：本技术 一种改善高速钢轧辊热处理中易断裂的辊身处理工艺 (Roller body treatment process for improving easy fracture in high-speed steel roller heat treatment ) 是由 郭平 于 2020-05-29 设计创作，主要内容包括：本发明公开了一种改善高速钢轧辊热处理中易断裂的辊身处理工艺,涉及高速钢轧辊技术领域,具体工艺如下：1)利用六水合硝酸镍和碱性硅胶液制得Ni/Si前驱体；2)将前驱体经高温焙烧得到Ni/Si纳米复合物；3)将高速钢轧辊的辊身溶炼后进行脱氧和变质处理,然后将其浇入离心机上铸模内进行旋转；4)向钢水中依次加入纳米铜颗粒、纳米钛颗粒、纳米铌颗粒以及Ni/Si纳米复合物,形成浇铸液,待辊身温度达到1200-1250℃,将浇铸液加入到离心机上,即可完成对辊身的加工处理。本发明通过增强辊身与芯部之间结合层的强度以及减小辊身与芯部之间由于膨胀系数差异产生的应力集中,使得结合层不易出现裂纹,从而杜绝了轧辊的断辊现象。(The invention discloses a roller body treatment process for improving the easiness in fracture in heat treatment of a high-speed steel roller, which relates to the technical field of high-speed steel rollers and comprises the following specific steps: 1) preparing a Ni/Si precursor by using nickel nitrate hexahydrate and alkaline silica gel liquid; 2) roasting the precursor at high temperature to obtain a Ni/Si nano compound; 3) carrying out deoxidation and modification treatment after smelting the roll body of the high-speed steel roll, and then pouring the roll body into a casting mould on a centrifugal machine for rotation; 4) and sequentially adding nano copper particles, nano titanium particles, nano niobium particles and the Ni/Si nano composite into the molten steel to form casting liquid, and adding the casting liquid onto a centrifugal machine when the temperature of the roller body reaches 1200-1250 ℃, so as to finish the processing treatment of the roller body. The invention enhances the strength of the bonding layer between the roller body and the core part and reduces the stress concentration between the roller body and the core part caused by the difference of expansion coefficients, so that the bonding layer is not easy to crack, thereby avoiding the roller breaking phenomenon of the roller.)

1. A roll body treatment process for improving the easiness in fracture in the heat treatment of a high-speed steel roll is characterized by comprising the following specific process steps:

1) weighing a certain amount of nickel nitrate hexahydrate, dissolving the nickel nitrate hexahydrate in deionized water, adding a corresponding amount of ammonia water into the solution, stirring for 10-20min, uniformly mixing, adding a proper amount of alkaline silica gel liquid to enable the pH of the solution to reach 11-12, stirring for 10-15h at room temperature, then evaporating ammonia by using water bath at 70-80 ℃ until the pH of the solution is neutral, centrifugally washing the suspension, drying the obtained precipitate, and grinding to obtain a Ni/Si precursor;

2) uniformly scattering a proper amount of precursor into a porcelain boat, flattening the porcelain boat, maintaining the porcelain boat horizontal, slowly putting the porcelain boat into a tube furnace, adjusting the vacuum degree in the tube furnace to-0.1-0.3 MPa by using a vacuum pump, continuously introducing nitrogen into the tube furnace in the calcining process, setting the temperature of the tube furnace to 750-850 ℃, and calcining for 4-5h to obtain a Ni/Si nano compound;

3) melting the roll body of the high-speed steel roll by using a medium-frequency induction furnace, discharging molten steel to a steel ladle when the temperature of the molten steel of the roll body reaches 1600-;

4) taking a small amount of molten steel of the roller body, sequentially adding a small amount of nano copper particles, nano titanium particles, nano niobium particles and Ni/Si nano composite into the molten steel, preserving heat for 30-50min to form casting liquid, adjusting the rotating speed of a centrifuge to 1300r/min when the temperature of the roller body in a casting mold of the centrifuge reaches 1250 ℃, adding the casting liquid onto the centrifuge, rotating the centrifuge for 20-30min, and preserving heat for 1-2h at 1260 ℃ of 1220 to finish the processing treatment of the roller body.

2. The roll body treatment process for improving the easiness in cracking in the heat treatment of the high-speed steel roll according to claim 1, wherein in the step 1), the molar ratio of the ammonia to the nickel nitrate hexahydrate is 8-10: 1; the stirring speed is 150-200 r/min.

3. The roll body treatment process for improving the easiness in breakage in the heat treatment of the high-speed steel roll as claimed in claim 1, wherein in the step 1), the mass fraction of the ammonia water is 20-25%; the mass fraction of the alkaline silica sol is 35-40%, and the average particle size is 10-20 nm.

4. The roll body treatment process for improving the easiness in cracking in the heat treatment of the high-speed steel roll according to claim 1, wherein in the step 2), the flow of the introduced nitrogen is 50-70ml/cm²Min; the heating rate is 5-8 ℃/min.

5. The roll body processing technology for improving the easy fracture in the high-speed steel roll heat treatment is characterized in that in the step 3), the chemical composition and the mass fraction of the roll body are controlled as follows: 1.5-2.4% of C, 1.1-2.6% of W, 2.8-5.1% of Mo, 1.6-2.7% of V, 3.8-5.2% of Cr, 0.3-0.6% of Mn, 0.3-0.5% of Si, 0.2-0.5% of Al, 0.5-0.8% of Co, less than 0.035% of S, less than 0.035% of P, and the balance of Fe.

6. The roll body processing technology for improving the easy fracture in the high-speed steel roll heat treatment as claimed in claim 1, characterized in that in the step 3), the deoxidizer is a siliceous multi-element alloy deoxidizer, the addition amount of the deoxidizer is 0.3-0.7% of the mass of molten steel of the roll body, and the chemical composition and the mass fraction thereof are controlled as follows: si50-55%, Al11-13%, Ca10-12%, Ba12-14%, Mn less than or equal to 0.04%, C less than or equal to 0.04%, P less than or equal to 0.05%, S less than or equal to 0.05%, and the balance of Fe.

7. The roll body processing technology for improving the easy fracture in the high-speed steel roll heat treatment as claimed in claim 1, characterized in that in the step 3), the modifier is Y-based heavy rare earth modifier, and the addition amount is 0.2-0.3% of the mass of molten steel of the roll body; the rotating speed of the centrifuge is 600-800 r/min.

8. The roll body treatment process for improving the easiness in fracture in the heat treatment of the high-speed steel roll as claimed in claim 1, wherein in the step 4), the taken molten steel of the roll body is the molten steel after deoxidation and modification treatment, and the temperature is 1430-1480 ℃; the mass of the casting liquid accounts for 1.2-2.8% of the mass of the molten steel of the roll body; in the roller body molten steel, the addition amounts of the nano copper particles, the nano titanium particles, the nano niobium particles and the Ni/Si nano composite are 0.1-0.5%, 0.4-0.8%, 0.02-0.05% and 1.0-1.8% of the mass of the molten steel.

Technical Field

The invention belongs to the technical field of high-speed steel rolls, and particularly relates to a roll body treatment process for improving the easiness in fracture in heat treatment of a high-speed steel roll.

Background

The roller is an important consumable spare part in steel rolling production, the quality of the roller not only influences the surface quality and the dimensional precision of rolled materials, but also influences the production operation rate of a rolling mill, so that the quality improvement of the roller is a major concern of roller developers in various countries around the world, and high-chromium cast iron rollers, chilled cast iron rollers, semi-steel rollers and high-speed steel rollers are widely used at home and abroad for a long time. The high-speed steel roll is a hot roll material which is developed fastest and has the widest application prospect in recent years, the high-speed steel roll is made of more complex alloy steel, and the high-speed steel roll can be hardened even if the high-speed steel roll is cooled in air after being quenched by a heat treatment process. The working layer material is high-carbon steel, the core material of the roller is nodular cast iron, graphite steel or forged steel, etc., the two different materials are compounded by centrifugal casting or CPC process, the matrix structure is generally tempered martensite + bainite + carbide, and the carbide is distributed in the matrix in a highly dispersed form, so that the high-speed steel roller has good wear resistance and toughness.

In the heat treatment process of the high-speed steel roller, because the re-dissolution amount of the high-temperature molten iron in the core part to the solidified outer layer high-speed steel is too large during core filling, the total amount of the alloy of the core part is increased, the number of carbides of the core part structure, particularly the bonding layer part, is too high, the strength of the bonding layer and the strength of the core part of the roller are reduced sharply, and the phenomenon of roller body fracture easily occurs in the heat treatment process of the high-speed steel roller. In the prior art, various process methods are adopted to improve the defect that a roller body is easy to break, for example, Chinese invention patent CN105033227 discloses a manufacturing method of a high-vanadium high-speed steel composite roller suitable for a narrow strip steel rolling mill, a centrifugal casting method is adopted to cast the outer layer of the roller body, after the high-vanadium high-speed molten steel of the outer layer of the roller body is cast, inert gas is continuously introduced into a cavity of the outer layer of the roller body, when the temperature of the outer layer of the high-vanadium high-speed steel reaches 1220-1280 ℃, the rotation of a centrifugal machine is stopped, meanwhile, the blowing of the inert gas is stopped, then molten iron of a core part of the roller body is cast in a box, the technical scheme obviously improves the bonding rate of the high-vanadium high-speed steel of the outer layer and the molten iron of the core part, the bonding rate is improved to 100 percent from 40 percent, the bonding strength is improved from about 350MPa to about 450MPa, so that the anti-stripping, thereby improving the structure of the roll neck, improving the tensile strength of the roll neck and effectively avoiding the roll breaking phenomenon in use; for example, the Chinese invention patent CN104525889 discloses a manufacturing method of high-speed steel roll suitable for small-sized steel mill, wire bar rolling mill, this technological scheme includes smelting raw materials, casting and shaping, machining and heat treatment process, on the basis of the molten iron of high-speed steel of centrifugal casting, pour into the molten iron of transition layer at first, then realize the complete replacement of the molten iron of transition layer through pouring the molten iron of core, this technological scheme has obviously improved the bond strength of outer high-speed steel and core molten iron, the bond strength is promoted to above 500Mpa from about 350Mpa in the past, make the resistance to spalling of the roller body bond coat of high-speed steel roll greatly improve, can remove the carbide formation element amount of the outer layer of molten iron corrosion of core at the same time effectively, thus has improved the organization of the roll neck, has improved the tensile strength of the roll neck, have effectively stopped the roller breaking phenomenon in use; according to the technical scheme, the roller breaking phenomenon in use is avoided by improving the bonding strength of the outer layer high-speed steel and the core molten iron and removing the carbide forming element content of the core molten iron corrosion outer layer, but the technical method cannot solve the problem that in the heat treatment and heating process of the roller, because the expansion coefficients of a roller body and the core are greatly different, the generated stress easily exceeds the strength of the bonding layer, cracks are formed near the bonding layer, and the roller is easy to break along with the diffusion of the cracks.

Disclosure of Invention

The invention aims to provide a roller body treatment process for improving the easiness in fracture in the heat treatment of a high-speed steel roller, aiming at the existing problems.

The invention is realized by the following technical scheme:

a roll body treatment process for improving the easiness in fracture in high-speed steel roll heat treatment comprises the following specific process steps:

1) weighing a certain amount of nickel nitrate hexahydrate, dissolving the nickel nitrate hexahydrate in deionized water, adding a corresponding amount of ammonia water with the mass fraction of 20-25% into the solution according to the molar ratio of the ammonia water to the nickel nitrate hexahydrate of 8-10:1, stirring for 10-20min at the speed of 200r/min of 150-; in the invention, nickel nitrate hexahydrate and alkaline sol solution are used as raw materials, an ammonia evaporation process is adopted to obtain a Ni/Si precursor, the precursor is formed by loading active metal nickel on silicate with a special layered structure, and metal Ni can be uniformly dispersed on the surface of the silicate by utilizing the layered structure of the silicate, so that highly dispersed Ni nanoparticles can be obtained;

2) uniformly scattering a proper amount of precursor into a porcelain boat, flattening, maintaining the porcelain boat horizontal, slowly putting into a tube furnace, adjusting the vacuum degree in the tube furnace to-0.1-0.3 MPa by using a vacuum pump, and adjusting the flow rate to 50-70ml/cm in the calcining process²Min, continuously introducing nitrogen into the tubular furnace, setting the temperature of the tubular furnace at 750-850 ℃, the heating rate at 5-8 ℃/min, and roasting for 4-5h to obtain a Ni/Si nano compound; in the invention, the Ni/Si precursor is roasted at high temperature in nitrogen atmosphere, so that the special layered structure of the silicate is completely destroyed at high temperature, unsaturated chemical bonds of oxygen on the surface of silicon dioxide and metal Ni atoms highly dispersed on the surface are bonded to form Ni-O bonds, thereby forming Ni/Si nano-composite, and under the action of high temperature, the nano-composite is preparedThe Si/C ratio of a contact area with the roller body can be improved, so that a liquid-solid phase crystallization area of the contact area is widened, the number of primary austenite is increased, dendritic crystal connection is tighter, the bonding force among atoms is enhanced, and the strength of a casting layer is enhanced;

3) melting the roll body of the high-speed steel roll by using a medium-frequency induction furnace, wherein the chemical composition and the mass fraction of molten steel of the roll body are controlled as follows: 1.5-2.4% of C, 1.1-2.6% of W, 2.8-5.1% of Mo, 1.6-2.7% of V, 3.8-5.2% of Cr, 0.3-0.6% of Mn, 0.3-0.5% of Si, 0.2-0.5% of Al, 0.5-0.8% of Co, S < 0.035%, P < 0.035% and the balance of Fe, when the molten steel temperature of the roller body reaches 1600-1650 ℃, the molten steel is taken out of the furnace to a steel ladle, and then siliceous multi-element alloy deoxidizer is added into the molten steel, the chemical composition and the mass fraction thereof are controlled as follows: si50-55%, Al11-13%, Ca10-12%, Ba12-14%, Mn not more than 0.04%, C not more than 0.04%, P not more than 0.05%, S not more than 0.05%, and the balance Fe, wherein the addition amount is 0.3-0.7% of the molten steel mass of the roll body, after the molten steel is deoxidized and deslagged, a proper amount of Y-based heavy rare earth modifier is continuously added into the molten steel to modify the molten steel, the addition amount is 0.2-0.3% of the molten steel mass of the roll body, when the modified molten steel is cooled to 1440-1470 ℃, the molten steel is poured into a casting mold on a centrifuge, so that the molten steel rotates 10-15min on a 600-800r/min centrifuge;

4) taking a small amount of molten steel of the roller body which is subjected to deoxidation and modification treatment and is at the temperature of 1430-DEG C and 1480 ℃, sequentially adding a small amount of nano copper particles, nano titanium particles, nano niobium particles and Ni/Si nano composite into the molten steel according to 0.1-0.5%, 0.4-0.8%, 0.02-0.05% and 1.0-1.8% of the mass of the molten steel, preserving heat for 30-50min to form casting liquid, adjusting the rotating speed of a centrifuge to 1300r/min when the temperature of the roller body in a casting mold of the centrifuge reaches 1200-; according to the invention, molten steel containing copper, titanium, niobium and Ni/Si nano-composite is used as casting liquid, the casting liquid is spin-coated on the inner surface of the roller body through the high-speed rotation of a centrifugal machine to form a casting layer, and the added metal titanium and metal niobium can refine the grain structure of the casting liquid and improve the strength of the casting layer; the added metal copper can be mutually dissolved with iron liquid in the high-speed steel redissolved on the outer layer of the roller body to form a liquid solid solution, so that carbon atoms are released from being combined with iron, the graphitization effect is enhanced, and free and separated carbon atoms exist and grow in a graphite sphere shape, so that the casting liquid has good graphite form and tissue uniformity, the fine graphite spheres can reduce stress concentration of a matrix around graphite, the binding force among metal atoms is increased, and the toughness of a casting layer can be improved; the metal Ni in the added Ni/Si nano composite can form a binary alloy phase with a high melting point with copper, and is dispersed in the casting layer in a particle form, so that the defect that the casting layer is easy to crack due to copper precipitation can be avoided.

Compared with the prior art, the invention has the following advantages:

according to the treatment process of the high-speed steel roller body, the casting layer is formed between the roller body and the core part of the high-speed steel roller, when the nodular cast iron molten iron of the roller core is poured, the Ni/Si nano compound contained in the casting layer can partially permeate into the bonding layer between the roller body and the core part in the redissolution process, so that dendritic crystal connection of the bonding layer is tighter, the interatomic bonding force is enhanced, the strength of the bonding layer between the roller body and the core part is enhanced, meanwhile, the stress concentration generated due to the difference of expansion coefficients between the roller body and the core part can be reduced due to the fact that the formed casting layer has high toughness, the stress generated in the heat treatment process of the roller is far lower than the strength of the bonding layer, cracks are not prone to occur in the bonding layer, and the roller breakage phenomenon of the roller is avoided.

Detailed Description

The present invention will be further described with reference to specific embodiments.