CN111922320A - Preparation method of nodular cast iron roller and roller - Google Patents
Preparation method of nodular cast iron roller and roller Download PDFInfo
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- CN111922320A CN111922320A CN202011094227.9A CN202011094227A CN111922320A CN 111922320 A CN111922320 A CN 111922320A CN 202011094227 A CN202011094227 A CN 202011094227A CN 111922320 A CN111922320 A CN 111922320A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D19/00—Casting in, on, or around objects which form part of the product
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B27/00—Rolls, roll alloys or roll fabrication; Lubricating, cooling or heating rolls while in use
- B21B27/02—Shape or construction of rolls
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D13/00—Centrifugal casting; Casting by using centrifugal force
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/38—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for roll bodies
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/08—Making cast-iron alloys
- C22C33/10—Making cast-iron alloys including procedures for adding magnesium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C37/00—Cast-iron alloys
- C22C37/04—Cast-iron alloys containing spheroidal graphite
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C37/00—Cast-iron alloys
- C22C37/06—Cast-iron alloys containing chromium
- C22C37/08—Cast-iron alloys containing chromium with nickel
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C37/00—Cast-iron alloys
- C22C37/10—Cast-iron alloys containing aluminium or silicon
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Abstract
The invention discloses a preparation method of a nodular cast iron roller and the roller, and the method comprises the following steps: s1, molding in a compound sand box mode, and presetting a primary pouring position in the upper roll neck molding process; and S2, putting the pre-proportioned raw materials into an intermediate frequency furnace for smelting, setting the smelting temperature to 1440-1540 ℃, and performing spheroidization, multiple inoculation and modification treatment by adopting an in-package pouring method. S3, setting the pouring temperature to be 1300-1360 ℃, pouring molten iron into the cavity from the ladle, judging whether the molten iron stops rotating and the liquid level stops lifting when the molten iron is poured to a preset primary pouring position, then carrying out secondary pouring on the molten iron from a riser, removing slag in the riser after pouring is finished, and adding a heat insulating agent; and S4, cooling at normal temperature, opening the box when the temperature is less than 100 ℃, and carrying out heat treatment after the roller is cooled to the room temperature. According to the method provided by the embodiment of the invention, the overall strength of the roller is effectively increased.
Description
Technical Field
The invention belongs to the technical field of casting manufacturing, and particularly relates to a preparation method of a nodular cast iron roller and the nodular cast iron roller.
Background
With the continuous change of the market demands, in order to meet the requirements of high-precision and high-operation-rate bar rolling, the roller of a bar production line is updated, so that the production quantity and the quality of the bar are improved, and the requirements on the roller are higher and higher. In recent years, the innovation and development of the roller manufacturing technology also accelerate the reasonable application and gradual optimization of new materials and rolling processes of bar rollers.
The main task of the bar rough rolling stand is to reduce the section of a blank at a high temperature, and the bar rough rolling stand has the advantages of large rolling force and low rolling speed. The performance requirements of the roll generally consider two aspects of tensile strength and heat cracking resistance, and in addition, a certain hardness is required to ensure the excessive steel amount. Therefore, when rolling small-sized bars, the nodular cast iron roll generally has good hardness, but the strength of the nodular cast iron roll is poor compared with that of a cast steel roll, and when rolling large-sized bars, the nodular cast iron roll has good strength, but the hardness of the nodular cast iron roll is poor compared with that of the cast steel roll.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art.
Therefore, the invention provides a preparation method of a nodular cast iron roller and the nodular cast iron roller, and the method can increase the integral strength of the roller on the basis of the original hardness.
The nodular cast iron roller prepared by the preparation method of the nodular cast iron roller provided by the invention has good strength on the basis of original hardness, and the depth of a working layer is effectively improved when a large-size bar is rolled and cogging is performed.
According to the first aspect of the invention, the preparation method of the nodular cast iron roller comprises the following steps:
s1, molding in a compound sand box mode, and presetting a primary pouring position in the upper roll neck molding process; s2, putting the pre-proportioned raw materials into an intermediate frequency furnace for smelting, setting the smelting temperature to 1440-1540 ℃, and carrying out spheroidization, inoculation and modification on discharged molten iron; s3, setting the pouring temperature to be 1300-1360 ℃, pouring molten iron into a cavity from a ladle by adopting bottom pouring type pouring, judging whether the molten iron stops rotating and the liquid level stops lifting when the molten iron is poured to a preset primary pouring position, then carrying out secondary pouring on the molten iron from a riser, removing slag in the riser after pouring is finished, and adding a heat preservation agent for heat preservation; and S4, cooling at normal temperature, opening the box when the temperature is less than 100 ℃, and performing heat treatment after the roller is cooled to room temperature.
According to the preparation method of the nodular cast iron roll, the strength of the cast roll is effectively increased through a heat treatment process on the basis of the existing hardness energy, the materials of the upper roll neck, the roll body, the lower roll neck and the bottom box are all made of the same nodular cast iron, the overall strength of the roll is guaranteed, when a certain position is poured in a bottom pouring mode, molten iron is poured for the second time from a riser of a sand box of the upper roll neck, the molten metal can be well supplied for the roll body, the sequential solidification of the roll body is guaranteed, the defects of shrinkage porosity, shrinkage cavity and the like are avoided, a compact roll is formed, the hardness of the roll is guaranteed, and the overall strength of the roll is improved through a heat treatment process.
According to an embodiment of the present invention, in step S4, the heat treatment includes the steps of:
s41, heating to 900-950 ℃ at a heating rate of 10-20 ℃/h, and preserving the heat of the roller for 10-20 h; s42, cooling the roller to 450-500 ℃ by rotating air; and S43, finally, tempering at 500-550 ℃, preserving heat for 10-20 h, and cooling the roller to room temperature.
According to an embodiment of the present invention, in step S1, the roll body is formed by a metal mold flask, and the upper roll neck, the lower roll neck and the bottom box are formed by quartz sand clay.
According to an embodiment of the present invention, in step S2, the spheroidizing, inoculating and modifying treatment includes the following steps: s21, adding an inoculant, a nodulizer and an alterant into the ladle before tapping, and completely covering the ladle with scrap iron; s22, pouring the molten iron from the frequency furnace into the ladle processed in the step S21 by an in-ladle pouring method; and S23, inoculating, spheroidizing and modifying the molten iron.
According to one embodiment of the invention, the inoculant added into the molten iron is 75 ferrosilicon, the addition amount of the inoculant is 0.4-1.0% of the total amount of the molten iron, the nodulizer is nickel-magnesium alloy, the addition amount of the nodulizer is 0.6-1.0% of the total amount of the molten iron, and the modifier is rare earth, and the addition amount of the modifier is 0.2-0.4% of the total amount of the molten iron.
According to one embodiment of the invention, the preparation method of the nodular cast iron roller further comprises the following steps: s3', adopting a centrifugal casting mode, pouring the working layer molten iron into the rotating roller body cold mold through a pouring track, stopping the machine after the working layer molten iron is solidified, hanging out the centrifugal machine, assembling the working layer molten iron on the roller core casting mold, pouring the core molten iron into the cavity through a top pouring mode, and adding a heat preservation agent for heat preservation after the pouring is finished.
According to one embodiment of the invention, the pouring temperature is set to be 1300-1360 ℃.
According to one embodiment of the invention, the roll material comprises the following alloy element components in percentage by weight: c: 3.10-3.60%, Si: 1.00-2.00%, Mn: 0.30-1.00 percent of P, less than or equal to 0.20 percent of P; s is less than or equal to 0.05 percent, Cr: 0.30-1.00%, Ni: 1.50-2.50%, Mo: 0.30-0.80%, V: 0.10-0.60%, Re: 0.05-0.1% of Mg, and more than or equal to 0.04%.
According to one embodiment of the invention, the roll material comprises the following alloy element components in percentage by weight: c: 3.30-3.50%, Si: 1.50-1.80%, Mn: 0.50-0.80% and P is less than or equal to 0.10%; s is less than or equal to 0.03%, Cr: 0.40-0.60%, Ni: 1.50-2.50%, Mo: 0.40-0.60%, V: 0.15-0.35%, Re: 0.05-0.07%, Mg: 0.40 to 0.60 percent.
The nodular cast iron roll according to the embodiment of the second aspect of the invention is obtained by any one of the preparation methods described above.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a flowchart of a method for manufacturing a spheroidal graphite cast iron roll according to an embodiment of the present invention;
fig. 2 is a schematic bottom pouring type pouring diagram of the preparation method of the nodular cast iron roller in the embodiment of the invention.
Reference numerals:
a seat bag 1;
a bottom case 2;
a lower roll neck 3;
a roll body 4;
an upper roll neck 5;
a primary pouring position 6;
and a riser 7.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention. Furthermore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
First, a method for manufacturing a spheroidal graphite cast iron roll according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
As shown in fig. 1 and 2, the method for manufacturing a nodular cast iron roll according to an embodiment of the present invention includes the steps of:
s1, molding in a compound sand box mode, and presetting a primary pouring position 6 in the molding process of the upper roll neck 5;
s2, putting the pre-proportioned raw materials into an intermediate frequency furnace for smelting, setting the smelting temperature to 1440-1540 ℃, and carrying out spheroidization, inoculation and modification on discharged molten iron;
s3, setting the pouring temperature to be 1300-1360 ℃, pouring molten iron into the cavity from the ladle 1 by adopting bottom pouring type pouring, judging whether the molten iron stops rotating and the liquid level stops lifting when the molten iron is poured to a preset primary pouring position 6, then carrying out secondary pouring on the molten iron from the riser 7, removing slag in the riser 7 after pouring is finished, and adding a heat preservation agent for heat preservation;
and S4, cooling at normal temperature, opening the box when the temperature is less than 100 ℃, and performing heat treatment after the roller is cooled to room temperature.
In other words, according to the method for manufacturing a nodular cast iron roll of the embodiment of the invention, firstly, the roll to be cast is molded, the roll body 4, the upper roll neck 5, the lower roll neck 3 and the bottom box 2 can be molded in a compound sand box manner, and the roll body 4 can be molded by a metal mold sand box or the upper roll neck 5, the lower roll neck 3 and the bottom box 2 can be molded by quartz sand clay;
smelting, namely smelting the pre-proportioned raw materials, obtaining molten iron at the smelting temperature of 1440-1540 ℃, and performing spheroidization, inoculation and modification treatment on the discharged molten iron, wherein the step can be performed in a foundry ladle;
then, casting a roller, finishing casting by two times of casting, firstly, performing primary casting, adopting bottom pouring type casting, pouring the treated molten iron into a cavity from a seat ladle 1 through a ladle, enabling the molten iron to enter the cavity through an L-shaped pipeline below the seat ladle 1, continuously pouring the molten iron in the period, stopping pouring when the molten iron reaches a preset primary pouring position 6, judging whether the molten iron stops rotating and the liquid level stops lifting in a visual mode, performing secondary casting after the molten iron stops rotating and the liquid level stops lifting, pouring the residual molten iron in the ladle from a riser 7, removing slag in the riser 7 after the pouring is finished, and putting a heat preservation agent for heat preservation;
and finally, cooling the roller in casting at normal temperature, namely adding a heat preservation agent in the step S3 for heat preservation, then not operating, opening the box of the cast roller after the temperature is reduced to be less than 100 ℃, and then performing heat treatment after the roller is cooled to room temperature.
Therefore, according to the preparation method of the nodular cast iron roll, the strength of the cast roll is effectively increased through a heat treatment process on the basis of the existing hardness energy, the upper roll neck 5, the roll body 4, the lower roll neck 3 and the bottom box 2 are made of the same nodular cast iron, the overall strength of the roll is ensured, when a certain position is poured in a bottom pouring mode, molten iron is poured for the second time from a riser 7 of a sand box of the upper roll neck 5, a metal supply liquid can be better provided for the roll body 4, the sequential solidification of the roll body 4 is ensured, the defects of shrinkage porosity, shrinkage cavity and the like are avoided, a compact roll is formed, the hardness of the roll is ensured, and the overall strength of the roll is improved through a heat treatment process.
According to an embodiment of the present invention, in step S4, the heat treatment includes the steps of:
s41, heating to 900-950 ℃ at a heating rate of 10-20 ℃/h, and preserving the heat of the roller for 10-20 h; s42, cooling the roller to 450-500 ℃ by rotating air; and S43, finally, tempering at 500-550 ℃, preserving heat for 10-20 h, and cooling the roller to room temperature. The mechanical property of the material can be effectively improved, the residual stress can be eliminated, and the cutting processing performance of the roller can be improved through three steps S41-S43.
In some embodiments of the present invention, in step S1, the roll body 4 is molded using a metal mold flask, and the upper roll neck 5, the lower roll neck 3, and the bottom box 2 are molded using quartz sand clay. The roller body 4 adopts a metal molding sand box, the upper roller neck 5, the lower roller neck 3 and the bottom box 2 are molded by quartz sand clay, the sand box of the upper roller neck 5 is equivalent to a dead head 7, the upper roller neck 5 can be poured, feeding of the whole cavity is realized, the casting defects of shrinkage cavity and shrinkage porosity are avoided, and the strength and hardness of the roller are prevented from being reduced.
Specifically, in step S2, the spheroidizing, inoculating, and modifying treatment includes the steps of: s21, adding an inoculant, a nodulizer and an alterant into the ladle before tapping, and completely covering the ladle with scrap iron. And S22, pouring the molten iron from the frequency furnace into the ladle processed in the step S21 by an in-ladle pouring method. And S23, inoculating, spheroidizing and modifying the molten iron.
Preferably, the inoculant added into the molten iron is 75 ferrosilicon, the addition amount of the inoculant is 0.4-1.0% of the total amount of the molten iron, the nodulizer is nickel-magnesium alloy, the addition amount of the nodulizer is 0.6-1.0% of the total amount of the molten iron, and the modifier is rare earth, and the addition amount of the modifier is 0.2-0.4% of the total amount of the molten iron. By spheroidizing, inoculating and modifying, the molten iron can be effectively purified, crystal grains can be refined, the matrix structure can be strengthened, and casting is facilitated.
In some embodiments of the present invention, the method for preparing the nodular cast iron roll further comprises the steps of: s3', adopting a centrifugal casting mode, pouring the working layer molten iron into the rotating roller body 4 cold mold through a pouring track, stopping the machine after the working layer molten iron is solidified, hanging out the centrifugal machine, assembling the centrifugal machine on a roller core casting mold, pouring the core molten iron into the cavity through a top pouring mode, and adding a heat preservation agent for heat preservation after the pouring is finished. The molten iron is filled and solidified under the action of centrifugal force, the metal feeding effect is good, the outer layer structure of the roll casting is compact, the impurities are few, and the performance is good.
According to one embodiment of the invention, the pouring temperature is set to be 1300-1360 ℃.
In some embodiments of the present invention, the roll material comprises the following alloy elements by weight: c: 3.10-3.60%, Si: 1.00-2.00%, Mn: 0.30-1.00 percent of P, less than or equal to 0.20 percent of P; s is less than or equal to 0.05 percent, Cr: 0.30-1.00%, Ni: 1.50-2.50%, Mo: 0.30-0.80%, V: 0.10-0.60%, Re: 0.05-0.1% of Mg, and more than or equal to 0.04%.
Preferably, the roll material comprises the following alloy element components in percentage by weight: c: 3.30-3.50%, Si: 1.50-1.80%, Mn: 0.50-0.80% and P is less than or equal to 0.10%; s is less than or equal to 0.03%, Cr: 0.40-0.60%, Ni: 1.50-2.50%, Mo: 0.40-0.60%, V: 0.15-0.35%, Re: 0.05-0.07%, Mg: 0.40 to 0.60 percent.
By reasonably designing the chemical components of the roller and optimally designing the addition of alloy elements Cr, Ni, Mo and V, the integral strength of the roller and the VC carbide with high hardness of a working layer are ensured to be obtained, and the hardness and the steel passing amount during rolling are improved.
In summary, according to the preparation method of the nodular cast iron roller provided by the embodiment of the invention, the upper roller neck 5, the roller body 4, the lower roller neck 3 and the bottom box 2 are made of the same nodular cast iron, so that the overall strength of the roller is ensured, and the depth of a working layer is effectively improved when a large-size bar is rolled and cogging is performed; the optimized alloy proportion can ensure that the roller can reach enough strength in the using process.
The spheroidal graphite cast iron roll according to the embodiment of the second aspect of the invention is obtained by the preparation method of any one of the embodiments. The nodular cast iron roller of the embodiment is prepared by the preparation method of any one of the embodiments, so the nodular cast iron roller of the embodiment also has the advantages of good hardness, good strength and effectively improved depth of a working layer when rolling large-sized bars and cogging.
The embodiment of the present invention will be described below by way of specific embodiments.
Example 1
A nodular cast iron roller suitable for rough rolling of bars and a preparation method thereof comprise a roller body, an upper roller neck and a lower roller neck,
the method is characterized in that: the chemical components of the upper roll neck, the roll body, the lower roll neck and the bottom box are consistent, and the chemical components and the weight percentage content are as follows:
C：3.2～3.3％、Si：1.6～1.7％、Mn：0.5～0.6％、Cr：0.6～0.7％、Ni：1.5～1.8％、Mo：0.3～0.45％、V：0.15～0.35％、Re：0.05～0.08％、Mg：0.04～0.06％、P≤0.04％、S≤0.04％；
the method comprises the following steps:
1) the smelting temperature of the molten iron is 1430 ℃, the addition of an inoculant is 0.35%, the addition of a nodulizer is 0.5% of the total amount of the molten iron, and the addition of an alterant is 0.2% of the total amount of the molten iron;
2) the detection in front of the furnace shows that the roller body comprises the following chemical components in percentage by weight: c: 3.26%, Si: 1.65%, Mn: 0.55%, Cr: 0.65%, Ni: 1.6%, Mo: 0.35%, V: 0.15%, Re: 0.06%, Mg: 0.046 percent, less than or equal to 0.04 percent of P and less than or equal to 0.04 percent of S;
3) the pouring temperature of the molten iron is 1300 ℃;
4) the heat treatment process comprises the following steps: normalizing at 920 ℃ and preserving heat for 12h, quenching at 460 ℃ and tempering at 520 ℃ and preserving heat for 10h, then furnace cooling to less than 100 ℃ and discharging.
Example 2
The present embodiment has the same process steps and different process parameters as those of embodiment 1, and the difference from embodiment 1 is that: the chemical components and the weight percentage in the embodiment are as follows:
C：3.3～3.4％、Si：1.7～1.8％、Mn：0.5～0.6％、Cr：0.5～0.6％、Ni：1.8～2.3％、Mo：0.4～0.5％、V：0.15～0.35％、Re：0.05～0.07％、Mg：0.04～0.06％、P≤0.04％、S≤0.04％；
the method comprises the following steps:
1) the smelting temperature of the molten iron is 1450 ℃, the addition amount of the inoculant is 0.45 percent, the addition amount of the nodulizer is 0.6 percent of the total amount of the molten iron, and the addition amount of the modifier is 0.15 percent of the total amount of the molten iron;
2) the detection in front of the furnace shows that the roller body comprises the following chemical components in percentage by weight: c: 3.34%, Si: 1.76%, Mn:
0.55％、Cr：0.56％、Ni：2.0％、Mo：0.48％、V：0.25％、Re：0.05％、Mg：0.043％、P≤0.04％、S≤0.04％；
3) the pouring temperature of the molten iron is 1320 ℃;
4) the heat treatment process comprises the following steps: normalizing at 920 ℃ and preserving heat for 15h, quenching at 480 ℃ and tempering at 550 ℃ and preserving heat for 12h, then cooling to less than 100 ℃ and discharging.
Example 3
The present embodiment has the same process steps and different process parameters as those of embodiment 1, and the difference from embodiment 1 is that: the chemical components and the weight percentage in the embodiment are as follows:
C：3.4～3.5％、Si：1.8～1.9％、Mn：0.5～0.6％、Cr：0.4～0.5％、Ni：2.2～2.5％、Mo：0.5～0.6％、V：0.15～0.35％、Re：0.05～0.06％、Mg：0.04～0.06％、P≤0.04％、S≤0.04％；
the method comprises the following steps:
1) the smelting temperature of the molten iron is 1480 ℃, the addition amount of an inoculant is 0.55 percent, the addition amount of a nodulizer is 0.7 percent of the total amount of the molten iron, and the addition amount of a modifier is 0.15 percent of the total amount of the molten iron;
2) the detection in front of the furnace shows that the roller body comprises the following chemical components in percentage by weight: c: 3.47%, Si: 1.88%, Mn:
0.55％、Cr：0.45％、Ni：2.4％、Mo：0.55％、V：0.35％、Re：0.05％、Mg：0.048％、P≤0.04％、S≤0.04％；
3) the pouring temperature of the molten iron is 1330 ℃;
4) the heat treatment process comprises the following steps: normalizing at 920 ℃ and preserving heat for 20h, quenching at 500 ℃ and tempering at 550 ℃ and preserving heat for 15h, then cooling to less than 100 ℃ and discharging.
Example 4
The existing nodular cast iron roll for rough rolling of bars and a preparation method thereof comprise the following chemical components in percentage by weight:
C：3.2～3.4％、Si：1.5～2.0％、Mn：0.3～0.8％、Cr：0.2～0.7％、Ni：1.5～2.5％、Mo：0.2～0.5％、Re：0.05～0.08％、Mg：0.04～0.06％、P≤0.04％、S≤0.04％；
the method comprises the following steps:
1) the smelting temperature of the molten iron is 1450 ℃, the addition amount of the inoculant is 0.45 percent, the addition amount of the nodulizer is 0.5 percent of the total amount of the molten iron, and the addition amount of the modifier is 0.2 percent of the total amount of the molten iron;
2) the detection in front of the furnace shows that the roller body comprises the following chemical components in percentage by weight: c: 3.35%, Si: 1.65%, Mn: 0.55%, Cr: 0.55%, Ni: 1.5%, Mo: 0.25%, Re: 0.06%, Mg: 0.046 percent, less than or equal to 0.04 percent of P and less than or equal to 0.04 percent of S;
3) the pouring temperature of the molten iron is 1320 ℃;
the ductile iron rolls for rough rolling of bars prepared in examples 1 to 4 were subjected to performance tests including roll body hardness, roll neck hardness, lower roll neck tensile strength, and ultrasonic flaw detection, wherein the ultrasonic flaw detection is performed according to the GB/T1504-2008 standard, and the detection results are shown in the following table (values are average values).
| Implementation case numbering | Hardness HSD of roll body | Hardness HSD of roll neck | Lower roll neck tensile strength MPa | |
| 1 | 48 | 38 | 500 | Qualified |
| 2 | 52 | 38 | 510 | Qualified |
| 3 | 55 | 40 | 530 | Qualified |
| 4 | 52 | 38 | 450 | Qualified |
As can be seen from the first table, the hardness of the roll body and the hardness of the roll neck of the examples 1, 2 and 3 according to the present invention are substantially identical to those of the example 4 according to the prior art, and the present invention can be embodied to have the same hardness as that of the prior art.
The existing normal nodular cast iron roll has different alloy proportions, no heat treatment process, the tensile strength of the lower roll neck is 450MPa, and the strength is obviously lower than that of the lower roll neck in the embodiments 1, 2 and 3 of the invention.
In summary, according to the feedback results in the table above, the roller manufactured by the method for manufacturing a nodular cast iron roller according to the embodiment of the invention has the advantages that on the basis of good hardness, the strength of the casting roller is effectively improved, the problem that the strength of the nodular cast iron roller is poor is solved, and the depth of a working layer is effectively increased when a large-sized bar is rolled and cogging is performed.
The foregoing is a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and improvements can be made without departing from the present invention, and these modifications and improvements should also be considered as the protection scope of the present invention.
Claims (10)
1. The preparation method of the nodular cast iron roller is characterized by comprising the following steps:
s1, molding in a compound sand box mode, and presetting a primary pouring position in the upper roll neck molding process;
s2, putting the pre-proportioned raw materials into an intermediate frequency furnace for smelting, setting the smelting temperature to 1440-1540 ℃, and carrying out spheroidization, inoculation and modification on discharged molten iron;
s3, setting the pouring temperature to be 1300-1360 ℃, pouring molten iron into a cavity from a ladle by adopting bottom pouring type pouring, judging whether the molten iron stops rotating and the liquid level stops lifting when the molten iron is poured to a preset primary pouring position, then carrying out secondary pouring on the molten iron from a riser, removing slag in the riser after pouring is finished, and adding a heat preservation agent for heat preservation;
and S4, cooling at normal temperature, opening the box when the temperature is less than 100 ℃, and performing heat treatment after the roller is cooled to room temperature.
2. The method for manufacturing a roll of spheroidal graphite cast iron according to claim 1, wherein in step S4, the heat treatment includes the steps of:
s41, heating to 900-950 ℃ at a heating rate of 10-20 ℃/h, and preserving the heat of the roller for 10-20 h;
s42, cooling the roller to 450-500 ℃ by rotating air;
and S43, finally, tempering at 500-550 ℃, preserving heat for 10-20 h, and cooling the roller to room temperature.
3. The method of claim 1, wherein in step S1, the roll body is formed by a metal molding flask, and the upper and lower necks and the bottom box are formed by molding quartz sand clay.
4. The method for preparing a roll of spheroidal graphite cast iron according to claim 1, wherein in step S2, the spheroidization, inoculation and modification treatment comprises the steps of:
s21, adding an inoculant, a nodulizer and an alterant into the ladle before tapping, and completely covering the ladle with scrap iron;
s22, pouring the molten iron from the frequency furnace into the ladle processed in the step S21 by an in-ladle pouring method;
and S23, inoculating, spheroidizing and modifying the molten iron.
5. The method for manufacturing the nodular cast iron roller according to claim 4, wherein the inoculant added into the molten iron is 75 ferrosilicon, the addition amount of the inoculant is 0.4-1.0% of the total amount of the molten iron, the nodulizer is nickel-magnesium alloy, the addition amount of the nodulizer is 0.6-1.0% of the total amount of the molten iron, the modifier is rare earth, and the addition amount of the modifier is 0.2-0.4% of the total amount of the molten iron.
6. The method for preparing the ductile iron roll according to claim 1, further comprising the steps of:
s3', adopting a centrifugal casting mode, pouring the working layer molten iron into the rotating roller body cold mold through a pouring track, stopping the machine after the working layer molten iron is solidified, hanging out the centrifugal machine, assembling the working layer molten iron on the roller core casting mold, pouring the core molten iron into the cavity through a top pouring mode, and adding a heat preservation agent for heat preservation after the pouring is finished.
7. The method for manufacturing a spheroidal graphite cast iron roller according to claim 6, wherein the casting temperature is set to 1300 to 1360 ℃.
8. The method for preparing the nodular cast iron roller according to claim 1, wherein the material of the roller comprises the following alloy element components in percentage by weight: c: 3.10-3.60%, Si: 1.00-2.00%, Mn: 0.30-1.00 percent of P, less than or equal to 0.20 percent of P; s is less than or equal to 0.05 percent, Cr: 0.30-1.00%, Ni: 1.50-2.50%, Mo: 0.30-0.80%, V: 0.10-0.60%, Re: 0.05-0.1% of Mg, and more than or equal to 0.04%.
9. The method for preparing the nodular cast iron roller according to claim 1, wherein the material of the roller comprises the following alloy element components in percentage by weight: c: 3.30-3.50%, Si: 1.50-1.80%, Mn: 0.50-0.80% and P is less than or equal to 0.10%; s is less than or equal to 0.03%, Cr: 0.40-0.60%, Ni: 1.50-2.50%, Mo: 0.40-0.60%, V: 0.15-0.35%, Re: 0.05-0.07%, Mg: 0.40 to 0.60 percent.
10. Ductile iron rolling mill roll, characterized by being obtained by the manufacturing process according to any one of claims 1 to 9.
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| CN113172213A (en) * | 2021-04-09 | 2021-07-27 | 燕山大学 | Casting method of centrifugal composite roller |
| CN114367649A (en) * | 2021-12-16 | 2022-04-19 | 中钢集团邢台机械轧辊有限公司 | Preparation method of high-speed steel working roll for hot rolling plate strip finish rolling |
| CN114918372A (en) * | 2022-06-14 | 2022-08-19 | 成都三强轧辊股份有限公司 | Large-sized roller upper neck casting process |
| CN115070004A (en) * | 2022-05-20 | 2022-09-20 | 中钢集团邢台机械轧辊有限公司 | Casting method of metal type centrifugal roll collar |
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Application publication date: 20201113 |