KR100245471B1 - Complex roll and its manufacturing method for metal rolling - Google Patents

Abstract

According to the present invention, an outer layer made of a high alloy steel having a hardness higher than that of the core is formed by melting the electroslag into a core made of a low alloy steel, and the roundness of the core is made 10 mm or less, whereby higher alloying is possible. The composite roll with high wear resistance was obtained.

By using the composite roll in part or all of the work rolls or intermediate rolls of a multi-stage rolling mill connected by tandems, the number of coils that can be rolled by one grinding becomes three or more, and the schedule-free rolling is possible.

Description

Composite roll for metal rolling and manufacturing method thereof

1 is a graph showing the relationship between the tempering temperature and hardness of the roll and the conventional roll according to the present invention.

2 is a graph comparing the thermal shock resistance between the roll according to the present invention and the conventional roll.

3 is a graph comparing the wear resistance between the roll according to the present invention and the conventional roll.

Figure 4 is a cross-sectional view of the main portion of the work roll according to the present invention.

5 is a front elevational view of a main part of a cold strip mill using a work roll according to the present invention.

6 is a graph showing the relationship between the tempering temperature and the residual stress of the roll and the conventional roll according to the present invention.

7 is a graph showing the relationship between hardness and residual stress and depth at the surface.

8 is a schematic diagram of an apparatus for manufacturing a composite roll by an electroslag addition welding method.

9 is a schematic view showing a fractional quenching method of a rolling roll.

10 is a diagram showing the relationship between the number of coils by rolling and the roll roughness.

11 is a layout view of the rolling mill.

* Explanation of symbols for main parts of the drawings

1: rolled material 3: intermediate roll

4: support roll 5: outer layer

6: heartwood 7: mandrel

8: tubular electrode 9: welding machine

10: water cooling mold 12: wiring

13: additional welding layer 14: molten metal

15 slag 16: ring-shaped bottom plate

20: roll 21: outer layer

22: guide coil 23: water spray bottle

The present invention relates to a novel composite roll for a metal rolling mill, a manufacturing method thereof, and a rolling system, and more particularly, to a work roll for a high axial strength shift type six-stage rolling mill suitable for cold rolling of a metal, a manufacturing method thereof, and a rolling system. .

In rolls for metal rolling mills, thermal shock is applied to the surface of the roll due to slips generated between the roll and the rolled material during rolling, rolling accidents in which the rolled material is wound on the roll, and in some cases, cracks occur.

The work roll is required to have excellent wear resistance in order to maintain good rolling in addition to the resistance to thermal shock. In order to improve the thermal shock resistance, it is effective to improve the tempering resistance of the roll itself and to temper at a higher temperature.

1%, Cr 3.0∼6.0%, Mo 0.2%이하로 되는 롤 소재를 켄칭한 후 템퍼링을 행하고 있었는데, H_S93이상의 경도를 얻기 위해서는 템퍼링 온도를 160℃이하로 하고 있다.Conventional work rolls are C 1.2-2.5% by weight, Si 0.8-3,0% Mn by weight, as described in the specification of JP-A-63-60258.

Tempering was performed after quenching the roll material to 1%, Cr 3.0 to 6.0%, and Mo 0.2% or less. In order to obtain a hardness of H _S 93 or more, the tempering temperature is set to 160 ° C or less.

10%, W

18.0%, Co

5.0%, V 0.5∼5.0%, 잔부가 실질적으로 Fe로 되는 용착금속을 5∼100mm형성시켜, HS 80이상의 경도로 하는 열간 압연용 롤을 제조하는 것이 개시되어 있다.In addition, Japanese Laid-Open Patent Publication No. 53-80351 discloses 1.0 to 3.0%, Si 0.5 to 1.5%, Mn 0.5 to 1.5%, Cr 3.0 to 5.0%, and W + ½Mo on the outer circumference of the core material by electroslag welding. Mo in the range of -20%

10%, W

18.0%, Co

It is disclosed to form a rolled metal for hot rolling having a hardness of HS 80 or more by forming 5 to 100 mm of a weld metal having 5.0%, V 0.5 to 5.0%, and the balance of which is substantially Fe.

In addition, a conventional cold rolling work roll is made of a steel-based material to which Mo, V, etc. are added in addition to C: 0.7 to 1.1% and Cr: 1.5 to 6%, as described in, for example, Japanese Patent Application Publication No. 50-7529. Cold-rolled die steel An integrally forged steel roll made of a 10% Cr steel-based material similar to JIS SKD-11 was the mainstream. In addition, Japanese Patent Laid-Open No. 62-148004 can be cited as another conventional technique.

On the other hand, in the recent cold rolling method, measures such as high-pressure rolling and solid state control rolling have been made in view of energy saving, production line improvement, and improvement of steel quality. As a rolling mill used for these rolling, the 6-stage rolling mill or the multi-stage rolling mill of the cluster type is popularized instead of the conventional 4-stage rolling mill. The common point of the work rolls used in these examples is that the roll diameter is small and a large bending is given because of the solid state control. For this reason, as a roll, abrasion resistance, surface roughness, and toughness which are excellent in the inside of a body and a neck are calculated | required than the conventional roll. In addition, in recent years, the level of quality requirements of the user's rolled material has become more advanced, and the flaws of the minute surface of the rolled material surface due to the roll surface properties are also a big problem. For this reason, further improvement of abrasion resistance and surface roughness is calculated | required by roll.

Conventionally, there has been no work roll with sufficient wear resistance and surface roughness. The high-speed steel developed for cutting steel is extremely excellent in wear resistance, and is used as a work roll for multi-stage rolling mills such as sand mill mills and long mills, and has excellent performance in wear resistance and surface roughness. However, since the toughness is inferior, there is a problem that it is difficult to endure use as an integrated roll as a work roll to which a large bending is applied. Moreover, in the said conventional integrated steel forging rolls, long-term use is difficult in terms of abrasion resistance and surface roughness. For this reason, there is a method of using a low alloy steel for the core material and providing a high alloy steel having a hardness higher than that in the outer layer by electroslag melting, but there is a problem in that an additional weld layer cannot be formed uniformly with respect to the core material.

SUMMARY OF THE INVENTION An object of the present invention is to provide a composite roll for metal rolling with an outer layer having a uniform thickness due to less thickness bias with respect to a roll core, a manufacturing method thereof, and a rolling mill and a rolling system using the same.

The present invention is a composite roll for metal rolling coating the outer periphery of the core material with an outer layer material, the core material is a low alloy steel having a Shore hardness of 35 or more, roundness of 10 mm or less and lower hardness than the outer layer material The outer layer material is a martensite structure having a Shore hardness of 80 or more and a residual austenite content of 15% by volume or less. The outer layer material is a high alloy steel solidified in the roll axial direction with a compressive stress of 70 kg / mm 2 or more at the outermost surface. It provides a composite roll for metal rolling, characterized in that.

The present invention contains C 0.5-1.5% by weight, Si 0.5-3.0%, Mn 1.5% or less, Cr 2-10%, V 0.5-2.0%, W 1-20% or less, and solidified in the roll axial direction. It is characterized in that the high alloy steel is the outer layer, the low alloy steel is the core, and the roundness is 10 mm or less.

According to the present invention, the core material contains C 0.5-1.0% by weight, Si 1% or less, Mn 1% or less, Cr 1-5%, Mo 0.5% or less, has a lower hardness than the outer layer material, and has a roundness of 10 mm or less. Alloy steel is used, and the outer layer material is C 0.5-1.5%, Si 0.5-3.0%, Mn 1.5% or less, Cr 2-10%, Mo 1-10%, V 0.5-2.0%, W 1-20% or less It is made into the high alloy steel which contains, and it is characterized by the welding layer solidified in the roll axial direction.

The present invention is also characterized by using a welding layer solidified in the roll axial direction made of a high alloy steel containing 5% or less of Ni or 1 to 15% of Co in the outer layer.

The present invention is a composite roll for metal rolling having a core made of a low alloy steel and an outer layer made of a high alloy steel having a higher hardness than the core, wherein the core has a roundness of 10 mm or less and the outer layer has an axial solidification structure. It provides a composite roll for rolling metal, characterized in that the crystal.

The present invention also provides a step of inserting a consumption electrode made of a high alloy steel that forms an outer layer having a hardness higher than that of the shaft material in a gap formed between the shaft material of the low alloy steel and the cooling mold arranged concentrically, and the shaft material and cooling. Rotating the mold in the circumferential direction and supplying an alternating current to the consumed electrode and the accumulator under a slag bath to supply alternating current, respectively, to dissolve the consumed electrode to melt, and to move the cooling mold in the axial direction of the accumulator; It provides the manufacturing method of the composite roll for metal rolling which includes the process of coagulating | solidifying and welding the outer layer integrally to a shaft material.

In addition, the present invention provides a method for producing a composite roll for metal rolling in which the outer layer material made of high alloy steel with higher hardness than the low alloy steel is solidified and welded in the roll axial direction on the outer circumference of the core material made of low alloy steel, the roundness of the core material After forming the outer layer material to be 10 mm or less, a quenching step of gradually heating the outer layer material to a temperature above the austenite transformation point and performing a quenching step of injecting a liquid refrigerant to the heated portion thereof, and after the quenching step, the outer layer There is also provided a method for producing a composite roll for metal rolling, comprising the step of performing a high temperature tempering treatment with a residual austenite phase of ash at 15% by volume or less.

The present invention solidifies and welds the above-mentioned high alloy steel in the roll axial direction to form an outer layer material, and heats the surface layer portion of a roll material having a roundness of 10 mm or less at a temperature above the transformation point by using a low alloy steel of lower hardness than the outer layer material as a core material. It is characterized by performing tempering at a temperature of 300 to 550 캜 after performing fractional quenching.

The present invention is characterized in that hot forging is performed before the quenching step of the outer layer material, and the sub agent is treated before the tempering treatment after the quenching step.

In addition, the present invention is a rolling mill having a work roll and a support roll for supporting the work roll, the work roll is made of low alloy steel and has a hardness higher than this core on the outer periphery of the core material having a roundness of 10 mm or less, Shore hardness 80 The rolling mill characterized by the above-mentioned outer layer material made of high alloy steel becoming a composite roll which solidified in the roll axial direction.

The present invention provides a rolling system having a work roll and a support roll supported by contacting the work roll in tandem with a tandem, wherein the work rolls of at least the first and second stages of the rolling mill are made of low alloy steel. It is composed of a composite roll having an outer layer made of a high alloy steel with a hardness higher than that of the core, the surface of the first stage is rougher than the surface roughness of the final stage, the outer diameter of the work roll is 250mm or more, The outer layer has a thickness of 30 mm or more.

An intermediate roll may be provided between the work roll and the support roll, and the work roll diameter may be the same or smaller from the first end to the last end.

In the above-described rolling system, all the working rolls of the rolling mill are constituted by a composite roll having a core made of low alloy steel and having an outer layer made of high alloy steel having a hardness higher than that of the core, wherein the working roll diameter of the ultra-short stand is at least the final end. It is characterized by being larger than the diameter of the work roll of the stand. At least the final end may have a diameter of 250 mm or more.

The present invention provides a rolling system having a work roll, an intermediate roll supporting and supporting the work roll, and a supporting roll supporting the intermediate roll, wherein the work roll of at least the ultra-short stand is low. It is comprised by the composite roll which has the core material which consists of alloy steels, and has an outer layer which becomes a high alloy steel with a hardness higher than this core material. It is characterized by the above-mentioned. The intermediate roll itself may also be a composite roll for some stands or all stands, with a lower hardness than the work roll.

The present invention is a rolling system having a work roll and a support roll supporting the work roll in a tandem multi-stage rolling system, wherein at least three coils are rolled by one grinding of the work roll and all of the work rolls The amount of wear is 1.5 mm or less per coil in terms of rolling of mild steel, and all of the work rolls are 250 mm or more in diameter.

It is preferable that the hardness of the work roll in this invention is Hs 90-100, Hs of a support roll is 60-70, and an intermediate roll is 70-80.

The work roll can be rotated by applying bending to further flatten the rolled material, and can also be rotated by applying bending in the middle roll. The intermediate roll can be slid left and right, and can be rolled by bringing the roll end closer to the rolled material depending on the rolling width.

In the case of a roll integrated with the outer layer material, there is a risk of splitting from the inside due to thermal stress during fountain quenching, and the toughness of the shaft portion is inferior. Therefore, the roll used the surface layer part as the said material, and the core material was made into the composite structure which consists of alloy steel with high toughness.

In addition, after installing an outer layer of a high alloy steel such as high speed tool steel, which is harder than this, on the outer circumference of the mandrel made of low alloy steel, hot forging is performed on the outer layer to disperse the carbides contained in the outer layer and to uniform the structure. It is preferable to carry out the treatment.

The composite roll of the present invention is a composite roll composed of a mandrel and an outer layer covering the core layer. If the entire roll is formed of the high speed tool steel (that is, an integral roll made of the high speed tool steel), the heat generated when fractional quenching is performed. There is a risk of cracking splitting from the inside due to stress, and the toughness of the shaft portion is reduced, so that the roll neck portion is easily broken during use. For this reason, a roll structure is employ | adopted as mentioned above. In the case of the quenching treatment, in the case of air cooling or oil cooling, the compressive residual stress of the surface layer is insufficient even if the material is used. That is, when the tempering treatment is performed at 300 to 550 캜 after the hardening treatment, it is difficult to obtain a hardness of Hs 93 or more. This is the reason for quenching by fractional cooling in the method of the present invention.

Tempering temperature in this invention is 300-550 degreeC, 450-550 degreeC is preferable and 500-550 degreeC is especially preferable. In the case of a cold rolled roll, the surface hardness is generally required to be Hs 90 or more. In the case of a hot rolled roll, the surface hardness is generally Hs 80 to 85.

As in the present invention, the residual stress in the case where only the outer layer portion is heated above the transformation point and subjected to the quenching treatment by rapid cooling means that the residual stress due to the thermal stress and the residual stress due to the transformation stress overlap. When the outer layer is quenched, compressive plastic deformation is generated in the plastic deformation temperature portion by the volume shrinkage. As a result, when it cools until the temperature inside and outside becomes the same, compressive residual stress will generate | occur | produce in an outer layer part and tensile residual stress inside. This is the residual stress due to thermal stress. In addition, the martensite generated in the outer layer portion due to transformation is relatively expensive, and due to the difference from the cost portion of the mandrel portion, tensile residual stress is generated in the mandrel portion and compressive residual stress in the hardened outer layer portion, respectively. As such, the residual stress generated by thermal stress and transformation stress is considerably larger than the residual stress generated by martensitic transformation alone (typically about -20 kg / mm2), and thus the compressive residual stress of the present invention is -70 kg / Mm <2>-20 kg / mm <2> (when processed by sub agent) can be obtained.

In addition, about 40% of austenite remains by water spray quenching alone, and in order to promote the decomposition of the retained austenite, sub-treatment at a temperature of -50 ° C. or lower is performed. It is performed by spraying liquid nitrogen on a roll surface, hanging a roll and rotating this. The amount of retained austenite after subzero treatment is generally less than 15%.

Subsequently, when tempering is performed at a temperature of 300 to 550 캜, the amount of retained austenite decreases from about 15% to about 1 to 5%. Finally, the retained austenite becomes a buffer to alleviate thermal expansion and contraction of the roll surface during use of the roll, and exhibits a function of preventing cracks on the roll surface. When the roll is tempered at a high temperature, when the roll is used for hot rolling, even if a high temperature steel sheet is wound on the roll due to an accident, the roll temperature may be increased, resulting in decomposition of residual austenite on the roll surface. Cracking is effectively prevented.

In general, when the tempering treatment is performed at a high temperature, it is known that deformation due to quenching tends to be released, and the amount of decrease in residual stress increases. However, since the high speed tool steel used in the present invention contains a large amount of alloying elements Si, Cr, Mo V, etc., which increase the tempering resistance, it is difficult to deform at tempering temperatures of about 5 ° C. when compared to general low alloy steels. Less liberation and high residual stress can be maintained.

In the present invention, the core material is preferably a low alloy steel having a tensile strength of 60 kg / mm 2 or more and an impact value of 1.5 kg-m / cm 2 or more, in particular, in weight% of C 0.5 to 1.0%, Si 1% or less, Mn 1% or less, Cr Forged steels containing 1 to 5% and Mo 0.5% or less are preferred.

The work roll for metal rolling according to the above configuration can be made to be sufficiently tolerated in terms of abrasion resistance, surface roughness, and toughness, even if it is used for rolling with a large bending, since it can be more alloyed to increase hardness. In particular, since the outer layer is welded to the shaft material by a specific manufacturing method by electro-slag remelting, the roundness of the core material is less than 10 mm, and the carbides crystallized from the molten metal solidify without flotation, sedimentation or segregation. It will be finely and evenly dispersed in the outer layer. As a result, the high pressure and solid state control of the rolling material are performed soundly, and the quality of the surface property of the rolling material is improved. Thus, the roundness of a core material becomes a problem especially in making the outer layer which highly alloyed like this invention. The roundness depends on the thickness of the outer layer material, and therefore, there is a fear of forming an unbalanced compressive residual stress in quenching and tempering, resulting in loss during use.

MEANS TO SOLVE THE PROBLEM In order to solve the problem of the prior art, and to achieve the said objective, the present inventors carried out experiment and reached the following invention.

In order to secure wear resistance and surface roughness, the outer layer needs to be made of higher alloy and heat treatment to maintain hardness of Hs 90 or more.

The specification of the chemical composition of the outer layer is based on the following reasons.

C is necessary for forming carbides and securing the known hardness to improve wear resistance. If the amount is less than 0.5%, the amount of carbide is small, which is not sufficient in terms of wear resistance. On the other hand, when C exceeds 1.5%, mesh-like carbides that precipitate at grain boundaries increase and deteriorate in terms of surface roughness and toughness. 0.8-1.2% is especially preferable.

Si is an element necessary as a deoxidizer and has 0.5% or more of it, and improves tempering resistance. However, when the amount exceeds 3.0%, embrittlement tends to occur, especially 1-3% is preferable, and 1.5-2.5% is more preferable.

Mn has a function of fixing the impurity S as MnS together with the deoxidation effect. However, if the amount exceeds 1.5%, the retained austenite increases, so that sufficient hardness cannot be maintained stably and the toughness decreases. 0.2-1.0% is especially preferable, and 0.2-0.5% is more preferable.

Cr is unreasonable because the hardenability is less than 2% and the Cr-based carbide becomes excessive when it exceeds 10%. Especially 3-7% is preferable and 3.5-5% is more preferable.

Mo and W, respectively, combine with C to form M ₂ C or M ₅ C-based carbides, and solid solution in the matrix to strengthen the matrix to improve wear resistance and tempering resistance. However, when excessive, M ₆ C-based carbides increase, leading to a decrease in toughness and surface roughness. The upper limit of Mo and W should be 12% and 20%, respectively, and the lower limit of W and Mo should be 1% or more. Mo is preferably 1.5 to 4.5% of semi-high steel, or 7 to 10% of high hess, and W is preferably 0.1 to 1% of semi-high steel or 0.5 to 5% of high-steel.

V contributes to the improvement of wear resistance by forming MC-based carbides, but less than 0.5% does not have sufficient effect. 0.7-2.0% is especially preferable.

Co is an element for solidifying at the base and quenching at high temperature to obtain high hardness, but the effect is insufficient at less than 5%. If it exceeds 15%, toughness will fall. 6 to 10% is particularly preferable. In particular, as the outer layer, the semi-high contains C, Si, Mn and Cr described above, and W 0.1-1%, V 0.5-2.0% and Mo 1-5% or Heis W 0.5-3%, 5-11% or 12 Co 20-20%, Mo 4-12%, V 0.5-1.5%, or 1.5-5%, or a combination thereof may be contained. In the composition considered based on Hot, since carbide amount considers abrasion resistance and seizure resistance, the amount of carbide increases.

The larger the amount of carbide, the harder it is to finish with grinding, the lower the toughness, and the less localized it is to withstand high local pressures, such as cold working rolls. For this reason, the alloy composition of the cold work roll reduces the amount of carbide (carbon amount) to the extent that the wear resistance is not impaired, and withstands the local pressure (rolling pressure) by strengthening the matrix (martensite, especially tempering martensite). . Co is effective as this matrix reinforcement, and high hardness can be obtained.

Moreover, the high alloy steel used for the outer layer of this invention may contain Ni other than the said element. Ni has an effect of improving the hardenability, and therefore Ni can be added in an amount of 5% or less. Exceeding this amount causes an increase in residual austenite, leading to a decrease in hardness and a decrease in surface roughness. In particular, 1% or less is preferable, More preferably, it is 0.1 to 0.5%.

In the present invention, it is preferable to use forged steel having Hs 35 or more as the material for the mandrel. That is, when a net stress of 10 kg / mm 2 is applied to the roll of the present invention as a nominal stress, the fatigue limit required as the dimensional effect factor 0.8, the surface effect factor 0.9 and the cutout factor 2.0 is 36 kg / mm 2. In order to obtain this, Hs 35 or more is preferable as the hardness.

As a method of providing an outer layer on the mandrel, hot welding is carried out using the continuous paste welding method using high frequency heating disclosed in Japanese Patent Application No. 44-4903, and the powder metallurgy method disclosed in Japanese Patent Application Laid-open No. 47-2851. The method of forming an outer layer by anti-pressurization, the addition welding method using the electroslag remelting method disclosed in Unexamined-Japanese-Patent No. 57-2862, etc. are mentioned. Electroslag remelting welding is particularly preferred.

In particular, a consumable electrode made of high alloy steel such as high-speed steel is inserted into a gap formed between the shaft and the mold arranged concentrically, and the shaft and the cooling mold are rotated in the circumferential direction, preferably 1 rpm or more, It was formed by supplying an alternating current to the consumable electrode and the accumulator under a slag bath to dissolve the consumable electrode and moving the cooling mold upward coaxially with the accumulator to solidify the molten metal by contacting it with the cooling mold. The outer layer is welded to the shaft. Rotation should be made between the shaft and the consumption electrode. Eccentricity of the core material can be prevented by allowing current and heat to flow evenly in each part.

The work roll for cold rolling by the above structure can be sufficiently endured in terms of abrasion resistance, surface roughness and toughness even when used for rolling with a large warpage. In particular, since the outer layer is rolled on the shaft material by electroslag remelting, carbides crystallized from the molten metal solidify rapidly without flotation, sedimentation, or segregation, so that they are dispersed finely and evenly in the outer layer. As a result, the high pressure and solid state control of the rolling material are performed soundly, and the quality related to the surface properties of the rolling material is improved.

The composite roll of the present invention can be used as a hot or cold working roll, and in particular, can be used for rolling by imparting warpage. Therefore, it can be used as a schedule preroll. In the rolling of carbon steel, the conventional roll life was about 4 to 5 hours, but the roll of the present invention has a lifespan of 2 to 5 times with a semi-high roll or 5 to 10 times with a high roll, and thus, in one polishing process. A life of 50 hours is obtained from 8 to 25 hours or 20 hours, and the taste recovery can be significantly lower.

According to the present invention, only one having a diameter of about 100 mm can be manufactured in the conventional single roll made of a high speed, but in the present invention, one having a diameter of 250 to 750 mm can be manufactured and can be used as it is in a conventional rolling mill.

Next, a preferred embodiment of the present invention is described.

Example 1

A roll having a body diameter of 750 mm and a body length of 1480 mm was used as a shaft material having a diameter of 665 mm to produce an ingot for a composite roll by an electro-dissolution method as follows.

8 is a schematic view of an apparatus for producing a composite roll by the electroslag addition welding method. The apparatus includes a welder (9), amplifier (17), electrical wiring (12), carbon brush (12a), temperature thermocouple (13), direct current motor (18), and manipulator (19). do. The manipulator 19 is moved by the DC motor 18, and the tubular consumption electrode 8, which is a consumed electrode made of high speed tool steel supported by the arm 12a of the manipulator, is moved upward. A low alloyed steel reshaft shaft 7 is provided on the rotary table 11. A water cooling mold 10 is provided concentrically with the mandrel 7, and a ring-shaped ignition plate (ie, a mold bottom) 16 is provided near the lower end of the mandrel 7 at both intervals. The core shaft 7 and the water cooling mold 10 are rotated at a speed of 5 rpm in the circumferential direction. The tubular electrode 8 supported by the manipulator 19 is placed in the gap portion defined by the mandrel 7 and the water-cooled mold 10, that is, the melting chamber, through the wiring 12 and the mandrel 7. The tubular electrode 8 is dissolved and consumed by an alternating current supplied to the tubular electrode 8. In the surface plate 11, five carbon brushes 12b are arranged evenly around, and a plurality of wires are arranged in the tubular electrode, and current flows evenly in each part, so that the slag 15 causes an arc to be generated by energization. At the same time, the molten metal 14 is melted by the resistance heat, cooled and solidified by contact with the water-cooled mold 10, and a uniform additional welding side 13 is formed on the surface of the mandrel 7. At this time, the water cooling mold 10 is moved upward coaxially with respect to the mandrel (7). The slag 15 is always adjusted to a thickness of 50 to 60 mm. In addition, the molten metal 14 is prevented from dropping downward by the ring-shaped bottom plate 16. The current voltage is controlled to be kept constant while being melted to control the thickness of the additional welding layer and the depth of penetration into the core material.

The forging welding layer of the composite roll thus obtained is forged at 1100 ° C. to have an outer diameter of 780 mm and an outer layer thickness of 42.5 mm. The quenching and tempering heat treatment may be performed on the delamination layer again to obtain a surface hardness of 90 or more Hs.

After heat treatment, cutting and polishing were cut and polished to a diameter of about 2 to 3 mm so that the finished outer diameter was 750 mm. Grinding was performed by abrasive stone so that the average surface roughness became about 0.5 micrometer.

The chemical components of the outer layer material are shown in the first table (% by weight). The balance is Fe. This roll was further subjected to quenching from 1000 to 1200 ° C and tempering heat treatment at 120 to 520 ° C for 10 to 20 hours. For comparison, rolls of the same dimensions were prepared for a conventional 5% Cr forged steel. Also about this material, a chemical component is shown in a 1st table | surface. The heat treatment was performed for the material. In addition, C 0.9% and 3% Cr forged steel were used for the shaft material of the roll of this invention, and the hardness was Hs40.

8 shows a method of fractional quenching. It is a part to which the outer layer 21 which is an additional welding layer of the roll 20 is quenched. The outer layer 21 of the roll 20 set vertically is surrounded by a ring-shaped device including an induction coil 22 and a water spray bottle 23 which are low frequency inductors. The roll 20 is rotated while the low frequency current flows in the induction coil 22 to operate downward. The outer layer 21 is a gradual quench that is continuously cooled and quenched by the cooling water injected from the water injection barrel 23 while being heated by the induced current generated. As a result, rapid cooling of 10 ° C / sec or more is achieved as the cooling rate. The cooling rate can be controlled by the amount of sprayed water and the spraying speed.

The heating to the quenching temperature was performed substantially so that only the outer layer 21 was carried out so that the boundary part with the core material might be below the austenite transformation point. As a result, the toughness of the core material at the boundary portion can be maintained high.

TABLE 1

FIG. 1 shows the relationship between the tampering temperature and the hardness, and FIG. 2 shows the relationship between the tampering temperature and the residual stress. Example No. of the present invention 1 and No. In the case of 2, the quenching temperature was 1060 degreeC, and the low frequency induction heating of only the outer layer part and the gradual quenching by continuous fountain cooling were performed by the method as shown in FIG. Thereafter, treatment was performed with a sebze at -50 ° C to perform tempering at each temperature. The cooling rate at this time was about 50 degreeC / sec.

In contrast with FIG. 1 and FIG. 2, it can be seen that the residual stress contributes to the hardness of the roll surface after tampering. In the conventional rolls, the tempering obtained by obtaining the hardness of Hs 93 is 160 ° C. In the case of 1, it turns out that the tampering temperature which can obtain the same hardness as 520 degreeC compared with the conventional roll is rising significantly. Moreover, Example No. of this invention in tampering temperature 5 degreeC 00 degreeC. 1 and No. The residual stress of the surface of 2 is larger than -70 kg / mm 2, and in the conventional rolls, the residual stress of the roll surface is about -30 kg / mm 2, which shows that a large residual stress can be ensured by the present invention.

No. The residual austenite amounts of 1 and 2 were 10-15% by volume.

No. In the case of 2, the hardness after tempering at 500 degreeC is Hs 88, and the Si addition effect is confirmed clearly.

2 is No. The comparison of the thermal shock resistance of 1 and the conventional roll is shown. In the test, the material is taken from the roll material surface after forging, processed, and then quenched. 1 was tempered at 520 degreeC and the conventional roll, respectively, and the test was done. In the test method, a test piece of 80 mm in diameter and 40 mm in thickness was rotated at 1420 rpm, and water cooling was performed while pressing a 20 mm soft steel material to the test piece under a load of 500 g / mm.

The crack length of the longitudinal axis of FIG. 2 is the sum of the crack lengths generated on the surface of the test piece, but the crack length of the conventional material is 54 mm, and in the case of No. 1, it is 23 mm or less, which is less than half of the conventional material, so that the effect of high temperature tempering is obvious. .

3 shows a comparison of wear resistance. The test was subjected to the same heat treatment on a test piece having a diameter of 18 mm on the sliding surface, and was slid with a load of 500 g on the # 100 emery paper. In the case of No. 1, the wear amount of the conventional roll is 230 mg, which is excellent even in the wear resistance at 120 mg.

No. The roll of 1 was made into the shape of FIG. 4, and this was used and the rolling mill shown in FIG. 5 was used as a tandem on a seven-stage stand of F ₁ to F ₇ as shown in FIG. As a result of cold rolling of a stainless steel foil and a sheet steel sheet for thin steel sheet having a thickness of 200 µm or less, it was confirmed that five times or more of abrasion resistance was obtained as compared with a conventional integrated roll. Reference numeral 1 denotes a rolled material, 2 a work roll according to the embodiment is assembled in an ultra-short stand, 3 an intermediate roll, 4 a support roll, 5 an outer layer, and 6 a core material. The middle roll 3 can be shifted left and right.

As a result of cutting several rounds of the composite roll of this invention and measuring roundness of the cross section several times, roundness was 5-6 mm in all. In addition, as a result of the tensile test performed at the boundary between the outer layer material and the core material, the core part was broken in any test.

The thickness of the hardened hardened layer was 40 mm or more, and the compressive residual stress of about 40 kg / mm <2> or more was formed in at least 40 mm.

In Fig. 5, bending is applied to the F _W and F ₁ rolls in the direction of the arrow so that the bending rate of the edge portion of the rolled material is made smaller. F ₁ to F ₃ is the stand was set to Figure 5a, F _4, and R ₅ is the Figure 5b, F ₆ and F ₇ are the degrees of the roll 5c disposed.

According to this embodiment, even if the surface hardness is the same as that of the conventional roll, it can be tempered at a high temperature of 300 ° C or higher, so that the resistance to thermal shock caused by slip, accident, etc. during rolling is maintained as compared with conventional rolls. It can be raised considerably.

7 is a diagram showing the relationship between hardness and residual stress and depth from the roll surface.

Example 2

Rolls having a body diameter of 425 mm and 750 mm and a body length of 1100 mm were prepared approximately the same in the apparatus shown in FIG. 8 as in Example 1 using shaft members having a diameter of 340 mm and 665 mm and a length of 3700 mm. The chemical component of the former roll outer layer material at this time is shown in a 2nd table | surface. In addition, since the latter uses the same electrode, no special analysis was performed. The roll was again heated by induction heating only at the surface layer portion at 1100 to 1200 ° C., and subsequently quenched by air cooling. Then, the whole roll was heated at 500 to 550 ° C. to perform tempering heat treatment. For comparison, rolls of the same size were also prepared for a conventional 3% Cr forged steel. Also about this material, a chemical component is shown in a 2nd table | surface. The heat treatment was performed for the material. The hardness of any surface portion was Hs 90 or more and 95. In addition, the shaft material of the roll of the present invention contained 0.9% C, 3% Cr and 0.2% Mo by weight, and used forged steel of Si: 0.3%, Mn: 0.7%, and the hardness thereof was Hs 40. The latter roll was forged before heat treatment. As a result of observing the microscopic structure of the cross section with respect to these rolls, no abnormality was confirmed in the joint portion of the outer layer and the shaft member irradiated by the roll body edge portion of the present invention. Each average surface roughness was about 0.1 mu m in the former, 0.5 mu m in the latter, and all of the cured layers of Hs 90 or more were about 50 mm.

As is evident from these results, the roll of the present invention satisfies the required characteristics while both the surface and the joint are satisfactory. The thickness of the additional welding layer of each roll was approximately uniform thickness of about 40 mm as a result of accurate measurement by an ultrasonic wave.

Cold rolling of ordinary steel was performed similarly to Example 1 using the roll obtained by the present Example. The former roll was used for the final stage and the latter roll for the first stage, and the relationship between the number of rolled coils and the roll surface roughness of each roll was examined. The result of the first roll is shown in FIG. In these rollings, the roll of the present invention has almost no roughness reduction and shows excellent wear resistance. In addition, the roll of the present invention did not have a cracking accident of the body portion or a breakage of the neck portion. The length of one coil was about 40 km. The big difference was not seen even in the roll of the last stage.

TABLE 2

Moreover, when the round was cut into several pieces and the roundness of the cross section was measured, it was 5-6 mm of some parts of a certain roll. The amount of retained austenite in the outer layer was about 15% by volume.

According to this embodiment, since it is a cold rolling work roll using steel having excellent toughness in the shaft material by using steel such as high-speed steel having excellent wear resistance and surface roughness in the outer layer material, the roll having excellent wear resistance, surface roughness and toughness can be obtained. . Accordingly, the present invention greatly contributes to the improvement in productivity and quality in cold rolling.

According to the production method of the present embodiment, a roll made of steel having excellent toughness in the shaft material can be easily produced by using steel such as high-speed steel having excellent abrasion resistance and surface roughness as the outer layer material without generating coagulation unevenness.

As in Example 1, water spray quenching was performed after high frequency heating, followed by subzero treatment at -70 ° C. As a result, the retained austenite structure was transformed into martesite, and the amount of retained austenite was further lowered and the hardness was slightly higher. High compressive residual stress was obtained.

Example 3

The composite roll obtained in Example 1 was used for the work rolls of F ₁ to F ₃ shown in FIG. 10, and the composite roll obtained in Example 1 was used for the work rolls of F4 and F ₅ with a slightly smaller diameter. In addition, the thin diameters obtained in Example 2 were used for the work rolls of F ₆ and F ₇ , respectively, and the intermediate rolls were made of mild steel as described above using an integral roll made of cold dietm steel having Hs 80 to 85. Rolling was performed. Five coils were rolled by one polishing in the two-rolling system, but they could be rolled with almost no problem, and the amount of wear per coil was 0.15 mm or less. The support roll used forged steel of 3% Cr steel. The weight of one coil was about 500 t.

Example 4

The composite roll obtained in Example 1 was used for the intermediate roll of the last stage, the thin diameter roll obtained in Example 2 was used for the work roll, and the remainder was the same as Example 3, and the mild steel was rolled similarly. The surface roughness of this intermediate roll was roughly the same as that of the work roll, the surface hardness of the intermediate roll was approximately Hs 90, and the hardness of the work roll was used as Hs 95. Abnormal abrasion was not found especially in this rolling, and a good rolling result was obtained.

From this point of view, it is possible to use a composite roll in which all the work rolls are adjusted, in particular, a hardness or a part or all of the intermediate rolls on all the stands. It was found that it was possible to roll a large amount in one grinding while rolling in accordance with the rolling schedule while grinding each time, so that it was possible to roll the schedule free without specially squeezing the schedule.

The composite roll of the present invention is particularly effective in cold rolling, but can also be used in hot rolling.

Claims (11)

In the composite roll for metal rolling coating the outer periphery of the core material with an outer layer material, the core material has a Shore hardness of 35 or more and a roundness of 10 mm or less, having a lower hardness than the outer layer material, C 0.5 to 1.0% by weight, Si It is made of low alloy steel containing 1% or less, Mn 1% or less, Cr 1-5%, Mo 0.5% or less, and the outer layer material is martensite structure having Shore hardness of 80 or more and residual austenite amount of 15 volume% or less, The residual stress at the outermost surface has a compressive stress of 70 kg / mm 2 or more, C 0.5 to 1.5% by weight, Si 0.5 to 3.0%, Mn 1.5% or less, Cr 2 to 10%, Mo 1 to 12%, V 0.5 A composite roll for metal rolling, comprising from 2.0% to 2.0% and W from 0.1% to 20% and made of a high alloy steel solidified in the roll axial direction. Outer layer of high alloy steel solidified in roll axial direction, containing C 0.5 to 1.5%, Si 0.5 to 3.0%, Mn 1.5% or less, Cr 2 to 10%, V 0.5 to 2.0%, W 1 to 20% by weight. A low alloy steel containing C 0.5 to 1.0% by weight, Si 1% or less, Mn 1% or less, Cr 1 to 5% and Mo 0.5% or less by weight, and the roundness is 10 mm or less. Composite roll for metal rolling. In the composite roll for metal rolling in which the outer circumference of the core material is covered with the outer layer material, the core material contains C 0.5 to 1.0%, Si 1% or less, Mn 1% or less, Cr 1 to 5%, and Mo 0.5% or less by weight. It is made of a low alloy steel having a lower hardness than the outer layer material, the roundness of less than 10mm, the outer layer material is C 0.5 to 1.5%, Si 0.5 to 3.0%, Mn 1.5% or less, Cr 2 to 10%, Mo A composite roll for metal rolling, comprising a welding layer made of a high alloy steel containing 1 to 12%, V 0.5 to 2.0%, and W 0.1 to 20% and solidified in the roll axial direction. It consists of a high alloy steel containing by weight 0.5 to 1.5%, Si 0.5 to 3.0%, Mn 1.5% or less, Cr 2 to 10%, V 0.5 to 2.0%, W 0.1 to 20% and Ni 5%, The welding layer solidified in the roll axial direction is used as the outer layer, and has a lower hardness than the outer layer, and C 0.5 to 1.0%, Si 1% or less, Mn 1% or less, Cr 1 to 5%, and Mo 0.5% or less by weight. A composite roll for metal rolling comprising a low alloy steel containing as a core material and having a roundness of 10 mm or less. Welding composed of high alloy steel containing by weight 0.5 to 1.5%, Si 0.5 to 3.0%, Mn 2% or less, Cr 2 to 10%, V 0.5 to 2.0%, W 1 to 20% and Co 1 to 15% by weight. The layer is made of an outer layer, and has a lower hardness than the outer layer, and a low alloy steel containing C 0.5 to 1.0% by weight, Si 1% or less, Mn 1% or less, Cr 1 to 5%, and Mo 0.5% or less as a core material. And the roundness is 10 mm or less, The composite roll for metal rolling characterized by the above-mentioned. A core made of low alloy steel containing C 0.5 to 1.0% by weight, Si 1% or less, Mn 1% or less, Cr 1 to 5%, and Mo 0.5% or less has a higher hardness than the core material, and C 0.5 to 1.5 by weight. Metal rolling composite having an outer layer made of high alloy steel containing%, Si 0.5 to 3.0%, Mn 1.5% or less, Cr 2 to 10%, Mo 1 to 12%, V 0.5 to 2.0%, W 0.1 to 20% The roll according to claim 1, wherein the core has a roundness of 10 mm or less, and the outer layer is an equiaxed crystal having a solidified structure in the axial direction. Air gap formed between the condensation material of the low alloy steel containing C 0.5 to 1.0%, Si 1% or less, Mn 1% or less, Cr 1 to 5%, Mo 0.5%, or less and a concentrically arranged cooling mold. On the other hand, the hardness is higher than the storage material and forms an outer layer, and C by weight is 0.5 to 1.5%, Si 0.5 to 3.0%, Mn 1.5% or less, Cr 2 to 10%, Mo 1 to 12%, V 0.5 to 2.0%, Inserting a consumption electrode made of a high alloy steel containing 0.1 to 20% of W, and rotating the shaft material and the cooling mold in the circumferential direction to supply an alternating current to the consumed electrode and the shaft material from a plurality of locations, respectively, in a slag bath. And melting the consumed electrode to form a molten metal, and moving the cooling mold in the axial direction of the shaft material and solidifying the molten metal to weld the outer layer integrally to the shaft material. On the outer circumference of the core material which consists of low alloy steel containing C 0.5-1.0%, Si 1% or less, Mn 1% or less, Cr 1-5%, Mo 0.5% or less by weight, hardness is higher than this low alloy steel, An outer layer material made of high alloy steel containing 0.5 to 1.5% of C, 0.5 to 3.0% of Si, 1.5% or less of Mn, Cr 2 to 10%, Mo 1 to 12%, V 0.5 to 2.0%, and W 0.1 to 20% A method of manufacturing a composite roll for metal rolling to solidify welding in a roll axial direction, wherein the outer layer material is formed so that the roundness of the core material is 10 mm or less, and then gradually heating the outer layer material to a temperature above the austenite transformation point. A quenching step of carrying out gradual quenching by injecting a liquid refrigerant into the heated portion, and a step of tempering at a temperature of 300 ° C. or higher to reduce the residual austenite phase of the outer layer material to 15% by volume or less after the quenching step. Characteristic The method of producing a composite roll for metal rolling which. Roll axial direction of high alloy steel containing C 0.7-1.5% by weight, Si 0.5-3.0%, Mn 1.5% or less, Cr 2.0-7.0%, Mo 1-5%, V 0.5-2.0%, W 20% or less To a low alloy steel containing less than 0.5% of 1.0% C, 1% of Si, 1% of Mn, 1% of Cr, and 0.5% of Mo. A method of manufacturing a composite roll for metal rolling, characterized in that the core layer is heated to a temperature above the transformation point of a roll material having a roundness of 10 mm or less, subjected to fractional quenching, and tempered at a temperature of 300 ° C or higher. The method for producing a metal-rolled composite roll according to claim 8 or 9, wherein hot forging is performed before the quenching step of the outer layer material. The method for producing a composite roll for metal rolling according to claim 8 or 9, wherein a subzero treatment is performed after the quenching step and before tempering.

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