TWI471420B - A forged roll meeting the requirements of the cold rolling industry and a method for production of such a roll - Google Patents

Description

Forging roll complying with cold rolling industry regulations and method for manufacturing the same

The present invention relates generally to the field of forging rolls and to the manufacture of forged rolls. More specifically, the present invention relates to forging rolls that meet the requirements of the cold rolling industry and is primarily directed to the use of forging rolls in the cold rolling industry.

background

General background

The general trend of cold rolling in the iron and non-ferrous metals industries is faster, thinner and wider rolling. The current challenge is to achieve this while achieving perfect control of flatness, thickness and surface appearance compatible with high productivity. Therefore, this trend requires the use of advanced rolling techniques that control critical rolling parameters.

Some key parameters such as roughness retention and surface appearance can be guaranteed by chrome plating of the work rolls. This practice is effective and efficient, but becomes increasingly problematic due to environmental constraints and becomes unacceptable in the near future.

Today, forged work rolls with surface chrome plating (2% to 6% Cr) are commonly used in cold rolling processes. The chrome plating of these rolls is applied to improve the wear resistance in terms of surface texture retention, which in turn will ensure, for example, the consistency and higher gloss of the body after painting. The chrome-plated hard electrolytic deposition technique was originally developed for tempering/skin rolling mill applications. In such applications, chrome-plated work rolls exhibit a life of 2 to 8 times longer than uncoated rolls, primarily due to better roughness maintenance. The implementation of this technology has gradually expanded to reduce rolling mills.

There are also forged rolls made of high speed steel (HSS) intended to be used without coating, but which require rolls with low residual internal stress and also require an industrial process for making the rolls, which is intended to be used in rolling mills. Used without coating and at the same time providing at least equivalent roughness maintenance with the coated rolls.

Concrete background

Rolls that are manufactured for use in the cold rolling industry must manage processing conditions or specific operating stresses during use without cracking or bursting. The bursting of the rolls can involve the safety of the operator and the damage in the mill. Therefore, there is a need for a roll having low residual internal stress.

An example of a prior art that reveals the development of an HSS roll without coating to achieve cold rolling goals is disclosed:

C. Gaspard, C. Vergne, D. Batazzi, T. Nylen, PH Bolt, S. Mul, KM Reuver: "Implementation of in-service key parameters of HSS work roll grade dedicated to advanced cold rolling", IST Conference, 2010 May 3-6, Pittsburgh, Pa, USA

C. Gaspard, S. Bataille, D. Batazzi, P.Thonus: "Improvement For Advanced Cold Rolling Reduction Mills By Using Semi-HSS and HSS Rolls" , 7th International Conference on Steel Rolling (ISIJ), Makuhari, Chiba, Japan , 1998

PH Bolt, D. Batazzi, NP Belfiore, C. Gaspard, L. Goiset, M. Laugier, O. Lemaire, D. Matthews, T. Nylen, K. Reuver, D. Stocchi, F. Stork, J. Tensen, M. Tornicelli, R. Valle, E. van den Elzen, C. Vergne, IM Williams: "Damage Resistance and Roughness Retention ofwork Rolls in cold Rolling Mills" , 5th European Steel Rolling Conference, June 23-25, 2009 , London, UK

Other examples of the prior art shown in the following patent publications are: JP09003603, JP53077821, JP57047849, JP2002285284, JP2002285285, JP10317102, JP1208437, EP0395477, and JP08158018, which describe work rolls for cold rolling to enhance wear and crack resistance.

However, such fragments of the prior art lack disclosure of the parameters and characteristics required to achieve and achieve operation of this HSS roll during cold rolling mill conditions.

total Body goal

It is a general object of the present invention to provide a preferably uncoated form of the roll which is operated during cold rolling mill conditions and an industrial process for making the roll. A more specific objective is to provide such a roll and process for making the roll while maintaining at least equivalent tribological properties to prior art coated rolls, such as low coefficient of friction, high roughness retention, and no iron filings. Dust contamination, and this roll exhibits improved mill performance in terms of higher crack resistance and higher safety in comparison to known rolls in operation.

Partial problem

The present invention further seeks to solve the following partial problems:

- Improved roll surface for higher efficiency

- Avoid roll spalling accidents

- Avoid non-environmental rolling manufacturing methods

- Improved roll spacing or life, allowing for longer runs per mill.

Summary of invention

The problems listed above, some of the problems and the solution of the aspect are the rolls according to the invention with improved resistance to cracking and low crack propagation, which will reduce the sensitivity to rolling mill accidents while maintaining a high Wear resistance.

The present invention provides a forging roll for use in the cold rolling industry and a method of manufacturing the same. The roll is preferably uncoated, but may also be coated.

A first aspect of the invention relates to a forged roll comprising a steel composition comprising, by weight percent, from 0.8% to less than (<) 1% C, from 0.2% to 0.5% Mn, 0.2. % to 2.0% Si, 7.0% to 13.0% Cr, 0.6% to 1.6% Mo, greater than (>) 1.0% to 3.0% V, the remainder of the steel is substantially Fe and may be incidental and/or possible Inevitable impurities; and wherein the microstructure of the roll comprises: - tempered martensite having a residual austenite ratio of less than (<) 5% by volume; and - an open eutectic carbide network having less than (<) 5 5% by volume of eutectic carbide; and wherein the roll exhibits: - a hardness between 780 HV and 840 HV; and - an internal compressive stress between -300 MPa and -500 Mpa.

In other embodiments of the invention, the rolls of the present invention comprise an open eutectic carbide network that scribes a cell-like pattern of eutectic cells.

Other variations of the roll include any of the following optional, individual or combinationable forms: a roll wherein the open eutectic carbide network of the roll comprises a dendrite arm.

A roll wherein the open eutectic carbide network of the roll is formed as a substantially isolated portion of the eutectic carbide network.

A roll wherein the microstructure of the roll is present at least in the working layer of the roll.

A roll having, by weight %, a steel composition consisting of 0.8% to less than (<) 1% C, 0.2% to 0.5% Mn, 0.2% to 2.0% Si, 7.0% to 13.0% Cr, 0.6% to 1.6% Mo, greater than (>) 1.0% to 3.0% V, less than (<)0.01.5% P, and less than (<)0.015% S, and less than (< 1% of Ni is less than (<)30 ppm of O ₂ , and less than (<) 100 ppm of N ₂ , and less than (<) 3 ppm of H _{2 is} less than (<) 2% of W, and less than (<) 1% Nb, and less than (<) 1% Ti, and less than (<) 0.5% Ta, and less than (<) 0.5% Zr, the remainder of the steel is substantially Fe and may be incidental and/or possible Inevitable impurities; rolls according to the invention wherein the C content of the steel composition is between 0.8% and 0.99% C by weight of the total roll weight.

The roll according to the present invention, wherein the C content in the steel composition is between 0.85% and 0.9% C by weight of the total roll weight.

The roll according to the invention wherein the Mn content in the steel composition is between 0.4% and 0.5% Mn by weight of the total roll weight.

The roll according to the invention wherein the Si content in the steel composition is between 0.2% and 1.5% Si by weight of the total roll weight.

The roll according to the present invention, wherein the Si content in the steel composition is between 0.85% and 1.15% Si by weight of the total roll weight.

The roll according to the invention wherein the Cr content in the steel composition is between 7.0% and 11% Cr by weight of the total roll weight.

The roll according to the present invention, wherein the Cr content in the steel composition is between 7.3% and less than (<) 8.0% Cr by weight of the total roll weight.

The roll according to the invention wherein the Mo content in the steel composition is between 1.45% and 1.55% Mo by weight of the total roll weight.

The roll according to the present invention, wherein the Ni content in the steel composition is less than (<) 0.3 Ni by weight of the total roll weight.

The roll according to the invention wherein the V content in the steel composition is between 1.3% and 2.1% V by weight of the total roll weight.

The roll according to the invention wherein the V content in the steel composition is between 1.3% and 1.6% V by weight of the total roll weight.

A roll according to the present invention, wherein the steel composition is composed by weight% by weight: 0.8% to 0.99% C, and 0.4% to 0.5% Mn, and 0.2% to 1.5% Si, and 7.0% to 11% of Cr, and 0.6% to 1.6% of Mo, and less than (<)1.0 of Ni, and 1.0% to 2.1% of V, and less than (<)0.015% of P, and less than (<)0.015% S, and O ₂ less than (<) 30 ppm, and N ₂ less than (<) 100 ppm, and H ₂ less than (<3 ppm), and the remainder of the roll is substantially Fe and may be incidental and/or Impurities that may be inevitable.

A roll according to the present invention, wherein the steel composition is composed by weight% by weight: 0.85% to 0.9% C, and 0.4% to 0.5% Mn, and 0.85% to 1.15% Si, and 7.3% to Less than (<)8.0% of Cr, and 1.45% to 1.55% of Mo, and less than (<)0.3 of Ni, and 1.3% to 1.6% of V, and less than (<)0.015% of P, and less than (< ) 0.01% S, and less than (<) 30 ppm O ₂ , and less than (<) 100 ppm N ₂ , and less than (<) 3 ppm H ₂ , and the remainder of the roll is substantially Fe and possible Incidental and/or potentially unavoidable impurities.

The rolls according to the invention are further configured for use as work rolls in cold rolling.

The rolls according to the invention further have a weight of more than 400 kg.

The rolls according to the invention further have a diameter in the range from 215 mm to 800 mm.

Another aspect of the present invention provides a forged roll manufactured by a process comprising the following steps:

a. A steel composition comprising, by weight %, 0.8% to less than (<) 1% C, 0.2% to 0.5% Mn, 0.2% to 2.0% Si, 7.0% to 13.0% Cr 0.6% to 1.6% Mo, greater than (>) 1.0% to 3.0% V, the remainder of the steel being substantially Fe and possibly incidental and/or possibly unavoidable impurities; in other embodiments, in accordance with the present invention The composition is any one of the above compositions or a combination of compositions.

b. manufacturing an ingot that maintains a solidification rate of greater than 15 ° C/min in the surface layer of the ingot during the setting interval, equivalent to the surface layer of the roll;

c. forging the ingot into a roll;

d. hardening the roller by induction heating;

e. tempering the roll; thereby achieving a microstructure of the roll, the microstructure comprising: - tempered martensite having a residual austenite ratio of less than (<) 5 vol%; and - an open total a crystalline carbide network having less than (<) 5% by volume of eutectic carbide; and wherein the roll (1) exhibits: - a hardness between 780 HV and 840 HV; and - between -300 MPa and -500 Internal compressive stress between MPa.

Other variations of the roll include any of the following optional, individual or combinable aspects with respect to the chemical composition or microstructure of the roll described above, and further comprising the following optional, individual or combinable combinations comprising the following The characteristics of any of the aspects.

According to the present invention, another aspect of the present invention provides a method of making a non-forged roll, the method comprising the steps of:

a. A steel composition comprising, by weight %, 0.8% to less than (<) 1% C, 0.2% to 0.5% Mn, 0.2% to 2.0% Si, 7.0% to 13.0% Cr , 0.6% to 1.6% MO, greater than (>) 1.0% to 3.0% V, the remainder of the steel is substantially Fe and possibly incidental and/or possibly unavoidable impurities; in other embodiments, in accordance with the present invention The composition is any one of the combinations of the above compositions.

b. producing an ingot that maintains a solidification rate of greater than 15 ° C/min in the working layer of the ingot during the setting interval, equivalent to the working layer of the roll;

c. forging the ingot into a roll;

d. hardening the roller by induction heating;

e. tempering the roll at a temperature between 450 ° C and 530 ° C to achieve a hardness of between 780 HV and 840 HV; thereby achieving a microstructure of the roll (1), the microstructure Including: tempered martensite having a residual austenite ratio of less than (<) 5% by volume; and an open eutectic carbide network having less than (<) 5% by volume of eutectic carbide; Roller (1) exhibits: - a hardness of between 780 HV and 840 HV; and - an internal compressive stress of between -300 MPa and -500 MPa.

Other variations of the rolls include any of the following optional, individual or combinable aspects.

According to one method of the invention, wherein the ingot is produced, which maintains a solidification rate in the working layer and core in the following range: 15 ° C / min to 55 ° C / min, or 17 ° C / min to 50 ° C / min, Or 35 ° C / min to 55 ° C / min, or 45 ° C / min to 55 ° C / min.

According to one method of the invention, the ingot is produced which maintains a solidification rate above 35 ° C/min in the working layer or surface of the ingot during the setting interval.

According to one method of the invention, wherein the ingot interval is between 1400 ° C and 1200 ° C for the ingot.

In accordance with one method of the invention, the ingot is fabricated by maintaining a preselected solidification rate in an electroslag refining furnace (ESR) process by controlling the amperage current source based on a predetermined function of the solidification rate.

A method wherein the step of forging the ingot into a roll comprises the steps of:

a. heating the ingot to a temperature between about 850 ° C and 1100 ° C or between 800 ° C and 1000 ° C, preferably for a period of about 6 hours;

b. forging the ingot at a temperature above about 800 ° C or above 850 ° C;

c. Repeat steps a-b until the ingot has been formed into a roll of the desired shape and size.

A method further comprises, after the forging step, a step of preliminary heat treatment applied to the roll blank, preferably to a temperature of between about 700 ° C and 1100 ° C or between 800 ° C and 900 ° C, the preliminary heat treatment comprising a hydrogen diffusion treatment.

One method further comprises the step of shallow hardening by progressive induction heating, preferably at a temperature of from about 900 °C to 1150 °C.

A method wherein the step of tempering the roll comprises the steps of:

d. heating the roll to between about 450 ° C and 530 ° C or between 450 ° C and 520 ° C, preferably 3 times.

e. Cool the roller with air between the heating steps.

A method further includes processing the roll to texturize a white layer comprising eutectic carbide.

Additionally, variations of the method of the present invention comprise any of the following optional, individual or combinable aspects with respect to the chemical composition or microstructure of the above-described rolls, and further comprising the following optional, individual Or the characteristics of any of the combinations can be combined.

Another aspect of the present invention provides an intermediate product ingot in the manufacture of a roll comprising a steel composition comprising, by weight percent, 0.8% to less than (<)1 % C, 0.2% to 0.5% Mn, 0.2% to 2.0% Si, 7.0% to 13.0% Cr, 0.6% to 1.6% Mo, greater than (>) 1.0% to 3.0% V, steel The remainder is substantially Fe and possibly incidental and/or possibly unavoidable impurities; and wherein the microstructure of the final roll formed from the ingot comprises: - tempered martensite having a residue of less than (<) 5 vol% Austenite ratio; and - an open eutectic carbide network having less than (<) 5% by volume of eutectic carbide.

Additionally, a variant of the intermediate ingot of the present invention comprises any of the following optional, individual or combinable aspects with respect to the chemical composition of the ingot described above, and further comprises the following optional, individual Or the characteristics of any of the combinations can be combined.

Another aspect of the present invention provides the use of a forged roll according to the present invention for a cold rolled material requiring a high rolling load.

Other embodiments of the present invention provide for the use of forging rolls for cold rolling of high strength materials such as AHSS steel grades.

The use of the forging rolls according to the invention for the following: - cold rolling reduction rolling mills for tinplate, sheet, tantalum, stainless steel, aluminum and copper early and finishing stands, reversible and irreversible stands; or Cold-rolled tempering and/or skin rolling mills; or - 2-roll (2-High), 4-high (4-High) and 6-high (6-High) machines with textured or untextured surfaces The rolling mill configuration.

The forged roll according to the invention is used as a work roll.

The rolls according to the invention can be used as uncoated rolls in many applications. However, in other aspects and embodiments of the invention, the roll may also have a coating selected for any current or specific application. The coating can be, for example, a chromium coating. This roll can also be used in warm rolling applications.

The invention will be further described by means of illustrative embodiments.

Foreword

The present invention is generally directed to a forge roll 1 which preferably has a weight of more than 400 kg or, as in a general application embodiment, has a weight of, for example, more than 1000 kg. The roll according to the invention is produced according to the method of manufacturing a forging roll, which is known per se in its general procedure but is specifically adapted according to the inventive concept to enable the manufacture of a roll according to the invention.

The invention is primarily directed to rolls having a weight between 400 kg and 10000 kg. The roller according to the invention has a diameter 2 of generally greater than 200 mm and, for example, between 215 mm and 800 mm, and a length of the cartridge 8 typically between 1 and 3 meters, and including the neck The maximum length of 10 is usually about 6 meters. The roller 1 has a working layer 4 which corresponds to a portion of the outer layer and which typically has a diameter ranging between 20 mm and 120 mm, depending on the application of the particular roller and/or on the total roller diameter 2. Typically, the outer 1/6 portion 6 of the diameter 2 of the roll is referred to as the working layer 4 of the roll 1, see Figure 1. In the text, the 1/6 portion 6 other than the diameter 2 of the ingot 34 is also referred to as the working layer 4 of the ingot 34.

Special problems and challenges are involved in the manufacture of large forging rolls due to the internal stresses involved in forming such large rolls. Rolls with smaller diameters will not require the same treatment because the internal application is lower and their rolls are not inclined, for example, to burst during hardening. The roll manufacturing method 12 according to the present invention is crucial for the manufacture of the roll 1 of this size according to the present invention. The improved mechanical properties, such as the low residual internal stress of the rolls of the present invention, are produced by the roll manufacturing process 12. In order to achieve the residual internal stress of the low level of the resulting roll, the internal stress induced by the thermal gradient and the allotropic state must be minimized in all stages of the manufacturing process through casting, forging, heat treatment and processing. The microstructure of the roll 1 according to the invention comprises tempered martensite having a residual austenite ratio of less than 5% by volume, due to the method of manufacture of the roll and to the chemical composition according to the invention.

The roll manufacturing method according to the present invention comprises the selection of the following basic steps schematically shown in the flow chart of Figure 2:

14. Providing steel compositions

16. Manufacturing ingot 34

18. Forging the ingot 34 into a roll 1

20. Initial heat treatment of the roller 1

22. Roughing the roller 1

24. Induction hardening of the roller 1

26. Tempering heat treatment of the roller 1

28. Processing the roller 1

Intermediate products are obtained after the individual steps. The specific control parameters of the rolls as well as the chemical composition are selected to produce a roll in accordance with the present invention.

Roll manufacturing method

The present invention relates to a forged roll (1) manufactured by a method comprising the following steps:

a. A steel composition comprising, by weight %, 0.8% to less than (<) 1% C, 0.2% to 0.5% Mn, 0.2% to 2.0% Si, 7.0% to 13.0% Cr , from 0.6% to 1.6% Mo, greater than (>) 1.0% to 3.0% V, the remainder of the steel being substantially Fe and possibly incidental and/or potentially unavoidable impurities;

b. producing an ingot that maintains a solidification rate of greater than 15 ° C/min in the working layer of the ingot during the setting interval;

c. forging the ingot into a roll;

d. hardening the roller by induction heating;

e. tempering the roll; thereby achieving a microstructure of the roll (1) comprising: - tempered martensite having a residual austenite ratio of less than (<) 5 vol%; and - An open eutectic carbide network having less than (<) 5% by volume of eutectic carbide; and wherein the roll (1) exhibits: - a hardness greater than 780 HV; and - an internal compression less than -500 Mpa (absolute) stress.

In the microstructure of the roll according to the invention, the chemical composition provided according to the invention is used in combination with the process steps described in accordance with the invention to impart the desired characteristics of the roll according to the invention.

The method of making a forged roll according to the present invention comprises the following steps: Step 14: Providing a steel composition.

In one embodiment of the invention, the steel composition comprises an alloy comprising or consisting of the following components as indicated by weight percent listed in Table 1. In Table 1, the effects of the components and the effects of the rolls of the present invention achieved by selected components and specific intervals are explained.

And further optionally H ₂ , N ₂ , O ₂ , Al, Cu, each of which is less than 0.4% by weight, and wherein the remainder of the steel composition is substantially Fe, in addition to incidental elements And impurities that may be inevitable.

In one embodiment of the invention, the steel composition comprises, by weight percent, from 0.8% to less than (<) 1% C, from 0.2% to 0.5% Mn, from 0.2% to 2.0% Si, from 7.0% to 13.0. % Cr, 0.6% to 1.6% Mo, greater than (>) 1.0% to 3.0% V, wherein the remainder of the steel is substantially Fe, in addition to incidental elements and possibly unavoidable impurities.

In various variations and embodiments of the invention, the compositions comprise or consist of combinations or selections of components (% by weight) according to the following examples. In some instances, the foregoing embodiments are combined with, by or substituted for, the following variants of the amount of components.

A roll having, by weight %, a steel composition consisting of 0.8% to less than (<) 1% C, 0.2% to 0.5% Mn, 0.2% to 2.0% Si, 7.0% to 13.0% Cr, 0.6% to 1.6% Mo, greater than (>) 1.0% to 3.0% V, less than (<)0.015% P, and less than (<)0.015% S, and less than (<)1 % of Ni is less than (<)30 ppm of O ₂ , and less than (<)100 ppm of N ₂ , and less than (<) 3 ppm of H _{2 is} less than (<) 2% of W, and less than (<) 1% Nb, and less than (<) 1% Ti, and less than (<) 0.5% Ta, and less than (<) 0.5% Zr, the remainder of the steel is substantially Fe and may be incidental and/or may be unavoidable Impurity; a roll according to the invention wherein the C content of the steel composition is between 0.8% and 0.99% C by weight of the total roll weight.

The roll according to the present invention, wherein the C content in the steel composition is between 0.85% and 0.9% C by weight of the total roll weight.

The roll according to the invention wherein the Mn content in the steel composition is between 0.4% and 0.5% Mn by weight of the total roll weight.

The roll according to the invention wherein the Si content in the steel composition is between 0.2% and 1.5% Si by weight of the total roll weight.

The roll according to the present invention, wherein the Si content in the steel composition is between 0.85% and 1.15% Si by weight of the total roll weight.

The roll according to the invention wherein the Cr content in the steel composition is between 7.0% and 11% Cr by weight of the total roll weight.

The roll according to the present invention, wherein the Cr content in the steel composition is between 7.3% and less than (<) 8.0% Cr by weight of the total roll weight.

The roll according to the invention wherein the Mo content in the steel composition is between 1.45% and 1.55% Mo by weight of the total roll weight.

The roll according to the present invention, wherein the Ni content in the steel composition is less than (<) 0.3 Ni by weight of the total roll weight.

The roll according to the invention wherein the V content in the steel composition is between 1.3% and 2.1% V by weight of the total roll weight.

The roll according to the invention wherein the V content in the steel composition is between 1.3% and 1.6% V by weight of the total roll weight.

A roll according to the present invention, wherein the steel composition is composed by weight% by weight: 0.8% to 0.99% C, and 0.4% to 0.5% Mn, and 0.2% to 1.5% Si, and 7.0% to 11% of Cr, and 0.6% to 1.6% of MO, and less than (<)1.0 of Ni, and 1.0% to 2.1% of V, and less than (<)0.015% of P, and less than (<)0.015% S, and O ₂ less than (<) 30 ppm, and N ₂ less than (<) 100 ppm, and H ₂ less than (<3 ppm), and the remainder of the roll is substantially Fe and may be incidental and/or Impurities that may be inevitable.

A roll according to the present invention, wherein the steel composition is composed by weight% by weight: 0.85% to 0.9% C, and 0.4% to 0.5% Mn, and 0.85% to 1.15% Si, and 7.3% to Less than (<)8.0% of Cr, and 1.45% to 1.55% of Mo, and less than (<)0.3 of Ni, and 1.3% to 1.6% of V, and less than (<)0.015% of P, and less than (< ) 0.01% S, and less than (<) 30 ppm O ₂ , and less than (<) 100 ppm N ₂ , and less than (<) 3 ppm H ₂ , and the remainder of the roll is substantially Fe and possible Incidental and/or potentially unavoidable impurities.

Step 16: Manufacturing of a cylindrical shaped ingot 34. In a typical application of the invention, an intermediate product (ingot 34 made in accordance with the method of the present invention) preferably has a relationship between 450 mm and 1100 mm. Diameter 32, length 30 up to 6 meters, and weight between 400 kg and 30,000 kg, see Figure 3. The method of making ingot 34 in accordance with the present invention involves the use of techniques for achieving rapid cooling during manufacture of ingot 34. For example, the ingot 34 can be fabricated using different ingot forming techniques. Suitable manufacturing techniques are those manufacturing techniques that can be controlled to achieve and maintain a particular minimum solidification rate.

According to an embodiment of the invention, the average solidification rate is controlled during formation of the ingot such that it is above 15 ° C/min in the surface and preferably also above 10 ° C/min in the core. Preferably, this rate of solidification is maintained while controlling the cooling of the ingot material in a setting interval, for example, between 1400 °C and 1200 °C. In other embodiments of the invention, the average solidification rate is controlled during the setting interval to be higher than 35 ° C/min in the working layer.

From a practical point of view, it is often difficult to achieve very high solidification rates in the practice of the present invention. Other embodiments of the invention include controlling the average solidification rate in the working layer and in the core to be in the range of 15 ° C/min to 55 ° C/min, or 35 ° C/min to 55 ° C/min, or 45 °C/min to 55 °C/min.

In accordance with the present invention, techniques for controlling the method with respect to solidification parameters in the present invention are, for example, different types of electroslag refining furnaces (ESR), such as moving mode ESR melting or ESR cladding or spray forming techniques.

According to the present invention, an ingot made using the solidification rate and chemical composition as described in any of the above embodiments has the following characteristics: - an extremely excellent dendritic macrostructure.

- Chemical uniformity.

- Macro segregation in the middle layer and lack of dark veins.

- No small segregation.

In addition, the ingot produced using the method according to the present invention has the following advantages on the rolled product: - the "orange peel" effect (which consists of the appearance of the dendrite pattern due to the difference in wear due to the area between the dendrites) ) Elimination.

- No pinhole problems.

- Extremely bright surface finish.

- Uniformity of the texture obtained by texturing.

- Missing of the mark associated with the non-uniformity of the structure.

In one embodiment of the invention, ingot block 34 is fabricated in accordance with the present invention using an electroslag refining furnace (ESR), see Figure 4 for a schematic view. The electroslag refining furnace (ESR) is capable of melting from about 300 kg/h to 1100 kg/h and includes an electrode holder 36, a guide rod 38, an electrode 40, a cooling jacket outlet 42 for cooling water, and a cooling jacket inlet 50. In the ESR, the ingot is formed by melting the electrode 40, and thus different layers are formed in the ingot material 48, such as the slag pool 44 (which is located near the electrode) and the molten metal pool 46.

The ESR also includes a starting plate 52 that is cooled by water 54, see Figure 4. In accordance with the present invention, ESR techniques may require re-melting a starting ingot (electrode 40) obtained by a conventional melting process to form ingot 48. In accordance with an embodiment of the present invention, remelting using ESR is carefully controlled to achieve an average solidification rate, such as an average of more than 15 ° C/min in the working layer of the ingot during the formation of the ingot and also in the core. Rate of solidification.

In accordance with the present invention, in an ESR process, electrode 40 is thus heated by a current (e.g., high amperage current) to re-melt the steel of the electrode to form an ingot. The high amperage current of electrode 40 is carefully controlled to control the rate of remelting, and this also affects the rate of cooling and thereby affects the rate of solidification. The rate of solidification depends on the ampere current fed to the electrode according to a predetermined function. Basically, the higher the amperage current, the higher the power supplied to remelt the electrode 40 (see Ohm's Law). The higher the power supplied, the higher the slag temperature and the lower the solidification rate.

By maintaining the correct remelting rate and slag temperature, directional solidification can be achieved in accordance with the present invention by the rate of solidification in the core and working layers as the ingot is cooled in certain intervals. For example, in one embodiment, the average value in the core and working layers of the ingot is greater than 15 ° C/min in the solidification interval from 1400 ° C to 1200 ° C during cooling of the ingot.

According to the invention and due to the combination of the inventive concept steel composition and method, the eutectic carbide content in the ingot remains below 5% by volume. This gives the resulting roll good grindability. The easy-to-grindability of the rolls is important because during the use of the final rolls, for cold rolling, grinding is an important process for achieving a sufficiently rough roll. It is known that concentrations of eutectic carbides above 5% give the roll an unsatisfactory grind.

In addition, another effect of the low eutectic carbide content is the lower tendency of the rolls to form dust during operation in the mill. On the contrary, dust formation can occur in rolls having a high concentration of carbides, which is negative for the rolling product and the working environment in the rolling mill.

Of particular importance is the control of the rate of solidification when the ingot is made from a composition comprising a high level of Cr (e.g., 7% to 13%). The high segregation obtained when the solidification rate is too slow makes the high chromium ingot defective.

The rate of solidification above 15 ° C/min during the setting interval during the manufacture of the ingot gives a low segregation rate, resulting in a eutectic carbide content of less than 5% by volume.

The invention will be more readily understood by reference to the following examples.

However, the examples are intended to illustrate the embodiment variants of the ingot forming step of the present invention and are not to be construed as limiting the scope of the invention.

Comparative example

Example 1 demonstrates the effect of the method of the invention on the microstructure of the roll 1 according to the invention. Example 2 is a comparative example. These embodiments are performed during the manufacture of a roll prototype in physical size. These experiments show the distribution of eutectic carbides in the ingot and important variants of the mesh shape after casting, depending on the solidification rate used, see Examples 1 and 2 and Table 2 below. According to the present invention, the distribution of the eutectic carbides seen in the ingot and the shape of the mesh remain in the final roll after forging and tempering.

Example 1

In accordance with the present invention, this example demonstrates the effect on the microstructure in the roll according to the present invention when a solidification rate of greater than 15 ° C/min is used during formation of the ingot 34.

5A to 5B show an example of the microstructure of the ingot 1 according to the present invention, which has an average of 50 ° C/min when the ingot is cooled from 1400 ° C to 1200 ° C (90 in the ingot). The method of solidification rate at mm depth) is manufactured. The eutectic cells in ingot 1 are small (940, 942) according to an embodiment of the invention, and Figure 5B shows a segmented network with an open eutectic network. Referring also to Figure 8, there are shown different temperature intervals in core 82, intermediate radius 84, 90 mm 86, 50 mm 88, 30 mm 90 and surface 92 for different solidification intervals in different portions of the ingot during solidification. Fig. 5B is an enlarged view of Fig. 5A. See also Table 2. 6A to 6B show an embodiment of the microstructure of the ingot 2 according to the present invention, which is used to cool the ingot from 1400 ° C to 1200 ° C with an average of 18 ° C / min (in the ingot) A method of solidification rate at a depth of 90 mm). Figure 6 shows eutectic cells in ingot 2 according to an embodiment of the invention, and such eutectic cells are small, see, for example, a cross-sectional distance of 1024. Referring also to Figure 9, for different coagulation intervals in different portions of the ingot during solidification 80, it shows the temperature rate in core 100, intermediate radius 102, 90 mm 104, 50 mm 106, 30 mm 108 and surface 110. Fig. 6B is an enlarged view of Fig. 6A. See also Table 2.

in conclusion

The method according to the invention ensures the absence of segregation in the intermediate radius of the ingot. The lack of segregation in the intermediate radius (or 5/6 of the inside of the diameter of the cylindrical roll) ensures the integrity of the roll during the hardening process. Thus, a solidification rate above 15 °C/min in the working layer results in a smaller microstructure which, as explained above, is better in terms of grinding and dust contamination, see Figures 5A-5B and 6A-6B .

Example 2

This example demonstrates the effect of using a solidification rate of less than 15 °C/min during the formation of Test 1 ingot.

7A-7C show an embodiment of the microstructure of the test 1 ingot, which has a lower than 15 (actually even below 10) °C when used to cool the ingot during solidification intervals from 1400 ° C to 1200 ° C. /min's method of solidification rate to manufacture. 7A-7C, the size of the cells 700 of the test ingot 1 is relatively large, see, for example, section 708, which according to the present invention has greater than, for example, the largest cross section in the ingot 1 of Example 1. Section length 708. Test 1 ingot also exhibited shrinkage porosity 704. The coarse coalescence eutectic network 702 is also visible in Figures 7A-7C. See also Table 2. 7B to 7C are enlarged views of Fig. 7A.

in conclusion

The solidification rate of less than 15 ° C/min during the solidification interval imparts high segregation of the carbide and coarse carbide web 702, the intermediate radius of the test 1 ingot structure, and the porosity 704, see Figures 7A-7C. High segregation of carbides and coarse carbide webs to produce white blank rolls or finished rolls made by ingots according to test 1 brittleness, and thus tilted in induction hardening (white billet rolls) or in cold rolling mills (finished rolls) ) bursting.

As in accordance with the present invention, Example 2 also exhibits a solidification rate of less than 15 ° C/min which also results in a larger and more eutectic cell structure than when the ingot is produced using a solidification rate greater than 15 ° C/min. Rough. The rate of solidification above 15 ° C/min during the setting interval during the manufacture of the ingot gives a low segregation rate, resulting in a eutectic carbide content of less than 5% by volume.

Table 2 shows experimental data for ingot testing by different average solidification rates (*) at a depth of 90 mm of the ingot when cooling the ingot from 1400 °C to 1200 °C.

Comparative example

Example 3 demonstrates, for example, the effect of the method of the present invention and the chemical composition of the ingot on the microstructure of the ingot and thus also on the rolls of the present invention. Example 4 is a comparative example. Examples 3 and 4 show the microstructure of ingots produced by experiments conducted in the laboratory with controlled solidification devices and controlled cooling rates.

The shape of the eutectic carbide network in the ingot is affected depending on the chemical composition used, see also Table 3.

Example 3

This example demonstrates the microstructure of ingot 1 made in accordance with the method of the present invention by experiments conducted in the laboratory with controlled solidification devices and controlled cooling rates above 15 °C/min in the solidification interval. When a chemical composition comprising 1.4% Mo is used in accordance with the present invention, an open eutectic carbide system 750 is achieved in the ingot structure, see Figures 10A-10B. See also Table 3. As seen in roll 1 according to the present invention, this open eutectic carbide system 750 is characterized as a dendritic pattern, and eutectic carbide structure 752 does not form a closed eutectic carbide network (as in Comparative Example 4, tested) 2), but instead forming a dendrite arm in the web, see Figures 10A-10B, which show a picture of the microstructure of an ingot having 1.4% Mo made according to the method of the present invention. In accordance with the present invention, this open eutectic carbide system allows the rolls to be more easily milled than rolls made using amounts of Mo greater than 1.6%.

Example 4

The test 2 ingot was produced using the method of the present invention and a composition in which the main component was different from the present invention in terms of the amount of Mo according to the above examples but the difference in the chemical composition. This test 2 ingot was made in accordance with the method of the present invention by experiments conducted in the laboratory with a controlled solidification device and a controlled cooling rate of more than 15 ° C/min in the solidification interval. In Test 2, the amount of Mo was 2.77%, see also Table 3. A eutectic carbide system for ingots shaped in cells occluding eutectic carbides is produced using a chemical composition comprising 2.77% Mo in the process of the invention for making ingots, see Figures 11A-11B, and The crystalline carbide 852 forms a substantially isolated portion 850, like the island or segregation cell structure of Figures 11A through 11B showing the microstructure of Test 2. The white areas in Figs. 11A to 11B indicate a matrix; mainly iron, and black is a secondary carbide.

Excessive addition of alloying elements in Test 2 resulted in the formation of a coarse carbide network, which was associated with segregation of carbides. See also Table 3.

Table 3 shows experimental data for ingot testing by different average solidification rates (*) when the ingot was cooled from 1400 ° C to 1200 ° C. Components other than Mo are within the intervals as described above.

Step 18: Forging the ingot 34 into a roll 1

In a typical application of the invention, the ingot 34 produced in accordance with the foregoing steps of the present invention is then forged. In one embodiment of the invention, a forged ingot 34 is hot pressed using a method known per se for simultaneously reducing the cross-sectional area and changing the shape by pressing the ingot between the hammer and the anvil. The ingot is formed into a roll 1 according to the invention. The ingot is heated in a special furnace, see Figure 12 for a schematic view of the forging step.

The forging step 18 in accordance with the present invention includes the following steps, see FIG. 12; preheating 56 the ingot 34 for a period of from about 6 hours to between 800 ° C and 1200 ° C or between 850 ° C and 1100 ° C. The preheating step 56 involves heating the ingot 34 from the surface of the ingot to the core. Adjusting the temperature during forging to be between 800 ° C and 1200 ° C or between 850 ° C and 1100 ° C. This is because the higher temperature above 1200 ° C causes defects in the ingot structure due to the burning of the rolls. . The reason for maintaining the temperature of the ingot at the indicated temperature interval is that the temperature below 800 °C causes crack formation of the ingot. As the ingot 34 cools, it becomes stronger and less ductile, and if the deformation continues, cracking can be induced.

After the pre-heating of the ingot 1 (step 56), the ingot 1 is forged using a forging ratio of 1.35 to 2.0 (step 60). The forging step 60 and the preheating step 56 are repeated, which is commonly referred to as heating 58. Heating was repeated 58 times as needed to form a roll according to the present invention, see Figure 12.

In one embodiment, 3 to 6 heats 58 are used to forge the roll 1 according to the present invention to forge the ingot into a roll blank. The roll blank is a roll that has the shape of a roll but still has a barrel that lacks the final treatment to become a roll that can be used in a rolling mill.

In another embodiment, the ingot 34 is forged in several heats 58, see Figure 13 for a schematic view of a forged roll:

a) first, adjusting the cross-sectional area of the ingot 34 in several or one to two heatings 58

b) making one of the necks of the roller in one heating,

c) Forging the other neck of the roll in the next heating.

The forged steel composition according to the present invention is more difficult to perform due to the alloy content according to the present invention which is higher than the standard steel grade of the forged embodiment.

During forging, the ingot 34 is reduced in diameter 32 by 30% to 50% when it is forged into the roll 1 according to the present invention. By way of example, the roller 1 according to the invention preferably has a diameter 2 of between 250 mm and 800 mm, see Fig. 1, and the ingot 34 according to the invention preferably has a range of between 400 mm and 1000 mm Or a diameter of 32 between 450 mm and 1100 mm.

Importantly, ingot 34 has the desired eutectic carbide microstructure formed during solidification step 80 during the manufacturing process of ingot 34. It is shown that it is possible to forge an ingot 34 having a eutectic carbide microstructure according to the present invention having a eutectic carbide content of less than 5% by volume using hot press forging techniques. These large rolls are made using ingots formed by another method (e.g., with a solidification rate of less than 15 ° C/min) to cause bursting during induction hardening or in a rolling mill.

Step 20: preliminary heat treatment of the roller 1

In the manufacturing method of the present invention, the roller is processed by a preliminary heat treatment step. In an embodiment of the invention, the roll is heated in a furnace during the preliminary heat treatment 20 according to the invention to be between 700 ° C and 1100 ° C, and then the roll is held at the temperature for a certain period of time Until a satisfactory hydrogen diffusion has occurred. A preliminary heat treatment (normalization treatment and spheroidizing annealing) is performed in order to improve the workability of the rolls.

Step 22: roughing of the roll 22

In the manufacturing method of the present invention, the roll is processed by a roughing step 22. The roughing 22 of the formed roll 1 according to the present invention means the removal of the outer layer of the forged roll. In an embodiment of the invention, the outer layer is removed during roughing. This roller is referred to as a black blank before being subjected to roughing. The black body roll is then converted into a white body by removing the oxide layer on the surface of the roll.

Step 24: induction hardening of the roller 1

In the manufacturing method of the present invention, the roller is treated by induction hardening. During the induction hardening of the roll, a hard surface of the roll is formed. See Figure 14 for a schematic of the induction hardening step.

In one embodiment of the invention, the roller is moved slowly downward while a current or voltage frequency between 50 Hz and 1000 Hz is applied to the roller via the inductor arrangement 70 during the induction hardening step. The water roll 72 is used to cool the roll 1 after the heating step, see Figure 14. The hard surface formed is also referred to as the working layer 4 of the roll and is about 1/6 of the total diameter 2 of the roll 1 (see Figure 1, number 6). The surface of the roll is rapidly heated via a series of inductors including electrical coils leading into the fire extinguishing tank as the surface temperature of the roll is lowered. Rapid thermal penetration of induction hardening and immediate extinguishment using water to create a defined layer of uniform hardness on the surface of the roll. The neck and core of the roll are maintained at low temperatures throughout the process. During induction hardening, a frequency generally between 50 Hz and 1000 Hz is applied to the surface of the roll 1 and a frequency selected from the lower half of the interval gives the working layer 4 deeper to the roll 1. Another factor that affects the depth of the working layer formed is the gap between the inductors 70 (if several inductors are used). The gap or distance between the inductor 70 and the roller 1 also affects the depth of the working layer 4 formed. In accordance with the present invention, the induction hardening step 24 can be a single frequency, a dual frequency, or more.

The rolls according to the invention are bursted using conventional hardening techniques and induction hardening is the most suitable technique for the hardening of rolls according to the invention. The cooling of the roller 1 during the induction hardening 24 is performed by the high fluidity of the cold water.

In an embodiment of the invention, the induction hardening 34 is performed by double induction hardening, and the cooling of the roller 1 after the induction hardening 24 is performed by high fluidity of water, the water having a temperature of 40 ° C and The flow rate is about 300 m ³ /h, and the roller moves downward at a speed of 0.3 mm/s to 1 mm/s. In one embodiment, the induction hardening step 24 is between 0.5 and 2 hours.

Step 26: Tempering the roll

In the manufacturing method of the present invention, the roll 1 is tempered. The purpose of the tempering step is to reduce the brittleness of the rolls and to adjust the hardness level. The tempering step 26 is a crucial step during the formation of the rolls because it reduces the internal stress. During the tempering step, the roll achieves its final microstructure by diffusion and secondary precipitation of the carbide. Air cooling is applied between the tempering heating steps. The rolls are preferably tempered 3 times at 450 ° C to 530 ° C. The tempering step causes the rolls to achieve a desired hardness level above 780 HV or between 780 HV and 840 HV. Precise control of time and temperature during the tempering process is critical to achieve a metal having a perfectly balanced microstructure (eg, tempered martensite) such that the rolls made according to the method of the present invention include after tempering Tempered martensite having a residual austenite ratio of less than 5% by volume.

Step 28: Processing of the roller

In the manufacturing method of the present invention, the rolls are preferably processed by processing step 28 prior to use in a rolling mill. For example, at the mill, the special application surface treatment of the roll is performed by grinding and other surface treatments to achieve the desired roughness and associated friction on the surface of the roll. Examples of surface treatment of rolls are, for example, laser beam texturing (LBT), electron beam texturing (EBT) or discharge texturing (EDT).

In one embodiment, the roll is processed by a grinding and discharge texturing (EDT) surface treatment. 15A to 15B show the microstructure of the surface of a roll containing a low chromium compound after discharge texturing. 15C-15D show the microstructure of the surface of the roll according to the present invention after discharge texturing. In Figure 15D below the white layer, there is a re-auped layer and a thinner softened zone because this grade has a high tempering temperature. Also note that in Figure 15D In the white layer, the eutectic carbide 302 has not been affected by the arc energy. For comparison, these types of carbides are not present in the rolls described in Figures 15A-15B. The rolls according to the present invention have better properties and performance than standard grade rolls (see Figures 15A-15B) due to the presence of hard eutectic carbides in the white layer.

Figure 18 shows a more schematic view of Figure 15D showing the microstructure of the roll surface in accordance with the present invention in which a newly formed eutectic carbide 302 (formed due to remelting) is present in the white layer 304. The previously formed eutectic carbide 300 is also shown in FIG. The roll surface in Figure 18 illustrates how the surface looks after discharge texturing in accordance with the present invention. Scale 306 represents 5 μm .

Roll 1 according to the present invention manufactured by the above method

A typical roller according to the invention has a diameter of between 215 mm and 800 mm or between 250 mm and 700 mm, including a total length of the neck of up to 6 meters, wherein the length of the barrel is between 1 and 3 meters between. The typical weight of the rolls is between 400 kg and 10,000 kg. The microstructure of the roll according to an embodiment of the invention is characterized by comprising tempered martensite having a residual austenite ratio of less than 5% by volume, and wherein the roll comprises less than 5% by volume of open eutectic carbide a eutectic carbide network; and the roll (1) exhibits a hardness between 780 HV and 840 HV; and an internal compressive stress between -300 MPa and -500 MPa. According to the chemical composition of the present invention, such characteristics of the roll are attributed to the roll manufacturing method of the present invention and also to the chemical composition of the roll.

The roll according to the invention is intended for use in a cold strip mill which requires High pressure roller. The roll according to the invention is intended to be used as a work roll in a cold strip mill and is suitable in any stand in a rolling process and suitable in a 2Hi to 6Hi mill and may have a surface of 0.3. A roughness of from μm to 0.5 μm requires a roughness of 1.5 μm to 2.5 μm in the finishing stand, which is required in the initial stand.

The invention will be more readily understood by reference to the following examples. However, the examples are intended to illustrate the characteristics of the rolls of the present invention and are not to be construed as limiting the scope of the invention. In Table 4, different rolls were compared to the rolls according to the invention. All rolls contain Mn in an amount between 0.2% and 0.5% by weight.

Two examples of the invention

The roller 1 according to the invention in Table 4 uses the method according to the invention, using a solidification rate higher than 15 ° C/min in the working layer during the setting interval and also using induction heating, using a frequency of 50 Hz to 250 Hz and Manufactured by tempering 3 times at 450 ° C to 530 ° C.

The roller 2 according to the invention in Table 4 uses the method according to the invention, uses a solidification rate of 18 ° C/min in the working layer during the setting interval and also uses induction heating, using a frequency of 50 Hz to 250 Hz and tempering Manufactured three times; first at 490 ° C, then at 490 ° C and last-time tempering at 480 ° C. Figure 19 shows the microstructure of the rolls after tempering and induction hardening at a depth of 4 mm from the surface of the roll 2. A microstructure 1034 having an open eutectic mesh of rolls and eutectic carbide 1032 is also shown in FIG.

The Mn contents of the rolls in Table 4 were all in the range of 0.4 to 0.5, and the Si contents of the rolls in Table 4 were all in the range of 0.2 to 2.0, and Ni was always less than 1%.

Roll application

The application of the roller is:

Aluminum industry:

-Single base 4Hi irreversible rolling mill

Steel industry;

-4Hi single stand reversible

- 4Hi multi-station tandem 4 and 5 stands for sheets in continuous and discontinuous methods

- 4Hi multi-station tandem 4 and 5 stands for tinplate

- 6Hi multi-station tandem mill for sheet

Roller use

The forging roll according to the present invention is suitable for use as, for example, a cold rolling mill or, for example, a work roll or an intermediate roll in each of the following;

- Cold rolling reduction rolling mill for tinplate, sheet, tantalum, aluminum or copper early and finishing stands, reversible and irreversible stands.

- cold rolling tempering and / or skin rolling mill;

- Rolling mill configurations with 2-roll (2-High), 4-high (4-High) and 6-high (6-High) stands with textured or untextured surfaces.

- Cold rolling of -AHSS steel grade.

Roll surface

Surface texture

One problem with known rolls is that the surface texture is worn during use of the rolls. The surface texture is important because it ensures a coefficient of friction to avoid slippage and/or derailment of the strip. In addition, it determines the surface texture of the strip that imparts shallow characteristics to the deep drawing and painting of the rolled strip. White layer due to the presentation of the roll of the roll according to the present invention increases while maintaining the ability of the surface texture of the roll and wherein the white layer comprises hard eutectic carbides as M ₇ C _3. In the working layer; the microstructure of the roll of the invention after the final heat treatment consists of tempered martensite having a residual austenite ratio of less than 5% by volume and carbides finely and uniformly dispersed into the matrix ( It is composed of MC and M ₂ C (M = metal, C = carbon). This type of microstructure has been shown to be important to maintain the surface texture of the roll.

Roughness transfer

The roughness transfer of the roll surface changes during use of the roll. The rolls according to the invention exhibit the ability to maintain a constant increase in roughness transfer during rolling, which is important for the life of the rolls. This is due to the specially claimed composition and also to the manufacturing method used when manufacturing the rolls.

Free rolling in rolling mill

One problem during the use of the rolls is that the dust accumulated on the surface of the rolls leaves a trajectory on the strip. In the working layer, the roll according to the invention has a strong surface due to the fact that the microstructure of the roll of the invention comprises tempered martensite having a residual austenite ratio of less than 5% by volume and is fine and Carbides (MC and M ₂ C) uniformly dispersed into the matrix, where M refers to the metal and C refers to the carbon. This special microstructure increases the likelihood of free-range rolling.

Peeling off

Another problem with known rolls is that the crack propagation inside the rolls is induced by cumulative stress control, by rolling of the rolls and by the field of residual internal stress. The roller in use is subjected to a set of composite stresses. The roll according to the invention exhibits a low level of residual internal stress and thus exhibits better resistance to spalling, and this results in a lower mill accident rate.

The mechanical strength of the roll of the present invention is better than that of the roll having the same alloy composition as the roll of the present invention but produced by another manufacturing method. The mechanical strength of the rolls according to the invention is due to the open eutectic network formed in the working layer of the rolls. This open eutectic network is formed during the cooling step in the roll manufacturing process. The rate of solidification above 15 ° C/min during the cooling step when making the ingot is critical to the formation of the open web present in the rolls according to the invention.

Furthermore, the accumulation of various tempering treatments at high temperatures (e.g., between 450 ° C and 530 ° C) after hardening during the manufacture of the rolls induces an important relaxation of the internal stress of the rolls. The internal stress is minimized by using differential heating of the outer layer. The hardness penetration depth of the roller according to the present invention can be controlled between 20 mm and 120 mm (diameter) measured from the surface of the roller and measured inward. The internal compressive stress of the rolls of the present invention is preferably between -300 MPa and -500 MPa (absolute) or, for example, less than -400 MPa.

Roll microstructure

Figure 17A shows a schematic of an exemplary roll microstructure in accordance with the present invention. The dendrite arm 210 is seen in Figure 17A and comprises a eutectic carbide that forms a eutectic cell structure 204 by forming an open carbide network. An open eutectic network comprising dendritic arms 210 forming eutectic cells 204 (which are visible in Figure 17A) is formed in the process due to the particular chemical composition in accordance with the present invention. Scale 208 represents 100 μm.

In one embodiment of the invention, the microstructure of the rolls of the present invention comprises an open eutectic network that is only distributed over one or both of the cellular structures.

In comparison, Figure 17B shows a closed eutectic network in which eutectic carbide 200 forms a closed eutectic network with distinctly separated eutectic cells 212. This type of web is undesirable in rolls according to the present invention due to the brittleness of the rolls when the rolls comprise this type of microstructure. Scale 214 represents 100 μm.

The invention has been explained by means of different embodiments within the scope of the appended claims.

1‧‧‧Forged rolls

2‧‧‧Roll diameter

4‧‧‧Working layer

6‧‧‧1/6 part of the roll diameter

8‧‧‧200

10‧‧‧ neck

12‧‧‧Roll manufacturing method

14‧‧‧Providing the steps of the steel composition

16‧‧‧Manufacture of ingot steps

18‧‧‧Forging the ingot into a roller step

20‧‧‧Preliminary heat treatment of the roller step

22‧‧‧ roughing steps

24‧‧‧ induction hardening step

26‧‧‧tempering heat treatment

28‧‧‧Processing steps

30‧‧‧Ingot length

32‧‧‧diameter

34‧‧‧Ingots

36‧‧‧electrode clip

38‧‧‧guides

40‧‧‧Electrode

42‧‧‧ Cooling jacket outlet

44‧‧‧ slag pool

46‧‧‧ molten metal pool

50‧‧‧ Cooling jacket inlet

52‧‧‧Starting board

54‧‧‧Water cooling

56‧‧‧Preheating step

58‧‧‧heating

60‧‧‧Forging steps

70‧‧‧ Sensor configuration

72‧‧‧Water cooling

80‧‧‧solidification step

82‧‧‧ core temperature rate

84‧‧‧temperature rate in the middle radius

Temperature rate in 86‧‧90mm

88‧‧50mm medium temperature rate

90‧‧30mm medium temperature rate

92‧‧‧ Surface temperature rate

100‧‧‧ core temperature rate

102‧‧‧temperature rate in the middle radius

104‧‧‧90mm medium temperature rate

106‧‧50mm medium temperature rate

108‧‧30mm medium temperature rate

110‧‧‧Surface temperature rate

200‧‧‧ Eutectic carbide

204‧‧‧ eutectic cell structure

206‧‧‧section

208‧‧‧ scale bar 100μm

210‧‧‧ dendrites

212‧‧‧Separated eutectic cells

214‧‧‧ scale bar 100μm

300‧‧‧ previously formed eutectic carbides

302‧‧‧New eutectic carbides

304‧‧‧White layer

306‧‧‧scale 5μm

502‧‧‧Hazardous defects

700‧‧‧ cells

702‧‧‧ coarse coalescence eutectic network

704‧‧‧ Shrinkage porosity

708‧‧‧section

750‧‧‧Open eutectic carbide system

752‧‧‧ Eutectic carbide structure

850‧‧‧Partially isolated part

852‧‧‧ Eutectic carbide

940‧‧‧ eutectic cells

942‧‧‧eutectic cells

1020‧‧‧ eutectic cells

1022‧‧‧ eutectic cells

1024‧‧‧section distance

1032‧‧‧ Eutectic carbide

1034‧‧‧Microstructure

Figure 1 shows a schematic picture of a roll according to the invention.

Figure 2 shows a schematic view of a method of making a roll in accordance with the present invention.

Figure 3 shows a schematic picture of an ingot according to the invention.

Figure 4 shows a method of making an ingot according to the present invention.

5A-5B show a cast microstructure of a roll grade manufactured using the manufacturing method according to the present invention. This roller grade is shown in a cross-sectional view of the working layer of the roller grade.

6A-6B show a cast microstructure of a roll grade manufactured using the manufacturing method according to the present invention. This roller grade is shown in a cross-sectional view of the working layer of the roller grade.

Figure 7 shows a cast microstructure of a roll grade made using the manufacturing method according to the present invention, but with deviations when using too low a solidification rate. This roller grade is shown in a cross-sectional view of the working layer of the roller grade.

Figure 8 shows a first set of examples of solidification rates for a roll making process in accordance with the present invention.

Figure 9 shows a second set of examples of the solidification rate of the roll making process in accordance with the present invention.

10A-10B show the cast microstructure of an ingot made under laboratory conditions when using the manufacturing method according to the present invention.

11A to 11B show the cast microstructure of an ingot manufactured under laboratory conditions when using the manufacturing method according to the present invention, but deviation occurs when an excessively high Mo content is used.

Figure 12 shows a schematic view of the forging according to the present invention.

Figure 13 shows a schematic view of the steps of forming an ingot by forging an ingot into a roll according to the present invention.

Figure 14 shows a schematic diagram of progressive induction hardening of rolls having different frequencies in accordance with the present invention.

15A-15B show the microstructure of the surface of a roll according to a standard grade after surface texturing (EDT texturing).

Figures 15C-15D show the microstructure of the surface of the roll according to the invention after surface texturing (EDT texturing).

Figures 16A through 16D show the detrimental defects on the rolls produced during the manufacture of rolls having a low chromium content and a high molybdenum content.

Figure 17A shows an embodiment of a microstructure in accordance with the present invention having an open eutectic network.

17B shows an example of a microstructure with a closed eutectic network in which eutectic carbide 200 forms a closed eutectic network with distinctly separated eutectic cells 212.

Figure 18 shows an example showing the microstructure of the roll surface according to the present invention after discharge texturing.

Figure 19 shows the roll microstructure at a depth of 4 mm on the surface of the roll after tempering and induction hardening of the roll.

1. . . Forging roller

2. . . diameter

4. . . Working layer

6. . . 1/6 part of the roll diameter

8. . . cylinder

10. . . neck

Claims (47)

A forging roll (1) comprising a steel composition comprising, by weight %, 0.8% to less than (<) 1% C, 0.2% to 0.5% Mn, 0.2% to 2.0% Si , 7.0% to 13.0% Cr, 0.6% to 1.6% Mo, greater than (>) 1.0% to 3.0% V, the remainder of the steel being substantially Fe and possibly incidental and/or possibly unavoidable impurities; And wherein the microstructure of the roll (1) comprises: tempered martensite having a residual austenite ratio of less than (<) 5% by volume; and an open eutectic carbide network having less than (<) 5% by volume a eutectic carbide; and wherein the roll (1) exhibits a hardness of between 780 HV and 840 HV; and an internal compressive stress of between -300 MPa and -500 MPa. The roll of claim 1, wherein the open eutectic carbide network delineates a cell-like pattern of eutectic cells. A roll according to claim 1 or 2, wherein the open eutectic carbide network comprises a dendrite arm. Such as the roller of claim 1 or 2, wherein the microstructure is Less present in the working layer of the roller. A roll according to claim 1 or 2, which has a steel composition which is composed by weight% by weight: 0.8% to less than (<) 1% C, 0.2% to 0.5% Mn, 0.2% to 2.0% Si, 7.0% to 13.0% Cr, 0.6% to 1.6% Mo, greater than (>) 1.0% to 3.0% V, less than (<)0.015% P, and less than ( <) 0.015% S, and less than (<) 1% Ni, less than (<) 30ppm O ₂ , and less than (<) 100ppm N ₂ , and less than (<) 3ppm H ₂ , less than (<) 2% of W, and less than (<)1% of Nb, and less than (<)1% of Ti, and less than (<)0.5% of Ta, and less than (<) of 0.5% of Zr, the remainder of the steel Essentially Fe and impurities that may be incidental and/or potentially unavoidable. A roll according to claim 1 or 2, wherein the C content in the steel composition is between 0.8% and 0.99% C by weight of the total roll weight. A roll according to claim 1 or 2, wherein the C content in the steel composition is between 0.85% and 0.9% C by weight of the total roll weight. A roll according to claim 1 or 2, wherein the Mn content of the steel composition is between 0.4% and 0.5% Mn by weight of the total roll weight. A roll according to claim 1 or 2, wherein the Si content in the steel composition is between 0.2% and 1.5% Si by weight of the total roll weight. A roll according to claim 1 or 2, wherein the Si content in the steel composition is between 0.85% and 1.15% Si by weight of the total roll weight. A roll according to claim 1 or 2, wherein the Cr content in the steel composition is between 7.0% and 11% Cr by weight of the total roll weight. A roll according to claim 1 or 2, wherein the Cr content in the steel composition is between 7.3% and less than (<) 8.0% Cr by weight of the total roll weight. A roll according to claim 1 or 2, wherein the Mo content in the steel composition is between 1.45% and 1.55% Mo by weight of the total roll weight. A roll according to claim 1 or 2, wherein the content of Ni in the steel composition is less than (<) 0.3 Ni by weight of the total roll weight. A roll according to claim 1 or 2, wherein the V content in the steel composition is between 1.3% and 2.1% V by weight of the total roll weight. A roll according to claim 1 or 2, wherein the V content in the steel composition is between 1.3% and 1.6% V by weight of the total roll weight. A roll according to claim 1 or 2, wherein the steel composition is composed by weight % by weight: 0.8% to 0.99% C, and 0.4% to 0.5% Mn, and 0.2% to 1.5% Si, and 7.0% to 11% of Cr, and 0.6% to 1.6% of Mo, and less than (<)1.0 of Ni, and 1.0% to 2.1% of V, and less than (<)0.015% of P, and S less than (<) 0.015%, O ₂ less than (<) 30 ppm, N ₂ less than (<) 100 ppm, and H ₂ less than (< 3 ppm), and the remainder of the roll is substantially Fe and Impurities that may be incidental and / or may be unavoidable. A roll according to claim 1 or 2, wherein the steel composition is composed by weight % by weight: 0.85% to 0.9% C, and 0.4% to 0.5% Mn, and 0.85% to 1.15% Si, and 7.3% to less than (<)8.0% of Cr, and 1.45% to 1.55% of Mo, and less than (<)0.3 of Ni, and 1.3% to 1.6% of V, and less than (<)0.015% P, and less than (<) 0.015% of S, and less than (<) 30ppm of O ₂ , and less than (<) 100ppm of N ₂ , and less than (<) 3ppm of H ₂ , and the remainder of the roller The top is Fe and may be incidental and/or may be unavoidable impurities. A roller as claimed in claim 1 or 2 is further configured to be used as a work roll in cold rolling. The roller of claim 1 or 2 further has a weight of more than 400 kg. The roller of claim 1 or 2 further has a diameter in the range of 215 mm to 800 mm. A method for making a non-forging roll, the method comprising the steps of: a. providing a steel composition comprising, by weight %, 0.8% to less than (<) 1% C, 0.2% to 0.5% Mn, 0.2% to 2.0% Si, 7.0% to 13.0% Cr, 0.6% to 1.6% Mo, greater than (>) 1.0% to 3.0% V, the remainder of the steel is substantially Fe and possibly incidental and/or possibly unavoidable impurities; b. manufacturing ingots, which are solidifying Maintaining a solidification rate higher than 15 ° C / min in the working layer of the ingot; c. forging the ingot into a roll; d. hardening the roll by induction heating; e. between 450 The roll is tempered at a temperature between ° C and 530 ° C to achieve a hardness of between 780 HV and 840 HV; thereby achieving the microstructure of the roll (1), the microstructure comprising: tempered martensite having a residual austenite ratio of less than (<) 5% by volume; and an open eutectic carbide network having less than (<) 5% by volume of eutectic carbide; and wherein the roll (1) exhibits: between 780 HV and 840 HV The hardness between; and the internal compressive stress between -300MPa and -500MPa. The method of claim 22, wherein the ingot is manufactured, the ingot is maintained in the working layer and the core at a solidification rate in the range of 15 ° C / min to 55 ° C / min, or 17 ° C / min To 50 ° C / min, or 35 ° C / min to 55 ° C / min, or 45 ° C / min to 55 ° C / min. The method of claim 22, wherein the ingot is manufactured, the ingot being maintained in the working layer of the ingot during the setting interval A solidification rate higher than 35 ° C / min. The method of claim 22, wherein the solidification interval is between 1400 ° C and 1200 ° C for the ingot. The method of claim 22, wherein the ingot is manufactured, the ingot maintaining a preselection in an electroslag refining furnace (ESR) process by controlling an amperage current source according to a predetermined function of the solidification rate The rate of solidification. The method of claim 22 or 23, wherein the step of forging the ingot into a roll comprises the steps of: a. heating the ingot to between 800 ° C and 1200 ° C or between 850 ° C to a temperature between 1100 ° C, preferably for a period of about 6 hours; b. forging the ingot at a temperature above 800 ° C or above 850 ° C; c. repeating step ab until the ingot has formed It is a roll with the desired shape and size. The method of claim 22 or 23, after the forging step, further comprising a preliminary heat treatment step, preferably heated to between 7 () 0 ° C and 1100 ° C or between 800 ° C and 900 ° C The intermediate heat treatment step may include a hydrogen diffusion treatment. The method of claim 22, wherein the step of tempering the roll comprises the steps of: a. heating the roll to about 450 ° C to 530 ° C, preferably 3 times, b. in the heating The roller was cooled with air between the steps. The method of claim 22 or 23, further comprising processing the roll to texture a white layer comprising eutectic carbide Chemical. The method of claim 30, wherein the eutectic carbides in the white layer are selected from the group consisting of M ₇ C ₃ . The method of claim 22, wherein the open eutectic carbide network delineates a cell-like pattern of eutectic cells. An intermediate product ingot in the manufacture of a roll according to claim 1 or 2, the ingot comprising a steel composition comprising, by weight %, from 0.8% to less than (<) 1% C, 0.2% to 0.5% Mn, 0.2% to 2.0% Si, 7.0% to 13.0% Cr, 0.6% to 1.6% Mo, greater than (>) 1.0% to 3.0% V, the steel The remainder is substantially Fe and possibly incidental and/or possibly unavoidable impurities; and wherein the microstructure of the final roll formed from the ingot comprises: tempered martensite having a residue of less than (<) 5% by volume An austenite ratio; and an open eutectic carbide network having less than (<) 5% by volume of eutectic carbide. For example, in the intermediate product ingot of claim 33, wherein the roller exhibits: Hardness between 780 HV and 840 HV; and internal compressive stress between -300 MPa and -500 MPa. . An intermediate product ingot as claimed in claim 33, wherein the open eutectic carbide network delineates a cell-like pattern of eutectic cells. A use of a roll as claimed in claim 1 or 2 for cold rolled materials requiring high rolling loads. A use of a roll as claimed in claim 1 or 2 for cold rolling of high strength materials such as AHSS steel grade. A use of a roller as claimed in claim 1 or 2 for the selection of: tinplate, sheet, tantalum, stainless steel, aluminum and copper early and finishing stands, reversible and irreversible stand Cold rolling reduction mill; or cold rolling tempering and / or skin rolling mill; or textured or untextured surface is 2-high (2-High), 4-high (4-High) and 6-roll ( 6-High) Mill configuration for the base. A roll as claimed in claim 1 or 2 is used as a work roll. A roll according to claim 1 or 2, wherein the roll is uncoated. A roll manufactured by the method of claim 22 or 23, wherein the roll is uncoated. A method for manufacturing a roll according to claim 22 or 23, wherein the roll is uncoated. A use of a roller as claimed in claim 1 or 2, wherein The roll is uncoated. A roll according to claim 1 or 2, wherein the roll is coated with an optional coating such as a chrome coating. A roll manufactured by the method of claim 22 or 23, wherein the roll is coated with an optional coating such as a chrome coating. A method for manufacturing a roll according to claim 22 or 23, wherein the roll is coated with an optional coating such as a chrome coating. A use of a roll as claimed in claim 1 or 2, wherein the roll is coated with an optional coating such as a chrome coating.