JP2012184471A - Forging roll meeting requirement of cold rolling industry and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forging roll for use in cold rolling industry in the field of forging roll, and method for manufacturing the forging roll.SOLUTION: The forging roll for use in the cold rolling industry and the method for manufacturing such the roll are provided. The forging roll comprises a steel composition and a microstructure that comprises: tempered martensite with retained austenite at a ratio of less than 5% per volume; and an open eutectic carbide network with eutectic carbides of less than 5% per volume. The roll exhibits a hardness of from 780 to 840 HV and an internal compressive stress of -300 to -500 MPa in absolute values.

Description

  This invention relates generally to the field of forged rolls and the production of forged rolls. More particularly, the present invention relates to a forging roll that meets the requirements of the cold rolling industry and is primarily directed to use in the industry.

General Background A general trend for development in cold rolling for both ferrous and non-ferrous metals industries is to roll faster, thinner and more widely. The current challenge is to do this while achieving full control of flatness, thickness and surface aspect compatible with high productivity. This trend therefore requires the use of advanced rolling techniques to control key rolling parameters.

  Some key parameters, such as roughness retention and surface aspect, can be ensured through chrome plating of the work roll. While this implementation is effective and efficient, it is becoming increasingly problematic and will not be accepted in the near future due to environmental regulations.

  Currently, forging work rolls (2-6% Cr) using surface chrome plating are commonly used in the cold rolling process. Such roll chrome plating is applied to improve wear resistance in terms of surface texture retention and thus, for example, to ensure a consistently high gloss body after painting. it can. Hard electrolytic deposition technology as chromium plating was first developed for tempering / skin pass mill applications. In these applications, chrome-plated work rolls exhibit a 2 to 8 times longer life than uncoated rolls, primarily due to better roughness retention. The implementation of this technology has been gradually extended to a reduction mill.

  There are also high-speed steel (HSS) forging rolls that are made for use without a coating, but there is a need for rolls with low residual internal stress and also producing such rolls. There is also a need for an industrial method to do this, which is intended to be used without a coating in the mill while providing a roughness retention at least equivalent to the roughness retention of the coated roll.

Specific Background Rolls produced for use within the cold rolling industry must manage processing conditions or specific operating stresses during use without cracking or tendency to rupture. Roll rupture can contribute to the safety of the operating personnel and associated damage in the mill. Thus, there is a need for a roll having low residual internal stress.

Prior art examples of prior art disclosing development on HSS rolls without coating for cold rolling purposes:
C. Gaspard, C. Vergne, D. Batazzi, T. Nylen, PHBolt, S. Mul, KMReuver: `` Implementation of in-service key parameters of HSS work roll grade dedicated to advanced cold rolling '', IST Conference May 3-6 , 2010, 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
PHBolt, D.Batazzi, NPBelfiore, 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, IMWilliams: `` Damage Resistance and Roughness Retention of work Rolls in cold Rolling Mills '', 5th European Rolling Conference, 23-25 June 2009, London, UK
Other examples of the prior art are shown in Patent Publications: JP09003603, JP53077821, JP57047849, JP2002285284, JP2002285285, JP10317102, JP1208437, EP0395477 and JP08158018, which are intended to improve wear resistance and peel resistance. A work roll for cold rolling is described.

  However, these prior art lacks the disclosure of the parameters and characteristics necessary to achieve and enable such HSS rolls that can operate during conditions in cold rolling mills.

Objects of the invention General objects The general object of the present invention is to provide a roll that operates in conditions in a cold rolling mill, preferably in uncoated form, and an industrial process for producing such a roll. Is to provide. More specific objectives compared to known rolls while maintaining tribological properties such as low coefficient of friction, high roughness retention, and no dust contamination with iron particulates, at least equivalent to prior art coated rolls It is therefore to provide such a roll and a method for producing such a roll that show improved mill performance in terms of higher crack resistance and higher operational safety.

Partial problem The present invention further provides a partial problem:
-Improving the roll surface which gives the roll a higher performance-avoiding roll peeling accidents-avoiding non-environmental rolling manufacturing methods-improving the rolling distance or shelf life of the roll and It is intended to solve the problem of enabling a longer run per mill campaign.

SUMMARY OF THE INVENTION A solution to the above-listed problems, partial problems, and embodiments provides improved heat crack resistance that can reduce sensitivity to mill accidents while maintaining higher wear resistance. It is a roll according to the invention having a crack resistance and low crack propagation.

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

The first aspect of the present invention is a forging roll, in weight percent,
0.8 to less than 1% C,
0.2-0.5% Mn,
0.2-2.0% Si,
7.0-13.0% Cr,
0.6-1.6% Mo,
V exceeding 1.0 to 3.0%
Including
The remainder of the steel comprises steel composition that is substantially Fe and possible incidental and / or inevitable impurities;
Here, the microstructure of the roll is
Tempered martensite having a retained austenite ratio of less than 5% by volume;
-An open eutectic carbide network with less than 5% eutectic carbide per volume;
Including:
Roll
A hardness between 780 HV and 840 HV,
-It relates to a forging roll showing an internal compressive stress between -300 MPa and -500 MPa.

  In another embodiment of the invention, the roll of the invention includes an open eutectic carbide network that defines a cell-like pattern of eutectic cells.

Additional various rolls, including any of the following optional, individual or combinable embodiments:
A roll whose open eutectic carbide network includes dendritic arms.

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

  A roll whose microstructure is present at least in its working layer.

% By weight
0.8 to less than 1% C,
0.2-0.5% Mn,
0.2-2.0% Si,
7.0-13.0% Cr,
0.6-1.6% Mo,
V exceeding 1.0 to 3.0%,
Less than 0.015% P, and less than 0.015% S, and less than 1% Ni;
Less than 30 ppm O ₂ , and less than 100 ppm N ₂ , and less than 3 ppm H ₂ ,
Less than 2% W, and less than 1% Nb, and less than 1% Ti, and less than 0.5% Ta, and less than 0.5% Zr
In which the remainder of the steel is substantially Fe and a steel composition that is a possible incidental and / or inevitable impurity.

  A roll according to the invention, wherein the C content in the steel composition is C by weight percent between 0.8% and 0.99% of the total roll weight.

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

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

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

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

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

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

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

  A roll according to the invention, wherein the Ni content in the steel composition is Ni by weight percent and less than 0.3 of the total roll weight.

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

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

The steel composition is in weight percent,
0.8-0.99% C, and 0.4-0.5% Mn, and 0.2-1.5% Si, and 7.0-11% Cr, and 0.6- 1.6% Mo, and less than 1.0 Ni, and 1.0-2.1% V, and less than 0.015% P, and less than 0.015% 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 possibly incidental and / or inevitable impurities.

The steel composition is in weight percent,
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% Cr, and 1 .45 to 1.55% Mo, and less than 0.3 Ni, and 1.3 to 1.6% V, and less than 0.015% P, and less than 0.015% S, and 30 ppm Less than 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 possibly incidental and / or inevitable impurities.

  Furthermore, a roll according to the invention which is configured for use as a work roll in cold rolling.

  A roll according to the invention further having a weight of more than 400 kg.

  A roll according to the invention further having a diameter in the range of 215 mm to 800 mm.

A further aspect of the present invention is a forging roll produced by a method comprising the following steps:
a. % By weight
0.8 to less than 1% C,
0.2-0.5% Mn,
0.2-2.0% Si,
7.0-13.0% Cr,
0.6-1.6% Mo,
V exceeding 1.0 to 3.0%
Providing a steel composition in which the remainder of the steel is substantially Fe and possible incidental and / or inevitable impurities; in other embodiments, the composition according to the invention comprises: Any of the above compositions or combinations of compositions,
b. Maintaining a solidification rate in the surface layer of the ingot corresponding to the surface layer of the roll at a solidification interval of greater than 15 ° C./minute to produce the ingot;
c. Forging the ingot into a roll;
d. Quenching the roll by induction heating;
e. Tempering the roll;
This
Tempered martensite having a retained austenite ratio of less than 5% by volume;
An open eutectic carbide network having less than 5% eutectic carbide per volume;
Achieving a microstructure of the roll comprising:
Roll (1) is
A hardness between 780 HV and 840 HV,
Providing a forging roll exhibiting an internal compressive stress of between -300 MPa and -500 MPa;

  Regarding the chemical composition or microstructure of the roll referred to above, including any of the following optional, individual or combinable aspects, including the following optional individual or combinable aspects: Further various rolls further comprising any of the features

A further aspect of the present invention is a method for producing a non-forged roll according to the present invention comprising:
a. % By weight
0.8 to less than 1% C,
0.2-0.5% Mn,
0.2-2.0% Si,
7.0-13.0% Cr,
0.6-1.6% Mo,
V exceeding 1.0 to 3.0%
Providing a steel composition in which the remainder of the steel is substantially Fe and possible incidental and / or inevitable impurities; in other embodiments, the composition according to the invention comprises: Any of the combinations of the above compositions,
b. Maintaining a solidification rate in the work layer of the ingot corresponding to the work layer of the roll at a solidification interval that exceeds 15 ° C./min; and producing the ingot;
c. Forging the ingot into a roll;
d. Quenching the roll by induction heating;
e. Tempering the roll at a temperature between 450 ° C. and 530 ° C. to reach a hardness between 780 HV and 840 HV;
And thus
Tempered martensite having a retained austenite ratio of less than 5% by volume;
An open eutectic carbide network having less than 5% eutectic carbide per volume;
Achieving a microstructure of the roll (1) comprising:
Roll (1) is
A hardness between 780 HV and 840 HV,
-Providing a method showing an internal compressive stress between -300 MPa and -500 MPa;

  Further various rolls, including any of the following, optional, individual or combinable aspects mentioned below.

  Ingots in the working layer as well as in the core 15 ° C / min to 55 ° C / min, or alternatively 17 ° C / min to 50 ° C / min, or alternatively 35 ° C / min to 55 ° C / min, or alternatively The method according to the present invention is produced while maintaining the solidification rate within a range of 45 ° C./min to 55 ° C./min.

  The method according to the invention, wherein the ingot is produced with a solidification rate in the working layer or surface of the ingot in the solidification interval that exceeds 35 ° C./min.

  The process according to the invention, wherein the solidification interval is between 1400 ° C. and 1200 ° C. for the ingot.

  The method according to the invention, wherein the ingot is manufactured maintaining a preselected solidification rate in an electroslag refining furnace (ESR) technology process by controlling the ampere current supply according to a function of a predetermined solidification rate.

The step of forging the ingot into a roll
a. Heating the ingot to a temperature between about 850-1100 ° C. or between 800 ° C. and 1000 ° C., preferably for about 6 hours;
b. Forging the ingot at a temperature above about 800 ° C. or above 850 ° C .;
c. Repeating steps ab until the ingot is formed into a roll having a desired shape and size.

  After the forging step, pre-heat treatment applied to the roll blank, preferably at a temperature between about 700-1100 ° C. or 800 ° C.-900 ° C., which may include hydrogen diffusion treatment A method further comprising:

  A method further comprising superficial hardening by progressive induction heating, preferably at a temperature of about 900-1150C.

The step of tempering the roll
d. Heating the roll between about 450-530 ° C. or between 450 ° C. and 520 ° C., preferably three times;
e. Cooling the roll during the heating step (s).

  The method further comprising machining the roll to texture a white layer comprising eutectic carbide.

  Regarding the chemical composition or microstructure of the roll referred to above, including any of the following optional, individual or combinable aspects, including the following optional individual or combinable aspects: Further various methods of the invention further comprising any of the features

A further aspect of the invention is an intermediate product ingot in the manufacture of rolls, in weight percent,
0.8 to less than 1% C,
0.2-0.5% Mn,
0.2-2.0% Si,
7.0-13.0% Cr,
0.6-1.6% Mo,
V exceeding 1.0 to 3.0%
Including
The remainder of the steel comprises steel composition that is substantially Fe and possible incidental and / or inevitable impurities;
The final roll microstructure from the ingot is:
Tempered martensite having a retained austenite ratio of less than 5% by volume;
Providing an ingot comprising an open eutectic carbide network having less than 5% eutectic carbide per volume.

  Regarding the chemical composition of the ingot mentioned above, including any of the following optional, individual or combinable embodiments, any of the following optional, individual or combinable embodiments mentioned below: Further various intermediate ingots of the present invention further comprising features.

  A further aspect of the present invention provides the use of a forging roll according to the present invention for cold rolled materials that require high rolling loads.

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

Less than:
-Cold rolling reduction mill for early and finishing stands for tinplate, sheets, silicon steel, stainless steel, aluminum and copper, reversible and non-reversible stands; or- Cold rolling tempering and / or skin pass mill; or-for selections selected from mill configurations as two, four and six stage stands with textured or untextured surfaces Of the forging roll according to the invention.

  Use of a forging roll according to the invention as a work roll.

  The roll according to the invention is useful for many applications as an uncoated roll. However, in further aspects and embodiments of the present invention, the roll may be provided with a coating that is selected for any current or specific application. The coating may be a chrome coating, for example. The roll can also be used for hot rolling applications.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is further described by way of illustration of embodiments:

1 shows a schematic view of a roll according to the invention. 1 shows a schematic view of a roll manufacturing method according to the present invention. 1 shows a schematic view of an ingot according to the invention. The manufacturing method of the ingot by this invention is shown. A to B show roll grade cast microstructures made using the manufacturing method according to the present invention. The roll grade is shown in a sectional view of the working layer of the roll grade. A to B show roll grade cast microstructures made using the manufacturing method according to the present invention. The roll grade is shown in a sectional view of the working layer of the roll grade. Fig. 4 shows a roll grade cast microstructure produced using the manufacturing method according to the invention, but with deviations when using too low solidification rates. The roll grade is shown in a sectional view of the working layer of the roll grade. 2 shows a first series of solidification rate examples for a roll manufacturing method according to the present invention. 2 shows a second series of solidification rate examples for a roll manufacturing method according to the invention. A to B show the cast microstructure of an ingot produced under laboratory conditions when using the production method according to the present invention. A-B show ingot cast microstructures that are made in laboratory conditions when using the manufacturing method according to the present invention, but deviate when using too high Mo content. 1 shows a schematic view of forging according to the invention. FIG. 3 shows a schematic diagram of the steps of forming an ingot by forging the ingot into a roll according to the present invention. Fig. 2 shows a schematic diagram of a progressive induction quenching with different frequencies of a roll according to the invention. A to B show the microstructure of the surface of the roll according to the standard grade after surface texturing (EDT texturing). C to D show the microstructure of the surface of the roll according to the invention after surface texturing (EDT texturing). A to D show disadvantageous defects in the rolls produced during the production of rolls having a low chromium content and a high molybdenum content. A shows an embodiment of a microstructure according to the invention with an open eutectic network. B shows an example of a microstructure having a closed eutectic network where the eutectic carbide 200 forms a closed eutectic network with clearly separated eutectic cells 212. An example representing the microstructure of the roll surface according to the invention after discharge texturing is shown. Fig. 4 shows a roll microstructure of 4 mm depth on the roll surface after tempering and induction quenching of the roll.

DETAILED DESCRIPTION INTRODUCTION The present invention generally relates to a forging roll 1 that preferably has a weight of over 400 kg, or preferably over a weight of, for example, 1000 kg as in the embodiment for general use. The roll according to the invention is produced according to a forged roll production method, which is known per se in its general steps, but is particularly modified according to the inventive concept by which the roll according to the invention can be produced.

  The present invention is primarily directed to rolls having a weight between 400 kg and 10,000 kg. A roll according to the invention comprises a diameter 2 of typically greater than 200 mm, for example between 215 mm and 800 mm, typically between 1 and 3 meters 8 and a neck 10. Typically has a maximum length of about 6 meters. The roll 1 corresponds to the outer layer portion and the diameter is typically in the range between 20 and 120 mm depending on the specific roll application and / or the overall roll diameter 2. 4. In general, the outer portion 6 of the roll diameter 2 is referred to as the working layer 4 of the roll 1. Please refer to FIG. A portion 6 of the outer 1/6 diameter 2 of the ingot 34 is also referred to herein as the working layer 4 of the ingot 34.

  Due to the internal stresses involved when forming these large rolls, there are special problems and challenges involved in making large forged rolls. A roll with a smaller diameter will not require similar treatment because the internal stress is less and the roll does not tend to burst, for example upon quenching.

  The roll production method 12 according to the invention is important for producing rolls 1 of this size according to the invention. Improved mechanical properties of the roll of the present invention, such as low residual internal stress, are obtained from the roll manufacturing method 12. In order to achieve low levels of residual internal stress in the resulting roll, internal stresses induced by temperature gradients and allotropic transformations must be minimized at all stages of the manufacturing process through casting, forging, heat treatment and machining. I must. 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 production method and chemical composition of the roll according to the invention.

The roll production method according to the invention comprises a selection from the following basic steps schematically shown in the flow diagram of FIG.
14 Prepare steel composition16. 18. Manufacture ingot 34 Forging the ingot 34 into the roll 1 20. 21. Pre-heat treatment of the roll 1 Rough machine the roll 1 24. 26. induction hardening the roll 1; 27. Tempering heat treatment of the roll 1 An intermediate product for machining the roll 1 is obtained after each step. Specific control parameters and the chemical composition of the roll are selected to produce the roll according to the invention.

The present invention relates to a forging roll (1) produced by the following method:
a. % By weight
0.8 to less than 1% C,
0.2-0.5% Mn,
0.2-2.0% Si,
7.0-13.0% Cr,
0.6-1.6% Mo,
V exceeding 1.0 to 3.0%
Providing a steel composition wherein the remainder of the steel is substantially Fe and possibly incidental and / or inevitable impurities;
b. Maintaining the solidification rate in the working layer of the ingot in the solidification interval at a solidification rate exceeding 15 ° C./min; and producing the ingot;
c. Forging the ingot into a roll;
d. Quenching the roll by induction heating;
e. Tempering the roll;
And thus
Tempered martensite having a retained austenite ratio of less than 5% by volume;
An open eutectic carbide network having less than 5% eutectic carbide per volume;
Achieving a microstructure of the roll (1) comprising:
Roll (1) is
-A hardness exceeding 780 HV;
-It shows an internal compression stress of less than -500 MPa in absolute value.

  The chemical composition provided according to the invention, used here in combination with the steps of the method according to the invention described here, gives the roll according to the invention the desired properties in the microstructure of the roll according to the invention.

  The method for producing a forging roll according to the present invention includes the following steps.

Step 14: Preparation of Steel Composition In one embodiment of the present invention, the steel composition comprises an alloy comprising or consisting of the following components shown in Table 1 in weight percent listed in Table 1. In Table 1, the effects of the components and the effects of the creative roll achieved by the selected components and specific intervals are described.

Each optionally further comprising H ₂ , N ₂ , O ₂ , Al, Cu, in an amount of less than 0.4% by weight, the remainder of the steel composition, apart from incidental elements and inevitable impurities , Substantially Fe.

In an embodiment of the present invention, the steel composition is in weight percent,
0.8 to less than 1% C,
0.2-0.5% Mn,
0.2-2.0% Si,
7.0-13.0% Cr,
0.6-1.6% Mo,
V exceeding 1.0 to 3.0%
And the remainder of the steel is substantially Fe, apart from incidental elements and inevitable impurities.

  In different variants and embodiments of the invention, the composition comprises or consists of a combination or selection of components (% by weight) according to the following examples. In some cases, the above-described embodiments are combined with, substituted for, or narrowed by the following variations of component amounts.

% By weight
0.8 to less than 1% C,
0.2-0.5% Mn,
0.2-2.0% Si,
7.0-13.0% Cr,
0.6-1.6% Mo,
V exceeding 1.0 to 3.0%,
Less than 0.015% P, and less than 0.015% S, and less than 1% Ni;
Less than 30 ppm O ₂ , and less than 100 ppm N ₂ , and less than 3 ppm H ₂ ,
Less than 2% W, and less than 1% Nb, and less than 1% Ti, and less than 0.5% Ta, and less than 0.5% Zr
In which the remainder of the steel is substantially Fe and a steel composition that is a possible incidental and / or inevitable impurity.

  A roll according to the invention, wherein the C content in the steel composition is C by weight percent between 0.8% and 0.99% of the total roll weight.

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

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

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

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

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

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

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

  A roll according to the invention, wherein the Ni content in the steel composition is Ni by weight percent and less than 0.3 of the total roll weight.

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

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

The steel composition is in weight percent,
0.8-0.99% C, and 0.4-0.5% Mn, and 0.2-1.5% Si, and 7.0-11% Cr, and 0.6- 1.6% Mo, and less than 1.0 Ni, and 1.0-2.1% V, and less than 0.015% P, and less than 0.015% 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 possibly incidental and / or inevitable impurities.

The steel composition is in weight percent,
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% Cr, and 1 .45 to 1.55% Mo, and less than 0.3 Ni, and 1.3 to 1.6% V, and less than 0.015% P, and less than 0.015% S, and 30 ppm Less than 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 possibly incidental and / or inevitable impurities.

Step 16: Manufacture 16 of the cylindrical ingot 34
In a typical application of the invention, the ingot 34 produced by the method of the invention, which is an intermediate product, has a diameter 32 between 450 mm and 1100 mm, a length 30 up to 6 meters, and 400 kg and 30000 kg. Preferably having a weight between. Please refer to FIG. The method of making the ingot 34 according to the present invention includes using a technique that allows for rapid cooling during manufacture of the ingot 34. For example, the ingot 34 can be manufactured using various ingot forming techniques. A suitable manufacturing technique is one that can be controlled to achieve and maintain a certain minimum solidification rate.

  According to an embodiment of the invention, the average solidification rate is controlled at the surface in excess of 15 ° C./min at the formation of the ingot and preferably at the core in excess of 10 ° C./min. Preferably, this solidification rate is maintained while controlling the cooling of the ingot material in a solidification interval, which may be, for example, between 1400 ° C and 1200 ° C. In another embodiment of the invention, the average solidification rate is controlled to exceed 35 ° C./min in the working layer during the solidification interval.

  From a practical point of view, it is generally difficult to achieve very high solidification rates when carrying out the present invention. Further embodiments of the invention are in the range of 15 ° C / min to 55 ° C / min, or alternatively 35 ° C / min to 55 ° C / min, or alternatively 45 ° C / min to 55 ° C / min. The average solidification rate in the working layer and core is controlled.

  Techniques used in the present invention to control the process with respect to solidification parameters according to the present invention are, for example, various types of electroslag refining furnaces (ESR), such as moving mold ESR melting techniques or ESR cladding techniques, or Such as spray formation technology.

An ingot made using the solidification rate and chemical composition described in any of the above embodiments according to the present invention has the following properties:
-Very fine dendritic macrostructures-homogeneity of chemical properties-lack of macrosegregation and deep baining in the intermediate layer-no minor segregation.

Furthermore, the ingot produced using the method according to the invention has the following advantages in the rolled product:
-Elimination of "orange peel" effect (consisting of manifestation of dendritic patterns due to differences in interdendritic area wear)-No pinhole problems-Very bright surface finish-Obtained by texturing Texture homogeneity-the absence of traces related to structural inhomogeneities.

  In one embodiment of the present invention, an electroslag refining furnace (ESR) is used to manufacture the ingot 34 according to the present invention. See FIG. 4 for a schematic diagram. The electroslag refining furnace (ESR) can melt about 300-1100 kg / h, and includes an electrode clamp 36, a stinger 38, an electrode 40, a cooling jacket outlet 42, and a cooling water cooling jacket inlet 50. In ESR, the ingot is formed by melting the electrode 40, and thus various layers such as a slag pool 44 and a molten metal pool 46 located near the electrode are formed in the ingot material 48.

  The ESR also includes a starting plate 52 that is water cooled 54. Please refer to FIG. The ESR technique may require a starting ingot (electrode 40) obtained by a conventional melting process that is remelted to form an ingot 48 according to the present invention. Remelting using ESR is to achieve an average solidification rate according to an embodiment of the present invention, eg, an average solidification rate exceeding 15 ° C./min, in the working layer of the ingot and also in the core during the formation of the ingot. Be carefully controlled.

  The electrode 40 is thus heated in an ESR process by a current, for example by a high ampere current, to remelt the steel of the electrode to form an ingot according to the invention. The high ampere current of electrode 40 is carefully controlled to control the remelting rate, which also affects the cooling rate and thereby the solidification rate. The solidification rate depends on the ampere current supplied to the electrode according to a predetermined function. Basically, the higher the ampere current, the higher the power supplied to remelt the electrode 40 (see Ohm's Law). When the supplied electric power is high, the slag temperature becomes high and the solidification rate becomes low.

  By maintaining an accurate remelt rate and slag temperature, directional solidification can be achieved using the solidification rate according to the present invention in the core and in the working layer while cooling the ingot at certain intervals. For example, in one embodiment, the solidification rate averages over 15 ° C./min in both the core and working layer of the ingot while cooling the ingot in a solidification interval of 1400 ° C. to 1200 ° C.

  According to the present invention, and as a result of the steel composition and process combination of the inventive concept, the eutectic carbide content in the ingot is kept below 5% by volume. This imparts good grindability to the resulting roll. The grindability of the roll is important because grinding is an important technique in achieving the proper roughness of the roll with respect to the cold rolling process during final roll use. Eutectic carbide concentrations greater than 5% are known to give such rolls with unsatisfactory grindability.

  Furthermore, another effect of low eutectic carbide content is that the roll is less prone to dust during operation in the mill. In contrast, dust formation can occur in rolls with high concentrations of carbides and is not good with respect to the rolled product and the working environment in the mill.

  When making ingots from compositions containing high levels of Cr (eg, 7-13%), it is particularly important to control the solidification rate. The high segregation obtained when the solidification rate is too slow causes defects in high chromium ingots. When making an ingot, the solidification rate during the solidification interval exceeds 15 ° C./min, giving a low segregation rate, resulting in a eutectic carbide content of less than 5% by volume.

  The present invention will be more readily understood with reference to the following examples. However, these examples are intended to illustrate variations of embodiments of the ingot forming step of the present invention and should not be construed to limit the scope of the present invention.

Comparative Example Example 1 shows the effect that the method of the invention has on the microstructure of the roll 1 according to the invention. Example 2 is a comparative example. These examples are implemented during the manufacture of roll prototypes on a natural scale. Experiments show significant changes in eutectic carbide distribution and network shape in the ingot after casting depending on the solidification rate used. See Examples 1 and 2 below and Table 2. The distribution of eutectic carbides and the network shape found in the ingot are maintained in the final roll after forging and tempering according to the invention.

Example 1
This example shows the effect on the microstructure in the roll according to the invention when using solidification rates in excess of 15 ° C./min in forming the ingot 34 according to the invention.

  FIGS. 5A-B show the fineness of an ingot 1 according to the invention made using a process with an average solidification rate of 50 ° C./min (at 90 mm depth of the ingot) while cooling the ingot from 1400 ° C. to 1200 ° C. An example of the structure is shown. The eutectic cell in Example Ingot 1 according to the present invention is small (940, 942) and FIG. 5B shows a fragmented network with an open eutectic network. For various solidification intervals in various parts of the ingot during solidification, the temperature rates at the core 82, mid-radius 84, 90mm 86, 50mm 88, 30mm 90 and surface 92 are shown. See also FIG. FIG. 5B is an enlarged view of FIG. 5A. See also Table 2.

  6A-B show the fineness of an ingot 2 according to the invention made using a process with an average solidification rate of 18 ° C./min (at 90 mm depth of the ingot) while cooling the ingot from 1400 ° C. to 1200 ° C. An example of the structure is shown. FIG. 6 shows eutectic cells in example ingot 2 according to the invention, which are small. For example, see cross-sectional distance 1024. For various solidification intervals in various parts of the ingot during solidification 80, FIG. 9 shows the temperature velocities at the core 100, the intermediate radius 102, the 90mm 104, the 50mm 106, the 30mm 108 and the surface 110. See also FIG. 6B is an enlarged view of FIG. 6A. See also Table 2.

Conclusion The method according to the invention ensures the absence of segregation in the middle radius of the ingot. The absence of segregation in the middle radius (or 5/6 inner diameter of the cylindrical roll) ensures roll integrity during the quenching process. Solidification rates in the working layer exceeding 15 ° C./min thus produce finer microstructures that are better in terms of grinding and dust contamination, as explained above. See FIGS. 5A-B and FIGS. 6A-B.

Example 2
This example shows the effect of using a solidification rate of less than 15 ° C./min when forming a Test 1 ingot.

  7A-C are test 1 made using a process with a solidification rate of less than 15 (actually lower than 10) ° C / min while cooling the ingot in the solidification interval from 1400 ° C to 1200 ° C. An example of the fine structure of an ingot is shown. The comparative test 1 ingot cell 700 in FIGS. 7A-C is larger in size. See for example cross section 708. The cross-section has a cross-section length 708 that is greater than the maximum cross-section in eg ingot 1 in Example 1 according to the invention. Test 1 ingots also exhibit shrinkage porosities 704. A coarse conglomerate eutectic network 702 can also be seen in FIGS. See also Table 2. 7B to 7C are enlarged views of FIG. 7A.

Conclusion Solidification rates less than 15 ° C./min within the solidification interval provide high segregation of carbides and a coarse carbide network 702 to the structure of the intermediate radius portion of test 1 ingot and also to pores 704. See Figures 7A-C. High segregation of carbides and coarse carbide network can be applied to white blank rolls or finished rolls made by ingots according to Test 1 during induction quenching (white blank rolls) or cold rolling mills. In the (finishing roll), it is brittle and therefore tends to burst.

  Example 2 also shows that a solidification rate of less than 15 ° C./min results in a more eutectic cell structure size compared to when the ingot is made using a solidification rate greater than 15 ° C./min as in the present invention. Also shown to be larger and rougher.

  Solidification rates exceeding 15 ° C./min during the solidification interval when making the ingot give a low segregation rate, resulting in a eutectic carbide content of less than 5% by volume.

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

Comparative Example Example 3 demonstrates, for example, the effect of the method of the invention and the chemical composition of the ingot on the microstructure of the ingot and thus also the roll of the invention. Example 4 is a comparative example. Examples 3 and 4 show the microstructures of ingots produced by laboratory experiments using controlled solidification equipment and controlled cooling rate.

  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 shows the microstructure of an ingot 1 manufactured according to the method of the present invention by laboratory experiments using a controlled solidification apparatus and a controlled cooling rate exceeding 15 ° C./min during the solidification interval. When a chemical composition containing 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-B. See also Table 3. This open eutectic carbide system 750 is characterized as a dendritic pattern as seen in roll 1 according to the present invention, and the eutectic carbide structure 752 does not form a closed eutectic carbide network (Comparative Example 4). , As in test 2) instead form dendritic arms in the network. See Figures 10A-B. The figure shows a photograph of the microstructure of an ingot containing 1.4% Mo produced by the method of the present invention. This open eutectic carbide system according to the present invention facilitates grinding of the roll compared to rolls made with more than 1.6% Mo.

Example 4
Test 2 ingots are made using the methods and compositions of the present invention, with the main components of the composition being according to the above embodiment, but with the difference that the chemical composition differs from the present invention with respect to the amount of Mo. This test 2 ingot is manufactured according to the method of the present invention by laboratory experiments using a controlled coagulator and a controlled cooling rate in excess of 15 ° C./min during the coagulation interval. In Test 2, the amount of Mo is 2.77%. See also Table 3. By using a chemical composition containing 2.77% Mo in the method of the present invention for producing an ingot, the ingot eutectic carbide system is in the form of a closed eutectic carbide cell. See Figures 11A-B. Eutectic carbide 852 forms a substantially isolated portion 850, such as the island or segregated cell structure in FIGS. The white areas in FIGS. 11A-B represent the matrix; mainly iron and black are secondary carbides.

  The excessive addition of alloying elements in Test 2 results in the formation of a coarse carbide network linked to carbide segregation. See also Table 3.

Table 3 shows experimental data for ingot tests using different average solidification rates ( ^* ) while cooling the ingot from 1400 ° C to 1200 ° C. The constituent components other than Mo are within the interval as described above.

Step 18: Forging said ingot 34 into roll 1 In a typical application of the present invention, the ingot 34 produced by the previous step of the present invention is then forged. In one embodiment of the invention, the ingot 34 changes shape while reducing the cross-sectional area by passing the ingot between an ingot and the anvil that forms the roll 1 according to the invention. Hot press forging is performed using a known process. The ingot is heated in a dedicated furnace. See FIG. 12 for a schematic diagram of the forging step.

The forging step 18 according to the present invention includes the following steps. See FIG. 12;
-Preheating the ingot 34 to a temperature between 800 ° C and 1200 ° C or between 850 ° C and 1100 ° C for about 6 hours 56; The preheating step 56 includes heating the ingot 34 all the way from the surface into the core of the ingot. The temperature during forging is adjusted within an interval range between 800 ° C. and 1200 ° C. or between 850 ° C. and 1100 ° C., because it causes defects in the ingot structure due to the firing of the roll at temperatures exceeding 1200 ° C. The The reason for keeping the temperature of the ingot in the temperature interval indicated is that a temperature below 800 ° C. results in the formation of cracks in the ingot. As the ingot 34 cools, it becomes stronger and less ductile, which can induce cracks as the deformation continues.

  After the ingot 1 is preheated (step 56), it 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 and this forging cycle is commonly referred to as heat 58. Heat 58 is repeated as many times as necessary to form a roll according to the present invention. Please refer to FIG.

  In one embodiment, roll 1 according to the present invention is forged using heat 58 3-6 times to forge the ingot into a roll blank. A roll blank is a roll that has the shape of a roll but still has a barrel that lacks final processing to become a usable roll in a mill.

In another embodiment, the ingot 34 is forged in several heats 58. See FIG. 13 for a schematic diagram for forging a roll:
a) First, the ingot 34 has its cross-sectional area adjusted by several or one or two heats 58.
b) One neck of the roll is made by one heat,
c) The other neck of the roll is forged by the next heat.

  Forging a steel composition according to the present invention is more difficult to implement due to the higher alloy content according to the present invention compared to the exemplary standard steel grade forging.

  During forging, the diameter 32 of the ingot 34 is reduced by 30% to 50% while being forged into the roll 1 according to the invention. For example, the roll 1 according to the invention preferably has a diameter 2 between 250 mm and 800 mm. Please refer to FIG. The ingot 34 according to the invention preferably has a diameter 32 of between 400 mm and 1000 mm, or between 450 mm and 1100 mm.

  It is important that the ingot 34 has the desired eutectic carbide microstructure that is formed during the method of manufacturing the ingot 34 during the solidification step 80. It is shown that an ingot 34 having a eutectic carbide microstructure according to the present invention having an eutectic carbide content of less than 5% by volume can be forged using hot press forging techniques. Another method, for example using ingots formed with a solidification rate of less than 15 ° C./min, causes these large rolls to burst during induction quenching or in the mill.

Step 20: Pre-heat treatment of the roll 1 In the production method of the present invention, the roll is treated by a pre-heat treatment step. In one embodiment of the invention, the roll is heated in a furnace between 700 ° C. and 1100 ° C. during the pre-heat treatment 20 according to the invention, and then the roll is for a period of time until satisfactory hydrogen diffusion occurs. , Kept at the temperature. Pre-heat treatment (normalizing and spheroidizing annealing) is performed to improve the machinability of the roll.

Step 22: Rough machining 22 of the roll
In the manufacturing method of the present invention, the roll is processed by a rough machining step 22. The rough machining 22 of the roll 1 formed according to the invention means removing the outer layer of the forging roll. In one embodiment of the invention, the outer layer is removed during rough machining. The roll is called a black blank before being processed by rough machining. By removing the oxide layer on the surface of the roll, the black blank roll is then converted to a white blank.

Step 24: Induction quenching of the roll 1 In the production method of the present invention, the roll is treated by induction quenching. During the induction hardening of the roll, a hard surface of the roll is formed. See FIG. 14 for a schematic diagram of the induction quenching step.

  In one embodiment of the present invention, the roll is slowly moved down while a current or voltage frequency between 50 Hz and 1000 Hz is applied through the inductor arrangement 70 during the induction quenching step. The roll 1 is cooled using water cooling 72 after the heating step. See FIG. The hard surface formed is also called the working layer 4 of the roll and is about 1/6 of the overall diameter 2 of the roll 1 (see FIG. 1, number 6). The roll barrel surface is rapidly heated as it is lowered through a series of inductors including electrical coils leading to a quench box. Rapid heat penetration with induction heating and rapid cooling immediately after using water produce a given layer with uniform roll surface hardness. Both the roll neck and core remain cold throughout the process. During induction quenching, a frequency typically between 50 Hz and 1000 Hz is applied to the surface of roll 1, and a frequency selected from the lower part of the interval provides a deeper working layer 4 of roll 1. Another factor that affects the depth of the working layer that is formed is the gap between the inductors 70 (if several inductors are used). The gap or distance between the inductor 70 and the roll 1 also affects the depth of the working layer 4 to be formed. Induction quenching step 24 according to the present invention may be single or double or more frequencies.

  The roll according to the present invention bursts using conventional quenching techniques, and induction heating is the most suitable technique for quenching the roll according to the present invention. Cooling of the roll 1 during the induction quenching 24 is performed with a high flow rate of cold water.

In one embodiment of the invention, induction quenching 34 is done by two induction quenching, and cooling of roll 1 after induction quenching 24 has a temperature of 40 ° C. and a flow rate of about 300 m ³ / h. The roll is moved downward at a speed of 0.3 mm to 1 mm / s.

  In one embodiment, induction quenching step 24 takes between 0.5 hours and 2 hours.

Step 26: Tempering of the roll In the production method of the present invention, the roll 1 is tempered. The purpose of the tempering step is to reduce the brittleness of the roll and adjust the level of hardness. The tempering step 26 is an important step in forming the roll in order to reduce internal stress. During the tempering step, the roll reaches its final microstructure by carbide diffusion and secondary precipitation. Air cooling is applied during the tempering heating step (s). The roll is preferably tempered three times at 450 ° C. to 530 ° C. The tempering step gives the roll the required hardness level above 780 HV or between 780 HV and 840 HV. Accurate control of time and temperature during the tempering process is a well-balanced fine so that after tempering the rolls made by the method of the invention have tempered martensite with a residual austenite ratio of less than 5% by volume. It is important to achieve a metal with a structure, for example tempered martensite.

Step 28: Machining of the roll In the production method of the invention, the roll is preferably processed by a machining step 28 before being used in a mill. For example, surface treatments specific to roll applications in mills are performed by grinding and other surface treatments to obtain the desired roughness and related friction at the surface of the roll. Examples of roll surface treatments are, for example, laser beam texturing (LBT), electron beam texturing (EBT) or discharge texturing (EDT).

  In one embodiment, the roll is treated by grinding and electrical discharge texturing (EDT) surface treatment. FIGS. 15A-B show the microstructure of the roll surface with a low chromium composition after discharge texturing. 15C-D show the microstructure of the surface of the roll according to the invention after discharge texturing. At the bottom of the white layer 300 in FIG. 15D, there is a re-austenite layer and a thinner softening zone. This is because this grade has a high tempering temperature. Note also that in the white layer in FIG. 15D, eutectic carbide 302 is not affected by the electric arc energy. For comparison, these types of carbides are not present in the rolls described in FIGS. The rolls according to the present invention have better properties and performance than standard grade rolls (see FIGS. 15A-B) due to the presence of hard eutectic carbides in the white layer.

  FIG. 18 shows a further schematic diagram of FIG. 15D, in which the newly formed eutectic carbide 302 formed due to remelting is present in the white layer 304 and the microstructure of the roll surface according to the invention. Represents. The previously formed eutectic carbide 300 is also shown in FIG. The roll surface in FIG. 18 shows how the surface looks after discharge texturing according to the present invention. Scale 306 represents 5 μm.

Roll 1 according to the present invention produced by the above method
A typical roll according to the present invention has a diameter between 215 mm and 800 mm, or between 250 mm and 700 mm, and the total length including the neck is up to 6 meters, where the barrel length is 1 meter. Between ~ 3 meters. The typical weight of the roll is between 400 kg and 10000 kg. The microstructure of the roll according to an embodiment of the invention is characterized in that it comprises tempered martensite having a residual austenite ratio of less than 5% by volume, wherein the roll is an open co-crystal of less than 5% by volume of eutectic carbide. Roll (1) contains a crystal carbide network and exhibits a hardness between 780 HV and 840 HV; and an internal compressive stress between -300 and -500 MPa. These characteristics of the roll are attributed to the roll manufacturing method of the present invention and also to the chemical composition of the roll according to the chemical composition of the present invention.

  The roll according to the invention is intended for use in cold strip mills that require a roll that can withstand high pressures. The rolls according to the invention are intended to be used in cold strip mills as work rolls and are suitable for any stand in the rolling process and suitable for 2 to 6 (2Hi to 6Hi) mills. The surface may have a roughness of 0.3 μm to 0.5 μm required at the finishing stand to a roughness of 1.5 μm to 2.5 μm required at the initial stand.

  The invention will be more readily understood by reference to the following examples. However, these examples are intended to illustrate the roll properties of the present invention and should not be construed to limit the scope of the present invention.

  In Table 4, various rolls are compared with rolls according to the present invention. All rolls contain Mn in an amount of weight percent between 0.2 and 0.5.

Two Examples of the Invention The roll 1 according to the invention in Table 4 uses the method according to the invention, using a solidification rate in the working layer of more than 15 ° C./min during the solidification interval, and even from 50 HZ to 250 HZ. And tempering three times at 450 ° C. to 530 ° C. using induction heating with a frequency of

  The roll 2 according to the invention in Table 4 is induction-heated using the method according to the invention, using a solidification rate of 18 ° C./min in the working layer during the solidification interval, and also using a frequency of 50 HZ to 250 HZ. And tempering three times at 490 ° C., then at 490 ° C., and 480 ° C. in the final tempering. FIG. 19 shows the microstructure of the roll after tempering and induction quenching (sampled at a depth of 4 mm from the surface of roll 2). A microstructure 1034 having an open eutectic network and eutectic carbide 1032 in a roll is also shown in FIG.

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

Applications of rolls Applications where rolls are suitable are:
Aluminum industry:
-Single stand, 4 stages, no reversing mill
Steel industry:
-4 steps, single stand, reversible-4 steps, tandem, 4 and 5 stands for sheets in continuous and discontinuous methods-4 steps, tandem, 4 and 5 stands for tinplate-6 steps for sheets Tandem mill.

Usage of the roll The forging roll according to the invention is in a cold rolling mill or for example;
-Cold rolling reduction mill for early and finishing stands, reversible and irreversible stands for tinplate, sheets, silicon steel, aluminum or copper.
-Cold rolling tempering and / or skin pass mill;
-Mill configurations as two-, four- and six-stage stands with textured or untextured surfaces;
-Suitable for use, for example, as work rolls or intermediate rolls in cold rolling of AHSS steel grades.

Roll Surface Surface Texture One problem with known rolls is that the surface texture wears during use of the roll. The surface texture is important because it ensures a coefficient of friction and avoids slipping and / or derailment of the strip. Furthermore, the surface texture determines the surface texture of the strip that imparts important surface properties to deep drawing and painting of the rolled strip. The roll according to the present invention exhibits an increased ability to maintain its surface texture due to the white layer of the roll, where the white layer comprises hard eutectic carbide as M ₇ C ₃ . In the working layer; the microstructure of the inventive roll after the final heat treatment is tempered martensite with a residual austenite ratio of less than 5% by volume and MC and M ₂ C (M = metal) finely and uniformly distributed in the matrix , C = carbon). This type of microstructure has been shown to be important for maintaining the surface texture of the roll.

Roughness transfer
The roll surface roughness shift varies during use of the roll. The roll according to the invention exhibits an increased ability to keep the roughness shift constant during rolling, which is important for the life of the roll. This is due to the specific claimed composition and even manufacturing method used when making the roll.

A challenge during the use of schedule-free rolling rolls in the mill is that the dirt accumulated on the roll surface leaves a linear trace on the strip. In the working layer, the roll according to the invention comprises MC and M ₂ C in which the microstructure of the roll according to the invention is finely and uniformly distributed in the matrix as well as tempered martensite with a residual austenite ratio of less than 5% by volume. And M represents a metal, and C represents carbon), and thus has a strong surface. This special microstructure increases the possibility of schedule-free rolling.

Delamination Another problem with known rolls is that the propagation of cracks inside the roll is dominated by the cumulative stress induced by the rolling operation and the residual internal stress field of the roll. A running roll is subjected to a series of complex stresses. The roll according to the invention exhibits a low level of residual internal stress and thus good peel resistance, thereby lowering the rate of mill accidents.

  The mechanical strength of the roll of the present invention is better compared to a roll having the same alloy composition as the roll of the present invention but made using another manufacturing method. The mechanical strength of the roll according to the invention is due to the open eutectic network formed in the working layer of the roll. This open eutectic network is formed during the cooling step in the roll fabrication method. It is important for the formation of open networks present in the roll according to the invention that the solidification rate exceeds 15 ° C./min during the cooling step when making the ingot.

  Also, after quenching, accumulating various tempering treatments at high temperatures, for example between 450 ° C. and 530 ° C., during the production of the rolls, induces significant relaxation of the internal stress of the rolls. Internal stress is minimized by using differential heating of the outer layer. The hardness penetration depth of the roll according to the invention can be controlled between 20 mm and 120 mm in diameter measured inward from the roll surface. The internal compressive stress of the roll according to the invention is preferably in absolute value between -300 MPa and -500 MPa or for example less than -400 MPa.

Roll Microstructure FIG. 17A shows a schematic diagram of an exemplary roll microstructure according to the present invention. In FIG. 17A, dendritic arms 210 composed of eutectic carbide forming eutectic cell structure 204 by forming an open carbide network can be seen. An open eutectic network composed of dendritic arms 210 forming the eutectic cell 204 can be seen in FIG. 17A and is formed in the present method due to the particular chemical composition according to the present invention. Scale 208 represents 100 μm.

  In one embodiment of the present invention, the microstructure of the roll of the present invention comprises an open eutectic network that extends only over one particle or two particles of the cell structure.

  In comparison, FIG. 17B shows a closed eutectic network where eutectic carbide 200 forms a closed eutectic network with clearly separated eutectic cells 212. This type of network, when including this type of microstructure, is undesirable for a roll according to the present invention due to the brittleness of the roll. Scale 214 represents 100 μm.

  The present invention has been described in terms of various embodiments within the scope of the appended claims.

Claims (42)

% By weight
0.8 to less than 1% C,
0.2-0.5% Mn,
0.2-2.0% Si,
7.0-13.0% Cr,
0.6-1.6% Mo,
V exceeding 1.0 to 3.0%
A steel composition comprising
The remainder of the steel is substantially Fe and possible incidental and / or inevitable impurities;
Here, the microstructure of the roll (1) is
Tempered martensite having a retained austenite ratio of less than 5% by volume;
An open eutectic carbide network having less than 5% eutectic carbide per volume;
The roll (1)
A hardness between 780 HV and 840 HV,
A forging roll (1) showing an internal compressive stress between -300 MPa and -500 MPa.   The roll of any preceding claim, wherein the open eutectic carbide network defines a cell-like pattern of eutectic cells.   A roll according to any preceding claim, wherein the open eutectic carbide network comprises dendritic arms.   The roll according to any one of the preceding claims, wherein the microstructure is present at least in a working layer of the roll. % By weight
0.8 to less than 1% C,
0.2-0.5% Mn,
0.2-2.0% Si,
7.0-13.0% Cr,
0.6-1.6% Mo,
V exceeding 1.0 to 3.0%,
Less than 0.015% P, and less than 0.015% S, and less than 1% Ni;
Less than 30 ppm O ₂ , and less than 100 ppm N ₂ , and less than 3 ppm H ₂ ,
Less than 2% W, and less than 1% Nb, and less than 1% Ti, and less than 0.5% Ta, and less than 0.5% Zr
A roll according to any preceding claim, comprising a steel composition comprising: the remainder of the steel being substantially Fe and possible incidental and / or inevitable impurities.   The roll according to any of the preceding claims, wherein the C content in the steel composition is C by weight percent between 0.8% and 0.99% of the total roll weight.   A roll according to any preceding claim, wherein the C content in the steel composition is C by weight percent between 0.85% and 0.9% of the total roll weight.   The roll according to any of the preceding claims, wherein the Mn content in the steel composition is Mn by weight percent between 0.4% and 0.5% of the total roll weight.   The roll according to any of the preceding claims, wherein the Si content in the steel composition is Si by weight percent between 0.2% and 1.5% of the total roll weight.   The roll according to any of the preceding claims, wherein the Si content in the steel composition is Si by weight percent between 0.85% and 1.15% of the total roll weight.   The roll according to any one of the preceding claims, wherein the Cr content in the steel composition is between 7% and 11% Cr by weight% of the total roll weight.   A roll according to any of the preceding claims, wherein the Cr content in the steel composition is between 7% and less than 8.0% of the total roll weight by weight%.   The roll according to any of the preceding claims, wherein the Mo content in the steel composition is Mo by weight percent between 1.45% and 1.55% of the total roll weight.   The roll according to any of the preceding claims, wherein the Ni content in the steel composition is Ni by weight percent and less than 0.3 of the total roll weight.   The roll according to any of the preceding claims, wherein the V content in the steel composition is between 1.3% and 2.1% of the total roll weight by weight%.   The roll according to any of the preceding claims, wherein the V content in the steel composition is between 1.3% and 1.6% of the total roll weight in wt%. The steel composition is in weight percent,
0.8-0.99% C, and 0.4-0.5% Mn, and 0.2-1.5% Si, and 7.0-11% Cr, and 0.6- 1.6% Mo, and less than 1.0 Ni, and 1.0-2.1% V, and less than 0.015% P, and less than 0.015% S, and less than 30 ppm O ₂ and less than 100 ppm N ₂ and less than 3 ppm H ₂
A roll according to any preceding claim, wherein the remainder of the roll is substantially Fe and possible incidental and / or inevitable impurities. The steel composition is in weight percent,
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% Cr, and 1 .45 to 1.55% Mo, and less than 0.3 Ni, and 1.3 to 1.6% V, and less than 0.015% P, and less than 0.015% S, and 30 ppm Less than O ₂ , and less than 100 ppm N ₂ , and less than 3 ppm H ₂
A roll according to any preceding claim, wherein the remainder of the roll is substantially Fe and possible incidental and / or inevitable impurities.   The roll according to any of the preceding claims, further configured for use as a work roll in cold rolling.   The roll according to any of the preceding claims, further having a weight of more than 400 kg.   The roll according to any of the preceding claims, further having a diameter in the range of 215 mm to 800 mm. A method for producing a non-forged roll,
a. % By weight
0.8 to less than 1% C,
0.2-0.5% Mn,
0.2-2.0% Si,
7.0-13.0% Cr,
0.6-1.6% Mo,
V exceeding 1.0 to 3.0%
Providing a steel composition wherein the remaining portion of the steel is substantially Fe and possible incidental and / or inevitable impurities;
b. Producing an ingot at a solidification interval while maintaining a solidification rate of greater than 15 ° C./min in the working layer of the ingot;
c. Forging the ingot into a roll;
d. Quenching the roll by induction heating;
e. Tempering the roll at a temperature between 450 ° C. and 530 ° C. to reach a hardness between 780 HV and 840 HV, whereby
Tempered martensite having a retained austenite ratio of less than 5% by volume;
Achieving a microstructure of the roll (1) comprising an open eutectic carbide network with less than 5% eutectic carbide per volume;
Roll (1) is
A hardness between 780 HV and 840 HV,
-A method showing an internal compressive stress between -300 MPa and -500 MPa.   Ingots in the working layer as well as in the core 15 ° C / min to 55 ° C / min, or alternatively 17 ° C / min to 50 ° C / min, or alternatively 35 ° C / min to 55 ° C / min, or alternatively The method according to claim 22, wherein the solidification rate is maintained within a range of 45 ° C / min to 55 ° C / min.   24. A method according to any of claims 22 to 23, wherein the ingot is produced at a solidification interval, maintaining a solidification rate of greater than 35 [deg.] C / min in the working layer of the ingot.   25. A method according to any of claims 22 to 24, wherein the solidification interval is between 1400 <0> C and 1200 <0> C for the ingot.   26. The ingot is manufactured maintaining a preselected solidification rate in an electroslag refining furnace (ESR) technology process by controlling an ampere current supply according to a predetermined function of the solidification rate. The method in any one of. The step of forging the ingot into a roll
a. Heating the ingot to a temperature between 800 ° C. and 1200 ° C. or between 850 ° C. and 1100 ° C., preferably for about 6 hours;
b. Forging the ingot at a temperature above 800 ° C or above 850 ° C;
c. 27. A method according to any of claims 22 to 26, comprising repeating steps ab until the ingot is formed into a roll having a desired shape and size.   28. The method further comprising the step of pre-heat treatment after the forging step, preferably to a temperature between 700 ° C. and 1100 ° C. or between 800 ° C. and 900 ° C., which may include a hydrogen diffusion treatment. The method in any one of. The step of tempering the roll
a. Heating the roll to about 450 ° C. to 530 ° C., preferably three times;
b. 30. A method according to any of claims 22 to 29, comprising air cooling the roll during the heating step (s).   30. A method according to any of claims 22 to 29, further comprising machining the roll to texture a white layer comprising eutectic carbide. The eutectic carbide in the white layer is selected from the M ₇ C _3, The method of claim 30.   32. A method according to any of claims 22 to 31 further comprising the features of any of claims 1 to 21. A forging roll (1) manufactured by a method comprising the following steps,
a. % By weight
0.8 to less than 1% C,
0.2-0.5% Mn,
0.2-2.0% Si,
7.0-13.0% Cr,
0.6-1.6% Mo,
V exceeding 1.0 to 3.0%
Providing a steel composition wherein the remainder of the steel is substantially Fe and possible incidental and / or inevitable impurities;
b. Maintaining a solidification rate in the working layer of the ingot at a solidification interval of greater than 15 ° C./min during the solidification interval;
c. Forging the ingot into a roll;
d. Quenching the roll by induction heating;
e. Tempering the roll;
This
Tempered martensite having a retained austenite ratio of less than 5% by volume;
A microstructure of the roll (1) comprising an open eutectic carbide network with less than 5% eutectic carbide per volume is achieved;
Roll (1) is
A hardness between 780 HV and 840 HV,
A forging roll (1) showing an internal compressive stress between -300 MPa and -500 MPa.   34. The roll of claim 33, further comprising the features of any of claims 1-32. An intermediate product ingot in the manufacture of a roll according to any of the preceding claims, in weight percent,
0.8 to less than 1% C,
0.2-0.5% Mn,
0.2-2.0% Si,
7.0-13.0% Cr,
0.6-1.6% Mo,
V exceeding 1.0 to 3.0%
Including
The remainder of the steel comprises a steel composition that is substantially Fe and possible incidental and / or inevitable impurities;
The final roll microstructure resulting from the ingot is
Tempered martensite having a retained austenite ratio of less than 5% by volume;
An ingot comprising an open eutectic carbide network with less than 5% eutectic carbide per volume.   35. The intermediate product ingot of claim 1, further comprising the features of any of claims 1-34.   35. Use of a roll according to any of claims 1 to 21 or 33 to 34 for cold rolled materials requiring high rolling loads.   Use of a roll according to any of claims 1 to 21 or 33 to 34 for cold rolling of high strength materials such as AHSS steel grade. -Cold rolling reduction mill for early and finishing stands for tinplate, sheets, silicon steel, stainless steel, aluminum and copper, reversible and irreversible stands; or-cold rolling tempering and / or skin pass mill; or 35. Any one of claims 1 to 21 or 33 to 34 for one selected from mill configurations as two-stage, four-stage and six-stage stands having a textured or untextured surface Use of the roll described in Crab.   Use of a roll according to any of claims 1 to 21 or 33 to 34 as a work roll.   A roll according to any of the preceding claims, a roll produced by the method, a method for producing a roll and / or use of a roll, wherein the roll is uncoated.   A roll according to any preceding claim, a roll produced by the method, a method for producing a roll and / or use of a roll, wherein the roll is coated with a selectable coating, for example a chromium coating.