FR2504418A1 - Centrifugally cast high chromium work roll - with intermediate layer metallurgically integrated with outer layer and axial core - Google Patents

Abstract

Centrifugally cast high chromium work roll, which is composed of outer layer of a cast iron consisting of C2.0-3.2% Si 0.5-1.5%, Mn 0.5-1.5%, P less than 0.08%, S less than 0.06%, Ni 1.0-2.0%, Cr 10-25%, Mo 0.5-1.5%, Nb less than 1.0%, V less than 1.0% and the balance substantially Fe, axial core material consisting of C3.0-3.8%, Si 2.3-3.0%, Mn 0.3-1.0%, P less than 0.1%, S less than 0.02%, Ni less than 0.2%, Cr less than 1.5%, Mo less than 1.0%, Mg 0.02-0.1% and the balance substantially Fe, and intermediate layer consisting of C1.0-2.5%, Si 0.5-1.5%, Mn 0.5-1.5%, Ni less than 1.5% Cr 5-10%, Mo less than 1.0% and the balance substantially Fe, and intermediate layer being metallurgically integrated with the outer layer and the axial core material.

Description

Roller cylinder b high chromium content
and its manufacturing process
The present invention relates to a high chromium rolling mill roll made by centrifugal casting and is particularly concerned with a high chromium rolling mill roll having high surface wear and roughness resistances as well as reliability properties as rolls of finishing mills including those for hot strip trains, cold band trains and hot surface work-hardening; the present invention also relates to a method for making said roll.

As is already known, for rolls of finishing rolling mills used in hot or cold rolling, etc., the following characteristics are necessary.
(1) Wear resistance:
This property is an important property having an influence on the surface property and the sheet thickness accuracy of the rolled product.

(2) $ reliability or foolproofness:
The roll of the mill must have a toughness or hardness adequate for an abnormal rolling.

(3) Resistance to surface roughness
Because the property of the cylinder surface has a great influence on the quality of the rolled product, resistance to surface roughness is necessary.

 As materials having the above three characteristics, Adamite, undefined cooled material, ductile material, shell molded material, cast steel or forged and tempered steel, etc., can be envisaged. Seriously and find wide use, but as they have respective advantages and disadvantages, they can not be considered suitable for rolls finishing band trains, etc.

 Thus, the Asdamite and an indefinitely cooled material, for example, in which free cementite is crystallized completely in large quantities are uncertain as to their resistance to surface roughness and toughness or toughness. In steel where graphite is totally crystallized, this graphite is detached, which results in surface roughness.

As a stembie, a uniform dispersion of hard carburals in the material is effective. To this end, it is advisable to make the cylinder with a material whose resistance to surface roughness and resistance to wear is improved by increasing the Cr content. However, obtaining a high hardness with the same material results in a high residual internal tension, which causes difficulties in the manufacture. Therefore, as is well known, a composite cylinder is used wherein the body portion and the trunnion portion (inner layer) are formed of different materials. Such a composite cylinder is generally formed by centrifugal molding.

 When in the composite cylinder mentioned above, a material having a high gold content and steel for its core or friend is used to make its shell, the tenacity of the material is considerably reduced even if a core exhibiting a high Cr content results from the Cr diffusion that occurs from the inner surface of the envelope into the core. However, in the manufacture of the steel core, it is necessary to increase the weight to pocket the cavities due to redone in the upper part of the mold frame, which results in an increase in the cost price and, because of the modulus of High elasticity, such a material is disadvantageous from the point of view of the thermal tensions and the residual tensions.

Therefore, to reduce the weight and reduce the modulus of elasticity of the core, thus releasing the thermal tensions and the residual tensions, it is desirable that the core is cast iron but if Cr of the envelope is melted again and diffuse in the nucleus, the core material becomes very brittle, so that the interest of the mixture is lost. On the other hand, when a material with a high Cr content is used for the shell, a film of oxide k is formed. high melting on the inner surface of the shell, resulting in inadequate weldability0
The subject of the present invention is a high chromium rolling mill roll which has extremely good qualities in terms of wear resistance, surface roughness and reliability properties through the elimination of defects and problems with rolling mill rolls for hot rolling and cold rolling.

The subject of the present invention is a rolling mill roll with a high chromium content, in which, on the one hand, the cast iron outer layer comprises 2.0 - 3.2% C, 0.5 - 1.5% Si , 0.5 - 1.5% Mn, less than 0.08% P, less than 0.06% S, 1.0 - 2.0% Ni, 10 - 25% Cr, 0.5 - 1.5 % Mo, less than 1.0% Nb and less than 1.0% V, the complement being essentially Fe, and secondly the core formed from 3.0 - 3.8% C, 2,3 - 3.0% Si, 0.3 - 1.0% Mn, less than 0.1% P, less than 0.02% S, less than 2.0% Ni, less than 1.5% Cr, less of 1.0% Mo and 0.02-0.1% Mg, the balance being essentially Fe, a cast iron intermediate layer containing 1.0 2.5% C, 0.5-1.5% Si is formed, 0.5 - 1.5% Mn, less than 1.5 r Ni, 5 - 10% Cr and less than 1.0% Mo, the balance being essentially Fe, this layer being integrally bonded in the metallurgical direction term to said outer layer and said core
The present invention also relates to a method for producing a high Cr mill roll, which process comprises an intermediate layer formation phase using a low-melting metal melt.
Cr between the molding phase for the formation of the outer layer and that for the formation of the core, thereby to prevent Cr from diffusing into the core from the outer layer having a high Cr content and to mix with this nucleus.

The present invention will now be described with reference to the accompanying drawings, in which
FIG. 1 is a front view of a rolling mill roll according to the present invention, the outer layer and the inner layer being shown in section 5 and
- Figure 2 is a sectional view of the rolling mill roll of Figure 1 by A of the latter.

 The outer layer of the high chromium rolling mill roll according to the present invention will be described below. This outer layer has a hardness of 70 - 80 H @ (Shore hardness). We will indicate below the constituent elements of this layer and their proportions.

C is determined by the amount of carbide provided and the establishment of equilibrium with Cr in the range where stable carbides of the type (Fe, Cr) 7C3 can be obtained. If the C content is smaller than 2.0, the amount of carbides formed is small, which results in reduced wear resistance, but if it exceeds 3.2%, the carbide amount becomes too great which results in a deterioration of the mechanical strength. Therefore, the C content must be 2.0 - 3.2% 0
Si is used to deoxidize the molten metal. With a percentage lower than 0.5%, this effect can not be achieved. If this percentage is greater than 1.5%, the mechanical properties deteriorate, or the temperature of modification of the iron increases, which causes difficulties in the conversion of iron and, consequently, does not easily reach a high hardness. For this reason, the Si content should be in the range of 0.5 - 1.5.

 The amount of Mn as an auxiliary for the Si deoxidation should be at least 0.5%. If it is less than 0.5, the deoxidation effect is not obvious, but if it is greater than 1.5%, the decrease in mechanical properties, particularly the toughness or hardness, becomes noticeable. Therefore, the Mn content should be 0.5 1.5%.

 With regard to P, the lower the P content of the particular cylinder material, the better, and given its embrittlement effect of the material, its content should be less than 0.08%.

 With regard to S, it is desirable that this content be low since, like P, it has the effect of weakening the material of the cylinder. Its content should preferably be less than 0.06%.

 Neither is present for a positive adjustment of the hardness or to improve the quenching properties. With a Ni content of less than 1.0%, no effect is obtained but if the Ni content is greater than 2%, the residual austenite increases, making hardness increase difficult.

In particular, to reach the hardness range of 70 - 80 HS, the Ni content should be in the range of 1.0 - 2.0%.

 Cr's role is to improve toughness and resistance to wear. If its content is less than 10, a large amount of carbides of the type M3 C crystallizes completely. as a result, toughness decreases and refinement and uniformity can not be achieved. If the Cr content is greater than 25%, the amount of carbides M23C6 type increases.

These carbides, which have a low hardness compared to M7C3 carbides, do not give adequate wear resistance.

Therefore, the Cr content should be 10-25%.

 Mo has the effect not only of increasing quenching and tempering resistance but also of promoting resistance to softening as a result of the tempering while increasing the hardness of the carbides by incorporating with them. This effect can not be obtained if its content is less than 05%, but if its content is greater than 1.5, this results in a hardness too high, greater than 80 HS. Therefore, the Mo content should be between 0.5 - 1.5%.

Since it has the effect of refining the structure of the casting, it is a constituent element which it is desirable to add, but the cylinder according to the present invention can be made without its addition. The Nb content promotes precipitation hardening thereby improving wear resistance. Especially in the hardness range of 70 - 80 Hs, this effect occurs at Nb contents less than 0.1. If the content of Nb is greater than 1.0%, this effect reaches saturation and it also results in an increase in the cost price. Therefore, the content of
Nb must be less than 1, 0%.

 V is present for the same reasons as Nb. Its addition is desirable, but the cylinder of the present invention can be made without its addition. To obtain a hardness range of 70-80 Hs, a V content of less than 1.0% is sufficient. If this content is greater than 1.0%, the amount of V carbides increases, thereby pre- proportionally decreasing the amount of Cr carbides, which in turn results in a decrease in wear resistance.

Therefore, the V content should be less than 1.0%.

 The above descriptions of the respective constituent elements are given in relation to the hardness range of 70-80 Hs. These limitations may be determined by the following reasons. In general, the wear resistance of the rolling mill roller during hot and cold rolling operations is closely related to the hardness. Thus, at hardnesses less than 70 Hs, the resistance to surface roughness and wear resistance decrease abruptly as reliability properties and anti-cracking properties tend to decrease rapidly as hardness increases and exceeds 80 Hs limits as a result of local heating of the product. cylinder under abnormal rolling conditions. Therefore, to ensure high resistance to surface roughness, high wear resistance, good reliability and anti-cracking properties, the hardness range of 70 - 80 Hs is preferred for rolling mill rolls. high chromium content.

 The constituent elements of the core material of the high chromium rolling mill roll of the present invention and their proportions will be described below.

 The penetration of Cr from the outer layer into the core material is greatly reduced as a result of the interlayer compared to what happens in a cylinder with no intervening layer, but it is impossible to completely prevent penetration. from Cr.

As a result of Cr diffusion from the outer layer, the Cr content of the core material is about 0.5 - 1.0%. The chemical compositions of the core material and their proBortions should be selected taking into account in the calculations of this increase in the content of
Cr.

 C is present to communicate toughness and mechanical strength With a C content of less than 3.0%, the cooling of the material continues, which brings about a noticeable reduction in the toughness of the core. If the C content is less than 3.8%, the graphitization becomes excessive. Not only the mechanical strength of the core then becomes insufficient but the part forming the trunnions tends to have a lower hardness and becomes susceptible to a surface roughness during which it is in use.

Therefore, the C content must be 3.0 - 3.8
If the tenemren Si becomes less than 2.3, the graphitization does not continue perfectly; the cementite precipitates considerably and if the content Etn is greater than 3.0%, graphitization is favored, which causes a decrease in the mechanical strength. Therefore, the Si content should be 2.3 - 3.0 *.

 Mn eliminates the deleterious effects of S by combining with S to form MnSO If its content is less than 0.3%, no effect results. On the other hand, levels greater than 1.0% cause the material to deteriorate rather than prevent the deleterious effects of S. Therefore, the Mn content should be 0.3 - 1.0%.

 P, in that it has the effect of increasing the fluidity of the molten metal, but making the material brittle, must desirably be present in smaller amounts.

The P content must be less than 0.1%.

 Since S, as P, weakens the material, the lower its content, the better. The core material, because it is malleable cast iron, combines with Mg to form MgS, which reduces S. However, for the graphite to be globular, the S content must be low. Therefore, the S content must be less than 0.02%.

 Ni is present to stabilize the graphite. Its content above 2.0% has no noticeable effect. The Ni content must be less than 2.0%.

 Because the outer layer has a high chromium content, some penetration of Cr into the core material is inevitable, even if the intermediate layer is present, the lower the content of the material on Cr is, the better, but in Since the precipitation of graphite is concerned it is preferable to establish the equilibrium of Cr with that its content is less than 1.5%.

This content, if it is greater than 1.5%, causes an increase in the cementite in the material and, as a result, a reduction in toughness. Therefore, the Cr content should be less than 1.5%.

 Mo is a desirable element because it hinders the crystallization of graphite. But a too high content of this element results in too much hardness. As a result, the Mo content should be less than 1.0%.

 Mg is a necessary element for the globular formation of graphite. But its content is less than 0.02%, the globular formation becomes inadequate; it follows that the material of the nucleus can not become tenacious and ductile. it is undesirable for Mg to have a content greater than 0.1% because of its cooling effect and because it is trapped in the product as an impurity. Therefore, the Ng content should be 0.02 - 0.1%.

 Cr, Ni and Mo contained in the core material are usually present in this material inevitably when not positively added. The present invention can be realized without the addition of these constituent elements.

 The constituent elements of the intermediate layer of the high chromium rolling mill roll according to the present invention and their proportions will be described below.

 This intermediate layer is used to prevent chromium from the high chromium outer layer from diffusing into the core material and thereby reducing the toughness of this material.

 This is for the purpose of communicating toughness and strength to the intermediate layer. If Cr of the outer layer is dissolved by the intermediate molten metal and if it is completely mixed uniformly with the intermediate molten metal, its content is 5-10% in total. If the C content is less than 1.0, the temperature of casting or molding of the intermediate layer takes a high value. The outer layer then tends to melt, causing an additional increase in Cr%. as a result, the intermediate layer loses all meaning as a means to prevent the diffusion of Cr into the core material.

 If the C content exceeds 2.5, the amount of carbides increases; the middle layer itself loses its tenacity which makes it lose its importance.

Therefore, the C content must be 1.0 - 2.5%.

 With regard to the casting of the intermediate layer, the lower the Cr content, the better. With regard to the chemical composition in the ladle before the molten metal is cast to form the intermediate layer, the Cr content must be less than 1.0%, a proportion that can be easily adjusted in practice industrial. The total amount of Cr of the molten metal of the ladle before this metal is poured and the amount of Cr from the outer layer when the intermediate layer is formed by casting is 5-10 r.

This Cr penetrates into the core material, resulting in an increase in the Cr content of this material.

 To set the amount of Cr of the core material to less than 1.5%, it is necessary to adjust the amount of Cr in the intermediate layer to be in the range of 5-10% by choosing appropriate casting conditions. Therefore, the Cr content must in addition to 5 - 10%.

If the effect is to deoxidize the molten metal. Its content less than 0.5% does not give this effect. At least 0.5% is necessary. But if its content exceeds 1.5%, the intermediate layer becomes fragile, which results in a deterioration of its mechanical properties. Content
If should be 0.5 - 1.5.

 Mn-has an effect similar to that of Si and, moreover, it eliminates the harmful effects of S by forming -NnS with it. Its content of 0.5% is necessary. If it is present in a percentage exceeding 1.5%, its effect is saturated and deterioration occurs in its mechanical properties. Therefore, the Mn content should be 0.5 - 1.5%.

 Neither is present to impart properties suitable for quenching as well as better toughness. Its content increases to above 0.3% as a result of its diffusion from the outer shell or layer without its positive addition Its content reaching 1.5% gives this effect without raising problems. If its content exceeds 1.5, quenching is favored to the point of giving a too hard matrix, a result which is undesirable from the point of view of toughness and residual stresses.

 Mo has an action similar to that of Ni. Its content greater than 1.0% makes the intermediate layer too hard. Its content must be less than 1.0%.

P, S and Ti call the comments below t
P raises the fluidity of the molten metal, but causes a reduction in the tenacity of the material of the cylinder. The P content must be less than 0.1.

 S as P weakens the material of the cylinder. Its truly harmless content must be less than 0.1%.

 Ni and Mo of the interlayer are elements that are desirable to add, but the present invention can be implemented without their addition.

 Addition of Ti is desirable for deoxidation of the molten metal. If its content is less than 0.01%, it has no deoxidizing effect. Its content greater than 0.1% places the molten metal in a superoxide state and causes a reduction in the fluidity of the molten metal. Therefore, the Ti content should be 0.01 - 0.1%. Al and Zr which are normally used as deoxidizing agents in place of Ti, can be used in an amount of the order of 0.01 - 0.1 *. Ti, Al and Zr give optimal results in the range of 0.03-0.05.

 The high chromium rolling mill roll of the present invention has the structure described in detail above. The method of manufacturing this high chromium rolling mill roll is described below with reference to an embodiment shown in FIGS. 1 and 2.

 First, after the molten metal for forming the outer layer 1 has been poured into the metal mold which is lined on its inner surface with a refractory product and which is rotated on a centrifugal casting machine, the intermediate layer 2 is molded into this mold before the inner surface of the outer layer 1 is solidified. Then, after these two parts, i.e., the outer layer 1 and the intermediate layer 2 have completely hardened, the The mold is arranged upright and, through its top, flows molten metal therein to form the malleable iron of the core 3, whereby the outer layer 1, the intermediate layer 2 and the core 3 combine completely, in the direction metallurgical of the term, so as to form a cylinder in one piece.

Alternatively, before the outer layer 1 and the intermediate layer 2 have both completely hardened, the core 3 can be molded using a suitable method using a centrifugal molding machine, the axis of rotation of the mold being kept horizontal or inclined while part of the inner surface remains in the non-solidified state,
The following is a description of a mode of réaisation of the rolling mill roll with a high chromium content according to the present invention.
Mode of realization
Three kinds of high chromium rolling mill rolls having a cylindrical body diameter of 680 mm, a cylindrical body length of 1800 mm and a total length of 3800 mm were manufactured using an alloy of Examples 1, 2 and 3. as shown in the table below.

 (1) A high chromium molten metal to form the 80 mm (2400 kg) thick outer layer was cast in a rotating mold on a 1400 C spinning machine.

 (2) Eighteen minutes after the start of molding of the outer layer, a molten metal for forming the 35 mm (1000 kg) thick intermediate layer was cast in the 1470 C rotating mold.

 (3) Thirty-three minutes after the beginning of the molding of the outer layer, the outer layer and the intermediate layer were not completely sodified.

 (4) Then, the mold was placed upright and, through its top, the molten metal intended to form the malleable cast iron of the core was cast at 1380 C and then, after the mold was completely filled, the cast iron was vented and covered with insulation.

 (5) After being completely cooled, the cylinder was extracted from the mold and then machined to give the final product.

 The results of an ultrasonic test and a break examination carried out on the cylinder body showed that the thickness of the outer layer was 60 mm, after the molding of the intermediate layer, that the intermediate layer had a thickness of 30 - 35 mm and a Cr content of 6.0 - 8.0%.

 It has been found that the outer layer, the middle layer and the core are one piece and it has been found that there is a structural continuity.

 The chemical compositions of Examples 1, 2 and 3 of the molten metals before beech cast to form the outer layer, the intermediate layer and the core are shown in the table below.

it should be noted that a small amount of Nb and
It enters the intermediate layer from the outer layer at the molding stage.

<SEP> C <SEP> If <SEP> Mn <SEP> P <SEP> S <SEP> Ni <SEP> Cr <SEP> Mo <SEP> Nb <SEP> V <SEP> Ti <SEP> Mg
<tb><SEP> Layer
<tb><SEP> External <SEP> 2.75 <SEP> 0.69 <SEP> 1.10 <SEP> 0.032 <SEP> 0.020 <SEP> 1.55 <SEP> 14.20 <SEP> 1, <SEP> - <SEP> - <SEP> - <SEP>
<SEP> Before <SEP> Layer
<tb><SEP> molding <SEP> Intermediate <SEP> 1.63 <SEP> 0.68 <SEP> 0.98 <SEP> 0.030 <SEP> 0.021 <SEW> 0.43 <SEP> 0.09 <SEP> 0, 06 <SEP> - <SEP> - <SEP> 0.042 <SEP>
<SEP> Core <SEP> 3.49 <SEP> 2.63 <SEP> 0.35 <SEP> 0.033 <SEP> 0.009 <SEP> 0.44 <SEP> 0.12 <SEP> 0.05 <SEP> - <SEP > - <SEP> - <SEP>
<SEP> Layer
<tb><SEP> External <SEP> Cylinder <SEP> 2.75 <SEP> 0.69 <SEP> 1.10 <SEP> 0.032 <SEP> 0.020 <SEP> 1.55 <SEP> 14.20 <SEP> 1, <SEP> - <SEP> - <SEP> - <SEP> 0.072
<tb><SEP> product <SEP> Layer
<tb><SEP> Intermediate <SEP> 1.90 <SEP> 0.68 <SEP> 1.01 <SEP> 0.031 <SEP> 0.021 <SEP> 0.76 <SEP> 5.32 <SEP> 0.30 <SEP> - <SEP> - <SEP> 0.080 <SEP>
<SEP> Core <SEP> 3.42 <SEP> 2.61 <SEP> 0.39 <SEP> 0.033 <SEP> 0.010 <SEP> 0.57 <SEP> 0.87 <SEP> 0.06 <SEP> - <SEP> - <SEP> - <SEP> 0.069
<tb><SEP> Layer
<tb><SEP> Before <SEP> external <SEP> 2.81 <SEP> 0.75 <SEP> 0.89 <SEP> 0.040 <SEP> 0.030 <SEP> 1.25 <SEP> 18.62 <SEP> 0.86 <SEP> 0.35 <SEP> 0.20 <SEP> - <SEP>
<SEP> molding <SEP> Layer
<tb><SEP> Intermediate <SEP> 1.75 <SEP> 0.76 <SEP> 0.92 <SEP> 0.027 <SEP> 0.030 <SEP> 0.52 <SEP> 0.12 <SEP> 0.30 <SEP> - <SEP> - <SEP> 0.07 <SEP>
<SEP> Core <SEP> 3.42 <SEP> 2.85 <SEP> 0.66 <SEP> 0.066 <SEP> 0.010 <SEP> 0.65 <SEP> 0.29 <SEP> 0.15 <SEP> - <SEP> - <SEP> - <SEP> 0.08
<tb><SEP> Layer
<tb><SEP> External <SEP> Cylinder <SEP> 2.81 <SEP> 0.75 <SEP> 0.89 <SEP> 0.040 <SEP> 0.030 <SEP> 1.25 <SEP> 18.62 <SEP> 0.86 <SEP> 0.35 <SEP> 0.20 <SEP> - <SEP>
<SEP> product <SEP> Layer
<tb><SEP> Intermediate <SEP> 2.08 <SEP> 0.76 <SEP> 0.91 <SEP> 0.032 <SEP> 0.030 <SEP> 0.85 <SEP> 6.8 <SEP> 0.42 <SEP> 0.08 <SEP> 0.03 <SEP> 0.058 <SEP>
<SEP> Core <SEP> 3.35 <SEP> 2.68 <SEP> 0.72 <SEP> 0.060 <SEP> 0.010 <SEP> 0.67 <SEP> 0.95 <SEP> 0.17 <SEP> - <SEP> - <SEP> - <SEP> 0.058
<tb><SEP> Layer
<tb><SEP> Before <SEP> External <SEP> 2.92 <SEP> 0.89 <SEP> 0.99 <SEP> 0.028 <SEP> 0.042 <SEP> 1.09 <SEP> 19.55 <SEP> 0.56 <SEP> 0.16 <SEP> 0.10 <SEP> - <SEP>
<SEP> molding <SEP> Layer
<tb><SEP> Intermediate <SEP> 2.23 <SEP> 0.92 <SEP> 0.95 <SEP> 0.021 <SEP> 0.044 <SEP> 0.06 <SEP> 0.35 <SEP> 0.25 <SEP> - <SEP> - <SEP> 0.066 <SEP>
<SEP> Core <SEP> 3.56 <SEP> 2.93 <SEP> 0.46 <SEP> 0.066 <SEP> 0.002 <SEP> 0.06 <SEP> 0.09 <SEP> 0.03 <SEP> - <SEP> - <SEP> - <SEP> 0.055
<tb><SEP> Layer
<tb><SEP> External <SEP> Cylinder <SEP> 2.92 <SEP> 0.89 <SEP> 0.99 <SEP> 0.028 <SEP> 0.042 <SEP> 1.09 <SEP> 19.55 <SEP> 0.56 <SEP> 0.16 <SEP> 0.10 <SEP> - <SEP>
<SEP> product <SEP> Layer
<tb><SEP> Intermediate <SEP> 2.41 <SEP> 0.90 <SEP> 0.97 <SEP> 0.025 <SEP> 0.043 <SEP> 0.32 <SEP> 7.21 <SEP> 0.35 <MS> 0.03 <SEP> 0.02 <SEP> 0.055 <SEP>
<SEP> Core <SEP> 3.49 <SEP> 2.76 <SEP> 0.55 <SEP> 0.070 <SEP> 0.009 <SEP> 0.09 <SEP> 0.59 <SEP> 0.09 <SEP> - <SEP> - <SEP> - <SEP> 0.051
<Tb>

An operating result obtained with the high chromium rolling mill roll according to the present invention will be illustrated below.
A cylinder having the same composition as that indicated in the embodiment described above was used as a rolling mill roll for hot strip trains.
The results revealed excellent wear resistance in the rolling of Hi-C materials which are extremely resistant to deformation.

Rolling with conventional cylinders,
consumption during a cycle s 0.21 mm
Rolling with conventional cylinders,
average amount of surface abrasion
consoe'e of the cylinder during a cycle: 0.35 mm
Rolling with the cylinder of this
invention, consumption during a cycle t
example 1 0.16 mm
example 2 0.14 mm
example 3 0.15 mm
Rolling with the cylinder of this
invention, average abrasion speed of
consumed surface of the cylinder during a
cycle
example 1 0.26 mm
example 2 0.23 mm
example 3 0.24 mm
With regard to the surface roughness, a surface roughness did not result in an abnormal replacement of the cylinder. The rolling operation is carried out until the cylinder has been reduced to its final diameter (the thickness of the consumed surface: 40 mm) without any problem with a satisfactory result.
The high chromium rolling mill roll according to the present invention and its method of manufacture are not limited to the embodiment described above with reference to the accompanying drawings, and it is understood that variations and modifications may be made thereto in the context of the present invention

Claims (10)

 the rolling mill cylinder having a high chromium content, characterized in that it comprises a cast iron intermediate layer comprising, by weight, 1.0 - 2.5% C, 0.5 - 1.5% Si, 0.5 1.5% Mn and 5-10% Cr, the balance being essentially Fe, this layer being placed between, on the one hand, a cast iron outer layer comprising 2.0 - 3.2% C, 0.5 1 , 5% Si, 0.5 - 1.5% Mn, less than 0.08% P, less than 0.06% S, 1.0 - 2.0 r Ni, 10 - 25% Cr and 0.5 - 1.5% Mo, the balance being essentially Fe, and secondly, a core comprising 3.0 - 3.8% C, 2.3 - 3.0% Si, 0.3 - 1.0 % Mn, less than 0.1% P, less than 0.02% S and 0.02 - 0.1% Mg, the balance being essentially Fe, said intermediate layer being metallurgically united to said outer layer and to this core by forming with them only one piece.  Rolling mill cylinder with a high chromium content, characterized in that it comprises a cast iron intermediate layer comprising, by weight, 1.0 - 2.5% C, 0.5 - 1.5% Si, O, 5 - 1.5% Mn, less than 1.5% Ni, 5 - 10 r Cr and less than 1.0% Mo, the balance being essentially Fe, this layer being disposed between, on the one hand, an outer layer cast iron comprising 2.0 - 3.2% C, 0.5 - 1.5% Si, 0.5 - 1.5% Mn, less than 0.08% P, less than 0.06% S, 1 , 0 - 2.0% Ni, 10 - 25% CR, 0.5 - 1.5% Mo, less than 1.0% Nb and less than 1.0% V, the complement being essentially Fe, and, secondly, a core comprising 3.0 - 3, 8% C, 2.3 - 3.0% Si, 0.3 - 1.0% Mn, less than 0.1% P, less than 0.02% S, less than 2.0% Ni, less than 1.5% Cr, less than 1.0% Mo and 0.02 - 0.1% Mg, the balance being essentially Fe, said intermediate layer being metallurgically united with said outer layer and said core and not forming a single piece with these.  High-chromium rolling mill cylinder according to Claim 2, characterized in that the hardness of the outer layer is 70 - 80 Hs.  High-chromium rolling mill roll according to Claim 2, characterized in that the intermediate layer contains 0.01 - 0.1% Ti.  5. High chromium rolling mill cylinder according to claim 2, characterized in that the intermediate layer contains 0.01 - 0.1% Al.  6. High chromium rolling mill cylinder according to Claim 2, characterized in that the intermediate layer contains 0.01 - 0.1% Zr.  A process for producing a high chromium rolling mill roll, wherein the rolling mill roll is formed by casting molten metals into a rotary mold of a centrifugal molding machine, characterized in that it comprises  a phase in which the outer layer is formed by pouring into the mold a molten metal containing, by weight, 2.0 - 3.2% C, 0.5 - 1.5% Si, 0.5 - 1.5% Mn, less than 0.08% P, less than 0.06% S, 1.0 - 2.0% Ni, 25% Cr, 0.5 - 1.5% No, less than 1.0% Nb and less than 1.0% V, the complement being Fe t  a phase in which, before the inner surface of the outer layer has solidified, the intermediate layer is formed by casting a molten metal comprising 1.0 - 2.5% C, 0.5 - 1.5% If, 0.5 - 1.5% Mn, less than 1.5% Ni, less than 1.0% Cr and less than 1.0% Mo, the complement being Fe; and  a phase in which, after the outer layer and the intermediate layer have completely hardened, the molten metal is poured into the mold, thereby forming a molten metal comprising 3.0 - 3.8% C, 2.3 - 3.0% If, 0.3 - 1.0% Mn, less than 0.1 'Yo P, less than 0.02% S, less than 2.0% Ni, less than 1.5' Yo Gold, less than 1, 0% Mo and 0.02 - 0.1% Mg, the balance being Fe.  8. A process for producing a high chromium screened cylinder according to claim 7, characterized in that the phase for forming the intermediate layer is made with a molten metal containing 0.01 - 0.1% Ti.  9. Process for producing a high chromium rolling mill roll according to Claim 7, characterized in that the phase for forming the intermediate layer is carried out with a molten metal containing 0.01 - 0.1 μm Al.  Process for producing a high chromium rolling mill roll according to Claim 7, characterized in that the phase for forming the intermediate layer is carried out with a molten metal containing 0.01 - 0.1% Zn.