WO2025186846A1

WO2025186846A1 - Metal alloy for a method for producing an article and article thus obtained

Info

Publication number: WO2025186846A1
Application number: PCT/IT2024/000006
Authority: WO
Inventors: Mauro ANDREUSSI; Olivia Andreussi; Eddy Pontelli; Enrico Veneroso
Original assignee: F A R - FONDERIE ACCIAIERIE ROIALE SpA
Current assignee: F A R - FONDERIE ACCIAIERIE ROIALE SpA
Priority date: 2024-03-07
Filing date: 2024-03-07
Publication date: 2025-09-12
Anticipated expiration: 2026-09-07
Also published as: WO2025186846A8

Abstract

Metal alloy for a method for producing an article (10, 10a) subject to wear comprising a main body (11) provided with a metal matrix (Ml) and, in correspondence with at least one zone (15) thereof to be reinforced, at least one reinforcing insert (12), at least partly comprising steel containing carbon by mass percentage lower than 0.5% and chromium by mass percentage lower than 3%.

Description

METAL ALLOY FOR A METHOD FOR PRODUCING AN ARTICLE AND ARTICLE THUS OBTAINED

FIELD OF THE INVENTION

5 The present invention concerns a metal alloy for a method for producing a foundry article subject to wear, for example for components of tools for crushing or abrading mineral substances or metal debris, mills, crushers, formworks, excavators, tracked vehicles or turbomachines. The present invention also concerns an article subject to wear obtained by means of this method and which0 uses this metal alloy. This article can be, for example, an element subject to wear of a cone mill or suchlike.

BACKGROUND OF THE INVENTION

Methods for producing articles of manganese steel subject to wear are known, for example anti-wear spare parts for crushing. Articles that use manganese steel5 as a metal alloy have a high toughness and a marked tendency to harden. Typically, before use a manganese steel article has a low hardness (about 190 HB, Hardness Brinell, approximately corresponding to 180 HV - 240 HV, Hardness Vickers); however, following specific types of impacts sustained during a correct use, through work hardening it can reach high hardness, up to about 600 HV - 700 HV. 0 Methods for producing articles subject to wear that use steel or chromium cast iron as a metal alloy, for example martensitic steels or white cast iron, are also known. These materials already have high hardness (respectively about 53 HRC - 58 HRC, Hardness Rockwell Cone, that is, approximately 560 HV - 650 HV, and about 60 HRC - 65 HRC, that is, approximately 700 HV - 820 HV) before the first 5 use. From this it can be said that their resistance to wear is already optimal from the beginning of use and does not depend on the type of impact sustained. However, martensitic steels and chrome cast iron have low toughness.

Methods for producing articles subject to wear that comprise one or more reinforcing inserts, generally of ceramic material, in a metal matrix are also known. 0 These inserts can comprise hard ceramic particles, kept in a desired shape by means of binders or adhesives, and can be disposed in a mold before the metal matrix is cast, in the zones of the final article particularly subject to wear that have to be reinforced. The metal matrix has to have a fluidity high enough to allow the optimal filling of the mold and the expulsion of any gases generated, for example, by the combustion of the binders used to prepare the ceramic inserts. For this reason, it is possible to make articles with reinforcing inserts made of steel or chrome cast iron, which has high fluidity, while the production in manganese steel is critical because of its low fluidity.

These articles subject to wear can be used in cone mills, provided with a bell or central cone and with an external shell. Generally, both the central cone and also the external shell are made of manganese steel. Due to the operating principle of the mill, the upper part of the cone, closer to the initial entry point of the aggregates, is subject to lower loads than the lower part (gauge zone). As a result, manganese steel tends to harden especially in the lower part and the wear of the central cone is not uniform over the entire surface. Consequently, the shape of the cone’s profile changes, lowering the mill’s performance and shortening its life. Ultimately, current cone mills can have a non-linear and non-uniform wear profile of the central cone, creating, for example, depressions that can negatively modify the crushing dynamics and therefore the process yield.

There is therefore the need to perfect a metal alloy for a method for producing articles subject to wear that can overcome at least one of the disadvantages of the state of the art.

The purpose of the present invention, in order to solve the technical problems identified above, is to perfect a metal alloy for a method for making a foundry' article subject to wear, which has a sufficient toughness for its use and a high hardness and resistance to wear.

Another purpose of the present invention is therefore to perfect a method by means of which it is possible to obtain an article subject to wear which has good toughness properties and is compatible with the arrangement of ceramic inserts, it therefore has good fluidity to integrate the ceramic insert, it has the capacity to bond with the ceramic particles of the reinforcing insert and has sufficient hardness to sustain the ceramic particles under load, rather than collapsing locally, nullifying the role of the reinforcing insert.

Another purpose of the present invention is to provide an article subject to wear that is hard, tough and compatible with the arrangement of reinforcing inserts.

The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea.

In accordance with the above purposes, the present invention concerns a metal alloy for a method for producing an article subject to wear comprising a main body provided with a metal matrix.

According to one aspect of the invention, the metal alloy at least partly comprises steel containing carbon by mass percentage lower than 0.5% and chromium by mass percentage lower than 3%.

By using this metal alloy, it is possible to obtain an article that has sufficient toughness, sufficient hardness and resistance to wear.

Therefore, the present article is compatible with the arrangement of ceramic inserts, therefore it has a good fluidity to integrate the ceramic insert, it has the ability to bond with the ceramic particles of the reinforcing insert and has sufficient hardness to sustain the ceramic particles under load, rather than collapsing locally, nullifying the role of the reinforcing insert.

When applied in a cone mill, the production of articles with the metal alloy disclosed above and reinforced with ceramic inserts allows to keep the shape of the profile for longer, and has a wear profile that is more uniform and freer of depressions compared to what currently happens in known cone mills.

According to another aspect of the invention, the steel has a predominantly bainitic structure.

According to another aspect of the invention, the metal alloy comprises carbon by mass percentage comprised between 0.19% and 0.35%, manganese by mass percentage comprised between 0.7% and 1%, silicon by mass percentage comprised between 0.4% and 0.7%, chromium by mass percentage comprised between 0.7% and 2%, nickel by mass percentage comprised between 0.35% and 0.4%, molybdenum by mass percentage comprised between 0.25% and 0.3% and aluminum by mass percentage comprised between 0.03% and 0.05%.

The invention also concerns a method for producing an article subject to wear comprising a main body provided with a metal matrix and, in correspondence with at least one zone thereof to be reinforced, at least one reinforcing insert.

According to one aspect of the invention, the method provides a first step of producing at least one pre-insert, comprising reinforcing ceramic material in a non- metal matrix, and a second step of producing the at least one reinforcing insert by replacing the non-metal matrix with the metal matrix in the pre-insert, so that the at least one reinforcing insert is embedded in the metal matrix, the metal matrix being made using a metal alloy as defined above.

According to another aspect of the invention, the first step provides to cast into a first mold, containing the at least one pre-insert, the steel, which replaces the non- metal matrix, thus forming the metal matrix.

According to another aspect of the invention, the reinforcing ceramic material comprises alumina; or zirconia; or alumina-zirconia; or silicon carbides; or titanium carbides or nitrides; or tungsten carbides; or chromium carbides, or a combination of several of these substances.

According to another aspect of the invention, the reinforcing ceramic material comprises alumina in quantities from 90% to 100% by mass; or zirconia in quantities from 90% to 100% by mass; or alumina-zirconia in respective mass percentages of from 55% to 75% and from 45% to 25% with respect to the total mass of alumina-zirconia.

According to another aspect of the invention, the reinforcing ceramic material is in the form of a plurality of ceramic granules, or powder, or particles with a predefined shape, made by means of melting or sintering.

According to another aspect of the invention, the metal matrix is subjected to a heat treatment cycle which provides a hardening followed by combined cooling steps. These combined cooling steps in particular allow to obtain the aforementioned predominantly bainitic structure.

The invention also concerns an article subject to wear, comprising a main body provided with a metal matrix and, in correspondence with at least one zone thereof to be reinforced, at least one reinforcing insert. The metal matrix is made using a metal alloy as defined above.

DESCRIPTION OF THE DRAWINGS

These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein:

- fig. 1 is a schematic lateral view of an article subject to wear according to the present invention;

- fig. 2 is a simplified perspective view, not to scale, of a reinforcing insert of the article of fig. 1 ;

- fig. 3 is a simplified perspective view, not to scale, of a reinforcing pre-insert of the reinforcing insert of fig. 2;

- figs. 4a-4c are simplified schematic representations, not to scale, of a production sequence of the article.

To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can be conveniently incorporated into other embodiments without further clarifications.

DESCRIPTION OF SOME EMBODIMENTS

We will now refer in detail to the various embodiments of the invention, of which one or more examples are shown in the attached drawings. Each example is supplied by way of illustration of the invention and shall not be understood as a limitation thereof. For example, the characteristics shown or described insomuch as they are part of one embodiment can be adopted on, or in association with, other embodiments to produce another embodiment. It is understood that the present invention shall include all such modifications and variants.

With reference to the attached drawings, see in particular fig. 1, an article 10, 10a subject to wear comprises a main body 11 provided with a metal matrix Ml. This article 10, 10a, in correspondence with at least one zone 15 thereof to be reinforced, comprises at least one reinforcing insert 12. The metal matrix Ml is made by means of a metal alloy at least partly comprising steel, in particular with a predominantly bainitic structure. Different structures such as perlite or martensite can also be present in said steel. The steel comprises carbon in quantities lower than 0.5% by mass and chromium in quantities lower than 3% by mass.

The metal alloy comprises steel added with carbon by mass percentage comprised between 0.19% and 0.35%, manganese by mass percentage comprised between 0.7% and 1%, silicon by mass percentage comprised between 0.4% and 0.7%, chromium by mass percentage comprised between 0.7% and 2%, nickel by mass percentage comprised between 0.35% and 0.4%, molybdenum by mass percentage comprised between 0.25% and 0.3% and aluminum by mass percentage comprised between 0.03% and 0.05%.

In this example, the article 10 is the shell of a cone mill, of which the article 10a is the central cone.

The material M to be shredded is introduced from the upper part of the mill, in a loading zone Z1 where the articles 10 and 10a are at a greater reciprocal distance. It is possible to provide that the reciprocal position between the articles 10 and 10a is variable as a function of the diameter of the material M to be shredded. The article 10a can for example be brought closer to the article 10 by means of a rotation in the direction R. In the gauge zone Z2, the articles 10 and 10a are at a minimum distance and the material M has an extremely small diameter.

By using a metal alloy at least partly containing steel with the components listed above, there is obtained a reinforcement of the zones most exposed to impacts, for example the gauge zone Z2, and a greater hardness of the steel in areas not very subjected to work hardening but exposed to abrasion, for example the zone Zl. This metal alloy therefore allows to maintain a profile without significant depressions and with substantially constant wear in the articles 10 and/or 10a.

The at least one zone 15 to be reinforced is generally a zone of the article 10 particularly subject to wear during the use for which the article 10 is intended. Therefore, the number, conformation and sizes of the at least one zone 15 to be reinforced depend on the intended use of the article 10. By way of a non-limiting example, fig. 1 shows two zones 15 to be reinforced in correspondence with the gauge zone Z2; however, such zones 15 to be reinforced could of course also be located elsewhere on the articles 10, 10a.

Preferably, the article 10 comprises at least as many reinforcing inserts 12 as its zones 15 to be reinforced, or a greater number of reinforcing inserts 12, as in fig. 1. In this case, the reinforcing inserts 12 can be supplied in sufficient number and suitably disposed so as to reinforce, as a whole, each zone 15 to be reinforced in its entirety.

The at least one reinforcing insert 12, see fig. 2, comprises at least one reinforcing ceramic material 13. The reinforcing ceramic material 13 can comprise alumina; or zirconia; or alumina-zirconia; or silicon carbides; or titanium carbides or nitrides; or tungsten carbides; or chromium carbides; or a combination of several of these substances.

The reinforcing ceramic material 13 comprises alumina in a quantity of from 90% to 100% by mass.

Or the reinforcing ceramic material 13 comprises zirconia in a quantity of from 90% to 100% by mass.

Or again, the reinforcing ceramic material 13 comprises alumina-zirconia, with alumina in a quantity of from 55% to 75% with respect to the mass of total aluminazirconia and zirconia in a quantity of from 45% to 25% with respect to the mass of total alumina-zirconia. For example, the reinforcing ceramic material 13 can comprise alumina-zirconia in respective mass percentages of 75% and 25%, or 70% and 30%, or 60% and 40%, or 55% and 45%, or intermediate percentages.

The reinforcing ceramic material 13 is preferably, but not necessarily, in the form of a plurality of ceramic granules. The ceramic granules can be obtained for example by means of melting or sintering; they may or may not be coated and can have various morphologies and granulometries.

The reinforcing ceramic material 13 is in the form of powder, or particles with a predefined shape.

We must clarify that the percentages disclosed above for the bulk composition of the reinforcing ceramic material 13 refer to the composition of each individual granule, or of each grain of powder, or of each particle constituting the reinforcing ceramic material 13.

For example, if the reinforcing ceramic material 13 is in the form of aluminazirconia granules, each of these granules can comprise alumina in a quantity of from 55% to 75% relative to its mass and zirconia in a quantity of from 45% to 25% relative to its mass.

The present invention also comprises a method for producing the article 10, 10a described heretofore. This method comprises a first step (not shown in the attached drawings) of producing at least one pre-insert 14 (fig. 3), and a second step (figs. 4a-4c) of producing at least one reinforcing insert 12 and the main body 11.

The first step provides to prepare, form and produce, in a known manner, at least one pre-insert 14 (fig. 3), comprising reinforcing ceramic material 13, preferably in the form of ceramic granules. This material 13 is preferably kept in a desired conformation by suitable binders, which form a non-metal matrix M2 of the preinsert 14.

The pre-insert 14 can be obtained for example by aggregating the material 13 by using binders in a special mold with a suitable shape.

In the second step, the non-metal matrix M2 is replaced with the metal matrix Ml. In a first preparation sub-step II (fig. 4a), this step provides to prepare at least one first mold 16, having sand walls which delimit and define a first internal cavity 16a suitably conformed to obtain the shape required for the at least one reinforcing insert 12.

The at least one pre-insert 14 can keep its disposition inside the corresponding first mold 16 in a known manner (not shown in the attached drawings), for example by means of suitable positioning and anchoring elements provided in a single body on its external surface, and/or by means of a load-bearing reinforcement, and/or by means of attachment elements such as nails, screws or suchlike.

In a subsequent casting sub-step 13 (fig. 4c), it is provided to cast molten metal material, preferably a metal alloy as defined above, into the first internal cavity 16a. During this casting, the molten metal material occupies all the free volume, both inside and outside the pre-insert 14. In particular, the molten metal material bums or sublimates almost all of the non-metal matrix M2, replacing it and thus forming the metal matrix Ml .

Consequently, the gases that are generated during the casting 13 due to the sublimation of the non-metal matrix M2 are more easily expelled from the molten metal material which forms the second metal matrix Ml.

Advantageously, each reinforcing insert 12 produced comprises the reinforcing ceramic material 13 in the metal matrix Ml, and does not comprise, or comprises only in minor traces, the non-metal binders that instead formed the non-metal matrix M2 of each pre-insert 14.

The metal matrix Ml can be subjected to a heat treatment cycle that provides a hardening followed by combined cooling steps to respect the correct cooling profile in order to obtain, in particular, the predominantly bainitic structure.

Additional heat treatment cycles at different temperatures can follow, to optimize the structure of the matrix. It is clear that modifications and/or additions of parts or steps may be made to the metal alloy for a method for producing a foundry article subject to wear and to the article thus obtained, as described heretofore, without departing from the field and scope of the present invention, as defined by the claims. It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art will certainly be able to achieve many other equivalent forms of a metal alloy for a method for producing a foundry article subject to wear and of an article thus obtained, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

Claims

1. Metal alloy for a method for producing an article (10, 10a) subject to wear comprising a main body (11) provided with a metal matrix (Ml), characterized in that it at least partly comprises steel containing carbon by mass percentage lower than 0.5% and chromium by mass percentage lower than 3%.

2. Metal alloy as in claim 1, characterized in that said steel has a predominantly bainitic structure.

3. Metal alloy as in claim 1 or 2, characterized in that it comprises carbon by mass percentage comprised between 0.19% and 0.35%, manganese by mass percentage comprised between 0.7% and 1%, silicon by mass percentage comprised between 0.4% and 0.7%, chromium by mass percentage comprised between 0.7% and 2%, nickel by mass percentage comprised between 0.35% and 0.4%, molybdenum by mass percentage comprised between 0.25% and 0.3% and aluminum by mass percentage comprised between 0.03% and 0.05%.

4. Method for producing an article (10, 10a) subject to wear comprising a main body (11) provided with a metal matrix (Ml) and, in correspondence with at least one zone (15) thereof to be reinforced, at least one reinforcing insert (12), characterized in that it provides a first step of producing at least one pre-insert (14), comprising reinforcing ceramic material (13) in a non-metal matrix (M2), and a second step of producing said at least one reinforcing insert (12) by replacing said non-metal matrix (M2) with said metal matrix (Ml) in said pre-insert (14), so that said at least one reinforcing insert (12) is embedded in said metal matrix (Ml), said metal matrix (Ml) being made using a metal alloy as in any claim hereinbefore.

5. Method as in claim 4, characterized in that said first step provides to cast into a first mold (16), containing said at least one pre-insert (14), said steel, which replaces said non-metal matrix (M2), thus forming said metal matrix (Ml).

6. Method as in either previous claim 4 or 5, characterized in that said reinforcing ceramic material (13) comprises alumina; or zirconia; or alumina-zirconia; or silicon carbides; or titanium carbides or nitrides; or tungsten carbides; or chromium carbides, or a combination of several of these listed substances.

7. Method as in any previous claim from 4 to 6, characterized in that said reinforcing ceramic material (13) comprises alumina in quantities from 90% to 100% by mass; or zirconia in quantities from 90% to 100% by mass; or aluminazirconia in respective mass percentages of from 55% to 75% and from 45% to 25% with respect to the total mass of alumina-zirconia.

8. Method as in any previous claim from 4 to 7, characterized in that said reinforcing ceramic material (13) is in the form of a plurality of ceramic granules, or powder, or particles with a predefined shape, made by means of melting or sintering.

9. Method as in any previous claim from 4 to 7, characterized in that said metal matrix (Ml) is subjected to a heat treatment cycle which provides a hardening followed by combined cooling steps.

10. Article (10, 10a) subject to wear, comprising a main body (11) provided with a metal matrix (Ml) and, in correspondence with at least one zone (15) thereof to be reinforced, at least one reinforcing insert (12), characterized in that said metal matrix (Ml) is made using a metal alloy as in any claim from 1 to 3.