WO2013060330A2

WO2013060330A2 - Wear-resistant roller

Info

Publication number: WO2013060330A2
Application number: PCT/DK2012/050389
Authority: WO
Inventors: Biju KARAKKUNNUMMAL
Original assignee: Flsmidth A/S
Priority date: 2011-10-28
Filing date: 2012-10-22
Publication date: 2013-05-02
Also published as: TW201330979A; WO2013060330A3

Abstract

A description is given of a wear-resistant roller for processing abrasive materials, such as crude ore, cement raw materials or similar materials, where a roller body is provided with a wear layer comprising a number of elements surrounded by a wear-resistant material suitable for being sintered and fixed to the roller body by means of a sintering process. The roller is characterized in that the elements, which have significantly lower resistance against wear than the surrounding wear-resistant material, are arranged with a space between each other and fixed to the roller body when the surrounding wear-resistant material by means of the sintering process is sintered to the roller body.

Description

Wear-resistant roller

The present invention relates to a wear-resistant roller for processing abrasive materials, such as crude ore, cement raw materials or similar materials, where a roller body is provided with a wear layer comprising a number of elements surrounded by a wear-resistant material suitable for being sintered and fixed to the roller body by means of a sintering process. The wear-resistant roller may for example be used in a high-pressure roller press, in a vertical roller mill or in similar equipment for processing of particulate material.

Wear-resistant rollers are well-known in the industry. In US6086003 a wear- resistant layer consisting of two different powder metallurgical steels is applied to the surface of a roller by means of sintering process. The advantage of using powder metallurgical steels is that a surface with a very high content of hard phases and a high toughness can be achieved due to a fine microstructure and small well-distributed carbides. The powder metallurgical technology furthermore allows for a composition of hard phases which is difficult or impossible to achieve by other techniques. Hexagonal tiles are preformed using a first material and placed on the surface of a roller covering the largest area of the surface and a second material is placed between the tiles. Whereas the first material has a very high content of carbides and thus a high wear resistance, the second material has a lower content of carbides and therefore a higher wear rate but also a higher toughness, i.e. high resistance to crack propagation. This difference in wear and mechanical properties of the two materials will ensure that an autogenous wear protection is obtained and that fractures in the surface due to tramp metal etc. are avoided. The sintering process used is Hot Isostatic Pressing (HIP) where the metallurgical powder is consolidated to 100% density by applying a pressure above 1000 bar and a temperature above 1000°C. Given that each tile in US6086003 is produced by means of a separate sintering and compaction process and due to the fact that each tile must be placed one by one on the surface of the roller with a relatively high degree of precision and since the entire circumference of the roller must be covered with tiles before the final sintering it is a very time-consuming process to manufacture such a roller. As a consequence hereof, the manufacture of such rollers involves significant costs.

It is the object of the present invention to provide a wear-resistant roller by means of which the manufacturing costs are significantly reduced.

This is obtained by a wear-resistant roller of the kind mentioned in the introduction, and being characterized in that the elements, which have significantly lower resistance against wear than the surrounding wear-resistant material, are arranged with a space between each other and fixed to the roller body when the surrounding wear-resistant material by means of the sintering process is sintered to the roller body.

By having elements with significantly lower resistance against wear than the surrounding sintered wear-resistant material the elements can be made from materials with low resistance against wear and not by use of the expensive and time-consuming powder technology. Hereby it is obtained that the elements are easy and cheap to manufacture. Furthermore, this makes it possible to manufacture the wear-resistant roller in a single process step with regard to sintering which reduces the time needed for manufacturing considerably and therefore also reduces the costs. It is preferred that the elements with low resistance against wear are made from carbon steel, such as mild or low carbon steel. However, also non-metallic materials could be used. The size of the elements and the distance between the elements will depend on the type and size of the material to be processed in order to ensure formation of the necessary autogenous layer which reduces the wear on the roller. During the operation of the roller the elements will be worn a lot faster than the surrounding sintered wear-resistant material, since the elements are made from plain carbon steel, preferably mild steel, which have very low wear resistance to the extremely abrasive materials being processed during operation. The holes appearing when the elements are worn will be effectively filled with fine particles of the crushed materials. The fines become compacted in the holes entailing an effective retention on the surface. This effect is referred to as autogenous wear protection since the crushed materials wear against themselves. The autogenous layer builds up naturally during operation of a roller, but may be further enhanced by a favourable layout of the holes. The autogenous effect impedes further wear of the holes filled with fines and also contributes to an increased throughput due to increased friction between the materials to be processed and the materials in the holes.

In principle the elements may have any conceivable shapes as long as an autogenous wear protection is established when the elements are worn. For example the wear elements may be cubically or cylindrically configured, however, it is preferred that the elements are ball-shaped, since this shape will ensure holes with a low stress concentration and an advantageous formation of the autogenous wear protection.

In one embodiment the elements are arranged in at least two layers on the roller body where the wear-resistant material fills out the spaces between the layers of elements. These layers are offset from each other in the radial direction of the roller. In this way a new layer of elements will be revealed when the ahead positioned layer is worn down. In a further embodiment the layers of elements are offset from each other both in the radial direction and the axial direction of the roller. In this way the elements can be more homogeneously distributed.

It is preferred that the elements are arranged on a fixture prior to the sintering process since it is very easy to machine mild steel and therefore easy to make such a fixture. For example the fixture may connect the elements by means of steel wire whereby all the elements could be fixed to each other in a hollow ring- shaped arrangement for subsequently being placed around the roller body prior to the sintering process. Such a fixture may furthermore ensure that the elements prior to the sintering process are arranged with a distance to the roller body, whereby the surrounding wear-resistant material can get between the elements and the roller body for improved bonding between the roller body and the sintered material in which the elements are encapsulated. Furthermore, it is preferred that the sintering is carried out by means of a Hot Isostatic Pressing (HIP) process since this process ensures an advantageous wear resistance and furthermore a strong bond between the elements and the surrounding wear-resistant material and the roller body. The wear-resistant material to be sintered is a powder metallurgical steel which may be blended with refractory particles such as carbides, nitrides, oxides, borides or silicides for obtaining a very high resistance against wear. In another embodiment the wear layer is provided on one or more tyres which are subsequently fastened to a roller body, for example by means of a shrinking process. Due to the lower weight of the tyres compared to a full roller body they will be easier to handle during the HIP process. Furthermore, a damaged tyre can be changed at site which will facilitate the maintenance of the wear-resistant roller.

The invention will now be explained in greater detail with reference to the drawing, being diagrammatical, and where Fig. 1 shows a three-dimensional view of a wear-resistant roller according to the invention.

Fig. 2 shows three cross-sectional views of a section of the roller shown in Fig. 1 . Fig. 3 shows an embodiment for a fixture for the elements used for the wear- resistant roller according to the invention.

Fig. 1 shows a three-dimensional view of a wear-resistant roller 1 where a roller body 2 is provided with a wear layer (the wear layer on the illustrated roller body 2 has been subjected to some wear - see Fig. 2). The wear layer comprises a number of elements 3 surrounded by a wear-resistant material 4 which is sintered to the roller body 2. The elements 3, which are ball-shaped and made of mild steel, are also fixed to the roller body 2 during the sintering process since the elements 3 are encapsulated by the wear-resistant material 4 which is sintered. The elements 3 are arranged with spaces between each other and also with a distance to the roller body 2 for ensuring presence of sintered wear-resistant material 4 between the elements 3 and the roller body 2 in order to achieve a strong bond. The sintering process is a Hot Isostatic Pressing (HIP) process.

Fig. 2 shows three cross-sectional views of a section of the wear layer on the roller body 2. The first view illustrates the wear layer before the wear-resistant roller 1 is put into operation. Here the elements 3 as well as the sintered wear- resistant material 4 are intact. The elements 3 are arranged in two layers on the roller body 2 where the wear-resistant material 4 fills out the spaces between the layers of elements. The two layers are offset from each other in both the radial and axial direction of the roller 1 by means of which the elements can be more homogeneously distributed. By having more layers of elements 3 a new layer will be revealed when the layer in front is worn down which means that the lifetime of the roller 1 is increased. The second view illustrates the wear layer after some hours of operation where some of the wear layer has been worn down but before an autogenous wear protection has been established. The third view illustrates the situation when the elements 3 are worn, either partly or the entire element 3 can be worn down. As the elements 3 are preferably made of mild steel, which has a significantly lower resistance against wear than the sintered wear-resistant material 4 made from powder, they will be worn rather quickly resulting in holes in the surface of the wear layer. The holes will be effectively filled with fine particles 5 of the crushed material 8. The fine particles 5 are compacted in the holes entailing an effective retention on the surface. Thereby the autogenous wear protection is established as the crushed material 8 wears against the fine particles 5 in the holes.

Fig. 3 shows a fixture 6 for the elements 3 used for the wear-resistant roller 1 . In order to achieve a desired layout of the elements 3 in an easy manner they are arrange in the fixture 6. As the build-up of the autogenous layer is enhanced by a favourable layout of the holes it is of great importance that the elements 3, which are worn during operation whereby the holes are formed, are arranged in an advantageous way. The autogenous effect reduces further wear of the holes and also contributes to an increased throughput due to increased friction between the materials to be processed and the materials in the holes. Thus an optimal texture of the surface of the roller 1 would have significant advantages for the operation given its importance for reducing wear and for increasing the production. Steel wire 7 connects the elements 3 in a hollow ring-shaped arrangement which is placed around the roller body 2 prior to the sintering process with the surrounding wear-resistant material 4. The fixture 6 also ensures that the elements 3 prior to the sintering process are arranged at a distance relative to the roller body 2.

Claims

1 . A wear-resistant roller (1 ) for processing abrasive materials, such as crude ore, cement raw materials or similar materials, where a roller body (2) is provided with a wear layer comprising a number of elements (3) surrounded by a wear-resistant material (4) suitable for being sintered and fixed to the roller body (2) by means of a sintering process characterized in that the elements (3), which have significantly lower resistance against wear than the surrounding wear-resistant material (4), are arranged with a space between each other and fixed to the roller body (2) when the surrounding wear-resistant material (4) by means of the sintering process is sintered to the roller body (2).

2. A wear-resistant roller according to claim 1 characterized in that the elements (3) are arranged in at least two layers offset from each other in the radial direction of the roller body (2) where the wear-resistant material (4) fills out the spaces between the layers.

3. A wear-resistant roller according to claim 2 characterized in that the layers are offset from each other both in the radial direction and the axial direction of the roller body (2).

4. A wear-resistant roller according to any preceding claim characterized in that the elements (3) are arranged on a fixture (6) prior to the sintering process.

5. A wear-resistant roller according to any preceding claim characterized in that the elements (3) prior to the sintering process are arranged with a distance to the roller body (2).

6. A wear-resistant roller according to any preceding claim characterized in that the elements (3) are made of a material with low resistance against wear, such as low carbon steel.

7. A wear-resistant roller according to any preceding claim characterized in that the elements (3) are ball-shaped.

8. A wear-resistant roller according to any preceding claim characterized in that the sintering process is a Hot Isostatic Pressing process.