AU629243B2 - Method for manufacturing a crushing roller and method for using the roller - Google Patents

Description

62 9 2 4 3 COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION NAME ADDRESS OF APPLICANT: Kurimoto, Ltd.

12-19, Kitahorie 1-chome Nishi-ku Osaka Japan NAME(S) OF INVENTOR(S): SToshiyuki ASHIDA Tomoo MIZUNO Hisao YOSHIDA ADDRESS FOR SERVICE: DAVIES COLLISON Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

S COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED: Method for manufacturing a crushing roller and method for using the roller The following statement is a full description of this invention, including the best method of performing it known to me/us:- 41399/89 FIGURE 1 FCT\C 1A

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la- 1 TITLE OF THE INVENTION 2 3 Method of Manufacturing a Crushing Roller and Method for 4 Using the Roller 6 BACKGROUND OF THE INVENTION 7 8 1. Field of the invention: 9 The present invention relates to a crushing roller of 11 the kind which is incorporated in a vertical roller mill and 12 serves as a main crushing member by rotating on its own axis 13 and to the manufacture and/or reconditioning of crushing 14 rollers.

o 16 2. Prior art: 17 18 Generally in vertical type roller mills, as shown in 19 Figure 3, a plurality of rollers, which turn horizontally on a crushing table, are biased so as to be pressed against the 21 upper surface of the crushing table; an object to be crushed 22 is charged from above into the crushing chamber and 23 introduced from the center of the table to the outer i 24 periphery thereof due to centrifugal force. The object is 1i 25 crushed between the rollers and the table by the compressive 26 sliding movement and ejected to the outside.

27 There has also been provided another vertical type II 28 roller mill in which, as shown in Figure 4, a plurality of 11 29 rollers Ib (usually three rollers) are driven in such a manner as to rotate on their own axes while pressing their 31 outer peripheries onto the surface of a fixed crushing 32 table. An object to be crushed is introduced between the 33 table surface and the rollers for crushing.

34 The foregoing vertical type roller mills have been popularly used in treating coal, cement clinker, blast 36 furnace slag, etc., and have enjoyed OEIVproductivity then W\ $O37 drum type mills such as ball mills.

J^ k In any type of roller mill, a problem exists in that px.A 890914.gjnspe. 007,korl.spe.

FIGURE 3 8a 1 2 3 4 6 7 8 9 11 12 13 14 16 17 18 19 21 22 23 t, 24 25 26 27 t 4 28 29 31 32 33 34 36 37 38 rollers are unavoidably worn away and gradually recede thereby. Moreover, the surfaces of rollers are not evenly worn away in actual use but suffer from irregular wear and tear, resulting in an uneven crushing surface profile longitudinally of the roller, though the manner of abrasion varies depending upon the kind of object to be crushed and the working conditions of the roller mill. Thus, crushing efficiency is gradually lowered due to such uneven and deformed crushing surfaces even though the pressure on the crushing surfaces is uniform. To meet such a situation, it has been conventional that either a seriously worn roller is replaced with a new one or worn parts of a roller are reconditioned by padding.

In this respect, for the purposes of increasing roller life prior to replacement and making it easy to process the portion which engages the rotary shaft, a method has been proposed wherein, as shown in Figures 5A and B, the outside portion of a roller is preformed with regard to the abrasion characteristic of the roller material and the anticipated extent of abrasion of the external surface produced by wear.

(Japanese Publication of Patent Application under No. 58- 10143). Figures 5A and B show an embodiment of this prior art, reprinted from the mentioned Publication, in which body portion Ic of a roller is made of a relatively soft easily processed metal, while external surface portion 4C is made of a relatively hard metal resistant to abrasion. In manufacturing a roller the outside portion of the roller is formed into a desired shape by casting or machining this portion into the desired shape, based on the predicted resultant contour of the external surface produced by wear.

A hard metal material is then uniformly and integrally welded onto the prepared outside portion, such that the surface of the roller is also formed with the crushing surface anticipated to be worn away in the future. When using a crushing roller of such construction, because a pattern of abrasion to which the roller surface is subjected is preliminarily traced at the time of forming the side portion of the soft metal body section to which hard surface i:l i,i:, i i i ir i i !9 890914 gjnspe.007kori.spe, 2 4L[C9 %9 FIGURE

(A)

~I I- 7 3 1 2 3 4 6 7 8 9 11 12 00Q, 13 0 14 o0 t o 0 00o 15 0 17 18 19 21 o 22 23 24 0 o 25 26 27 0 °0 28 29 0 0 31 32 33 34 36 37 38 is applied, it is reported that the roller surface is worn away uniformly and evenly without partial abrasion.

In the foregoing embodiment of the prior art (referring to Figures 5A and there may be an expectation that abrasion of the roller surface proceeds almost evenly either throughout the surface, as shown in Figure 5A or throughout the surface with the exception of the upper end portion on the wider side, as in Figure 5B. The resulting profile is thus almost linear. Accordingly, it seems that the external surface of the periphery formed of a different kind of hard metal with even thickness on the body section exhibits a straight line profile formed by parallel displacement following the aforesaid linear outline of the body section., Such a manner of abrasion may be acknowledged by the inventor of this prior art. However, as described by this prior art itself, the actual abrasion may differ largely from the expected abrasion, depending upon the object to be crushed, working conditions of the mill, type of mill, etc..

The applicant has found, at least as far as cement clinker is concerned, that, without fail, actual abrasion does not proceed evenly, producing a linear profile, but takes place irregularly, resulting in an uneven profile.

More specifically, in vertical type roller malls as shown in Figure 3, starting from the state shown in Figure 6A, the abrasion of the periphery la of the roller is concentrated on the front portion which is in contact with crushing material, producing more wear to this portion than the back portion (Figure 6B). The resultant profile is shown in Figure 6C. The roller is then removed, turned through 1800 and reattached. Thus the abrasion is now concentrated on what was previously the back section, with the resultant profile shown in Figure 6D. With such a worn roller as shown in Figure 6D, it is impossible to any longer achieve a desired crushing efficiency and therefore the worn roller is either discarded or reconditioned with padding.

If the external periphery of a new roller body is formed according to the method mentioned above, and a hard layer of even thickness is additionally superposed on the roller 890914, gJnspe.007kori.spe.3 1~1399 1~~ FIGURE 7 I 4 1 2 3 4 6 7 8 9 11 12 o0 13 2 14 16 17 2* ~18 19 21 22 23 24 26 27 28 29 31 32 33 34 36 37 38 body, it can be expected that abrasion will proceed almost evenly throughout the crushing surface portion, but a roller of this kind may be put into operation with rather poor crushing efficiency from the start of the operation.

In the vertical type roller mill shown in Figure 4, it can be said, from the experiences of the inventors, that abrasion of the roller produces a profile as shown in Figure 7. If the crushing surface of the roller is worn away like this, crushing efficiency will be seriously reduced, since crushing is achieved by placing an object between the two full surfaces.

Another problem arises with respect to the superposition of a different kind of metal on the body portion to form the outer periphery of the roller. The prior art mentioned above does not specifically refer to this point, but merely states that any layer formed from either welding material or other hard-finished material is sufficient. In most cases, the superposition process will be carried out in the form of padding, and automatic welding such as submerged arcwelding is most effective. In carrying out this padding, the formation of starting points at corner sections of opposite ends of the roller creates a significant problem.

To be more specific, referring to Figure 8A, the thermal capacity of the corner section C is rather small, and therefore the corner section is fusible, melts away and does not serve as a metal to be welded if carrying out padding under ordinary conditions. To prevent the corner section from melting away the welding is done in stages by the superposition of small segments of welding metal. Thus a separate technique is required for the corner sections, resulting in a troublesome process and low productivity.

When employing submerged arcwelding, generally believed to be more advantageous, a problem still exists in that stabilisation of flux is difficult and the exact shape required is difficult to form.

Figure 8B shows a known solution of this problem, in 890914. gjnspe. 007.kori. spe. 4 which a ring 10 of band steel material is temporarily arranged at the corner section C to provide a starting point for automatic welding. In this countermeasure, however, formation of the ring and its provisional instalment are troublesome, and moreover if composites of the band steel material and welding material are excessively different, there arises a further problem of welding performance which may cause some difficulty during the operation at the diluted layer portion formed between the band steel material and the welded metal.

SUMMARY OF THE INVENTION The invention provides, a crushing roller comprising a roller body having an outer peripheral surface with respective integral step portions defining spaced recessed portions of said surface and a raised portion disposed between and bounded by said step portions, and padding in said recessed portion which thereby forms a crushing surface of the roller.

Also provided by the invention is a method of manufacturing a crushing roller comprising forming in the outer peripheral surface of a roller body a recessed portion disposed between and bounded by respective integral step portions in said outer peripheral surface, which step portions result from said forming and define spaced relatively raised portions of said surface, and evenly applying padding to the recessed portion by automatic welding, wherein support is provided by said integral step portions during said automatic welding, and wherein said padding is adapted to form a crushing surface of the roller in subsequent use thereof.

The invention still further affords a method of reconditioning a used crushing roller according to the second preceding paragraph comprising superposing replacement padding material on unevenly worn padding material in said recessed portion by automatic welding, when the roller body is first exposed by wear through the full depth of the padding in the recessed portion, wherein support is provided rl A 7- E VX"/ r C1 -6by said integral step portions during said automatic welding, and wherein said replacement padding material is adapted to form at least part ofAh crushing surface of the roller in subsequent use thereof.

In preferred embodiments of the invention, a most effective and qualitatively stable welding process can be specified, and furthermore, the most stable working conditions in practical use are systematically summarlsed on a unified basis showing general evaluation with respect to manufacture and use of the crushing roller. In other words, a new software assuring excellent economical results achieved by establishing a desirable relationship between manufacturing 10 sector and operating sector is proposed by the invention.

Other objects and advantages of the invention will become apparent in the course of the following description with reference to the accompanying drawings.

4 BRIEF DESCRIPTION OF THE DRAWINGS In the drawings forming a part of the present application: Figures 1 and 2 are sectional front views respectively illustrating different embodiments in accordance with the invention; Figures 3 and 4 are front views respectively illustrating different vertical type roller mills incorporating the crushing rollers of the invention; Figures 5A and B are front sectional views in accordance with the prior art; Figures 6A, B, C and D are schematic partial views illustrating successive stages in the abrasion of crushing roller surface of the type shown in Figure 3; Figures 7 is a front sectional view illustrating a surface of a crushing roller showa in Figure 4 after suffering from abrasion; and Figures 8A and B are schematic partial views for explanation of problems existing in the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment in accordance with the present invention is now described 31 C L I -7with reference to Figures 1 and 2.

Figure 1 shows the crushing roller 1A which is used in association with a rolling table shown in Figure 3. When using this roller for fine crushing to produce cement clinker for example, the crushing surface suffers uneven abrasion and thereby gradually recedes. When reversing the roller to replace the less worn inner end with the more worn outer end for further use, the surface is finally deformed as shown in Figure 6D. This wearing process is described in detail above.

In the initial manufacture of a new roller, a concave portion 2A of smaller diameter corresponding to a certain depth HA is formed on the roller surface, o~O irrespective of the supposed uneven abrasion, and step portions 3A are :O respectively provided at opposite ends of this smaller diameter portion. The superposition of padding on the smaller diameter portion 2A by automatic welding can be started and carried out successfully on the same conditions as 15 other processes because of support rendered by the step portions 3A. More specifically, several processing conditions are required to be considered including arc current, arc voltage, preheating temperature, arc moving rate, property of welding wire, characteristic of power source. Also to be taken into account are requirements for processing a material of high alloy and high carbon later described since a welding metal of high hardness resistant to abrasion and difficult rits,, to be welded are essentially employed as mentioned above. In view of assuring effective and qualitatively high welding of the difficult-to-weld material, it is to be noted that formation of the step portions 3A at both ends of the smaller diameter portion is very useful.

With the progress of abrasion, even the welded portion 4A of high hardness is gradually worn and reccdes, exhibiting a like profile. When the tip end PA of the abrasion has reached any part of the smaller diameter portion 2A beyond the full depth HA thereof, the roller body is exposed and the fact of such abrasion can be visually recognised from the appearance presented by different metal surfaces. Operation of the crusher should be immediately suspended.

Matters to be inspected before replacement with a spare roller are preferably standardised beforehand. In the removed worn crushing roller, the step portions 91112,gjnda075,korLs r ~91116,gjniatO5,korisj I I II- I I 3A still remain unchanged at both ends, and making use of these step portions, being supported and held by the step portions, padding of the worn portion with welded metal is carried out by automatic welding to restore the original peripheral surface. The depth HA of the smaller diameter portion is established as a requirement of manufacturing a crushing roller as well as a requirement of using the roller based on the relationship between the progress of abrasion and lowering of crushing efficiency, both experimentally known.

Figure 2 shows another embodiment of the crushing roller 1B incorporated in another type of roller mill, and in which the same reference numerals HB, 2B, 3B, and PB as the foregoing first embodiment are assigned to like parts. In this embodiment, a crushing roller is preliminarily provided with step portions comprising thickened parts 5 and 6 at opposite ends. After completing the welding of padding in the portion between parts 5, 6, with support provided by the thickened parts, these thickened parts are cut away. In this manner, not only requirements for automatic welding can be satisfied in the manufacturing process, but also portions not so resistant to abrasion are prevented from being exposed as a crushing surface in actual use.

In the foregoing embodiments of the invention, it is preferable that the following materials be employed or combined for successful welding.

A material favourable in view of machinability, free-cutting and economy such as common cast iron or ductile cast iron is used as a base material forming a roller. Other -P 9 911126,gjndat075,kor.s -9- 1 2 3 4 6 7 8 9 11 12 o o 13 09 0 io~ 14 15 16 17 18 19 21 22 23 24 26 27 28 29 31 32 33 34 36 37 38 materials which are resistant to abrasion but a little difficult to work and expensive such as Nihard cast iron or high chromium cast iron may also be employed. Though any of these materials is to be selected according to application and intended use, it is preferred that the selected material is provided with a harder layer at its external surface, thereby substantially improving durability and working life.

As is well known, a harder layer formed on the external surface may be mainly composed of 3 to 7% carbon and 20 to 30% chromium, to which 1 to 4% manganese, 0.5 to silicon and a small percent (0 to of molybdenum, zirconium, titanium, etc. are usually added. Such a harder layer section is preferably fused with a welded metal in a short time by using any of various automatic welding typically represented by submerged arcwelding. For the purpose of securing high economy and quality, it is important that the welding is carried out under well-established stable conditions.

In the foregoing method according to the invention wherein the step portions are provided at the ends of the external surface on which the harder layer is to be formed, the process for forming the harder layer on the external surface can be carried out under constant stable conditions from starting of the process until the completion thereof.

In fact, it is found that the time required for the process is shortened by 20 to 25% as compared with the process without step portions.

It is also found that, in the method according to the invention, there is no irregularity in hardness throughout the formed harder layer, but uniform and stable harder layer is formed all over the surface and welded layer.

Claims (6)

1. A crushing roller comprising a roller body having an outer peripheral surface with respective integral step portions defining spaced recessed portions of said surface and a raised portion disposed between and bounded by said step portions, and padding in said recessed portion which thereby forms a crushing surface of the roller.

2. A method of manufacturing a crushing roller comprising forming in the outer peripheral surface of a roller body a recessed portion disposed between and bounded by respective integral step portions in said outer peripheral surface, which step portions result from said forming and define spaced relatively raised portions of said surface, and evenly applying padding to the recessed portion by automatic welding, wherein support is provided by said integral step portions during said automatic welding, and wherein said padding is adapted to form a crushing surface of the roller in subsequent use thereof. 0

3. A method according to claim 2 wherein the depth of said recessed 0 portion and padding is predetermined according to a maximum allowable 0 20 reduction in crushing efficiency corresponding to abrasion of the padding to 00*000 0 the depth of said recessed portion.

4. A method of reconditioning a used crushing roller according to claim 1 comprising superposing replacement padding material on unevenly worn padding material in said recessed portion by automatic welding, when the roller body is first exposed by wear through the full depth of the padding in the recessed portion, wherein support is provided by said integral step portions during said automatic welding, and wherein said replacement padding material is adapted to form at least part of a crushing surface of the roller in subsequent use thereof.

A crushing roller or a method of manufacturing a crushing roller or a -11- method of reconditioning a used crushing roller, substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

6. A crushing roller or a method of manufacturing a crushing roller or a method of reconditioning a used crushing roller, substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings. Dated this 28th day of July, 1992 KURIMOTO, LTD. By its Patent Attorneys Davies Collison Cave 1 t i 4 lt