JPS62197161A - Crushing roll - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

TECHNICAL FIELD This invention relates to articles of the type intended for use under highly abrasive operating conditions. The conditions of use require such articles to have at least an outer surface layer made of a material with good abrasion resistance.

More particularly, the present invention relates to a grinding (grinding) roll for use in a grinding mill of the type suitable for use in carrying out the grinding of materials such as coal, and selected internal areas of the grinding machine. Regarding mill liners used in

BACKGROUND OF THE INVENTION An essential component of various steam generation systems in which coal is used as a fuel is the equipment used to pulverize the coal so that it is suitable for use as a fuel. To this end, one of the devices frequently used to pulverize coal to make it suitable for use as a fuel in coal-fired steam generation systems is what is referred to in the art as a bowl mill. . This bowl mill is capable of pulverizing the coal, that is, grinding (grinding).
It gets its name from the fact that it is carried out on a grinding surface with a shape somewhat similar to that of a bowl.

In the following description, two essential components will be identified: the main body part, namely the housing, in which the grinding surface, or grinding table (from which the name bowl mill derives), is rotatably mounted; and the inside of this housing. A plurality of grinding rolls supported at equal intervals from each other (these are in contact with a grinding table, and the coal placed on the grinding table is pulverized by the grinding force applied to the coal by the plurality of grinding rolls.
(i.e., pulverizing) with reference to a type of bowl mill. The grinding rolls are each configured to be attached to a shaft-like member for this purpose. Furthermore, it preferably has a through hole along its center for attaching the grinding roll to the shaft-like member. Through this through hole, a shaft-like member can be inserted and the grinding roll can be carried by it. Therefore, in order to facilitate the formation of such through-holes in the grinding roll, it is desirable that the grinding roll be made of an easily processable material, that is, a relatively soft material such as gray cast iron.

While it is desirable to form the grinding roll from a relatively soft material, there is also a requirement that at least the outer surface layer of the grinding roll should be formed from a material characterized by good abrasion resistance. The reason for this is that, while the pulverization of materials is carried out using these grinding rolls, the grinding rolls are necessarily subjected to severe abrasive action depending on the nature of the material being ground and the manner in which the pulverization is carried out. This is to become. As a result, the grinding roll becomes unusable due to excessive wear within a relatively short period of time. In other words, the service life of the grinding roll is relatively short. Such consequences should be avoided if possible. In this context, the actual wear experienced by the grinding rolls used in a bowl mill depends primarily on the grinding characteristics of the material to be pulverized and the production rate of the bowl mill (i.e. the amount of material pulverized in the bowl mill over a given period of time). It must be noted that this depends on the amount of

If the outer surface layer of a grinding (grinding) roll becomes worn to the point that it cannot be used for pulverizing the material, the other parts of the roll are usually still usable. That is, even though the outer surface layer is worn, the grinding roll is still usable. For this reason, various attempts have been made in the art to improve the wear life of grinding rolls.

Attempts that have been made to improve the wear life of grinding rolls fall into three basic categories. The first is to achieve improvements through the manufacture of the grinding roll itself and/or by resurfacing the grinding roll after wear. The second is aimed at producing improved high chromium alloys for the purpose of forming the wear surfaces, or outer surfaces, of grinding rolls. The third objective is to produce an improved nickel-chromium alloy for use in forming the wear surface, or outer surface, of grinding rolls.

A first attempt in the above category is, for example, commonly assigned U.S. Pat. No. 4,389,767 (198
Patented on June 28, 2013). This U.S. patent states that the worn surface (outer surface) of the grinding roll is shaped to follow the shape of the grinding roll after wear, depending on the degree of wear expected from the action that the grinding roll is subjected to depending on the intended use. discloses a method of making a grinding roll, which comprises providing a substantially uniform layer of wear-resistant material on the outer surface of the grinding roll to form a wear surface of the grinding roll.

Another attempt considered to belong to the first category is U.S. Patent Application No. 764,800, filed by the same applicant.
There is No. 2 (filed on August 12, 1985).

This patent application relates to a three-layer metal grinding roll, in which the central material (i.e., the first or inner layer) is composed of a relatively soft material with good workability; the next layer of the layer roll (i.e. the second or intermediate layer) is composed of a material with medium abrasion resistance;
The last layer (i.e. the third or outer layer) of a three-layer metal roll
Constructed of materials with a high degree of wear resistance.

Next, we will discuss the second category of attempts that have been made to improve the wear life of grinding rolls used in bowl mills. Examples of attempts in this regard have yielded good results. This effort is the development of a material known industrially as rstoody IOJ. This substance (i.e. 5toody
103) is available from 5toody (California). Allegedly, 5tood
For the composition of y 108, this material contains ~4.0% carbon
It is said to be free of molybdenum and boron, except for ~5.0% manganese and ~5.0% chromium. For the formation of grinding rolls, a material known as 5toody 103 is most commonly used in the form of a welded overlayer attached to the grinding roll to form the outer surface of the grinding roll.

=8= That is, the attached layer of 5toody 103 forms the wear surface of the grinding roll. 5toody 103
The wear resistance of the conventional material (rNihard J
It is said to be 1.5 to 2 times better than that of

Other attempts in this second category of attempts to improve the wear life of bowl mill grinding rolls relate to the development of materials according to PCT/US82100976. This international patent application relates to wear-resistant white cast iron. More specifically, the white cast iron according to the international patent application is made of iron as a base material and has a carbon content of 2.0 to 4.5.
%, boron 0.001-4.0% and o, oot-ao
% of vanadium, titanium, niobium, lantalum, molybdenum, nickel, copper, or chromium or mixtures thereof.

Another example of a prior attempt that appears to belong to the second category mentioned above is U.S. Patent Application No. 70, filed by the same applicant.
No. 703,160, filed February 19, 1985. Because of these properties, the alloy is suitable for use on the outer surface of grinding rolls (or pulverizing rolls) used in bowl mills that cooperate with other surfaces to pulverize materials such as coal. This highly wear-resistant alloy contains 4.0-6.0% (by weight) carbon, 3.0-14.0% manganese
%, silicon 1.0-2.5%, chromium 15.0-30.
0%, molybdenum 4.0 = 6.0% and boron 0.5-
2.0%, with the remainder consisting of iron and accompanying impurities. From the results of tests conducted thereon, it was observed that the high wear resistant alloy according to US Patent Application No. 703,160 has twice the wear life of that known as 5toody 103.

Turning now to the third category mentioned above, there is, for example, British Patent Application No. 2,027,702A. The outer surface layer (e.g. wear layer) of grinding rolls for bowl mills is made from a material commonly referred to as rNihardJ.
It has been widely practiced among those skilled in the art for some time. In contrast, the UK patent application describes a white cast iron alloy (Sheepbridge Equi, the applicant of this application).
pment Limlted is r PremiumNi
(referred to as hardJ). This alloy has better wear resistance than the previous alloy called rNihardJ. According to British Patent Application No. 2,027,702A, this white cast iron alloy rPremium N
1 hardJ is carbon 2.8-3.5% (by weight), silicon 0.6-2.0%, manganese 0.05-0.5%, sulfur 0.05-0.25%, phosphorus 0.5 -1.5%, nickel 3.5-5.0%, chromium 2.5-4.5%, molybdenum 0. L-0.7%, with the remainder consisting of iron and accompanying impurities. In addition, bismuth ~
It is stated that the content may be 0.01%.

The main reason for trying to obtain a longer service life for new grinding rolls is to extend the point at which it is necessary to take the bowl mill out of service in order to remove a worn grinding roll and replace it with a non-worn one. It is from. In this regard, a plurality of bowl mills are commonly used to provide the desired amount of pulverized coal to a coal-fired steam generation system, each bowl mill having three grinding rolls. When these grinding rolls become worn, they must be removed and replaced. However, there are problems with the time and effort required to remove and replace worn grinding rolls, and the associated costs. Therefore, if the degree to which the grinding rolls wear out and require replacement is reduced, costs can be saved in terms of time and labor required for replacement.

In addition to the grinding rolls mentioned above, there are other parts of the bowl mill that are also subject to wear during operation of the bowl mill. For example, as mentioned above, the top surface of a grinding table that cooperates with grinding rolls to pulverize materials such as coal.

Furthermore, another part of the bowl mill that is subject to wear is that part of the travel path through which the coal grains, carried by a gas such as air, flow through the bowl mill. More specifically, it is a region that is subjected to abrasion caused by collisions of coal grains moving through the bowl mill. For this reason, past experience has shown that liners have been selectively provided in internal areas of bowl mills where wear has been highest.

Regarding the top surface of the grinding table of a bowl mill, this top surface generally has a shape known among those skilled in the art as a bull ring. According to this, the bull ring is an integrated object,
Alternatively, it is known to be formed as a collection of multiple segments.

The bull ring is suitably rotatably supported on the grinding table. The operation of the grinding table of the bowl mill is as follows. First, the material to be pulverized is suitably fed onto a bull ring. Then, when the grinding table and thereby the bull ring are rotated by the grinding roll, the substance placed on the bull ring is pulverized by the force applied by the grinding roll when the bull ring is rotated in conjunction with the grinding roll. be done.

After being pulverized as described above, the coal is attracted and entrained by an air stream flowing upward around the periphery of the grinding table. Once entrained in this air stream, the coal grains are moved into the bowl mill in an appropriate manner. carried through.

While being conveyed in this way, coal grains larger than the desired ones are returned to the grinding table and further pulverized, while coal grains of the desired size move further through the bowl mill, from where they are finally discharged. be done. When the coal grains are transported in this manner, they collide with the members within the bowl mill and are subject to the abrasive effects described above.

Thus, the prior art has described the need to arrange articles as liners having at least an outer surface formed of new and improved materials characterized by high abrasion resistance. Furthermore, there was a need for a highly wear-resistant material that is suitable for use as at least the outer surface layer (i.e., the wear surface) of a grinding roll and that can provide a grinding roll that is characterized by an improved wear life. . There was also a need for a highly wear-resistant material that could be used to resurface worn grinding rolls (forming at least the outer surface of the grinding roll with a highly wear-resistant material). Such highly wear-resistant materials are inherently
Despite its nature as a material to be used as the outer surface layer of a grinding roll, it must also be suitable for use in resurfacing worn grinding rolls. Furthermore, such highly wear-resistant materials are suitable for the formation of bull rings that are placed on the grinding table of a bowl mill, whether the bull rings are constructed as one piece or in the form of multiple segments. It must be suitable for

Highly wear-resistant materials can also be used in liners that are selectively placed in interior areas of the bowl mill where they would be worn by impinging coal grains while flowing through the bowl mill entrained by a fluid such as air. It must be suitable for forming.

It is therefore an object of the present invention to provide an article with an abrasion-resistant surface layer of a new and improved material characterized by good abrasion resistance.

Another object of the invention is to provide an article with an abrasion resistant surface layer that is particularly suitable for use in bowl mills used to carry out the atomization of materials such as coal.

Yet another object of the present invention is to provide an article including a grinding roll used in a bowl mill, comprising an abrasion resistant surface layer.

It is a further object of the invention to provide an article comprising a wear-resistant surface layer, which includes a bull ring placed on the grinding table of a bowl mill.

Another object of the present invention is to provide an article with an abrasion resistant surface layer, the article including a liner that is selectively placed in areas of a bowl mill that are believed to be prone to abrasion based on past experience. It's about doing.

Yet another object of the present invention is to provide an article with a wear-resistant surface layer that is relatively inexpensive, relatively easy to use, and has improved wear life.

SUMMARY OF THE INVENTION -16 = According to one aspect of the invention, a grinding roll particularly suitable for use in a bowl mill produces grinding forces utilized in carrying out the pulverization of materials such as coal in the bowl mill. rolls are provided. Each crushed nickel 4.5-5.0%,
Chromium 4.0-4.25%, phosphorus 0.4-0.5%, sulfur 0.9-0.11%, molybdenum 0.4-0.6%
(contains no bismuth).

According to another aspect of the invention, a bull ring is provided for placement on a grinding table of a bowl mill for pulverizing materials such as coal. This bull ring is a cast product,
Carbon 3.5-3.7% (by weight), Silicon 1.2-1.6
%, manganese max. 0.4%, nickel 4.1-5.0%
, chromium 3.7-4.4%, phosphorus 0.15-0.25%
, sulfur 0.9-0.11%, molybdenum 0.4-0.
6% and 0.015% bismuth.

In accordance with yet another aspect of the present invention, a liner is provided that is selectively placed in wear-prone areas within a bowl mill. Both liners are cast as carbon 3
．． 5-3.7% (by weight), silicon 1.2-1.6%, manganese max 0.4%, nickel 4.3-5.0%, chromium 3.7-4.4%, phosphorus 0. 15-0.25%, sulfur 0.9-0.11%, molybdenum 0.4-0.6%
and a wear-resistant surface layer containing 0.015% bismuth.

DESCRIPTION OF PREFERRED EMBODIMENTS Next, description will be made with reference to the drawings. In FIG. 1, a bowl mill IO is illustrated. Since the construction and operation of bowl mills are well known to those skilled in the art, a detailed description of the bowl mill lo shown in FIG. 1 is not considered necessary. Rather, for an understanding of the bowl mill 10 which may be equipped with an article comprising an outer surface layer formed of a material characterized by good abrasion resistance according to the invention, it is necessary to simply refer to the construction of the components of the bowl mill and their operation. It will suffice to state this in general terms. In lieu of a detailed description of the construction and operation of the components of bowl mill 10, the prior art, such as U.S. Pat. No. 3,465,971 and U.S. Pat.
No. 002,299.

Referring to FIG. 1, the illustrated bowl mill IO includes a substantially closed separator body 12. Referring to FIG.

The grinding table 14 is mounted on a rotationally driven shaft 16 connected to a suitable drive mechanism (not shown). With respect to the above-mentioned components located within the separator body 12 shown in FIG. 1, the grinding table 14 is driven clockwise.

In the bowl mill 10, conventionally a plurality (preferably three) of grinding rolls 18 are supported within the separator body 12 and equally spaced from each other around the body. In FIG. 1, only one grinding roll is shown for clarity.

Each grinding roll of bowl mill 10 is supported on a suitable shaft 20 for relative rotation, as can be seen from grinding roll 18 in FIG. Additionally, the grinding rolls are also supported for movement relative to the upper surface of grinding table 14. For this purpose, each grinding roll of the bowl mill 10, including the roll 18, is controlled by the hydraulic means 2 cooperating therewith.
It has 2. Hydraulic means 22 of the bowl mill (as known in the art) provide a hydraulic load to cooperating grinding rolls 18;
The grinding rolls 18 thereby apply the desired degree of force to the coal placed on the grinding table to effect the desired pulverization.

The material to be pulverized in the bowl mill (e.g. coal) is
The bowl mill is fed by a variety of suitable feeding means. For example, one of such supply means used for this purpose
One is a belt feeder (not shown). Once discharged from the supply means (not shown), the coal is delivered to the coal supply means 2
4 to enter the bowl mill. Coal supply means 24 feed coal onto the surface of grinding table 14 .

According to the mode of operation of the bowl mill having the configuration shown in FIG.
A gas, such as air, is used to transport the coal from the grinding table 14 through the interior of the separator body 12 and out of the bowl mill 10 .

Air enters the separator body 12 through suitable openings (not shown) formed for this purpose.

From this opening (not shown) in the separator body 12, air flows into and flows through the annular passage 26, which is an annular space existing between the vicinity of the grinding table 140 and the inner wall surface of the separator body 12. Air passing through the annular passage 26 is diverted above the grinding table 14 by an impeller structure, preferably formed in accordance with the disclosure of US Pat. No. 4,523,721. For clarity, only the deflector portion 28 of this impeller structure is shown. Furthermore, it is believed that the description of deflector portion 28 in FIG. 1 will provide a sufficient understanding of its purpose. However, if further information is desired regarding the construction and operation of the impeller assembly included in the bowl mill 10 shown in FIG. 1, reference may be made to the aforementioned U.S. Pat. No. 4,523,721.

While the air flows through the path, the coal placed on the surface of the grinding table 14 is pulverized by the action of the grinding rolls 18. When the coal is pulverized, the coal grains are scattered outward by centrifugal force from the center of the pulverizing table 14.

Upon reaching the peripheral area of the grinding table 14, the coal grains are attracted by the air entering from the ring passage 26 and are transported by this air.

The mixed flow of air and coal particles is then captured by the deflector portion 28 of the impeller structure.

Therefore, the mixed flow of air and coal particles is
The direction of the flow path of the mixed flow changes. During this change in direction, the heaviest coal grains are separated from the air due to the large inertial forces and fall onto the surface of the grinding rolls 14 where they undergo further atomization. On the other hand, lighter coal grains still continue to be carried by the air flow due to their small inertia.

After leaving the influence of the deflector part 28, the mixed stream of air and still remaining coal particles flows into the classifier 30. The classifier 30 (which is known in the art) includes:
Coal particles remaining in the air stream are further separated. That is, pulverized coal of a desired particle size passes through the classifier 30 and is discharged from the bowl mill 10 together with air. On the other hand, coal grains with a larger size than the desired ones are removed from the grinding table 1.
4, where it is further micronized. These coal grains are then again subjected to the above treatment.

During pulverization, i.e., crushing, the force exerted on the coal placed on the crushing table is generated by the crushing rolls 18, and the force that must be generated by the crushing rolls 18 in order to achieve the desired degree of pulverization of the coal is The amount of will vary depending on a number of factors.

For example, one important factor in this regard is the nature of the coal itself. That is, the amount of force required to pulverize coal depends on the pulverizability of the coal to be pulverized (ease of pulverization of the coal).

Grinding rolls 18 to achieve the desired degree of pulverization of the coal.
Other important factors that determine the force landscape that should occur are:
The thickness of the layer of coal placed on the grinding table, which itself depends on the production rate of the bowl mill.

For a detailed description of the grinding roll for a bowl mill according to the invention with an outer surface layer made of a material characterized by good abrasion resistance, reference is made in particular to FIG. FIG. 2 briefly explains the structure of the crushing roll 18. As can be seen, the grinding roll 18 is made of a material according to the invention, which has a body portion 32 that embodies the overall shape of the roll, and which has better wear resistance than the material forming the body portion 32. It is composed of an outer surface layer 34. To this end, body portion 32 is formed of a relatively soft and easily machined material (e.g., gray cast iron), and outer surface layer 34 has good abrasion resistance (i.e., exhibits good abrasion resistance). ) made of relatively hard material. Further, as can be seen in FIG. 2, body portion 32 has a through hole 36 formed substantially along its center. The through hole 36 is configured to accommodate the shaft 20, thereby allowing the grinding roll 18
is supported and performs the function described with reference to FIG.

In summary, the reasons for constructing the crushing roll from two different materials are: firstly, it is necessary to form a body portion with through holes 36; The reason is that the surface layer 34 is subjected to a strong abrasion effect. That is, on the one hand, it is desirable to form the body portion 32 of a relatively soft and easily processable material to facilitate the formation of the through holes, and on the other hand, it is desirable to make at least the outer portion (i.e., the outer surface) of the body portion 32 less susceptible to wear. This is because it must be made of a relatively hard material characterized by its ability to withstand.

As previously mentioned, the outer surface layer 34 of the grinding roll 18 according to the present invention is formed of a material that is wear resistant and particularly suitable for forming the outer surface (or wear surface) layer 34 of the grinding roll. Furthermore, the material forming the outer surface layer of the grinding roll 18 according to the invention is characterized in that it is castable and can be used to strengthen the surface of the grinding roll 18. Typically, the material forming the outer surface layer of the grinding roll 18 is cast and contains 3.2-3.4% (by weight) carbon, 1.45-1.65% silicon, and up to 0.5% manganese.
4%, nickel 4.5-5.0%, chromium 4.0-4.
25%, phosphorus 0.4-0.5%, sulfur 0.9-0.1
1%, molybdenum 0.4-0.6%, and no bismuth.

A bull ring according to the invention having at least an outer surface which is placed on the grinding table 14 of the bowl mill 10 and is characterized by good wear resistance will now be described in detail with reference to FIG. In FIG. 3, bull ring 38 is made of a material with good wear resistance. In more detail,
Bull ring 38 is comprised of a first portion 40 and a second portion 42 . The first portion 40 is suitably sloped relative to the second portion 42 to mate with the outer surface layer 34 of the grinding roll 18. In other words, the first portion 4 of the bull ring 38
The inclination angle of 0 is appropriately selected depending on the inclination angle of the outer surface layer 34 of the grinding roll 18, and in other words, the inclination angle of the first portion 40 of the bull ring 38 is
The angle of inclination of the outer surface layer 34 is adapted to the angle of inclination of the outer surface layer 34. According to the best mode of the invention, bull ring 38 is preferably constructed of a plurality of segments. However, the bull ring 38 can also be formed in one piece. Typically, the material forming the bull ring 38 of the grinding table 14 contains 3.5-3.7% (by weight) carbon, 1.2-1.6% silicon, up to 0.4% manganese, as a casting. %, nickel 4.15.0%, chromium 3.7-4.4%, phosphorus 0.
15-0.25%, 0.9-0.1.1% sulfur, 0.4-0.6% molybdenum and 0.015% bismuth.

For a complete description of an article comprising an abrasion resistant outer surface layer in accordance with the present invention, reference is made to FIGS. 4, 5 and 6. In these figures, a first type of bowl mill liner 44 (Figure 4), a second type of bowl mill liner 46 (Figure 5), and a third type of bowl mill liner 48 (Figure 6) are shown. This is an indication. The bowl mill liner 44 of FIG. 4 is used in the deflector portion 28 of the impeller assembly described in connection with the bowl mill 10 illustrated in FIG. More particularly, in accordance with the construction of deflector portion 28, a plurality of bowl mill liners are used to form each row of deflector liners that make up deflector portion 28. To this end, each of the bowl mill liners has a predetermined shape so that, when assembled in a suitable manner, they function as members forming the deflector portion 28. In other words, as can be seen from FIG. 4, the bowl mill liner 44 has two sides 44a and 44b extending parallel to each other, and a third side 44c extending parallel to both sides 44a and 44.
4b and extends substantially at right angles to fourth side 44.
d extends in a non-parallel relationship to the third side 44c. Furthermore, the end surfaces of the bowl mill liners 44 are shaped to be compatible with the end surfaces of the bowl mill liners 44 to be joined together. This not only facilitates the initial installation of the bowl mill liner 44 within the separator body of the bowl mill of FIG. 1, but also facilitates its removal and replacement when it becomes worn. Finally, the bowl mill liner 44 is made of a material with good wear resistance due to the abrasive effects of the impact of air-entrained coal grains. Typically, the material forming the bowl mill liner 44 is cast and contains 3.5-3.7% carbon (by weight) and 1.5% silicon.
2-1.6%, manganese max. 0.4%, nickel 4J-
5.0%, chromium 3.7-4.4%, phosphorus 0.15-0
．． 25%, sulfur 0.9-0.11%, molybdenum 0.
4-0.6% and 0.015% bismuth.

A bowl mill liner 46 of the construction shown in FIG. 5 is used in the deflector portion 28 of the impeller assembly described above.

That is, depending on the configuration of deflector portion 28, bowl mill liner 46 is used as a side liner.

More particularly, a plurality of bowl mill liners 46 are used in deflector portion 28, with each bowl mill liner 4
6 is mounted so that its back edge is placed in abutment with the separator body of the bowl mill 10 of FIG. 1, and its bottom edge is placed in abutment with an intermediate liner (not shown). For this reason, each bowl mill liner 4
6 has a predetermined shape such that each bowl mill liner 46 functions as a component of the deflector portion 28 when assembled with each other in a suitable manner.

That is, as understood from FIG. 5, the bowl mill 4
6, the first side 46a extends on a first surface, the second side 46b extends on a second surface substantially perpendicular to the surface of the first side 46a, and the third side 46b extends on a second surface substantially orthogonal to the surface of the first side 46a. 46c is inclined relative to the first side 46a and extends in a non-parallel relationship to the second side 46b, and the fourth side extends in a parallel relationship to the first side 46a. and a second portion that is inclined relative to the third side 46c and extends in a non-parallel relationship to the first side 46a. The bowl mill liner 46 is made of a material with good abrasion resistance due to the abrasive effects caused by the impact of air-entrained coal grains. Typically, the material forming the bowl mill liner 46 is 3.5-3.7% (by weight) carbon, 1.5% silicon, as a casting.
2-1.6%, manganese max 0.4%, nickel 4.3
-5.0%, chromium 3. L-4.4%, Phosphorus 0.15-
0.25%, sulfur 0.9-0.11%, molybdenum 0
．． 4-0.6% and 0.015% bismuth.

A bowl mill liner 48 of the construction shown in FIG. 6 is also used in the deflector portion 28 of the impeller assembly in the same manner as described above. A plurality of bowl mill liners 48 are used in the form of intermediate liners and constitute deflector portion 28. To this end, each bowl mill liner 48 has a predetermined shape such that each bowl mill liner 48, when assembled with each other in a suitable manner, functions as a component of the deflector portion 28. . In other words, as can be seen from FIG. 6, the bowl mill liner 48 includes a first portion 48a extending on a first surface and a first portion 48a extending at a predetermined angle with respect to the surface of the first portion 48a. and a second portion 48b extending on two planes. Bowl mill liner 48 due to the abrasion effect caused by the collision of coal particles entrained in the air.
is made of material with good wear resistance.

Typically, the materials forming the bowl mill liner 48 include, as a cast, 3.5-3.7% carbon (by weight), 1.2-1.6% silicon, up to 0.4% manganese, nickel. 4.3-5.0%, chromium 3.7-4.4%, phosphorus 0.
15-0.25%, 0.9-0.11% sulfur, 0.4-0.6% molybdenum and 0.015% bismuth.

Thus, in accordance with the present invention there is provided an article with an abrasion resistant surface layer formed from a new and improved material characterized by good abrasion resistance. moreover,
Articles of the invention with a wear-resistant surface layer are particularly suitable for use in bowl mills of the type utilized to carry out the pulverization of materials such as coal. Further in accordance with the present invention, the article provided with the abrasion resistant surface layer includes a grinding roll used in a bowl mill. Also,
According to the invention, the article provided with the abrasion resistant surface layer includes a bull ring that is placed on the grinding table of a bowl mill. Additionally, articles of the present invention with abrasion resistant surface layers include liners that are selectively placed in areas of the bowl mill that are known to be susceptible to abrasion based on past experience. Also, according to the invention, articles comprising a wear-resistant surface layer are characterized by being relatively inexpensive, easy to use, and having an improved wear life.

Although the present invention has been described above in detail with reference to specific examples, the present invention is not limited to these specific examples, and it goes without saying that many changes and modifications can be made without departing from the spirit of the invention.

[Brief explanation of drawings]

FIG. 1 shows a partially cutaway view of a bowl mill equipped with an article according to the invention having an outer surface layer made of a material with good wear resistance, and FIG. FIG. 3 is an enlarged cross-sectional view of a grinding roll for a bowl mill having an outer surface layer made of a wear-resistant material according to the present invention, with a bull ring having an outer surface layer made of a wear-resistant material placed on a grinding table of a bowl mill. The illustrated partial cross-sectional views, FIGS. 4-6, each illustrate a variety of bowl mill liners having an outer surface layer formed of a wear-resistant material in accordance with the present invention. 10. Bowl mill, 12. Separator body, 14.
- Grinding table, 16... Shaft 18... Grinding roll, 28... Impeller structure, 34... Outer surface layer, 36... Through hole, 38... Bull ring, 44.46.48... Bowl mill. liner.

Claims (1)

[Claims] 1. A grinding roll used in a bowl mill, as a casting, containing 3.2-3.4% (by weight) of carbon and 1.5% of silicon.
45-1.65%, manganese max 0.4%, nickel 4
．． 5-5.0%, chromium 4.0-4.25%, phosphorus 0.
4-0.5% sulfur, 0.9-0.11% sulfur, and 0.4-0.6% molybdenum (no bismuth). , grinding roll. 2. A grinding roll according to claim 1, comprising a main body portion made of a relatively soft and easily processable material. 3. A grinding roll according to claim 2, wherein the relatively soft and easily machined material is gray cast iron. 4. A grinding roll according to claim 2, wherein the body portion has a through hole formed substantially along the center. 5. In articles used in bowl mills, as castings, carbon 3.5-3.7% (by weight), silicon 1.2-1
．． 6%, manganese max 0.4%, nickel 4.3-5.
0%, chromium 3.7-4.4%, phosphorus 0.15-0.2
5%, sulfur 0.9-0.11%, molybdenum 0.4-
An article comprising an outer surface layer formed of an anti-wear material containing 0.6% and 0.015% bismuth. 6. The article according to claim 5, which constitutes a bull ring. 7. The article of claim 6, wherein the bull ring is formed as a plurality of segments. 8. The article of claim 6, wherein the bull ring is formed as a single piece. 9. The article according to claim 5, which constitutes a bowl mill liner. 10. The invention of claim 9, wherein the bowl mill liner has first and second sides extending in parallel relation to each other, and a second side extending perpendicularly to each of the first and second sides. an article comprising three sides and a fourth side that is inclined at an angle to the first and second sides and extends in a non-parallel relationship to the third side. . 11. The bowl mill liner of claim 9, wherein the bowl mill liner has a first side extending on a first side, and a second side substantially perpendicular to the first side. a third side extending at a predetermined angle to the first side and extending in a non-parallel relationship to the second side; a first portion extending in a parallel relationship to the third side; and a second portion inclined at an angle to the third side and extending in a non-parallel relationship to the first side. An article comprising four sides. 12. The bowl mill liner according to claim 9, wherein the bowl mill liner has a first portion extending on a first surface and a second surface inclined at a predetermined angle with respect to the first surface. an article comprising: a second portion extending at a second portion;