EP0916407B2 - Method for manufacturing a milling roller - Google Patents

Description

The invention relates to a process for the preparation a grinding roller for the comminution of brittle Grindings in a good bed roller mill, according to the preamble of claim 1.

It is already well known that relative brittle regrinds, such as Cement raw materials, cement clinker, Ore material, coal and the like. especially economical or energy-saving in a so-called Good-bed roller mill can be crushed in the two counter-rotating rotating drivable grinding rollers with relatively high pressure pressed against each other (see, e.g., Walter Duda, Cement-Data-Book, Vol. 1, 3rd edition, 1985, p.255 to 261).

Since the roll surfaces (outer peripheral surfaces) especially with the mentioned brittle and abrasive Grindings very high demands both in terms of abrasion (abrasion) as well as in terms of the pressures are exposed, the roll shell every grinding roller used here accordingly resistant and in particular wear-resistant Material produced. To these roll materials especially chilled cast iron and alloyed hard materials, the by contract welding on the base material be applied. In this crushing in a good-bed roller mill, the effect on the roll surfaces or Walzenmänteln occurring high Press that after appropriate running or operating times the roll material especially of today mostly used job-welded roller shells especially near the surface tired, apart from the sometimes considerable wear. This material fatigue causes the Service life of these grinding rollers are limited; there The roll coats can no longer make sense regenerate.

In EP-B-563 564 there is therefore a good-bed roller mill been proposed in the grinding rolls be used according to the preamble of claim 1, i. the particular a roll shell of a wear-resistant Have chilled casting, which u.a. from a highly wear-resistant bainitic cast material act can. The special feature of these known grinding rollers is that on the surface of the chilled cast roll shell every grinding roller profiling in Form of weld beads made of wear-resistant hardfacing material are applied. It has Although shown by this production of the grinding rollers made of chilled cast iron with hardfacing a clear higher pressure resistance and thus longer service life Wear as in the above mentioned order-welded grinding rolls can be achieved can. In these known grinding rollers with a However, roll casing made of chilled cast iron should be noted that the chilled cast iron or the hard cast material a relatively has brittle behavior. The latter can be especially in relatively stoßweiser or beating Crushing work or stress of the grinding rollers, as it is especially with very brittle and coarse-cheeked Grindings often the case, cause the hard cast material spontaneously breaks. In addition, can it is already undesirable in the production of grinding rolls Breaks come; this can already be done at one Shrinking the roll jacket onto the roll main body by the resulting shrinkage stresses happen.

In the journal "ZKG International", no. 7/1997, pages 348 to 392, are "operating experience with wear protection for high-pressure roller mills " (Good bed roller mills), where it in particular, the training of the used there Rolls different in wear resistance Materials for the associated roll shells and when using these roll mills in the cement industry goes. In terms of wear protection will be highlighted above all three different versions, namely the so-called build-up welding, the bandaged or segmented cast armor and the so-called napkin armor. As a particularly positive Development will be the use of bandages made of alloyed ductile iron. On p.388, left Sp., Last paragraph, it is mentioned that nodular cast iron by alloying can achieve high pressure resistance; he in terms of hardness, however, below that Hard cast material Ni-Hard 4 is located. Its wear resistance is therefore much lower than others Hartgußwerkstoffen. Nodular cast iron, however, has the advantage be weldable, so that the wear protection be applied over Hartlagenaufschweißung can, with the elongation at break ductile iron higher than with other cast materials. Details for the elongation at break, the compressive strength or for the Alloy compositions are in this publication not included.

The invention is therefore based on the object a method as defined in the preamble of claim 1 presumed kind in the way to further improve that with still relatively high wear and pressure resistance a particularly high operational safety of the Roll mantle (and thus the whole grinding roller) opposite Fractures can be achieved.

This object is achieved by the characteristics of claim 1 solved.

Advantageous embodiments and developments This invention is the subject of the dependent claims.

An essential thought of the present Invention is seen in that the roll shell from a ductile bainitic ductile iron with a Elongation at break of 0.1 to 2.5% and a compressive strength from 1,000 to 1,800 MPa is produced, with a preferred maximum value of the aforementioned elongation at break at 2.0%. Compared to the above described known grinding rollers (from EP-B-563 564), in which the roll shell of relatively brittle Chilled casting is produced by the invention Production of grinding rolls a roll shell material, which in addition to its high pressure resistance and wear resistance by a relatively large Toughness distinguishes, making this material and Thus, the roll shell made therefrom a special high security against breakage of the roll mantle guaranteed. In the underlying the invention extensive attempts this could high security against fractures as well as a relative high compressive strength of the material detected are, i. in this roll shell material occur even with relatively large and uneven loads during the crushing of brittle Grindings in a good bed roller mill no material fatigue on.

According to a preferred embodiment of the invention becomes a breaking elongation of the casting material and thus the roll mantle of at least 0.5%, So an elongation at break of 0.5 to 2.5%, especially preferably from 0.5 to 2.0%, and a compressive strength from 1,200 to 1,600 MPa.

It is also considered to be particularly advantageous if in this case the roll shell with a hardness from 42 to 55 HRc, preferably from 45 to 50 HRc, i. Hardness according to Rockwell, is produced.

In order to comminute brittle grinding materials always a reliable one in a good bed roller mill Feeding of regrind into the between the two Ensuring grinding rolls formed nip to be, is in this invention roll production on the outer circumferential surface of the roll mantle a known surface profiling appropriate. Although this surface profiling is general already produced when casting the roll shell or can be formed, it is in general preferred, this surface profiling by a build-up welding of hard material form the outer peripheral surface of the roll shell.

According to a much expedient embodiment it is also possible on the outer peripheral surface the roll mantle first several complete additional layers of hard material applied by welding and to the utmost Additional layer of the surface profiling Hard material also by hardfacing to build.

In the mentioned experiments could be found and confirmed that the invention Cast material used for the roll shell previously awarded contract welds tolerates. As with this casting material, as mentioned above, no material fatigue occurs, the result is the Another advantage is that worn build-up welds repeated as desired and thus the wear surface the roll mantle accordingly easily and often can be regenerated. Because of this surfacing on the inventively used Cast material results in a very wear-resistant Roll shell, which thus one compared to the known Versions extra long life has. The latter is further supported by the fact that as the experiments have also shown - by Hardfacing applied hard material still harder than in the above-mentioned known embodiments. Even when cooling the hardfacing material Should form cracks, then these are only relatively short cracks, for the wear resistance and pressure resistance and thus for the life of the roll mantle thus produced are harmless.

For the inventive production of Roll mantle a grinding roller are below Examples of typical compositions mentioned.

For the manufacture of the roll mantle, i. for the actual mantle body, becomes a ductile bainitic Ductile cast iron from a casting alloy with - in % By weight - 3.0 - 3.5% carbon, 1.5 - 2.0% silicon, 0.3-0.4% manganese, 0.05% phosphorus, 1.5-4.0% nickel, 0.7-1.0% molybdenum and 0.04-0.07% magnesium selected, wherein in a preferred embodiment the proportion of silicon also 1.8 to 2.0 wt .-% can amount.

As a hardfacing material is preferably a highly wear-resistant chrome-carbon alloy used in addition to chromium carbides to train special carbides. Alternatively The hard material can also by highly wear-resistant Tungsten carbide surfacing welds are formed.

After a typical example, the hardfacing material becomes by a hard alloy with - in% by weight - 5.0% carbon, 2.0% manganese, 1.5% Silicon, 22.0% chromium, 7.2% niobium and 0.5% vanadium educated.

In this preparation according to the invention the grinding roller and in particular the roll shell can the material properties of the ductile bainitic Ductile iron by controlled cooling and / or heat treatment of the roll mantle in the be set desired or required manner.

It should be noted that the invention manufactured grinding roller in constructive or structurally, as well as in their shape otherwise may be generally similar, such as it is well known in the case of good bed roller mills and also essentially in the cited EP-B 563 564 is described. This therefore means that this grinding roller generally in two parts from the roller body (sometimes also called roller shaft) and the it is firmly applied roll shell. Of the Roller body can be in the usual way as be prepared forged component, on which the roll shell for example, by a detachable Shrink fit is fixed firmly and reliably.

• der erfindungsgemäße Walzenmantel besitzt eine ähnlich hohe Druckfestigkeit wie bekannte Walzen aus Hartgußwerkstoffen, ohne daß bei ihm jedoch Werkstoffermüdungen auftreten, mit der Folge einer besonders hohen Standzeit;
• die hohe Druckfestigkeit des duktilen bainitischen Sphärogusses erlaubt höhere Mahldrücke als bei auftragsgeschweißten Mahlwalzen;
• neben der ausgezeichneten Druckfestigkeit besitzt der aus dem duktilen bainitischen Sphäroguß hergestellte Walzenmantel besonders gute Zähigkeitseigenschaften, wodurch er besonders hohe Sicherheiten gegenüber einem spröden Versagen bzw. Sprödbrüchen aufweist;
• durch sinnvolle Variationen in der chemischen Analyse des Gußwerkstoffes sowie durch eine gesteuerte Abkühlung und/oder Wärmebehandlung des Walzenmantels nach dem Guß können die Werkstoffeigenschaften optimal den Beanspruchungen bei der Zerkleinerung in einer Gutbett-Walzenmühle angepaßt werden.

Finally, there are again some important advantages of the roll shell produced from ductile, bainitic spheroidal graphite cast iron:

• the roll shell according to the invention has a similar high compressive strength as known rollers made of chilled cast iron, but without him material fatigue occur, with the result of a particularly long service life;
• the high compressive strength of the ductile bainitic nodular cast iron allows higher grinding pressures than on job-welded grinding rolls;
• In addition to the excellent compressive strength, the roll shell produced from the ductile bainitic ductile iron has particularly good toughness properties, whereby it has particularly high security against brittle failure or brittle fractures;
• by meaningful variations in the chemical analysis of the casting material as well as by a controlled cooling and / or heat treatment of the roll shell after casting, the material properties can be optimally adapted to the stresses during comminution in a good bed roller mill.

Claims (10)

1. Method of producing a grinding roll for the comminution of brittle feed materials in a material bed roll mill in which two grinding rolls which can be driven in rotation in opposite directions are pressed against one another with a high pressure, wherein a roll tyre is firmly applied to a basic roll body and this roll tyre is produced from a highly wear-resistant bainitic cast material, characterised in that for the production of the roll tyre a ductile bainitic spheroidal graphite cast material consisting of a cast alloy with - in % by weight - 3.0 - 3.5% carbon, 1.5 - 2.0% silicon, 0.3 - 0.4% manganese, 0.05% phosphorus, 1.5 - 4.0% nickel, 0.7 - 1.0% molybdenum and 0.04 - 0.07% magnesium is chosen and is produced with a breaking elongation of 0.1 to 2.5% and a compression strength of 1,000 to 1,800Mpa.
2. Method as claimed in Claim 1, characterised in that a breaking elongation of the roll tyre of at least 0.5% and a compression strength of 1,200 to 1,600 MPa is chosen.
3. Method as claimed in Claim 1, characterised in that the roll tyre is produced with a hardness of 42 to 55 HRc (Rockwell hardness).
4. Method as claimed in Claim 1, characterised in that a surface profiling is applied to the outer circumferential surface of the grinding roll.
5. Method as claimed in Claim 4, characterised in that the surface profiling is formed by build-up welding of hard material onto the outer circumferential surface of the roll tyre.
6. Method as claimed in Claim 4, characterised in that first of all a plurality of complete additional layers of hard material are applied by build-up welding onto the outer circumferential surface of the roll tyre and the surface profilings of hard material are formed on the outermost additional layer, likewise by hard build-up welding.
7. Method as claimed in Claim 5 or 6, characterised in that a highly wear-resistant chromium/carbon alloy in which special carbides form apart from chromium carbides is used as hard build-up welding material.
8. Method as claimed in Claim 7, characterised in that the hard build-up welding material is formed by a hard alloy with - in % by weight - 5.0% carbon, 3.0% manganese, 1.5% silicon, 22.0% chromium, 7.2% niobium and 0.5% vanadium.
9. Method as claimed in Claim 5 or 6, characterised in that the hard material is formed by highly wear-resistant tungsten carbide build-up welds.
10. Method as claimed in Claim 1 or 10, characterised in that the material characteristics of the bainitic spheroidal graphite cast material are set by controlled cooling and/or heat treatment of the roll tyre.