EP0916407B1 - Method for manufacturing a milling roller - Google Patents

Description

The invention relates to a method for manufacturing a grinding roller for the comminution of brittle regrinds in a material bed roller mill, according to the Preamble of claim 1.

It is already well known that relatively brittle Regrind such as Cement raw materials, cement clinker, Ore material, coal and the like particularly economical or energy-saving in a so-called Gutbett roll mill can be crushed in two in opposite directions rotating drivable grinding rollers with relatively high pressure against each other (cf. e.g. Walter Duda, Cement Data Book, Vol. 1, 3rd ed., 1985, pp. 255 to 261).

Because the roller surfaces (outer peripheral surfaces) are straight very much with the brittle and abrasive grinding materials mentioned high demands both with regard to abrasion (Wear) and exposed to the pressures the roller shell will be used here every Grinding roller made of accordingly resistant and especially made of wear-resistant material. To These roller materials mainly include chilled cast iron as well Alloyed hard materials by cladding be applied to the base material. At this Crushing in a material bed roller mill causes this occurring on the roll surfaces or roll shells high pressures that after appropriate running or Operating times of the roller material, especially those of today mostly used surfaced roll shells tired especially near the surface, apart from the sometimes considerable wear. This material fatigue leads to the The service lives of these grinding rollers are limited; leave with it the roller shells also no longer regenerate sensibly.

In EP-B-563 564 there is therefore a material bed roller mill proposed to be used in the grinding rollers which according to the preamble of claim 1 are manufactured, i.e. which in particular a roller shell from a wear-resistant chilled cast iron, at which is among others from a highly wear-resistant bainitic Cast material can act. The special thing about this known grinding rollers is that on the Surface of the chill roll shell of each grinding roller Profiles in the form of welding beads made of wear-resistant Cladding material applied are. It has been shown that by this production the milling castors made of chilled cast iron with build-up welding a significantly higher compressive strength and thus longer life in terms of wear than with the above-mentioned weld-welded grinding rollers can be achieved. With these known grinding rollers with a chilled cast iron roller jacket, please note that the chilled cast iron or the chilled cast iron material is a relative has brittle behavior. The latter can especially in the case of relatively intermittent or striking Shredding work or stress on the grinding rollers, as is especially the case with very brittle and large pieces Regrind is often the case, cause the hard cast material breaks spontaneously. Besides, it can already undesirable during the manufacture of the grinding rollers Breaks come; this can already happen with one Shrinking the roll cover onto the roll base due to shrinkage stresses happen.

In the trade journal "ZKG International", No. 7/1997, Pages 348 to 392, are "Operating Experience with the Wear protection for high-pressure roller mills "(material bed roller mills) described, in particular the Training of the rollers used there with regard to Wear resistance of various materials for the associated roller jackets and when using these roller mills in the cement industry. With regard the wear protection are mainly three different Emphasized versions, namely the so-called surfacing, the bandaged or segmented cast armor and the so-called stud armor. As one Use is particularly positive called bandages made of alloyed nodular cast iron. On S.388, left column, last paragraph, it is mentioned that nodular cast iron achieve high compressive strength through alloying can; he however under in terms of his harshness the hard cast material Ni-Hard 4. Its wear resistance is therefore much less than that of others Hartgußwerkstoffen. Ductile iron did, however Advantage of being weldable, so that wear protection be applied by hard layer welding can, the elongation at break being higher than nodular cast iron with other cast materials. Details for elongation at break, compressive strength or for the alloy compositions are in this release not included.

The invention is therefore based on the object Method of the prerequisite in the preamble of claim 1 Way to further improve in such a way that still relatively high wear and pressure resistance particularly high operational reliability of the roll shell (and thus the entire grinding roller) against breakage can be achieved.

This object is achieved according to the invention by the indicator of claim 1 solved.

Advantageous refinements and developments of these Invention are the subject of the dependent claims.

An essential idea of the present invention is seen in the fact that the roll shell consists of a ductile bainitic nodular cast iron with an elongation at break of 0.1 to 2.5% and a compressive strength of 1,000 to 1,800 MPa is produced, with a preferred maximum value of the aforementioned elongation at break is 2.0%. Compared to the ones above known grinding rollers described (from EP-B-563 564), where the roll shell is made of relatively brittle chilled cast iron is produced, results from the invention Production of grinding rolls a roll shell material, which in addition to its high compressive strength and wear resistance due to its relatively high toughness distinguishes what this material and thus the roller jacket made therefrom a particularly high Security against breakage of the roller jacket guaranteed. In the extensive underlying the invention This high security could try Fractures and a relatively high compressive strength of the material, i.e. at this Roller jacket material also occur with relatively large ones and uneven loads during shredding of brittle regrind in a material bed roller mill no material fatigue.

According to a preferred embodiment of the invention an elongation at break of the cast material and thus the roll shell of at least 0.5%, i.e. an elongation at break from 0.5 to 2.5%, particularly preferably from 0.5 to 2.0%, and a compressive strength of 1,200 to 1,600 MPa selected.

It is also considered particularly advantageous if if the roller jacket has a hardness of 42 to 55 HRc, preferably 45 to 50 HRc, i.e. Rockwell hardness.

In order to shred brittle regrinds in one Gutbett roll mill always reliable feeding of regrind in the between the two grinding rollers To be able to ensure the nip formed in this roll production according to the invention on the Outer peripheral surface of the roll shell is known per se Surface profiling attached. Although these Surface profiling generally already during casting the roll shell are manufactured or formed , it is generally preferred to use this surface profiling by a weld overlay from Hard material on the outer circumferential surface of the roll shell train.

According to a multi-purpose design variant there is also the possibility of on the outer peripheral surface of the roll shell initially several complete additional layers made of hard material by welding apply and on the outermost additional layer Surface profiling made of hard material also to be formed by hard surfacing.

In the experiments mentioned it was possible to determine and confirm be that the invention for the roll shell cast material used the previously mentioned surfacing tolerates excellently. Because with this Cast material - as mentioned above - no material fatigue occurs, there is the further advantage that worn overlay welds repeated any number of times and thus the wear surface of the roll shell can be regenerated accordingly easily and often. Because of these build-up welds on the invention The cast material used is extremely wear-resistant roller jacket, which is therefore a Particularly long compared to the known versions Has lifespan. The latter is supported by that - as the experiments have also shown - the hard material applied by build-up welding is even harder than the known ones mentioned above Versions. Even if it cools down of the hard surfacing welding material should form cracks, then it is only a matter of proportion short cracks for wear resistance and Compressive strength and thus for the life of the sun manufactured roll shell are harmless.

For the production of the roll shell according to the invention a grinding roller are examples of typical below Called compositions.

For the manufacture of the roll shell, i.e. for the real one Sheath body, can be a ductile bainitic Ductile iron from 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 are selected, in a preferred embodiment the proportion of silicon can also be 1.8 to 2.0% by weight.

As the hard overlay welding material is preferably one highly wear-resistant chrome-carbon alloy used, in addition to chrome carbides there are also special carbides form. Alternatively, the hard material can also thanks to highly wear-resistant tungsten carbide surfacing be formed.

According to a typical example, the hard overlay welding material through 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 formed.

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

It should also be noted that the invention manufactured grinding roller in a constructive or structural In terms of general terms and shape can be carried out in the same way as it is with Gutbett roll mills well known and also essentially is described in the mentioned EP-B 563 564. this means thus that this grinding roller generally in two parts from the roller body (sometimes also as roller shaft referred to) and firmly attached to it Roll jacket exists. The roller body can manufactured in the usual way as a forged component be on which the roller shell, for example, by a removable shrink fit firmly and reliably attached becomes.

• 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 some key advantages of the roll shell made from ductile, bainitic nodular cast iron:

• the roll shell according to the invention has a similarly high compressive strength as known rolls made of hard cast materials, but without material fatigue occurring, with the consequence of a particularly long service life;
• The high compressive strength of the ductile bainitic nodular cast iron allows higher grinding pressures than with welded-on grinding rollers;
• In addition to the excellent compressive strength, the roll shell made from ductile bainitic nodular cast iron has particularly good toughness properties, which means that it has particularly high security against brittle failure or brittle fractures;
• through sensible variations in the chemical analysis of the cast material and through 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 material bed roll mill.

Claims (11)

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 the roll tyre is produced from a ductile bainitic spheroidal graphite cast material 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 cast material and thus 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, 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.
11. Method as claimed in Claim 1 or 10, characterised in that the material characteristics of the ductile bainitic spheroidal graphite cast material are set by controlled cooling and/or heat treatment of the roll tyre.