Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
  • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
  • B02C17/00—Disintegrating by tumbling mills, i.e. mills having a container charged with the material to be disintegrated with or without special disintegrating members such as pebbles or balls
  • B02C17/18—Details
  • B02C17/20—Disintegrating members
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/36—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.7% by weight of carbon
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/49—Method of mechanical manufacture
  • Y10T29/4998—Combined manufacture including applying or shaping of fluent material
  • Y10T29/49988—Metal casting

Definitions

• the grinding bodies are long bars (80 mm in diameter by a few meters in length), arranged in a cylindrical grinder approximately horizontally.
• These grinding bars are used in fine or coarse grinding, dry or wet, and the products obtained are optionally further processed in ball mills.
• These materials are made of low-alloy steel, with a carbon content less than or equal to 1.1% for, for example, a steel, according to AISI 52100 or 1095 with more or less manganese (Steel 50 MC 4 developed by CREUSOT LOIRE).
• the bars are rough of rolling and dressing and, possibly, treated according to processes which preserve the straightness of the bar (U.S. Patent 3,255,053; communication from the CREUSOT LOIRE Company to the Abrasion Congress of 1979).
• the treatment consists of an austenization heater, followed by cooling (quenching) to obtain an approximately martensitic structure of 55 to 60 RC.
• Bimetallic bars have also been used, the core of which is made of mild steel and the surface of which is hard steel.
• the present invention aims to provide grinding bars made of a material sufficiently loaded with carbon and alloy to produce quantities and types of carbides providing satisfactory resistance to wear.
• the invention also aims to propose a method for manufacturing such bars which does not involve rolling.
• the subject of the invention is a grinding bar made of ferrous metal, coming directly from directed solidification casting, characterized in that it has a fine-grained surface structure and a core with a dendritic structure oriented radially, and in that it comprises, in% by weight, between approximately 1.1 and 3% of carbon, between approximately 3 and 30% of chromium, between approximately 0.3 and 1.5% of manganese and between approximately 0.3 and 1% silicon.
• these bars may also contain, in% by weight, from 0 to 1% of copper, from 0 to 5% of nickel, from 0 to 1% of molybdenum, from 0 to 1% of titanium , from 0 to 0.5% boron, from O to 2% of vanadium and from O to 2% of tungsten.
• the invention also relates to a method of manufacturing such a grinding bar, characterized in that it is carried out by continuous casting of a ferrous metal of suitable composition, with directed solidification, to the exclusion of any phase rolling.
• the grinding bars according to the present invention do not have fibers oriented in the longitudinal direction, that is to say parallel to the axis of the bar.
• this structure will have to be thinner and thinner going from the core to the surface of the bar.
• the grinding bars are subject to wear and corrosion from their surface, until they reach a certain diameter, where they are eliminated. It is therefore preferable that they break into small pieces, rather than bending and becoming entangled with the other bars.
• the internal structure should preferably be coarse, case-sensitive.
• the object of the present invention is to propose a grinding bar whose characteristics are much superior, thanks to the use of a different material and due to a particular structure obtained by an original process.
• such a grinding bar is made of a steel having a high carbon content and a high percentage of carbide.
• Table 1 below compares different types of grinding bars known in the art and those according to the invention.
• the bar object of the invention has, on the surface, a homogeneous grain structure not oriented in the longitudinal direction; it is not a laminated structure with stretching of the fibers, elongation of inclusion, possible line, it is a clean structure resulting from the process.
• this structure comprises a high percentage of carbide of the type M 3 C, M 7 C 3 , M 23 C 6 depending on the type of alloy, M denoting a compound iron-alloy.
• the internal structure of the bar object of the invention has an orientation perpendicular to the cylindrical surface, in the form of a dendrite.
• the hardness of carbides oriented in this direction is greater than their lateral hardness; the micro-hardness of the surface of the bar will therefore remain high even after reduction of the diameter by abrasion.
• the radial dendrite structure ensures sufficient fragility of the metal to cause it to break into pieces below a certain diameter of the bar.
• the bar according to the invention therefore has, on the surface, over a certain thickness, a fine-grained structure, while its core is of radial dendritic structure.
• austenitic martensitic or bainitic, with hardnesses and constitutions of matrices and variable carbides.
• Such a bar can only be produced by the method according to the invention, which will now be described in more detail.
• the manufacture of the bar must also be eliminated by compacting sintered powder, an expensive process which gives a homogeneous structure in all directions without any particular advantage.
• the bar according to the invention is produced by continuous horizontal casting, with a final diameter of 50 to 100 mm and at the required length, from 2 to 6 m and more. Directed solidification and the formation of the fine structure on the surface and dendritic at heart are obtained by appropriate adjustments of the conditions of extraction of the bar from the production ingot mold, either at a pitch of between 1 and 50 mm or a ratio P / D (length of step relative to the diameter of the bar) from 5/100 to 5/10.
• the bar is cooled in a controlled manner to obtain the matrix and the morphology of the desired carbides.
• This cooling can be a thermal cycle down in temperature, then up, followed by a bearing and cooling.
• the process according to the invention provides a product which can be used directly in ordinary mills.
• an additional or complementary heat treatment may be carried out.
• the shredding bars In the event of a particularly high impact stress in very high power shredders, or of large shredder diameter, the shredding bars must have no surface defect, crack line, etc. These faults are well known in the state of the technique, are generally linked to the rolling process and to the possible segregations due to the ingot or the rough billet.
• the bar which is the subject of the invention does not have any faults of this kind.
• the constituent alloy of the bar and its manufacturing process there may be adherent calamines, surface reliefs or surface microsegregations on the product.
• adherent calamines, surface reliefs or surface microsegregations on the product.
• This bar has on the whole a diameter of 80 mm and is obtained by horizontal continuous casting in a machine with controlled extraction parameter giving a pitch of 10 mm.
• the cooling of the bar between 1180 ° C temperature at the outlet of the mold and 400 ° C, will be done in 30 minutes.
• the bar is cut in hot line to a length of 3.10 m.
• Such a bar according to the invention has a hardness of 40 RC. Its surface structure is austenitic and has a fine grain layer over a thickness of 5 mm. The core of the bar has a hardness of 32 RC and its structure is dendritic.
• the bars according to the invention therefore have a wear resistance much higher than the usual bars.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Food Science & Technology (AREA)
• Crushing And Grinding (AREA)
• Polishing Bodies And Polishing Tools (AREA)
• Heat Treatment Of Steel (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=9286380

Family Applications (1)

Country Status (9)

Cited By (3)

Families Citing this family (3)

Citations (6)

Family Cites Families (2)

• 1983
  • 1983-03-01 FR FR8303327A patent/FR2541910B1/fr not_active Expired
• 1984
  • 1984-02-08 GR GR73741A patent/GR79813B/el unknown
  • 1984-02-09 ZA ZA84976A patent/ZA84976B/xx unknown
  • 1984-02-15 CA CA000447489A patent/CA1208613A/fr not_active Expired
  • 1984-02-22 US US06/582,340 patent/US4602416A/en not_active Expired - Fee Related
  • 1984-02-28 JP JP59035471A patent/JPS59162956A/ja active Pending
  • 1984-02-28 MA MA20267A patent/MA20045A1/fr unknown
  • 1984-02-29 EP EP84400405A patent/EP0120748A1/de not_active Withdrawn
  • 1984-02-29 ES ES530173A patent/ES8504485A1/es not_active Expired

Patent Citations (6)

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