Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B1/00—Preliminary treatment of ores or scrap
  • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
  • C22B1/24—Binding; Briquetting ; Granulating
  • C22B1/248—Binding; Briquetting ; Granulating of metal scrap or alloys
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F8/00—Manufacture of articles from scrap or waste metal particles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B30—PRESSES
  • B30B—PRESSES IN GENERAL
  • B30B9/00—Presses specially adapted for particular purposes
  • B30B9/32—Presses specially adapted for particular purposes for consolidating scrap metal or for compacting used cars
  • B30B9/327—Presses specially adapted for particular purposes for consolidating scrap metal or for compacting used cars for briquetting scrap metal
• • 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
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P10/00—Technologies related to metal processing
  • Y02P10/10—Reduction of greenhouse gas [GHG] emissions
  • Y02P10/122—Reduction of greenhouse gas [GHG] emissions by capturing or storing CO2
• • 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
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
  • Y02W30/00—Technologies for solid waste management
  • Y02W30/50—Reuse, recycling or recovery technologies

Definitions

• This invention relates to the recycling of scrap metal. It has particular application to recycling by rolling or otherwise hot- working a billet made up of scrap metal swarf compacted in a tubular jacket.
• swarf comprehends the off cuts from machining operations in general and is intended to include the off cuts from turning, boring, shaping and milling operations on engineering steels. The fine off cuts from some stamping and punching operations may also be suitable.
• engineing steel is intended to describe those low alloy steels which are commonly subjected to machining operations including mild steel (a term which itself includes carbon steel), forging steel and axle or shaft steel all of which contain significant amounts of carbon.
• British patent #1313545 there is disclosed, inter alia, a process in which steel swarf is pressed into compact masses (which for convenience will be called “briquettes").
• the briquettes are pressed together and jacketed in a closed tube, usually of steel or stainless steel.
• the billet so formed is then heated and worked by a process such as rolling into a finished or semi-finished product.
• briquettes may take place in a cavity die prior to being jacketed.
• briquettes may be formed directly in the bore of the tube.
• the tube is inserted in a supporting die during the compaction process and the bore of the tube serves as the cavity.
• the compaction is carried out by means of a press having a ram which presses a quantity of the swarf previously inserted in the cavity into a briquette.
• the ram is then withdrawn and a new charge of swarf is inserted in the cavity.
• the ram is again inserted in the cavity to form a new briquette pressed up against the earlier formed briquette.
• the cycle is repeated until the cavity is substantially filled up with briquettes.
• the oxides on the swarf inside the jacketing tube are reduced and during the working process the metal particles of which the briquettes are composed are consolidated into a unitary mass which are sintered to each other and to the jacket.
• the reduction of oxides on the swarf occurs as a result of the combination thereof with carbon which is either introduced into the jacket or which diffuses out of the steel or other metal of which the swarf is composed.
• the jacketing tube serves to maintain reducing conditions within the billet. Attempts to produce an acceptable hot worked product from a billet of unjacketed swarf have been unsuccessful even when great care was taken to try to prevent atmospheric oxygen from getting to the hot billet.
• One of the commercially and technically important products of the process is a billet comprised of a stainless steel jacket filled with briquettes of mild steel or carbon steel which can be worked into a finished product having the desirable properties and low cost of engineering steel but which has a stainless steel cladding.
• a product comprising a core of steel clad with a non-ferrous metal such as copper also has commercial potential.
• Billets comprising stainless steel tubes filled with compacted swarf have heretofore presented special problems which are discussed later in this specification and it is an object of the invention to address these problems.
• a billet of recycling swarf including the steps of making up a billet comprising a mass of the swarf jacketed in a tubular jacket, characterised in that at least one end of the jacket is joined to an end piece which surrounds an end portion of the mass of swarf, the end piece and the jacket being of metals of different composition.
• the jacket is of stainless steel.
• the end piece is of engineering steel.
• the end piece is in the form of an open ended sleeve.
• the end piece may be in the form of a cap.
• a sealing member is provided which is inserted in the sleeve and which overlies the said one end of the mass of swarf.
• the invention has particular application to swarf composed substantially of engineering steel.
• the billet is heated and hot worked into a product in which the swarf and the jacket are bonded together and from which the end piece is removed.
• Still another advantage of the invention is that wastage of the stainless steel or copper material comprising the jacket is reduced.
• the ends of a finished product produced by any rolling operation are always defective. They are therefore cut off and discarded. Up to 8% of the jacket of a billet which is 1 metre long prior to rolling is discarded in this way. If the part of the jacket which is ultimately discarded can be at least partially replaced by a less expensive material, substantial savings on the cost of the jacketing material may be achieved.
• Figure 1 is a schematic cross-sectional side view of a billet comprised of a core of briquettes of engineering steel swarf inserted in a tubular jacket;
• Figure 2 to 5 are cross-sectional side views each of one end of modified billets;
• Figure 6 is a side view of one end of yet another modified billet.
• Figure 7 is a sectional view on arrows A-A in Figure 6.
• the billet 10a comprises a body or core 12a made up of briquettes of compacted mild steel or carbon steel swarf pressed into a jacket 14a.
• the swarf Prior to compaction the swarf should be cleaned and crushed as described in British patent #1313545. Swarf so treated will still have normal surface oxidation. This oxidation will be removed when the billet is heated. It may however be preferable to use swarf which, after cleaning and crushing, has been preheated and allowed to cool in reducing conditions to remove the surface oxides. This has two advantages. First, the amount of oxygen and of carbon dioxide which may be evolved in the interior of the tube will be much diminished if not eliminated. In the presence of either of these gases chrome oxides are formed on the surface of austenitic stainless steels above about 900 C. When they occur they are visible as a green layer at the interface of the core and the jacket. Once formed these oxides are not reduced. The presence of these oxides impairs the bond between the core and the stainless steel jacket.
• the second advantage of prereducing and cooling the swarf is that the swarf is annealed in the process. This enables the briquettes to be compacted to a substantially greater density.
• the jacket is comprised of a tube 16a of austenitic stainless steel to each end of which an open ended sleeve 20a of mild steel is butt welded, as indicated at 22a.
• the interfaces between the briquettes are indicated at 24a.
• the core is formed substantially in the manner described in British patent #1313545. Discrete charges of the swarf are fed successively into the bore of the tube through the sleeve 22a at, say, the left hand end of the tube.
• a hydraulic press is used to compact each load in turn into a briquette.
• the press comprises a ram (indicated at 26a) which is extended into the bore of the tube from the left hand end.
• the first load of swarf is compacted between the ram against a stop 28a at the right hand end of the tube to form the first briquette.
• Each subsequent load of swarf is compacted by the ram against the last-formed briquette. Pressing of briquettes continues until the tube 16a is substantially filled up. A small space is left in the bore between the core and each end of the tube.
• the core should in any case project well into the sleeve 20a at each end of the tube.
• the press may alternatively comprise two rams which are advanced one into each end of the tube.
• the first briquette is formed at the longitudinal centre of the tube and charges of swarf are thereafter fed into each end of the tube so that two briquettes are formed in each subsequent cycle of the press.
• the billet 10a may now be heated and rolled without further modification.
• the particles of swarf at each end of the core sinter together and to the sleeves 20a as the temperature increases. Extraneous gases, particularly atmospheric oxygen, are thus prevented from entering the interior of the tube.
• carbon diffuses out of the swarf and combines with residual oxygen in the tube and with the surface oxides on the swarf to form carbon monoxide and carbon dioxide. Substantially all of the surface oxides are reduced in this manner.
• Rolling can be carried out by conventional techniques in a conventional rolling mill. In the process of rolling, sintering of the particles of swarf is completed and the core becomes bonded to the stainless steel jacket. The ends of the rolled product which are jacketed by the deformed sleeves 20a are cut off and discarded.
• Both of these steps remove residual oxygen from the interior of the tube so that, particularly when the surface oxides on the swarf have been reduced prior to jacketing, the occurrence of both CO and CO2 may be eliminated or at least much reduced.
• a preformed cap 20c is welded to at least one end of the jacket 16c in place of the open ended sleeve.
• the cap has an integrally formed roof 32c which serves the same function as the plate
• Another simple way to at least partially seal the tube is to apply a paste 32e of graphite (or other suitable agent which evolves a reducing gas when heated) in water to the end faces of the core 12e.
• An advantage of applying graphite to the end face of the body of swarf is that, because it is exposed directly to the furnace heat, the end heats up far more quickly than the interior of the body or even the inside of the jacketing tube. With heat the graphite starts to burn, generating CO2 at the exposed face of the graphite layer. However, at the interface between the graphite layer and the body of swarf, CO is generated. The reason for the difference is that there is a carbon rich environment at the interface.
• the CO starts to form at a very early stage in the heating cycle and is believed to help prevent some of the constituents of the stainless steel such as chrome and nickel from forming oxides which once formed cannot be reduced by CO. These oxides would probably only start to form at temperatures above the temperature (700° C) at which CO is formed from the graphite. (Stainless steels starts to scale at about 870 C. ) In fact the graphite at the ends may provide an assurance against oxidation anywhere inside the system. The only way for oxidation to occur in the swarf before the generation of CO by the diffusion of carbon out of the swarf has started is for oxygen to enter the system from the two ends. Before this oxygen can get to the inner part of the system at least the bulk of it will be converted by the graphite to CO.
• the tube 16a is of copper it is essential to keep the copper below its melting point. At the same time the body 12a must not be allowed to cool below the hot working temperature of the swarf. The billet may have to be heated between passes through the rolls for this purpose.
• the sleeve 20b and end cap 20c may be of mild steel brazed on the ends of the tube. It may be desired to use stainless steel swarf in some cases. Certain types of stainless steel (for example ASTM A304L and A316L) have specified carbon contents of 0.03% maximum. The application of graphite to the ends of the body of swarf in such cases may be particularly advantageous.
• the end pieces may be joined to the ends of the jacket in any suitable manner. They may be butt welded as shown in the drawings, for example by arc welding or friction welding. They may alternatively be pressed over or into the ends of the tube to form a seal therewith. It is of course necessary that the integrity of the seal be maintained during subsequent hot working.
• the jacket of a billet comprises a tube of 89 mm bore and 6 mm wall thickness.
• the tube is welded from ASTM A304L stainless steel plate. This tube is cut to a length of 85 cm. Open ended end pieces are used. Each end piece has the same bore and wall thickness but is welded from mild steel plate and is 75 mm long. The end pieces and the ends of the tube are chamfered and butt welded by an automatic arc welding process.
• the jacket is filled with briquettes pressed from mild steel swarf which has been cleaned and crushed into particles sieved to +3 mm giving an average size of finished shavings equal to about 7 mm.
• the density of the briquettes is more than about 85% of solid steel.
• the interfaces 24 of the briquettes may be provided with complemental interlocking protuberances and recesses to help prevent them from separating during rolling.
• Various sizes of flat bars have been rolled from these billets.
• the thickness of the cladding is remarkably constant and depends of course on the size of the end product. For example in a 40 mm x 6 mm flat bar the average thickness of the cladding is about 0.5 mm. Although in some cases there has been evidence of the formation of a limited amount of chrome oxide at the interface between the core and the cladding the bond therebetween is considered satisfactory for many applications.
• 30 cm diameter is therefore reduced from about 63 to about 58 .
• the billets are rolled to form finished products such as flats, sections and reinforcing rods.
• finished products such as flats, sections and reinforcing rods.
• similarly formed billets of the same or different size and shape may equally well be subjected to alternative hot working procedures such as extrusion or forging.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Metallurgy (AREA)
• Geochemistry & Mineralogy (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Materials Engineering (AREA)
• Environmental & Geological Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• Organic Chemistry (AREA)
• Geology (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Processing Of Solid Wastes (AREA)
• Pressure Welding/Diffusion-Bonding (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
• Superconductors And Manufacturing Methods Therefor (AREA)
• Powder Metallurgy (AREA)
• Breeding Of Plants And Reproduction By Means Of Culturing (AREA)
• Sealing Devices (AREA)
• Reinforcement Elements For Buildings (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

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Cited By (8)

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Citations (5)

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• 1990
  • 1990-09-19 AT AT90914215T patent/ATE146226T1/de not_active IP Right Cessation
  • 1990-09-19 DK DK90914215T patent/DK0501966T3/da active
  • 1990-09-19 CA CA 2066564 patent/CA2066564A1/en not_active Abandoned
  • 1990-09-19 AU AU64316/90A patent/AU659601B2/en not_active Ceased
  • 1990-09-19 KR KR1019920700646A patent/KR100202439B1/ko not_active Expired - Lifetime
  • 1990-09-19 ES ES90914215T patent/ES2097761T3/es not_active Expired - Lifetime
  • 1990-09-19 EP EP19900914215 patent/EP0501966B1/en not_active Expired - Lifetime
  • 1990-09-19 DE DE69029401T patent/DE69029401T2/de not_active Expired - Fee Related
  • 1990-09-19 JP JP51331990A patent/JP3256762B2/ja not_active Expired - Lifetime
  • 1990-09-19 WO PCT/GB1990/001437 patent/WO1991004346A1/en not_active Ceased
  • 1990-09-20 ZA ZA907516A patent/ZA907516B/xx unknown
• 1991
  • 1991-03-14 TW TW80102039A patent/TW201278B/zh active

Patent Citations (5)

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