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SURFACING VATERIALS
The main advantage of  the technology for manufacture of the  flux-cored strips is elimination of the drawing process. A sheath is formed and a filling  powder is compacted by rolling, which is less  power consuming and allows the use of a strip sheath with lower ductile properties.

At  present, the annual production of the flux-cored  strips in the CIS countries makes up about 25% of that of self-shielding flux-cored wires for cladding.

The flux-coed strip whose design is shown in Fig. I received the widest commercial application. Existing equipment makes it  possible to manufacture  three standard sizes  of the  flux-coned strips, i.e. with the 16.5x4.0.15.0x4.0 and 10.0x3.0 mm sections. The flux-cored strips are supplied in bundles with the row  arrangement having  the inner diameter of 400...460mm.the  outer diameter of up to 850mm and the width of 155...130mm. Mass of one bundle is 100...150 kg. reliable sealed joining of the flux-cored strips, their delivery in massive bundles ensure  continuous high-efficiency cladding, this being especially important for strengthening of large-sized

Flux –cored strip cladding can  be   performed both by the  open –arc and submerged-arc processes. flux-cored strip submerged-arc cladding does not practically differ from submerged-arc welding using electrode  materials other than the  said ones. Standard  sizes  of    the flux-cored strips, cladding   conditions and flow charts are  selected depending on a standard size of a part to be strengthened. Cladding  can  be carried out in one, two or more layers, by single beads or by wide layers, with the amplitude of weaving from 50 to 400 mm. here, cladding current can vary  from 300 to 1200 A, arc voltage-from 25 to 38V and electrode speed ranges from 5 to 100 m/h Twin-arc or multiarc  cladding can be  used to raise deposition efficiency, this being ensured by the specials zed equipment. One –pass single-arc cladding provides deposition of a wear-resistant  layer from 2 to 8 mm thick. Deposition efficiency in flux-cored strip single-arc cladding reaches 25...30kg of deposited metal per hour.

Consumption of the flux-cored  strip  per kg of deposited metals is 1.1-1.2 kg, providing the powder filler contains easily evaporating components, and 1.1-1.35 kg-in case of mineral components.

Mass produced welding equipment fitted with additional specialized nozzles and feeding rollers providing the reliable feed of the electrode material is used for flux-cored strip cladding. The self-shielding flux-cored strips combined with the mass produced equipment are used for the processes of strengthening the cone crusher lines, bulldozer blades, cement pump sleeves, coke crusher rolls, grinding fan  blades and other pieces operating under the conditions of intensive abrasive and gas-abrasive wear.

Advantages of the flux-cored strips are best realized in cladding the mass-production pieces. In this case the original  processes using the specialized equipment are employed for strengthening.

One of  the examples of such comprehensive approach to solving the problems of strengthening is cladding the sheets from 5 to 15 mm thick. The specialized cladding machine –380 is used for these purposes. It consists of a carriage  with   two welding heads that moves along a guide and of two tables fox fixing a street sheet measuring 2600 [ 1400 mm. the carriage can be displaced at working and travel speeds. The machine is equipped with two power supplies having flat volt-ampere characteristics.

 The self-shielding flux-cored strip is used as an electrode material providing the following  composition of deposited metal:C-4.5%.Cr-30.0%.Mo-1.0%. The deposited layer has the 60 HRC hardness.

The 10.0x3.0mm flux-cored strip is used to clad sheets from 5 to 7 mm trick and the 16.5x4/0 mm one –to clad sheets from 8 to 15 mm trick.

The machine is controlled from the microcontroller-based circuit diagram that allows two programs of sheet cladding.

The first program provides for deposition of beads along a sheet being clad by displacing the arc in the both directions and by interrupting it at the extreme positions when going over to another deposition pitch. After displacement by a deposition pitch. the arc is automatically  ignited and  moves to the direction opposite to that  of the preceding bead. The value of a deposition pitch is controlled by the electronic unit. This program is applied for cladding the sheets 8 mm and thicker.

The  second program intended  for cladding the 5...7 mm trick sheets realizes deposition of beads along a sheet being clad by displacing the arc only  in  one direction in order to decrease the penetration depth of base metal. Electrode is returned to  the initial position at the uplifted freed  mechanism without arc burning. Displacement by a deposition pitch is made in one of extreme positions preset by the program. In this case the value of a deposition pitch is also controlled by the  electronic control unit.

The machine allows cladding to be performed in the automatic mode following the set program on the two tables successively, the  productivity being 1 sheet measuring 2600x1400 mm per shift in twin arc cladding. The sheet cladding machine and a strengthened sheet are shown ,respectively Bimetal sheets produced by layout, cutting and bending can be readily transformed into a wide  range of products for  various metal structures, making the service life of the latter several times longer.

Another example of the wide application of the flux-cored strips for wear-resistant cladding is the process for strengthening   the coal crushing mill hammers.

The hammers are clad using the specialized machines-877The machine -877 consists of a  cladding apparatus. Apparatus, a rotating table and of 5 water-cooled moulds  mounted on it, wherein the hammers to be clad are placed. Cladding of  the hammers is carried out in the  automatic mode with electrode weaving over the entire width of a piece being clad. One machine can provide cladding of 100-120  hammers per shift.

Cast billets of low –carbon steel can be clad using the    PLAN-T 101  flux-cored strip providing a deposited layer of the following chemical composition:C-3.0%,Cr-25.0%,Si-3.0%.Ni-2.0%.Mn-2.0%. One hammer is clad with 1/6-1.8 kg of a wear-resistant alloy. Application of this technology and  of the flux-cored strip as an  electrode material allowed the 2 timer increase in the service life of the strengthened products, as compared to the earlier used all-cast Had field  steel   hammers.

An example of utilization of  the flux– cored strip for strengthening metallurgical production parts is  cladding of blast furnace charging apparatuses. The unique machines –50 and –75 (Fig.7) were  developed for one-or two-strip wide-layer cladding of cones and cups of the charging apparatuses. The said machines comprise  manipulators having capacities of 50 or 75 t and  a movable column with a specialized cladding  device mounted on it. The latter provides electrode weaving with an  amplitude  from 50 to 500 mm, while the manipulator displaces  a  work piece   by a deposition pitch. The designs of the machines provide also for circumferential cladding and welding of large-sized pieces by the open– arc and submerged-arc processes   using the flux-cored or solid-drawn wires. Circuit diagrams of the machines are microcontroller based.

Mechanized self-shielding flux-cored strip cladding of cones and cups is 4 times as productive as the process of flux-cored wire cladding.

Positive results were obtained also in strengthening of the cone-free   charging apparatuses for blast furnaces  using the flux-cored strips. We developed the process for cladding the fast-wearing parts of chutes and other elements of the charging apparatuses designed by the “Paul Wurt” Company (Luxemburg)

The flux-cored strips found application also in strengthening the wide ranges of parts of mining equipment. This electrode material  is used for strengthening of bulldozer blades, cone crusher liners, grinding fan blades and many other parts operating under the intensive abrasive wear conditions
 
Категория: English | Добавил: als2007 (25.06.2007)
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