The technological process of hot welding consists of the following: I - Preparation for welding products; II - pre-heating parts; III - Welding; IV - subsequent cooling.
Preparation for welding depends on the type of the corrected defect. However, in all cases, the preparation of the defective site is thoroughly cleaned of dirt and cutting to form cavities that provide access to manipulate the electrode and the arc is struck. To prevent leakage of flowable metal weld pool, and in some cases to make the weld metal, the corresponding form, weld position is formed. Forming perform three depending on the size and location correct flaws with the graphite plates, held together forming a mass consisting of quartz sand, zameshennogo liquid glass, or other molding materials, as well as in flasks molding materials used in the manufacture of Lisino.
After forming the needed drying forms a gradual increase in temperature from 60 to 120 ° C, then spend a further heating of welding at a speed of 120-150 ° per hour v.pechah, furnaces or temporary heating devices. Slow cooling after welding is achieved by insulating layer harboring products (sheets of asbestos and backfilling with sand, slag or other) or by cooling with the furnace, furnace. Methods of heating and heating devices are used depending on the nature of production (elimination of casting defects, repair welding, etc.). For example, in mass production in the foundry of automobile and tractor plants should be used conveyor furnace for maintenance work easy heating in muffle furnaces or furnaces with an open hood, and for one-time repair of large products manufactured temporary heating devices of refractory bricks, including the furnace -holes in the earthen floor of the shop. Welding using a consumable electrode and a rod of iron grades A or B.
The composition of coatings deposited on the alloy rods with a diameter of 5-20 mm, are stabilizing and alloying materials. As the last typically use graphite, silicon carbide, ferrosilicon, calcium silicon, and other silikomagny containing elements - grafitizatory. Hot welding of cast iron can perform at high current (Isv = (60 - 100) de) without interruption until the end of welding defects, with larger amounts of brew defect two welders working alternately. Hot welding electrode to ensure good contact with the iron electrode and a shield to protect the welder's hands from thermal burns.
Hot welding of cast iron, you can use a carbon arc welding electrode. If possible, maneuvering the thermal effects on the base metal welding of carbon electrode is intermediate between gas welding and welding consumable electrode. Welded with direct current straight polarity carbon electrodes with a diameter of 8-20 mm. The diameter of the electrode and the power of the welding current is selected depending on the thickness of base metal as a filler rods are used. For transfer of refractory oxides in the low-melting compounds are used in the flux of boron-based, mostly technical anhydrous (calcined) borax.
Hot welding of cast iron by hand, especially bulky items - hard work. A very innovative way to facilitate labor and increase productivity - mechanized welding flux cored wire. The composition of such components of the charge is introduced, which allow to obtain the composition of the weld metal, which is cast iron.
Hot welding of cast iron produces weld joints, weld metal equivalent (in mechanical properties, density, workability, etc.), but this is time consuming and expensive process. At the same time, in some cases virtually welded joints of cast iron is not imposed such requirements. Often, for example, it is sufficient to provide only the strength balance or just a good workability and density of the welds. With the help of various metallurgical and technological means you can get welded joints of cast iron with certain properties when welding with low or no heating without preheating (ie, using for semi or cold welding).
See also:
Welding of Cast Iron
Composition and Properties of Iron
Marking of Iron
Basic Information on Weldability and Technological Advice
Structural Transformations in the Heat Affected Zone during Welding of Cast Iron
Effect of Cooling Rate on the Structure of the Weld Metal and Heat Affected Zone
The Technological Process of Hot Welding
Cold Welding of Cast Iron with Simple Electrodes
Cold Welding Electrodes, Cast Iron, Providing the Receipt of the Weld Metal Color
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