Cast iron technology is an extremely difficult and important technique. Usually, this method is only used for repair, not to connect details to each other. Cast iron not only requires high welding techniques and must adhere to safety rules to avoid causing technical errors. Here are some easy to follow tips as well as tips when using welding machines
Difficulties when welding cast iron:
Firstly: The plastic deformability of cast iron is very low. In the towing chart of the cast iron, there is almost no significant deformation.
Second: Cast iron is very sensitive to heat, so it is easy to change the organization during the welding and the process of cooling after welding. Because of the large cooling speed of the cast iron, the weld and the metal are easy to form, making the white cast iron with high hardness (up to 800HB) easily cracking the weld.
Third: Cast iron products are very diversified in terms of chemical composition, organization. It is difficult to accurately determine the welding mode and heat processing mode.
Fourth: cast iron liquids have high dilution properties, hard to solder in another posture.
The type of welding process to apply:
Cold process: Sold separately short 2-3 cm then cool to touch the weld before tig and arc welding machine running. The welding sequence should be applied in reverse or symmetric welding.
Hot process: The heating up to 600-650 ° C phase temperature and simultaneously keep heat in the welding process. After welding, it is necessary to slow down the solder (120 ° C / s) in the furnace or by insulating cover (difficult to carry with large structures).
Additional tips for hot welding process is to heat the iron to be soldered to see the tomatoes are ripe tomatoes (tips dry pine wood swept on the place where the baked canker saw is flying).
Choosing the right materials for cast iron: Normally, cast iron requires very high plasticity, so the nickel content in it is very high, up to 90%
Should choose welding rod and welding mode, the most common type of welding rod is copper welding rod, innox welding rod. The best way to do this is to use a copper nickel alloy rod and use a carbonized tip to compensate for the carbon content of the cast iron.
For cracked surface we can still weld with special welding rods.
Kind of welding rods: Eutectic 240 (Welding rod and fill for cast iron)
Sources of welding: AC / DC +
Ingredients: Ni Fe Mn C
Tensile strength: 55 000 psi (380 MPa)
Some techniques, experience when welding cast iron:
Due to the hard and brittle cast iron, the excess residuals in the cast iron are quite large, the cracks will continue to grow during use and especially during welding. Therefore, in order to prevent further rupture break, it is common to block the two ends of the crack before welding. The next step is to use the order of welding from the beginning of the crack to the point where they meet. Finally, proceed with welding the holes.
With large details, we can go to brake (ie create the same V-groove steel welding) then machining the threaded hole can be threaded holes 6, 8, 10 … as depending and try as much Good order in sequence. Come here and take the bolts in and cut off (remember to excess 5 to 10 mm so that we will welding on it).
Thanks to the addition of the excess bulb bulge and have eaten in the details of the welding process will be much better and better texture (by this time we will weld both cast iron and steel that will be easy to solder).
When welding the cast iron must be performed in the environment separated from the wind if not the process of burning and welding will occur the phenomenon of separation, cracking.
With high rigidity details, it is possible to carry out local heating (cross section) instead of heating it completely. The purpose of preliminarily heating is to enable the metal to be welded and adjacent to the metal to have a baking rate and to cool evenly, avoiding cracking due to heat stress.