Introduction to nickel-based alloy steel electrodess—electrodess-coated electrodes

1.Suggestions for welding material selection：

  The selection of nickel-based welding materials mainly depends on the alloy composition of base metal, the application properties of workpieces, the design type of workpieces, working temperature, environmental corrosion and other factors to select suitable welding materials and welding methods.

  According to the classification of specifications and class numbers of AWS A5.11 "Code for Arc Welding of Nickel and Nickel Alloy Shielded Metals", the classification is based on the main components of dissolved gold. The information of tensile strength grade will not be displayed on the specifications. The welding current of such materials is mostly DC (+) design, and a small part ：

2.Key points of welding operation：

(1)Storage management of welding rod：

①The welding rod shall be stored in a relatively dry warehouse to avoid excessive moisture absorption caused by the simultaneous existence of high humidity (≥ 80% R.H) and high heat (≥ 30 ℃).

 

②Before use, it must be dried at high temperature and placed in a heat preservation barrel or low-temperature oven on the construction site. It shall be stored at 100 ~ 150 ℃. A small amount of it shall be taken each time to reduce the moisture content of the weld and avoid the problem of weld channel pores. Please refer to the instructions in the appendix for drying conditions.

 

 

(2)Precautions for welding：

①Before operation, clean treatment shall be carried out at the welding part and the workpiece part within 50mm around it to avoid cracks or pores caused by weld pollution.

 

②The core wires of nickel-based coated electrodess are all made of nickel alloy, with slow heat conduction speed and high expansion coefficient. Therefore, excessive welding current will cause the resistance heat of the core wires to become higher, causing the coated electrodes to generate red heat and fall off.

 

③The fluidity of molten iron in nickel-based alloy is poor. For example, if the rod is transported by weaving, the weaving amplitude should be less than 3 times of the rod diameter; It is also necessary to avoid the phenomenon of hot cracking of electrodes caused by excessive heat input, especially at the position of finishing pit

 

④The arc starting point of butt slotting welding is recommended to move the arc to the position of the welding starting point after arc starting is done on the slotting surface; It is suggested to stop the filler at the finishing pit before breaking the arc, so as to avoid excessive cracking of the pit; The finishing pit of the previous electrodes must be ground clean to avoid cracking, slag inclusion, air holes and other problems.

 

⑤Short arc welding shall be maintained to avoid air holes caused by water vapor and nitrogen dissolving into the welding channel; The arc force is usually weak, so attention should be paid to the matching of arc and molten iron flow to avoid poor dissolution or slag inclusion.

 

⑥ The arc starting method shall be handled by the "forward and backward method", i.e. the arc starting point shall be located about 1 ~ 2cm after the welding point. After arc starting, the "forward method" shall be used to bring the arc forward to the welding point for welding operation, so as to eliminate the air hole problem at the welding point.

 

⑦There is no need to preheat during welding, and the temperature between tracks is suggested ≤ 150 ℃.

 

⑧ Welding slag is usually thick and needs to be cleaned to avoid slag inclusion. Steel wire brushes must be made of stainless steel and avoid sharing with other materials.