Weld metal alloying | Alloy transition coefficient

The alloying of the weld metal is the process of transitioning the required alloying elements into the weld metal through the welding material. There are two types of alloying methods: direct transition and indirect transition. Alloy welding wire or strip electrode, flux-cored wire or flux-cored electrode, alloy coating or bonding flux, and alloy powder can be added to the weld metal. Indirect transition to the weld metal by displacement oxidation. In the actual welding process, it can be selected according to specific conditions and requirements. In order to explain the level of utilization of alloy elements in the welding process, the concept of transition coefficient is often cited, and its expression is as follows:

η = CF / CT    (3-2)

η  ——transition coefficient of alloy element,%;
CF——content of an alloy element in the weld metal;
CT——The original total content of this element in the electrode.

The greater the affinity of alloying elements for oxygen, the easier it is to oxidize and lose, and the smaller the transition coefficient. Properly increasing the particle size of the alloy element can reduce its contact area with oxygen, thereby reducing burnout and improving the transition coefficient. When the acidity and alkalinity of the alloying elements are consistent with the slag, the transition of the alloying elements is facilitated. In addition, adding a deoxidizer with stronger deoxidizing ability than the alloy element in the coating and flux composition, and adjusting the welding process parameters (such as using short arc welding) can increase the amount of alloy element transition.