FORMATION OF AN INADEQUATE FUSION (weld fins) REASONS AND PREVENTIVE MEASURES.
Ajay K Singh
CEO at Ora India Pvt Ltd, An Alumino-Thermic Portion manufacturer for Rail Welding, approved by Research Design & Standard Organisation(RDSO), Ministry of Railway, Gov. Of India
#thermit002 FORMATION OF AN INADEQUATE FUSION (weld fins) REASONS AND PREVENTIVE MEASURES.
As I have mentioned in my previous article 001, the types of weld defects which influence the weld service life. My friend Mr. #Amitkhapre has once posted a picture and the article is based on it.
The most and very common thermic weld defect is inadequate fusion on the surface of cold rail. In this point flash butt welding has an advantage over AT welding as mould is not used in FB.
FIG:1
i). How and where inadequate fusion for weld fins forms:
?Weld fins can often be found at collar toes in the rail base and are caused by inadequate fusion between weld metal and the surface of rail ends. Fig 1 shows a weld fins defect through out head to web profile and web to foot profile. These two junction location are vulnerable for fatigue cycle. ?The weld fins caused by the improper adjustment between weld mould and rail surface. It can occur even at the locations where the proper mould adjustment to the rail surface. Weld metal profile and rail gap play a significant role to avoid serious weld fin.
领英推荐
?These influence the weld fins formation.
i). Preheating time and molten metal temperature.
?It can be seen with an increase in preheating time. The fusion depth increases and molten metal temperature is in a term as antagonistic with preheating time for better fusion depth. If both term are synergistic and in decreasing in order then its favor to increase weld fins depth.
ii).?Weld gap and weld profile dimension of mould.
?The fusion depth does not vary substantially with weld gap width. The variation of fusion depth with weld gap is very small, only for the high molten metal temperature can a little increase in rail end fusion depth.
In short, ?a smaller weld metal profile is more favorable for weld fins avoidance. By reducing the weld metal dimension, the minimum requirements on both preheating time and molten metal temperature to avoid weld fins formation can be much reduced.
Welcome People who have done more research in this field or having knowledge regarding this topic ??may suggest their opinion and add here how to control weld fins and increase the weld service life. ?
Thermite welding Technician/Technicien soudure aluminothermique chez Railwel ( Now Pandrol )(Railtech Intl. Delachaux)
3 年Do I understand that what you call " fin" is an overlap of metal over the outside of the gap, similar or where flashing would be. I cant see the photo clearly.. Unless there are problems with the manufacturing of the welding charges, conservation, or at time of use, the temperature of the molten metal must be quite stable. Therefore, a preheating problem is to be suspected. In your previous article, the weld defects illustrated can all, in my opinion, be linked to the preheating. Even with a 25 to 28mm gap, an excessive preheating can produce a melted zone excessivly wide that, when cooling, will produce defect at weld center. I do not know if it is the case here, but these defect are very easy to obtain with oxy propane. When starting with a 25mm gap, the melted zone at the mid height of the web should be just a bit wider than the 25mm gap. Penetration was more than that, but the weld as it cools, shrincks and pulls the rails together a bit.