กรณีศึกษา Case welding - Repairing Railway KTMB Malaysia railway
CUSTOMER: KTMB Malaysia railway
MAGNA - Repairing Railway Manganese Frog
- A. For welding of Austenitic Manganese Steel Points and crossing ,
M402 to be used and welding to be carried out without preheating and at relatively
low temperature ( interpass temperature shouldnot go above 100 deg C ).
The procedure for welding of Austenitic Manganese Steel will be like this –
(a) Give a buffer layer of MF100, M303 Gold . Welding to be done in relatively cold
condition and interpass temperature should preferably kept below 100 deg.C. Small amount
of welding to be done in one place in a staggered way and then welding to be done in
another place away from the previous place to avoid any heat build up. The crater of
each bead should be minimised by using a slight back step welding to cover the crater.
Good cleaning of slag is necessary . Use DC electrode positive polarity , use current in the
middle of the range . Use stringer to slight weaving bead with weaving not more than 3
times the diameter of electrode. Use of 4.0 mm is preferred.
(b) The build up and surfacing layers to be given with M402 , preferably with 4.0 mm
and in the same way like buffer layer with welding in small areas and going to other area
to avoid heat build up . Interpass temperature should preferably below 100 deg. C. Use DC
electrode positive polarity and medium current range and use stringer to slight weaving like
what is used for M303g .
(c) After welding of each layer , use light grinding and carry out LPT to check any defect in
each layer and then proceed for welding of next layer ( if possible )
For any further information / clarification , please feel free to contact us.
In case of major welding of crane lines by arc welding the following procedure may be adopted
(a) The gap between straight rail ends ( made by SAW Cutting or Grinding )
ends to be joined should be 15- 20 mm.
(b) The ends to be joined are raised 1.5-2.0 mm to avoid shrinkage or distortion
(c) Place a copper block at the bottom of the steel backing plate to extract heat faster
from bottom side. .( Fig 3 )
(d) Put a small mild steel strip of around 5 – 6 mm thick as backing bar below the gap.
Fix the backing plate with welding by M305 in the foot ( Fig 3 )
(e) Preheating of around 250 -350 deg. C. It is better if the preheat can cover around 100 mm
from each end. The preheating requirement is dependent of Carbon content . For medium
carbon steel rails the preheating temperature can be 250 -300 deg C and for high carbon steel
rails preheating temperature can be 300 -350 deg C.
(f) Use M305 , 3.20 or 4 mm and make the runs in the foot ( bottom part ) . Remove the slag
and clean the pass well if required by light grinding. Avoid any notch or undercut. Keep
interpass temperature of 250 -350 deg. C . Give 1st run on one side – 2nd run on other
side and 3rd run ( if reqd. 4th ) in the middle and complete the foot welding in the same manner.
(g) Then put suitable sized copper blocks in web ( middle ) and head ( top ) portion . The joint
looks like a smallmould within which the welding goes on . Here the welding to be continuously
done in squared pattern – the run will start from one side (side 1 ) – take 90 degree turn and continue
welding in the side( side 2 ) - take 90 deg turn come to the other side of the rail (side 3 ) – complete
welding on that side – take 90 deg turn the electrode to the remaining side ( side 4 ) as so on. The
slag formed inside to be quickly removed from the mould by suitable brush ( can be done by removing
copper block of one side quickly – removing the slag and then quickly refitting the block and then starts
welding again ) . Care should be taken that the welding should not be done on copper blocks. . Maintain
interpass temperature during welding in the range of 250 – 350 deg C
(h) In last 3 layers , you can give deposit of M405 .Sequence of welding inside mould is shown in
(i) Then a stress reliving treatment is given while the weld is hot – heating the welded part to 600 - 650
deg C for 10 minutes by electrical heaters ( weld plus around 100 mm in each side ) followed by
immediate insulation of the area by insulating pad / asbestos cloth.
After that a final inspection to be done – remove all notches , sharp corners etc. by light grinding. The bottom
part to be checked by a mirror to find out such defects.
THIS IS STANDARD PROCEDURE OF RAIL WELDING FOLLOWED IN DIFFERENT PARTS OF WORLD
( NOT WITH MAGNA ELECTRODES BUT WITH OTHER ELECTRODES - In above procedure we had
given the suitable Magna Product combination of M305 & M405 in case you have to do such
conventional procedure welding. )