Welding of Rails by Gas Pressure Method (Report 2)

Abstract

Earlier the authors reported the results of bending test on the rails welded by gas pressure method. The present report deals with elaborate examinations subsequently carried out.
The flash-butt process has been widely practised on the National Railways with nearly satisfactory results; some comparison of results is made here between this process and gas pressure method. Heat treatment after pressure welding is not also made in the tests reported.
First, hardness, structure etc have been investigated of important spots in the tread of rail top or the interior.
The results show that weldes as such are perfect ; especially in the pressure welds, there are no decarburized layer observed. But picric etch has revealed that actual grain sizes are considerably coarse, particularly at the base.
Next, tension, charpy, Matsumura's repeated impact and Schenk type repeated bending specimens were take test the mechanical strength of each part. In the tension test, all specimens except one broke in the mother part, with tensile strength proving to be higher than that of base metal and to be distri. buted generally even for each area. The impact value of base metal was found unexpectedly low ; individual comparison showed that pressure welds had had sometimes higher impact values, but in the aggregate, more often had lower values. Repeated impact value for the tread of rail top was in general satisfactory, i.e. as high as that of base metal; but at the base it fell to 64.7% of that of the latter.
In the Schenk test, 15.5% lower than of the top of pressure welded rail gave a fatigue limit (45 kg/mm2) 15.5% less than that of mother metal against 28.5% less for both ends of the base and 22.2% less for the centre of the base.
Lastly, the full size specimenss of pressure welded rail with stood a rotating fatigue test under working loads up to 2, 000, 000 loadings without starting any crack and now tliey are being put to the field test.