OCTOBER 19-20, 2012 - YMCA University of Science & Technology

Proceedings of the National Conference on
Trends and Advances in Mechanical Engineering,
YMCA University of Science & Technology, Faridabad, Haryana, Oct 19-20, 2012
(b)
(b)
Fig. 1: (a) Dimensions of two plates used for welding (b) Actual picture of welded plates.
60 0
1.6mm
10mm
110mm
110mm
Fig. 2: Edge preparation (all dimensions in mm).
2.2. Nitriding
Initially the specimens was pickled or chemically descaled in a solution of nitric and hydrofluoric acid. The
process was done to remove the tightly adherent oxide layer from the surface of the specimen. Electrically heated
furnace with stainless steel pot was used to carry out the processing. Base salt was filled up in the pot and heated
to 560 - 570°C. After the aging of 24 hours to saturate the pot, the bath chemistry was checked and brought to
normal by the addition of regenerator salt. Then the bath was ready to use. The components were pre heated for 1
hour at 300 – 400 0 C, degreased and soaked in the furnace for required time durations. Then the specimens were
kept in salt bath for required soaking time. Afterward the specimens were quenched in oxynit. After quenching,
the components were washed in hot water. The specifications of liquid nitriding are shown in Table 2.
Table 2: Specifications of liquid nitriding.
Pre-heating temperature
300-400 o C for 1 hour
Loading temperature
560-570 o C
Soaking time
55-65 mins
Quenching media
Oxynit
Total time
2.5 hours approx.
Tempering temperature
145-155 o C
Soaking time
115-125 mins
2.3. Carburizing
The chief carburizer (Table 3) for solid case carburizing were activated charcoal grains of 3.5mm to 10 mm in
diameter, coal semi-coke and peat coke. Carbonates were added to the charcoal to accelerate the carburizing
process. They included barium carbonate (BaCO 3 ) and soda ash (Na 2 CO 3 ) that was added in an amount from 10
to 40 percent of weight of the charcoal.
Table 3: Composition of solid carburizers.
Barium Calcium Sulphur Silica Moisture Volatile Charcoal
Carbonate Carbonate
matter
20 to 25% 3.5% 0.06 (max.) 0.5% 5.0% 10.09 (min.)% Remainder
605