Experimental methods of hydrogen testing to prevent Hydrogen Assisted Cracking (HAC) during the Submerged Arc Welding (SAW) process

One of the main problems associated with the welding of ferritic steels is that of hydrogen assisted cracking (HAC), popularly known as cold cracking or delayed cracking. As the name suggests, it is caused by hydrogen present in the weld metal. One of the methods to mitigate this type of cracking is to control and minimize the amount of diffusible hydrogen content in the welds. This in turn calls for standard test methods to measure diffusible hydrogen present in weldments made with different welding consumables, processes etc. The methods employed to measure hydrogen vary from simple manometer to sophisticated mass spectrometers and sensors. The present volume of this paper highlights identification, causes and factors responsible for hydrogen cracking. Each factor influencing the risk of hydrogen cracking is described in detail with clear figures and mathematical formulation. Different methods of measurement of diffusible hydrogen and methods of hydrogen testing are also covered. The paper explains the welding procedure of hydrogen testing using SAW (submerged arc welding) process. T

[...] The main source of hydrogen is the moisture present in the flux coating of the welding electrodes in the case of shielded metal arc Hydrogen cracking can happen during various manufacturing operations or operational use, anywhere where the metal comes in contact with atomic or molecular hydrogen. Processes which can lead to this include cathodic protection, phosphating, pickling, and electroplating. A special case is arc welding, in which the hydrogen is released from moisture (for example in the coating of the welding electrodes; to minimize this, special lowhydrogen electrodes are used for welding highstrength steels). [...]

[...] In stead of 24 hours, it is only 6 hours with gas chromatography and is almost instantaneous if the arc hydrogen sensors are used. Instead of diffusible hydrogen content which requires separate specimen preparation and long time completion of measurement, hydrogen in the welding arc would be used as a parameter to assess the susceptibility of the weld to cracking and with the helpof intelligent welding systems, welding parameters would be suitably altered to prevent cracking REFERENCES: [1]Jewett, R.P. (1973), “Hydrogen Environment Embrittlement [...]

[...] As the main source of hydrogen is the flux coating in the welding consumables, the unit used to represent the value of Hd is ml / 100 gm of weld metal. High-strength and low-alloy steels, nickel and titanium alloys are most susceptible Steel with an ultimate tensile strength of less than 1000 MPa or hardness of less than 30 HRC are not generally considered susceptible to hydrogen cracking. The tests have shown that aluminium and beryllium copper alloys are some of the least susceptible to hydrogen cracking along with few other metals IDENTIFICATION: VISAUL APPEARANCE HYDROGEN CRACKING Hydrogen cracks can be usually have the following characteristics: 1. [...]