The technique of welding armor varies only slightly from the techniques used in welding other alloy steels. Armor plate is essentially a high carbon-chromenickel- molybdenum alloy. Specifications for electrodes which produce successful welds on this highcarbon alloy include ballistic requirements, high weld strength, and good toughness, yet with sufficient ductility so that there is some flexibility under impact. The welds must also be relatively free of porosity and should have all these physical characteristics without preweld or postweld heat treatment.
Historical Background
During World War II, welding armor plate for the armed services became a critical issue for the United States, and the welding industry responded with the development of electrodes that would perform this job.
The carbon content of early armor plate ranged between 0.45 and 0.50%. Because of this high carbon content and the combination of alloys, a very difficult welding problem was presented. The solution seemed to be to weld with a 25% chrome, 20% nickel stainless steel electrode. This type of welding material was satisfactory; however, it became necessary to change because of a critical shortage of nickel and chrome.
The next electrode developed for welding armor plate was an 18/8 stainless steel, modified with 1.5% molybdenum, which was used until a shortage of molybdenum developed. A third electrode used to weld armor plate was a 3.5% manganese-modified 18/8 stainless. Some difficulties were experienced with the manganese-modified electrode, because root cracks would frequently develop when weld metal was deposited without preheating. This condition was not wholly caused by the electrode, since the high carbon content of the armor plate as well as poor fit-up in the root of the weld were contributing factors.
When the supply situation improved, the arsenals returned to a molybdenum modified 18/8 stainless and used that for most of the armor plate welding.
A ferritic type of electrode was developed for the welding of cast armor. This electrode was essentially a manganese-molybdenum-silicon alloy used primarily for the repair of cast armor while the castings were still hot in the mold. Since welding had to be done on castings other than in the mold, it was necessary to preheat them to a temperature of 200 to 315°C (400 to 600°F) prior to welding.