A high strength weldable seamless tube of low alloy steel containing 0.24 to 0.28 percent carbon, 1.30 to 1.50 percent manganese, 0.15 to 0.35 percent silicon, not more than 0.01 percent sulphur, not more than 0.03 percent phosphorous, not more than 0.20 percent copper, 0.13 to 0.20 percent chromium, 0.15 to 0.60 percent molybdenum, 0.007 to 0.05 percent of aluminum, not more than 0.02 percent nitrogen, 0.02 to 0.04 percent titanium, 0.0007 to 0.0025 percent boron, 0.02 to 0.10 percent niobium, and the balance iron. The tube is preferably heated to an austenization temperature of about 1,670.degree. F. and simultaneously internally and externally quenched by a special process that provides for high internal cooling rates followed by tempering at about 1,050.degree. F.