High performance material for coiled tubing applications and the method of producing the same

A coiled steel tube having improved yield strength and fatigue life at weld joints of the coiled tube, the coiled steel tube comprising:

• a plurality of strips welded together end to end by a bias weld and formed into a coiled steel tube, each of the plurality of strips having base metal regions, bias weld joints, and heat affected zones surrounding the bias weld joints, each of the plurality of welded strips comprising:
• a yield strength greater than about 80 ksi;
• a composition comprising iron and:
• 0.17-0.35 wt. % carbon;
• 0.30-2.00 wt. % manganese;
• 0.10-0.30 wt. % silicon;
• 0.010-0.040 wt. % aluminum;
• up to 0.010 wt. % sulfur;
• and
• up to 0.015 wt. % phosphorus;
• and
• wherein the coiled steel tube has a final microstructure formed from a full body heat treatment applied to the coiled steel tube;
• wherein the final microstructure comprises a mixture of tempered martensite and bainite;
• wherein the final microstructure of the coiled steel tube comprises more than 90 volume % tempered martensite in the base metal regions, the bias weld joints, and the heat affected zones;
• wherein the final microstructure across all base metal regions, bias weld joints, and heat affected zones is homogeneous;
• and
• wherein the final microstructure comprises a uniform distribution of fine carbides across the base metal regions, the bias weld joints, and the heat affected zones.