Drill Collars and Bore 1) AISI 4145H Drill Collars Modified Alloy Steel, forged, heat treated to API requirement, round tubes withlower sulfur and ... feet length, ID 2 13/16" to 3" 2) AISI 4145H Solid Round Bars Modified Alloy Steel, forged, heat treated to API ... manganese austenitic steel, forged, heat treated to API requirement,solid round bars with lower sulfur and phosphorous content to meet sour ...