φ12×9.19mmG105钻杆NC50内螺纹接头直角台肩根部裂纹原因分析
φ12×9.19mmG105찬간NC50내라문접두직각태견근부렬문원인분석
An Analysis of the Cause of the Crack in the Base of 90° Shoulder of NC50 Screw Joint of ψ127×9.19mm G105 Drill Pipe
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