Groove of steel pipe

　　Definition: According to the design or process needs, the weldments to be welded processed and assembled into a certain groove geometry, called groove.
　　Purpose: the open groove is to get all of the weldment thickness penetration welds. Groove is primarily for welding parts, to ensure the welding degrees, with machining methods machined-surface under ordinary circumstances, can also be gas cutting when requirement is low (if it is A class of welds, ultrasonic testing required, you can only use the machine processing methods), but need to remove the oxide slag.
　　Common groove forms are: butt groove and angular contact groove (on the project in order to distinguish the butt corner joints and general butt welds, now divided into docking, pick bevel, fillet three categories).
　　Butt groove mainly: I type, V-type, X-type, U-type, Y-type, UV type, VV type, etc.
　　Fillet groove are: T-type, lap, J type, etc.
　　Welding groove criteria:
　　CB 1220-1993 921A, 922A steel welding groove basic types and sizes
　　CB / T 3190-1997 hull structure welding groove types and sizes
　　GB 985-88 welding, SMAW basic form and GMAW weld groove basic types and sizes
　　GB 986-88 submerged arc weld groove basic types and sizes
　　Welding groove index
　　1, Appearance: no cracks, delamination, inclusions and other defects
　　2, Size: as required examination direction drawings and WPS, angle, blunt edge, set gap
　　3, low-alloy steel material Rm≥540Mpa and Cr-Mo steel bevel should be in accordance with JB / T4730.4-2005 to do MT detection.
　　4, non-ferrous and stainless steel bevel with special requirements on the drawing should be carried out to do PT detection.

　　5, the slope of the base metal surface on both sides of the mouth, at least within the range of 20mm should remove the descaling, oil, slag and other harmful contaminants