Heat Treated Drill Pipe Welds for Impact Toughness
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Solution Overview
Problem
Existing drill pipes face challenges with impact loading and bending stresses, particularly at the interface between the tube body and tool joints, leading to potential fatigue damage and premature failure due to differences in material properties and welding characteristics.
Innovation Solution
A heavy weight drill pipe is designed using a tube body of AISI 1340 alloy steel with tool joints made of AISI 41XX series alloy steel, where the weld lines and surrounding regions are heat treated to enhance Charpy impact toughness and strength, specifically through austenitizing, quenching, and tempering processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tool joints are welded to the tube body, then the drill pipe can be assembled with tool joints, but the weld line and surrounding region have lower impact toughness and strength compared to the base materials
Solution Approach 1:
The patent applies heat treatment (austenitizing at 1550-1700°F followed by tempering at 1200-1300°F) to the weld line and surrounding region, changing the thermal parameters to transform the microstructure and improve mechanical properties. This parameter change resolves the contradiction by making the weld region's impact toughness and strength comparable to the base materials.
Solution Approach 2:
The heat treatment is performed as a preliminary action after welding but before the drill pipe enters service. This preliminary treatment modifies the weld region's properties in advance, ensuring it has sufficient impact toughness and strength before experiencing operational stresses.
2Strength
If heavy weight drill pipe is used to reduce impact loading, then bending stresses on drill pipe are reduced, but the complexity of manufacturing increases due to heat treatment requirements
Solution Approach 1:
The heat treatment is applied locally to the weld line and surrounding region rather than the entire drill pipe. This localized treatment achieves the necessary quality improvement where needed (at the weld) without unnecessarily complicating the manufacturing of the entire component, thus resolving the contradiction between strength improvement and manufacturing complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The heat treatment significantly increases the yield strength and Charpy impact toughness of the weld lines and surrounding regions, matching or exceeding those of the tube body, thereby enhancing the drill pipe's resistance to impact and bending stresses and minimizing the risk of fatigue and premature failure.
Implementation Method 1
The heat treatment may include austenitizing the weld line and/or the surrounding weld region by heating to a temperature of at least 1,550° F. (843.5° C.), quenching, and tempering
Implementation Method 2
austenitizing the weld line and/or the surrounding weld region by heating to a temperature of at least 1,550° F. (843.5° C.), quenching, and tempering
Implementation Method 3
austenitizing the weld line and/or the surrounding weld region by heating to a temperature of at least 1,550° F. (843.5° C.), quenching, and tempering by heating to a temperature of at least 1,200° F. (649.0° C.)
Data Source
AI summary
A heavy weight drill pipe may include a tube body formed of AISI 1340 alloy steel, and first and second tool joints at respective ends of the tube body, and which are formed of an AISI 41XX series alloy steel. The first and second tool joints may be welded to the tube body at a weld line within a weld region. A Charpy impact toughness at the weld line or surrounding weld region may be least 12 ft-lbs. (16.5 N-m). Yield and tensile strengths at the weld line or weld region may be at least 65 ksi (448.0 MPa) and at least 106 ksi (731.0 MPa), respectively. Material properties at the weld line or weld region may be achieved by heat treating after welding. Heat treating may include austenitizing, quenching, and tempering the weld line and/or the surrounding weld region.