Drill Pipe Hardbanding With Low-Temperature DC Welding
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Solution Overview
Problem
Conventional hardbanding re-application methods for drill pipe tool joints in the oil and gas industry face challenges in maintaining the integrity of the internal polymer coating and achieving Rockwell hardness within industry specifications, often resulting in rejected tool joints due to high preheating and welding temperatures.
Innovation Solution
A method involving arc welding with direct current (DC) at a surface temperature of 50° F to 170° F, using a stringer bead weld zone with reduced heat affected zone depth, and optional cooling to control metallurgical phase and hardness, preserving the internal polymer coating and preventing excessive hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high preheating and welding temperatures are used during hardbanding re-application, then the hardbanding material can be properly applied to the worn surface, but the internal polymer coating deteriorates and base metal hardness exceeds specifications
Solution Approach 1:
The patent applies parameter changes by reducing the preheating temperature range to 70°F-170°F and welding temperature to 170°F-250°F, significantly lower than conventional high-temperature processes. This temperature parameter adjustment allows proper hardbanding material application while preventing polymer coating deterioration and base metal hardness exceeding 40 Rc
Solution Approach 2:
The patent introduces an intermediary cooling medium (water or compressed air) applied to the outside surface of the tool joint during welding. This intermediary substance acts as a heat sink to extract excess heat from the base metal, preventing excessive hardness while allowing proper weld deposition
2Reliability
If water cooling is introduced during welding to preserve the polymer coating, then coating integrity is maintained, but the base metal HAZ hardness exceeds the maximum industry specification of 40 Rc
Solution Approach 1:
The patent changes the temperature parameters by implementing controlled cooling that maintains the base metal temperature below critical thresholds. By combining low preheating temperatures (70°F-170°F) with controlled cooling during welding, the process achieves both polymer coating preservation and base metal HAZ hardness below 40 Rc
Solution Approach 2:
The patent applies dynamics by using continuously flowing water or compressed air during the welding process to dynamically extract heat as it is generated. This dynamic cooling approach allows real-time temperature control, preventing both polymer degradation and excessive base metal hardness
3Productivity
If conventional hardbanding re-application is performed without temperature control, then the process is simpler and faster, but tool joints are rejected due to excessive HAZ hardness and polymer coating degradation
Solution Approach 1:
The patent implements specific temperature parameter controls (preheat: 70°F-170°F, welding: 170°F-250°F) that enable proper hardbanding deposition while maintaining base metal HAZ hardness below 40 Rc. These controlled parameters ensure manufacturing precision without significantly reducing productivity
Solution Approach 2:
The patent introduces water or compressed air as an intermediary cooling medium applied during welding. This intermediary provides simple, effective heat extraction that controls base metal temperature and HAZ hardness, preventing tool joint rejection while maintaining process efficiency
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
This approach effectively maintains the internal polymer coating integrity and achieves a Rockwell hardness of less than 40 Rc, reducing tool joint rejection rates and enhancing durability without the need for additional coating processes.
Implementation Method 1
arc welding a consumable metal welding wire to a previously applied hardband metal
Implementation Method 2
During the subsequent cooling process, a portion of the base metal beneath the welding arc forms a low hardness metallurgical phase
Data Source
AI summary
Various methods of hardbanding an apparatus are described. In one aspect of the invention an improved method of re-applying a hardbanding alloy to worn tool joints of a previously hardbanded drill pipe results in preservation of the metallurgical properties of the drill pipe and preservation of the internal polymer coating that lines the drill pipe. A method for applying hardbanding includes arc welding a consumable metal welding wire to a tool joint having a surface temperature that ranges from about 50° F. to about 170° F. and the arc welding power supply utilizes DC current. The method herein produces a hardbanded tool joint comprising a heat affected zone (HAZ) of a based metal having a Rockwell hardness of 40 Rc or less.