Tool Joint Hardbanding with Low-Temperature DC Arc 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 the required Rockwell hardness, often resulting in rejected tool joints due to high preheating and welding temperatures that degrade the coating and exceed hardness specifications.
Innovation Solution
A method involving arc welding a consumable metal welding wire onto a tool joint with a surface temperature ranging from 50° F to 170° F using direct current (DC), which includes applying stringer weld beads with reduced penetration and cooling to maintain a base metal heat affected zone hardness of less than 40 Rc, thereby preserving the internal polymer coating and preventing excessive hardening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional preheating and welding temperatures are used to apply hardbanding, then the hardbanding material is properly deposited, but the internal polymer coating deteriorates and the 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 controlling welding amperage between 75-150 amps, which fundamentally alters the thermal parameters of the hardbanding process to prevent polymer degradation while maintaining acceptable hardbanding deposition quality
Solution Approach 2:
The patent implements dynamics by using controlled cooling rates after welding, where the cooling process is dynamically managed to achieve the desired base metal hardness within specification limits while preserving the polymer coating integrity
2Reliability
If high preheating temperatures are applied during hardbanding, then the welding process is more stable, but the base metal heat affected zone hardness exceeds the maximum Rockwell hardness of 40 Rc
Solution Approach 1:
The patent changes the temperature parameter from conventional high preheating (250°F-600°F) to a reduced range (70°F-170°F), which maintains welding process stability through controlled parameters while ensuring the base metal HAZ hardness remains below 40 Rc
Solution Approach 2:
The patent employs feedback control by monitoring and adjusting welding amperage (75-150 amps) and preheating temperature to maintain process stability while preventing excessive hardening of the base metal heat affected zone
3Object-affected harmful factors
If water cooling is used during welding to preserve the polymer coating, then the coating integrity is maintained, but the base metal HAZ hardness exceeds industry specifications
Solution Approach 1:
The patent replaces water cooling with controlled air cooling and adjusts the preheating temperature parameter to 70°F-170°F, which preserves polymer coating integrity while achieving acceptable base metal HAZ hardness through parameter optimization rather than aggressive cooling
Solution Approach 2:
The patent uses controlled cooling as an intermediary process between welding and final inspection, managing the cooling rate to simultaneously protect the polymer coating and achieve the desired base metal hardness properties
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 re-applies hardbanding while maintaining the integrity of the internal polymer coating and ensuring the base metal heat affected zone does not exceed the maximum Rockwell hardness of 40 Rc, reducing the need for additional coating processes and minimizing tool joint rejection.
Implementation Method 1
an arc welding process in which a consumable metal welding wire is arc welded to a previously applied hardband metal
Implementation Method 2
Hardbanding is a surface welding process that is commonly used in the oil and gas industry to apply metal welding wire onto the surface of many industrial parts
Implementation Method 3
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.