Drill Pipe Tool Joint Re-Hardbanding With a Non-Hardenable Buffer Layer
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Solution Overview
Problem
Existing re-hardbanding methods for drill pipes often result in high mechanical stresses and the risk of cracks, despite reduced surface temperatures, due to the thinness of stringer weld beads compared to original weave weld beads, which can still cause damage to heat-sensitive components and coatings.
Innovation Solution
A method involving a first metal layer of non-hardenable steel, which acts as a buffer layer, is used for re-hardbanding, where this layer is metallurgically bonded to the base material and a second hardbanding layer is applied on top, avoiding additional heat-affected zones and reducing mechanical stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard re-hardbanding is performed with preheating to 288-316°C, then adequate bonding and prevention of martensite formation is achieved, but heat-sensitive components and internal polymer coatings are damaged
Solution Approach 1:
A buffer layer of non-hardenable steel is introduced between the base material and the hardbanding layer. This intermediary layer absorbs the thermal stress and prevents direct heat transfer to the base material, allowing lower preheating temperatures (50-150°C) that protect heat-sensitive components while still preventing martensite formation in the buffer layer itself.
Solution Approach 2:
The hardbanding structure is made composite with three distinct layers: base material, buffer layer of non-hardenable steel, and hardbanding layer. This composite structure allows each layer to perform its specific function - the buffer layer prevents hardening while the hardbanding layer provides wear resistance, solving the contradiction between bonding quality and heat protection.
2Temperature
If stringer weld beads are used for re-hardbanding, then surface temperature is reduced, but mechanical stresses increase and crack risk rises due to thinness compared to original weave weld beads
Solution Approach 1:
The buffer layer of non-hardenable steel is applied beforehand to cushion and absorb mechanical stresses during the welding process. This pre-positioned cushioning layer prevents stress concentration and crack formation in the underlying base material, allowing the use of thin stringer weld beads without compromising structural integrity.
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 reduces the likelihood of cracks and damage to heat-sensitive components by maintaining low preheating and interpass temperatures, ensuring effective bonding without further heat treatment, thus protecting internal polymer coatings and electronics.
Implementation Method 1
the first metal layer comprises a layer of non-hardenable steel... This approach reduces the likelihood of cracks and damage to heat-sensitive components
Implementation Method 2
a first metal layer, which is metallurgically bonded to the base material
Implementation Method 3
metallurgically bonded to the base material
Implementation Method 4
preheating the tool joint to a preheating temperature... maintaining low preheating and interpass temperatures
Implementation Method 5
depositing at least one second metal layer containing hardbanding material onto the grinded and/or machined metal deposit
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
In a known method of re-hardbanding a tool joint (3) of a drill pipe (1), the tool joint (3) has a worn weld deposit (4; 7; 14) that comprises a first metal layer (7), which is deposited at least partially into a groove (12) of the tool joint (3). In this cases re-hardbanding comprises the steps of: machining and/or grinding the worn weld deposit (4; 7; 14), preheating the tool joint (3) to a preheating temperature, and depositing at least one second metal layer (14) containing hardbanding material onto the ground metal deposit (4; 7; 14). In order to ensure that the base material is subjected to a low temperature during re-hardbanding, and at the same time, any problems due to mechanical stresses and the risk of cracks are reduced, it is suggested that the first metal layer comprises a layer (7) of non-hardenable steel.