Drill Bit Weldment Root Gap Design for Stress Reduction

Solution Overview

Problem

Attaching roller cone subassemblies to drill bit bodies often results in service failures due to stress concentrations and inconsistencies at the attachment points, leading to reduced service life.

Innovation Solution

A manufacturing method that creates a multi-pass weldment with a predetermined root gap and root face, combining higher strength materials with a synergistic balance to reduce stress concentrations and enhance the service life of drill bits.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If roller cone subassemblies are attached to drill bit bodies using conventional welding methods, then the attachment is achieved, but stress concentrations and inconsistencies occur at the attachment points leading to reduced service life

Engineering Contradiction:

Improveweldment strengthVSAvoidservice life

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent applies local quality by creating a multi-pass weldment with different properties at different locations: the root gap and root face are specifically engineered with predetermined dimensions to control stress distribution at the critical attachment interface, while the crown portion provides overall structural strength. This localized optimization of weldment geometry resolves the contradiction by making the attachment point specifically designed for stress reduction rather than uniform welding throughout.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes physical parameters of the weldment by specifying predetermined root gap dimensions (0.005 to 0.030 inches) and root face dimensions (0.010 to 0.060 inches), and controlling interpass temperatures (75°F to 300°F). These parameter changes optimize the weldment structure to reduce stress concentrations while maintaining strength, thereby improving service life without sacrificing weldment integrity.

Inventive Principle:

Principle #35Parameter changes

2Strength

If higher strength materials are used in the weldment, then tensile strength is increased, but stress concentrations may worsen without proper structural design

Engineering Contradiction:

Improvetensile strengthVSAvoidresidual stress

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The patent applies local quality by creating a multi-pass weldment with different properties at different locations: the root gap and root face are specifically engineered with predetermined dimensions to control stress distribution at the critical attachment interface, while the crown portion provides overall structural strength. This localized optimization of weldment geometry resolves the contradiction by making the attachment point specifically designed for stress reduction rather than uniform welding throughout.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes physical parameters of the weldment by specifying predetermined root gap dimensions (0.005 to 0.030 inches) and root face dimensions (0.010 to 0.060 inches), and controlling interpass temperatures (75°F to 300°F). These parameter changes optimize the weldment structure to reduce stress concentrations while maintaining strength, thereby improving service life without sacrificing weldment integrity.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If a multi-pass weldment with predetermined root gap and root face is created, then fatigue resistance is enhanced, but manufacturing complexity increases

Engineering Contradiction:

Improvefatigue resistanceVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies preliminary action by establishing the root gap and root face dimensions before completing the weldment process. The predetermined dimensions are set during the welding setup phase, allowing the multi-pass weldment to be executed with controlled parameters that ensure fatigue resistance. This preliminary configuration simplifies the overall manufacturing by providing clear dimensional targets rather than requiring post-weld adjustments.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes physical parameters of the weldment by specifying predetermined root gap dimensions (0.005 to 0.030 inches) and root face dimensions (0.010 to 0.060 inches), and controlling interpass temperatures (75°F to 300°F). These parameter changes optimize the weldment structure to reduce stress concentrations while maintaining strength, thereby improving service life without sacrificing weldment integrity.

Inventive Principle:

Principle #35Parameter changes

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 method significantly increases the tensile strength and fatigue resistance of the weldment, resulting in a longer service life for drill bits by minimizing residual stresses and improving the attachment interface.

Implementation Method 1

creating a multi-pass weldment

Methodology Applied

Scientific EffectWelding: Welding

Data Source

PatentEP3099884B1Hybrid drill bit having increased service life

Publication Date: 2020.02.26 BAKER HUGHES CO

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AI summary

A method of improving the service life of a drill bit comprises creating a weldment between load bearing portions of the drill bit where the weldment has a preselected root gap greater than about 25 mils and a preselected root face greater than about 25 mils, and where the weldment has a material property greater than the materials being joined.