Bi-Material Screw Weld Seam Hardness Gradient for Lower Tool Wear
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Solution Overview
Problem
Existing screw manufacturing methods face challenges in achieving both corrosion resistance and high material hardness in different parts of a screw, particularly in corrosive environments, leading to significant wear on forming tools due to uniform high material hardness in weld seams.
Innovation Solution
A screw design featuring a weld seam with a carbon concentration that decreases from the inner core to the surface, using two steel sections with different carbon concentrations, where the second section has a higher carbon concentration, resulting in a weld seam with varying material hardness, minimizing tool wear during surface deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-carbon steel is used for the second shank section to achieve high material hardness, then the material hardness of the weld seam increases, but tool wear during surface deformation increases significantly
Solution Approach 1:
The patent applies local quality by creating a non-uniform carbon concentration distribution within the weld seam. The core region maintains high carbon concentration for high hardness, while the surface region has reduced carbon concentration for lower hardness. This gradient structure allows the weld seam to simultaneously provide high strength in the interior and tool-friendliness at the surface where forming tools contact.
Solution Approach 2:
The patent changes the carbon concentration parameter spatially within the weld seam. By controlling the carbon concentration to decrease from the core to the surface, the material hardness parameter也随之 changes. This parameter gradient resolves the contradiction by having high hardness where needed (core) and low hardness where tool contact occurs (surface).
2Strength
If uniform high carbon concentration is used in the weld seam to ensure high material hardness, then corrosion resistance decreases, but if low carbon concentration is used, then material hardness decreases
Solution Approach 1:
The patent applies local quality by creating different carbon concentration zones within the weld seam. The core region has high carbon concentration for high hardness and wear resistance, while the surface region has lower carbon concentration that maintains corrosion resistance. This spatial differentiation of material properties resolves the contradiction between hardness and corrosion resistance.
3Ease of manufacture
If thermal tempering is applied to reduce weld seam hardness, then tool wear decreases, but the material hardness of the entire screw including the high-carbon section decreases
Solution Approach 1:
The patent applies local quality by creating a non-uniform carbon concentration distribution within the weld seam. The core region maintains high carbon concentration for high hardness, while the surface region has reduced carbon concentration for lower hardness. This gradient structure allows the weld seam to simultaneously provide high strength in the interior and tool-friendliness at the surface where forming tools contact.
Solution Approach 2:
The patent segments the weld seam into different functional zones based on carbon concentration. The core zone maintains high hardness for structural integrity, while the surface zone has reduced hardness for tool compatibility. This segmentation eliminates the need for thermal tempering that would compromise overall screw hardness.
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 solution reduces tool wear by maintaining low material hardness on the surface of the weld seam, allowing for efficient deformation without the need for extensive thermal tempering, while maintaining sufficient hardness for drilling and threading.
Implementation Method 1
the weld seam having a greater material hardness than the first shank section, in that the material hardness of the weld seam differs from an internal core of the weld decreases to a surface of the weld
Data Source
Figure 1~2
AI summary
The invention relates to a screw (10), comprising a shank (20), which has a first shank portion (12), a second shank portion (14), and a welding seam (50) connecting the first shank portion (12) to the second shank portion (14). The first shank portion (12) is made of a first steel having a first carbon concentration and a first material hardness, and the second shank portion (14) is made of a second steel having a second carbon concentration and a second material hardness, wherein the second carbon concentration is higher than the first carbon concentration, and wherein the welding seam (50) has a greater material hardness than the first shank portion (12). The invention is characterized in that the material hardness of the welding seam (50) decreases from an inner core (52) of the welding seam (50) to a surface (54) of the welding seam (50).