Thread-Forming Screw With Laser Welded Beads
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Solution Overview
Problem
Existing thread-forming screws made of corrosion-resistant steel struggle to achieve sufficient hardness for effectively forming threads in hard materials like concrete, with previous solutions either being too costly, having weak weldability issues, or losing coating integrity during use.
Innovation Solution
The development of a thread-forming screw with weld beads in recesses, having a carbon content less than 0.8% by weight, formed through laser welding, which reduces thermal stresses and maintains corrosion resistance while allowing precise geometry and improved cutting behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the steel of the outer thread is hardened to high strength, then the screw can form a female thread in constructional components, but corrosion-resistant steels cannot achieve sufficient hardness through heat treatment
Solution Approach 1:
The patent applies local quality by creating weld beads with high carbon content (greater than 0.8% by weight) only in specific regions where cutting edges are needed, while the base material maintains lower carbon content (0.1%-0.5% by weight) to preserve corrosion resistance. This localized high-carbon region provides the necessary hardness for cutting concrete and other hard materials, while the majority of the screw retains corrosion-resistant properties.
Solution Approach 2:
The patent creates a composite structure by welding high-carbon steel cutting elements onto a corrosion-resistant low-carbon steel base material. This composite approach combines the advantages of both materials: the high-carbon steel provides extreme hardness and cutting capability, while the low-carbon steel base provides corrosion resistance and structural integrity.
2Strength
If pin-shaped cutting inserts are driven into receiving bores to enable thread-cutting in hard mineral materials, then cutting capability is improved, but manufacturing cost increases significantly
Solution Approach 1:
The patent merges the cutting element and the screw body into a single integrated component through welding. Instead of separately manufacturing cutting inserts and screw bodies then assembling them, the high-carbon cutting elements are welded directly onto the low-carbon steel screw body, creating a unified structure that eliminates assembly steps and reduces manufacturing complexity.
Solution Approach 2:
The patent replaces the mechanical assembly system (driving pin-shaped inserts into bores, requiring cutting heads, grinding operations, and friction-based retention) with a welding process that fuses the cutting elements directly to the screw body. This substitution eliminates the need for complex mechanical retention mechanisms and post-assembly grinding operations.
3Strength
If weld bodies of high-carbon steel are welded into the thread to form cutting elements, then cutting capability is achieved, but the base material and weld deposits experience thermal stresses that can cause fissures
Solution Approach 1:
The patent carefully controls the carbon content parameter of the base material to be between 0.1%-0.5% by weight, which provides optimal balance between weldability and final hardness. The weld beads use high-carbon filler material (greater than 0.8% by weight) to achieve cutting-edge hardness while the controlled base material composition minimizes thermal stress and fissure formation during the welding process.
4Strength
If a coating is applied over the entire surface through ion-nitration to increase hardness, then cutting capability is improved, but the coating is rubbed off after several revolutions in hard mineral materials
Solution Approach 1:
Instead of applying a coating over the entire screw surface, the patent creates localized high-carbon weld beads only at the cutting edges and thread engagement surfaces where cutting capability is needed. This localized approach provides the necessary surface hardness without creating a thin coating that would be prone to rubbing off during use.
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 results in a screw with enhanced cutting ability and reduced manufacturing costs, maintaining high hardness and corrosion resistance, enabling efficient thread formation in concrete without the need for expensive mechanical treatments or fragile high-carbon weld inserts.
Implementation Method 1
weld beads which are arrangeable in the recesses formed in the thread... formed through laser welding
Data Source
AI summary
A thread-forming screw (11; 21; 31; 51), has a stem (12) with at least one thread (14; 24; 34; 54) arranged, at least regionwise, over its circumference, and a plurality of cutting elements (16; 26; 36; 56) arranged in a respective plurality of recesses (15; 25; 35; 55) formed in the at least one thread (14; 24; 34; 54), with the cutting elements (16; 26; 36; 56) having a hardness greater than a hardness of the at least one thread (14; 24; 34; 54) and formed as weld beads received in the recesses (15; 25; 35; 55).