Stainless Self-Drilling Screw Cold Forming Without Heat Treatment
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Solution Overview
Problem
Existing methods for producing self-drilling screws from stainless steel face challenges in achieving high strength and penetration capability without pre-drilling, while also being cost-effective and avoiding the complexity of bimetallic screws.
Innovation Solution
A method for manufacturing self-drilling screws entirely from stainless steel using a multi-stage cold forming process, which includes upsetting the screw head, reducing the shank diameter, preforming and final forming of the drill tip, and applying a thread, all without heat treatment to achieve high surface hardness and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stainless steel is used for self-drilling screws, then corrosion resistance is improved, but penetration capability and strength are worsened
Solution Approach 1:
The patent applies different surface conditions to different parts of the screw. The drill tip receives a coating or surface treatment that increases hardness and penetration capability, while the shank maintains the stainless steel's inherent corrosion resistance. This local differentiation allows each part to optimize its function without compromising the whole.
Solution Approach 2:
The patent changes the surface properties of the stainless steel through coating or surface treatment processes. By modifying surface hardness, friction, and other parameters locally at the drill tip, the screw achieves enhanced penetration capability while the bulk material retains its corrosion-resistant properties.
2Strength
If heat treatment is applied to increase hardness, then strength is improved, but corrosion resistance is worsened
Solution Approach 1:
The patent segments the screw into functionally distinct zones: the drill tip receives hardening treatment for penetration, while the shank remains untreated to preserve corrosion resistance. This segmentation allows differential property optimization without compromising either strength or corrosion resistance overall.
Solution Approach 2:
Instead of uniform heat treatment, the patent applies surface treatment or coating only to the drill tip area. This local quality approach concentrates hardness where needed for penetration while leaving the corrosion-sensitive shank in its original stainless steel state.
3Reliability
If bimetallic screws are used to combine carbon steel tip and stainless steel shank, then penetration capability and corrosion resistance are both improved, but manufacturing complexity and cost are worsened
Solution Approach 1:
The patent merges the carbon steel tip and stainless steel shank into a single monolithic component. By forming the drill tip from the same stainless steel material through cold forming and surface treatment, it eliminates the need for welding or assembly operations required by bimetallic screws, thereby reducing manufacturing complexity while achieving similar functional results.
Solution Approach 2:
The patent changes the surface parameters of the stainless steel drill tip through coating or surface treatment to achieve properties similar to carbon steel. This allows a single-material construction to replicate the bimetallic performance characteristics without the associated manufacturing complexity.
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 enables the production of high-strength self-drilling screws that can penetrate steel sheets thicker than 1.5 mm without pre-drilling, while reducing production time and energy, and eliminating the need for bimetallic screws.
Implementation Method 1
Basically, the person skilled in the art understands cold forming to be the plastic forming of metals below the recrystallization temperature, which is known to lead to work hardening of the formed material.
Data Source
AI summary
A method for producing an entirely stainless steel, high-strength self-drilling screw that does not need heat treatment downstream of manufacturing to improve material hardness. A stainless steel wire section blank is provided. A screw head is cold-formed at a first end. Subsequently, the diameter at the second end section is reduced by cold forming. A drill tip is produced at the second end by a tweaking movement transverse to the longitudinal axis. Subsequently, the drill tip is finished. Any protruding material flags remaining on the drill tip cutting edges are sheared off during subsequent thread rolling. During preforming, contour edges are formed in the region of the subsequent cutting edges, with the remaining material thickness between 0.3 mm and 1.0 mm. The drill tip final forming forms these contour edges into the cutting edges, and the remaining material thickness between the cutting edge and the material flag is between 0.05 mm and 0.2 mm.