Hot and cold composite formed square and rectangular steel tube with thickened corners and production method
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Solution Overview
Problem
Traditional cold-rolled square and rectangular steel tubes suffer from secondary work hardening, large residual stresses, and excessive corner radii, limiting their use in high-rise buildings and weakening welding performance.
Innovation Solution
A hot and cold composite forming process that involves local induction heating of corners followed by precision rolling forming, controlling thermal tension and cooling to achieve thickened corners with reduced residual stress and improved plasticity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional cold-rolled forming process is used, then production efficiency is improved, but secondary work hardening occurs causing large residual stress and excessive corner radius
Solution Approach 1:
The patent applies hot rolling followed by cold rolling, changing the temperature parameter during forming. Hot rolling at elevated temperatures reduces material strength and increases plasticity, allowing for smaller corner radii without excessive work hardening. The subsequent cold rolling achieves final dimensional precision. This parameter change resolves the contradiction by enabling precise corner radius control while maintaining production efficiency.
Solution Approach 2:
The hot rolling process performs preliminary forming with larger deformations when material is more ductile at elevated temperatures. This preliminary action reduces the burden on the subsequent cold rolling process, allowing the cold rolling to focus on achieving final precision without excessive work hardening. This preliminary action at different temperature conditions resolves the contradiction between efficiency and precision.
2Ease of manufacture
If traditional cold-rolled forming process is used, then manufacturing cost is reduced, but welding performance is weakened due to large corner radius
Solution Approach 1:
By implementing hot rolling followed by cold rolling, the patent achieves smaller corner radii that improve welding performance. The hot rolling process enables the material to undergo larger deformations with reduced resistance, and the controlled cooling and cold rolling processes ensure final dimensional accuracy. This resolves the contradiction by improving welding reliability without significantly increasing manufacturing cost, as the dual-rolling process is a established industrial method.
3Device complexity
If traditional cold-rolled forming process is used, then process simplicity is maintained, but corner thickness reduction occurs due to excessive deformation
Solution Approach 1:
The patent uses hot rolling to perform the majority of corner deformation when material plasticity is enhanced by elevated temperature. This reduces the deformation burden on the subsequent cold rolling process, preventing excessive thinning during final forming. The temperature parameter change enables thicker corners to be achieved while maintaining process simplicity through established hot and cold rolling equipment.
4Shape
If hot rolling is applied to reduce corner radius, then corner thickness increases, but residual stress may increase
Solution Approach 1:
The hot rolling process performs preliminary corner deformation when material is more ductile, creating a pre-formed shape with reduced corner radius. The subsequent cold rolling process applies controlled deformation to achieve final precision while work hardening the material to reduce residual stress. This two-stage preliminary action resolves the contradiction by addressing corner radius reduction first, then managing residual stress through controlled cold working.
Solution Approach 2:
The patent controls the temperature parameter during hot rolling and the deformation parameters during subsequent cold rolling to balance corner radius reduction with residual stress management. By optimizing these parameters, the process achieves smaller corner radii with controlled residual stress levels, resolving the contradiction between shape improvement and stress control.
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 process results in steel tubes with enhanced strength, ductility, and welding performance, suitable for larger scales and various steel types, with smaller corner radii and increased corner thickness, addressing the limitations of traditional methods.
Implementation Method 1
heating four corners of the square and rectangular steel tube locally by an induction coil
Implementation Method 2
performing controlled cooling on the square and rectangular steel tube with a water-cooling system
Data Source
AI summary
A hot and cold composite formed square and rectangular steel tube and a production method for the same are provided. The radius of an outer corner of the square and rectangular steel tube meets the following conditions: when t is less than or equal to 6 mm, R is greater than 0 and less than 2.0 t; when t is greater than 6 mm and less than or equal to 10 mm, R is greater than 0 and less than 2.5 t; when t is greater than 10 mm, R is greater than 0 and less than 3.0 t, wherein t is the wall thickness of a straight tube part of the square and rectangular steel tube; R is the radius of each of the outer corners of the four corners of the square and rectangular steel tube; and the wall thickness of each corner of the square and rectangular steel tube is between 1.0 t and 1.8 t.