Threaded Rebar Hot Rolling Without Longitudinal Ribs
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Solution Overview
Problem
Current methods for manufacturing threaded rebar are costly and time-consuming due to the need for additional processing steps to remove longitudinal ribs, which also compromise the strength and continuity of the threads.
Innovation Solution
A method involving hot rolling a billet into a lead pass bar with a cross-sectional area that reduces the formation of longitudinal ribs, allowing for the production of substantially continuous threaded rebar using standard rebar manufacturing equipment without additional machining or shearing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cold rolling is used to manufacture threaded rebar, then the strength of the metal increases and surface finish improves, but the metal becomes brittle and susceptible to cracking at the base of formed threaded ribs
Solution Approach 1:
The patent changes the temperature parameter by switching from cold rolling to hot rolling above the recrystallization temperature, which fundamentally alters the metal's mechanical properties to prevent work hardening and brittleness while maintaining strength through controlled cooling and tempering processes
2Reliability
If hot rolling is used to manufacture threaded rebar, then work hardening is prevented and uniform tensile strength is achieved, but the formed ribs become coarse and unable to meet tight thread tolerances
Solution Approach 1:
The patent segments the manufacturing process into distinct stages: hot rolling to form coarse ribs above recrystallization temperature, followed by a separate cold rolling stage to precision-form the threads. This segmentation allows each stage to optimize for its specific function without compromising the other
Solution Approach 2:
The patent performs preliminary action by hot rolling the rebar to establish the basic rib structure and prevent work hardening before the final thread forming operation, ensuring the metal is in the optimal state for precision threading without premature brittleness
3Manufacturing precision
If machining is used to add threads to rebar, then tight thread tolerances are achieved, but manufacturing costs significantly increase due to multiple processing steps and handling
Solution Approach 1:
The patent replaces the mechanical machining system with a rolling system that forms threads through plastic deformation. This substitution eliminates the need for multiple machining steps, reduces handling requirements, and lowers manufacturing costs while maintaining thread precision through controlled rolling processes
4Productivity
If cylindrical rolls with grooves are used to form threaded rebar, then the rebar can be manufactured in a single pass, but longitudinal ribs are formed that prevent free rotation within nuts or couplings
Solution Approach 1:
The patent applies local quality by using flat dies instead of cylindrical rolls, creating a localized contact area that forms threads without generating longitudinal ribs. This local quality change in the forming mechanism eliminates the rotational interference problem while maintaining manufacturing efficiency
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 reduces manufacturing costs and time while maintaining the strength and continuity of threads, enabling threaded rebar with improved tensile strength and rotational compatibility within nuts or couplings.
Implementation Method 1
In a hot rolling process the bar is passed through the rolls above the recrystallization temperature of the metal
Implementation Method 2
heated bar stock is fed through rolls to form the cylindrical shaped rebar and protruding ribs
Implementation Method 3
When threaded rebar is manufactured using cold rolling, the bar is passed through the rolls below the recrystallization temperature of the metal, which increases the strength of the metal, improves the surface finish
Implementation Method 4
the bar is passed through the rolls below the recrystallization temperature of the metal
Data Source
AI summary
Embodiments of the invention comprise forming a billet from molten steel and hot rolling the billet to reduce the cross sectional area of the billet. Thereafter, the billet is hot rolled into a lead pass bar having a cross-sectional area comprising a reduced width dimension located adjacent to the center longitudinal axis of the bar. In one embodiment of the invention, the billet can be formed into a lead pass bar having a cross-sectional area in the shape of an hourglass or peanut by feeding the billet through a first set of rolls. After the lead pass bar is formed, it is passed through a second set of rolls in order to form the substantially continuous threaded rebar without longitudinal ribs. The cross-sectional area of the lead pass bar helps to produce a substantially continuous threaded rebar product without longitudinal ribs using standard rebar manufacturing tooling and equipment.