Interstand Rapid Cooling for Fine-Grain Hot-Rolled Strip
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Solution Overview
Problem
Existing hot rolling systems struggle to achieve a fine grain structure in metallic hot strips due to long cooling times, especially for thick strips, which affects material properties, and previous solutions like stand coolers or compact cooling units are either inefficient or complex.
Innovation Solution
A system with rapid cooling spray bars that apply a cooling medium to the hot strip between rolling stands, covering at least 30% of the strip length, using high-pressure water to cool the strip immediately after exiting the roll gap, with a specific cooling rate of over 600 K/s per mm of strip thickness to prevent grain growth and achieve optimal mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thick strip is finish-rolled before the last rolling stand, then the reduction in thickness is reduced, but the time to reach cooling section increases leading to insufficient cooling
Solution Approach 1:
The cooling action is moved forward in time by installing cooling devices between rolling stands, allowing cooling to begin before the strip reaches the final cooling section, thus reducing total cooling time while maintaining thickness control
Solution Approach 2:
Intermediary cooling devices are introduced between the rolling stands to provide cooling functionality at an intermediate location, bridging the gap between rolling and final cooling sections
2Temperature
If stand cooler is installed in place of work rolls, then cooling capability is improved, but plant availability is reduced due to conversion effort
Solution Approach 1:
The rolling stand is designed to perform both rolling and cooling functions through multi-functionality, with cooling devices that can be activated independently without requiring conversion, thus maintaining plant availability while improving cooling capability
3Device complexity
If cooling fluid jet is limited to 25% of distance between stands, then system complexity is reduced, but cooling effectiveness is insufficient for strip interior
Solution Approach 1:
The cooling system is segmented into multiple cooling zones along the strip path, with each zone having dedicated cooling devices, allowing extended cooling coverage without excessive complexity in any single component
Solution Approach 2:
Cooling is applied from multiple dimensions including upper and lower surfaces of the strip, enabling heat removal from the strip interior through extended surface area exposure to cooling fluid
4Speed
If cooling fluid exposure time is limited, then transport efficiency is improved, but insufficient cooling prevents fine grain structure formation
Solution Approach 1:
Cooling begins earlier in the process by placing cooling devices between rolling stands, extending the effective cooling period without reducing transport speed, allowing sufficient time for fine grain structure formation
Solution Approach 2:
Multiple cooling methods are combined including direct fluid jet cooling and spray cooling to create a composite cooling system that achieves rapid cooling at high transport speeds
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 enables rapid and continuous cooling, ensuring a fine grain structure and improved mechanical properties such as strength and toughness in the hot strip, while simplifying the system design and reducing maintenance efforts.
Implementation Method 1
A system with rapid cooling spray bars that apply a cooling medium to the hot strip between rolling stands, using high-pressure water to cool the strip immediately after exiting the roll gap
Implementation Method 2
The cooling device is designed to cover at least 30 percent of the length L of the hot strip between the n-1st rolling stand and the nth rolling stand with the cooling medium
Data Source
Figure 1
AI summary
The invention relates to a system (A) for producing metal hot-rolled strip (B), comprising: a hot-rolling line for carrying out one or more rolling passes, the hot-rolling line having at least two roll stands n-1, n, which are arranged one behind the other in the conveying direction (F) of the hot-rolled strip (B); and a cooling device, the cooling device having at least one first upper rapid-cooling spray bar (SK1o) for discharging a cooling medium (W) onto the top side (O) of the hot-rolled strip (B) between the (n-1)th roll stand and the nth roll stand, and the cooling device having at least one first lower rapid-cooling spray bar (SK1u) for discharging the cooling medium (W) onto the bottom side (U) of the hot-rolled strip (B) between the (n-1)th roll stand and the nth roll stand. The system is characterized in that the cooling device is designed to cover at least 30 percent of the length (L) of the hot-rolled strip (B) between the (n-1)th roll stand and the nth roll stand with the cooling medium (W). The invention further relates to a method for producing metal hot-rolled strip (B) using said system.