TruStir  Patent Number: 6,264,716

Reliable - Consistent - Accurate

- avoid uncontrolled stirring -

TruStir Brochure in PDF Format

Argon Stirring Control & Arc Monitor

- Proven Technology with over 10 installations worldwide.

- Can be applied to any combination of multi-plug, single plug, lance, and electromagnetic systems.

- Our implementation training teaches you when and how much to stir.

- TruStir combined with the included Nupro training optimizes your stirring practice, yielding controlled results.

Clean Steel Practice

Experienced operators and metallurgists recognize the importance of accurate and consistent argon gas stirring in the ladle. Clean steel and good castability depend on a consistent and gentle rinse stir. During ladle arc reheating, slag line life and heating efficiency rely on an optimum medium stirring rate. Alloy addition and desulfurization require more vigorous but controlled stirring. To facilitate the reproducible and accurate argon stir rates and durations required to meet these objectives, Nupro Corporation has developed TruStir^TM, a vibration based argon stirring control system.

Advanced Technology

This is an advanced technology that uses an accelerometer and digital signal processing to deliver accurate gas flow measurement in ladle stirring applications.

An accelerometer in contact with the ladle, sends amplified signals to the system that filters and digitally processes the signals through a proprietary software package. The system is fully automatic, non-intrusive, and is customized and tuned on site to meet the specific needs of each ladle stirring operation.

The system is then fully integrated with the existing PLC to provide accurate and reproducible stirring. A customized operator interface with touch screen input is provided to suite for ease of use and convenience.

Example user interface

 An arc noise measurement option can be added to indicate excessive arc noise and recommend flux additions.

Applications

TruStir can be utilized at any location where gas stirring is used for steel processing. Some examples follow:

ladle stirring.

ladle furnace.

vacuum tank degasser.

Additionally, TruStir can be applied at the caster for temperature homogenization. In one application, ineffective stirring at the caster was found; despite flow controller indications to the contrary.

Immediate Benefits

- lower argon consumption

- longer stir plug life

- better alloy recoveries

- improved desulfurization

- longer slag line life

- decreased nozzle clogging

- cleaner steel

- ability to "blind stir" at the caster

- real time stirring history

- optional arc noise level for optimal flux addition

- decreased arc flare

- improved arc reheating efficiency

- lower carbon pick-up during arc reheating

- typical payback in less than one year

TruStir^TM: Minimize Problems

In argon plug stirring, several conditions may hamper the ability to achieve and maintain the correct stirring energy in the ladle. Some problems include:

- argon channeling, resulting in lower than expected stir rate.

- leaks in the supply system.

- variable back pressure due to changing plug condition.

- operator error in judging the stir rate due to variable slag thickness and consistency.

- lack of real time record of stir history on each ladle.

These problems can be costly, with the following negative results:
- excessive argon consumption.

- poor castabiltiy (nozzle clogging).

- aluminum fade.

- ladle slag line refractory wear.

- arc flare and low heating efficiency.

- inability to desulfurize.

- higher total oxygen in the final product.

- carbon pick-up during ladle furnace reheating.

Improve Process Control

In present systems, the desired stir rate is set according to the argon supply flowrate. Unfortunately, the stirring energy actually achieved may not be proportional due to the abovementioned problems. TruStir^TM alleviates these difficulties and ensures consistent and accurate stirring by monitoring ladle vibration, which is directly linked to stirring energy. In this manner, the argon flowrate is continuously adjusted to compensate for changing process conditions and thereby maintain a consistent specified stir rate.

As an example, the figure below shows the stirring energy increasing during the heating cycle due to opening of the porous plug. TruStir^TM can sense the change in flow and compensate by adjusting the argon gas controller. The arc noise decreases after the addition of fluxes.

Measured vibration amplitude at a ladle furnace (control disabled).

Thus, during excessive arc noise periods,TruStir^TM recommends the addition of fluxes to reduce arc flare.

Ease of Installation

The Nupro TruStir system is comprised of an accelerometer in contact with the ladle, a signal conditioning unit, a central processing unit, and an interface to the PLC or Level II for data reporting. Example accelerometer deployment devices are shown below.

Accelerometer installed on ladle transfer car and connected using cable reel.

Accelerometer deployed using installed arm.

Contact Nupro for additional information about this system.