Fotolia 9040518 L

Electrics & Automation for Casting

Mould Level Master

Mould Level Master (MLM) is a highly sophisticated control program that reduces mould level fluctuations to a minimum. Designed around more than 20 years of experience with mould level control for continuous casting machines, this software ensures exact mould levels throughout the entire casting process regardless of influencing factors such as bulging, clogging, waving, casting speed changes, automatic start, etc.

Mould Level Master is suitable for all stopper-controlled continuous casting machines. A similar package is available for tundish slide gate-controlled continuous casting machines featuring an algorithm control package with similar characteristics to guarantee a stable mould level.

Features

  • Average mould level stability is accurate to within +/- 2 mm
  • Automatic start-up for small billet to slab formats, including automatic protection against breakout and freezing
  • The mould level remains undisturbed in the case of bulging or waving 
  • Automatic clogging detection and reaction (corrective action)

Applications

The control program is available for all continuous casting machines

  • Billet
  • Bloom
  • Slab
  • Thin slab
  • Special caster applications

The standard MLM package includes operating routines such as automatic start-up, high-level or low-level-protection, clogging prevention, breakout detection, bulging compensation (pending patent), submerged entry nozzle, refractory wear distribution and safety features. 

HMI example of MLM

HMI - Operation View

Main strand conditions

  • Mould level setpoint
  • Actual mould level stopper opening
  • Casting speed

Stopper positions

  • Absolute position
  • Relative position
  • Start-up position
  • Fully closed positions
  • Bending of the rigging
  • Clogging and wearing positions

SEN wear distribution tuning tool

Fast recording and analysis tool with all required information (recording rate, 5 ms)

Message window displays alarms and status information

MLM Functionality Overview

Automatic system calibration

With each new casting sequence or flying-tundish exchange the system initiates a zero calibration of the automatic stopper and mould level sensors. This procedure is disabled during normal casting mode (throttle mode).

CONSIDERATION OF STOPPER RIGGING MECHANICAL DEFLECTION

Due to the highly dynamic movements which generate mechanical deflection, the exact zero flow position needs to be identified in order to determine the actual stopper opening at any given time. This procedure is triggered automatically whenever a sequence starts and is disabled during normal casting mode. 

Auto Start-UP

The automatic start-up function includes automatic protection against breakout and freezing (mould filling protections). The MLM software reproducibly oversees the automatic start-up of the casting sequence for all casting formats. Automatic start-up is the phase when the stopper opens for the first time and the mould level reaches a predefined value in the sensor range which triggers the start of the withdrawal machine. If necessary, the stopper position can be modified manually by pushing the “Open” and “Close” buttons on the electrical actuator. This function, however, is disabled as soon as the casting machine starts withdrawing the strand.

This auto start-up procedure is fitted with a protection mechanism to avoid filling the mould too quickly (defined filling times) and reaching breakout conditions. Furthermore, the flow is adapted to avoid freezing in the nozzle and shroud. Thus, a reproducible start-up of casting can be achieved across the entire casting process. 

MOULD LEVEL ACCURACY

The average mould level stability is accurate to within +/- 2 mm, with automatic control under all casting conditions. The nonlinear algorithm control with dynamic modification of control parameters means the casting speed can be increased by up to 20% whilst maintaining a stable mould level.

  • Increased productivity (in terms of quality and quantity)
  • Capacity to increase casting speed
  • Stable mould level under all conditions
  • No special operator training is required 

Anti-clogging function

This function reduces the clogging behaviour by oscillation of the stopper. The period and amplitude are set so that the motor never mismatches a synchronisation phenomenon because of its mechanical/electrical inertia. Due to the high vibration speed, the average steel flow variation is zero and therefore does not affect the mould level stability. The vortex effect in the SEN will be reduced through dithering which also prevents clogging.

  • Stable mould level also under clogging conditions
  • Longer casting sequences possible
  • Reduced costs (refractory, energy, manpower)
  • Higher output possible
  • Increased product quality 

BULGING AND WAVING DETECTION

The MLM incorporates special algorithms to detect mould level fluctuations in case of bulging and waving. Controller auto-tuning results are traced continuously through the constant analysis of the disturbances amplitude and period before being optimized where necessary. Bulging and waving are detected through a reliable logic and continuous analysis of the mould level behaviour. Both logics – each based on different set values to distinguish between unsteady bulging and waving – are always active. 

Safety functions

Automatic stopper closing in case of high mould level with automatic casting resumption, or in case of breakout.

  • Safe operation for operators
  • No damage to the casting machine
MLM System Configuration

The complete MLM system consists of the following components:

  • Mould Level Master control cabinet
  • Operator panel on the casting floor
  • Visualization and operation devices in the control room (PC)

Each control cabinet is fitted with enough equipment for two strands. The basic equipment installed by default is:

  • Main switch
  • Circuit breakers
  • Contactors and relays
  • Motor protection switches
  • I/O modules
  • Communication modules
  • Emergency stop device
  • etc.