Continuous Casting : Get More from your caster

7th India Steel Summit

“Realizing 300MT – Challenges Ahead”

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Axcend Automation & Software Solutions

Continuous Casting: Get more from your Caster

Steel, being the most important Engineering raw material, is the key for the growth

of Manufacturing Industry. A strong steel sector propels industry growth, which in

turn drives economy’s growth. Such is the might of this metal which is facing turbulent

times in its growth trajectory.

While Steel is the base of all industries, Continuous Casting is emerging as the preferred

choice in steel making. The basic concept in continuous casting is the use of an open

ended mold to cast an indefinite length of the desired cross sectional shape.

Continuous casting transforms molten metal into solid on a continuous basis and

includes a variety of important commercial processes. These processes are the most

efficient way to solidify large volumes of metal into simple shapes for subsequent

processing. Most basic metals are mass-produced using a continuous casting process.

The molten metal solidifies against the mold walls while it is simultaneously withdrawn

from the bottom of the mold at aratewhich maintains the solid / liquid interface at a

constant position with time. The process works best when it operates such that all the

parameters remain steady.In case of Continuous casting, the capital cost is higher, but

the operating cost is lesser, when compared to other casting processes. It is the most

cost-efficient and energy-efficient method to mass-produce semifinished metal products

with consistent quality in a variety of sizes and shapes. Continuous Casting, along with

other benefits, provides benefits such as considerably lower pollution, improved labour

productivity and improved quality, as compared to the conventional methods.

The main challenges facing the steel industry

today are under-utilization of capacity, high

raw material costs, high energy costs and price

volatility. There’s an adage which says “Even

the best can be bettered.” It perfectly applies

to Continuous casting. Industry leaders always



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work on this concept of “there is a better way” and don’t settle for less. One of the

thought processes is how to get more from the investments on continuous casters

by optimization of the operations. This thought process is vital in the current tough

market conditions. Evolution of manufacturing processes through perfect application

of technology provides the

right platform to optimized manufacturing operations. Steel manufacturers consistently

focus on to attend high quality of the yield and reduce scrap. This article contains the

overview of all the processes involved to get more from your caster.

Challenges

In the continuous casting process of steel making, the challenges are manifold. As the

plant operates on 24/7 basis, it demands enormous manual efforts to continuously

monitor and ensure desired quality of steel output. Continuous monitoring of the mold

signals is important to detect common issues that occur during the casting process.

Taking appropriate actions such as reducing cast speed, controlling water spray,

cascading, secondary processing, up/down grading through manual inspection at the

right time becomes important to achieve intended quality.

Presently, Quality inspection of samples takes place after the production which leaves

no opportunity for corrective action. Defect at specific points leads to lower grading

of entire length of bloom/billet. Blooms graded to lower quality levels need to be sold

at lower cost, thus adversely impacting the profitability. In fact, severe defects force

categorization to scrap grade. Minimizing these scrap levels is a key plant objective.

Solution Approach

Considering above challenges, here is a real time probabilistic system that helps in

grading by identifying and segregating different quality levels, while casting. It also

enables optimization of production by reducing wastage. It helps in identifying the

defects and taking corrective actions to achieve better quality of steel. Defects can

be analyzed and specific affected area of bloom made visible. Operators can use this

information and decide the quality levels for each slab/bloom/billet. Best processes are

defined from the knowhow of the steel casting process and any deviation while casting

is recorded and analyzed to identify the quality levels achieved. It also enables users



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to define a framework wherein standard practices are set and necessary corrective

actions can be built incrementally.

Input: Grading Rules & Actual Process Signal

Grading rules provide standard set points for categorizing quality. Application Software

defines rules for quality, which can be customized for the different customers and

grades. Process signals like liquid metal temperature (especially the superheat value),

level of liquid steel in the mold, quality of electromagnetic stirring, casting speed,

tundish weight, tundish temperature, spray cooling and other real time signals are

logged from field instruments and control system. These act as inputs for the grading

system.

Output: Grading & Assign Quality Levels

Application software receives the input data, which is weighed against the predefined

rules. Based on these results, system will identify the quality level of the slab/bloom/

billet. The system identifies a specific length in a slab/bloom/billet as poor or best

quality, thus providing an opportunity for the operators to take corrective actions like

surface treatment for the specific length. Hence, cast product can be upgraded to

better quality which commands higher price. The algorithms developed based on the

rich tacit knowledge gained over the years helps in defining the quality (both surface

quality and internal composition) of steel. It is observed that the results produced by

this kind of analysis could be fine-tuned to get 70-80% accuracy.



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Implementation

The above diagram gives an overview of the implementation of online grading and tracking

application at different layers. The required information is gathered by integrating PLC

and SCADA.PLC monitors and controls all the casting machine operations, and SCADA

serves as visualization application for operators.

to monitor and control. All critical operations of the casting process are controlled by

operators. Data acquisition system is put in place to collect key process signals from

PLC, SCADA and then logged into database at regular intervals. Application software

fetches the process data from the database and required analysis is carried out based

on algorithms and set of defined rules to identify the quality level of cast products.

For a given heat/sequence, it is assumed that chemical composition of the steel grade

remains same. However, based on event generation the quality level of each bloom

produced can be segregated as 1st Best, 2nd best, and 3rd best and so on.

Spray Cooling is also one of the key processes which would have direct impact on

quality levels. In order to maintain right cooling based on chemical composition and

its grade, water volumes to be sprayed for each zone are decided and are sent back to

SCADA to spray. This is done to reduce the deviations.



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In water flow levels and to ensure optimal cooling based on specific grade of steel.

Hence, it helps in achieving better quality of a product. Based on production, process

& quality parameters we can:

• Monitor and track production & inventory system.

• Define better pricing strategy based on quality levels achieved during

production.

Data Integration layer from production control systems to enterprise layer gives a

realistic view of production details, process and inventory. This would help in doing a

better planning and control of production on an enterprise level.

Solution Benefits

• Optimized process flow and plant utilization through real time application.

• Optimized schedule to obtain maximum output from the tonnage cast.



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• Customer specific configurations for casting, quality, strand cutting etc.

• Advanced spray cooling system to avoid sudden changes in the strand thermal

history resulting in more consistently better quality of steel and reduce incidents

of surface defects and cracks.

• Informed decision making through improved real time visibility.

• Increased price realization by improving quality grade& higher profitability by

reducing scrap.

The Steel industry is facing tough challenges in meeting profitability goals. By making

caster operations more visible, we can have significant contribution in revenue by

segregating the quality levels & billing them according to appropriate pricing strategy.

At the other end, growing demands of production can be met by process optimization

and reduction of wastages caused by surface defects, cracks and other defects.

HHH

Technology

Continuous Casting : Get More from your caster