Optimizing your steelmaking process

Every step in the steel manufacturing process has its own challenges.
To fulfill the need of the customer at every step, Heraeus Electro-Nite offers applications specific for each step of the steel manufacturing process.

Find out which solutions are applicable for your process and how they can help you to optimize a specific step of the steel making process.

Challenges on the iron making process

Optimize your process by making use of our solutions. Samplers, sensors and continuous probes can be used to control the steel manufacturing process from the very early stages.

The iron making process can influence the rest of the steel manufacturing process. Control your process with accurate and quick results to optimize your mathematical models and make earlier decisions rather than having unnecessary costs due to overtreatment or unnecessary waiting times.

Blast Furnace and desulphurization

After the blast furnace has delivered hot metal to the torpedo (or ladle), Celox Hot metal helps to enable an instant decision on what to do next: send the ladle to the desuphurization station or directly to the BOF.

The results of the measurement are given within seconds and an instant decision can be made on the next steps of the process. Precious time can be saved by not having to wait for the lab results, and overtreatment can be avoided.

Before desulphurization: Perform a Celox Hot Metal Sulphur measurement before starting the injection process:

  • No sample analysis necessary
  • Desulphurization process can start immediately

After desulphurization: Perform a Celox Hot Metal Sulphur measurement after desuplhurization:

  • Ladle can be released to the BOF: time saving of at least 4 minutes
  • Straight forward measurement: accurate and fast
  • No overtreatment: costs involved can be eliminated
  • Faster decision on an additional treatment

Cost savings on reagent: standard over-addition becomes obsolete, thus saving up to 15% on material per treatment

Advantages

  • time savings: results are obtained in seconds compared to the longer waiting time required for the lab sample analysis
  • chemistry: true sulphur and silicon content, not influenced by non-metallics
  • plant logistics: improved because of the fast and easy to use Celox HM Sensor

Basic Oxygen Furnace / Convertor

Convertor

Products

Fast Converter Sample Analysis

The main aim of the converter process is to get the temperature and carbon within specifications and to reduce the amount of phosphorus at the end of blowing. Until now, because of steel grades with tighter specifications on phosphorus and also increased phosphorus content in iron ore, steel makers have been waiting for the final sample (TSO measurement with sublance) to know the phosphorus content before deciding if they need to reblow the heat or can tap it immediately.

QuiK-Lab II offers the potential to analyze phosphorus within 80 seconds of the TSC inblow measurements. This offers operators critical information on the P flight path and they can continue the oxygen blow until all the critical elements and the temperature are within specification. QuiK-Lab II and QuiK-Spec enable to reduce the converter tap-to-tap time by a few minutes and increase the productivity of the convertor shop.

QuiK-Spec Multi-Lance with QuiK-Lab II: your critical link to a fast converter sample analysis

Decarburization Control

Quick Carbon Determination in EAF or Converter

Accurate and quick carbon determination enables the steel maker to make faster decisions about when to tap. Waiting for the final sample analysis from the lab to determine the Carbon content is no longer necessary. Tap-to-tap time is shortened and expensive energy and refractory costs are reduced.

Calculation of pre-deoxidation additions to eliminate or reduce over– or reblows

Mathematical models provide the steelmakers with an indication about the amount of additions to be added. Accurate and fast oxygen measurements enable to calculate the deoxidation additions to be added to the tapping stream or to the transfer ladle more precisely. This method is beneficial for low carbon steels having relatively high and fluctuating oxygen levels.

Control of bottom stirring efficiency

Inert gas is blown into the converter to reduce the C-O product and to enhance the decarburization rate.The argon bubbling will shift the C-O equilibrium downwards.By measuring the oxygen by celox and carbon with a sample after blowing, it is possible to check the argon stirring efficiency.

Advantages of using Celox®

  • Accurate Carbon and Oxygen determination
  • No waiting for lab analysis: quick-tapping praxis
  • Shortened tap-to-tap time
  • Increased productivity and steel output
  • Energy and refractory savings
  • Decrease of redundant over– or reblows
  • Reduction of unnecessary and expensive additions to a minimum

Celox for on-line process control in modern steelmaking

Electric Arc Furnace

EAF

Products:

Fast and reliable temperature measurement at end of melting cycle in EAF

In modern mini-mill setups, accurate end temperature control is key to achieve efficient operational performance of the EAF

Fast and reliable temperature measurement at end of melting cycle in EAF

Current automatic lances use disposable probes to determine temperature of steel bath.

Temperature Control Traditional

Equipment description:

  • Mechanical automated lancing system fitted with disposable thermocouple on probe holder at tip of lance
  • Temperature measurement is done by dipping the probe in liquid steel

Points of concern of current automatic lancing systems:

  • Low measurement frequency (60 seconds between dips)
  • High risk of failure (disposable probe can hit piece of scrap during dip)
  • Lance operator is present at dangerous area in EAF plant near slag door (fits probe to lance system)

These single dip measurement systems are however not accurate enough to guarantee problem-free tapping at all times.

Erratic temperature profiles and significant fractions of residual solid scrap near the end of the production cycle are observed despite considerable safety margins being applied. A next generation of temperature measurement techniques is needed to further improve operational performance of EAF.

Introduction of CoreTemp

A new, optical fiber based, measuring system has been developed, capable of delivering accurate temperature readings every 20 seconds. Black body radiation from inside the liquid steel pool in the EAF is transmitted through a shielded optical fiber onto a light emission detector where Planck’s law is applied. A semi-continuous temperature profile can now be established to help accurately define the desired end point of the melting cycle.

Advantages of the CoreTemp system:

  • Decreased energy consumption
    • Furnace control near end of melting cycle
    • Increased frequency of temperature measurements
    • Tapping temperature reduced by 10°C
  • Increased efficiency of the furnace
    • Increased thermal arc efficiency
    • Deep foamy slag conditions allowed (+2min won)
    • Opening slag door not necessary
  • Assessment of residual scrap (solid) at the end of the melting cycle
    • Avoiding blockages of the tap hole

Ladle Treatment

Ladle

Products

Hydrogen Control

Hydrogen Control is applied to:

  • Meet the hydrogen specification,
  • Avoid blowholes in as cast or as rolled products
  • Avoid hydrogen related breakouts in the cc mould
  • Decide if (additional) degassing is necessary

Hydrogen is the cause of a number of steel defects and cases of failure. These defects are caused by internal pressures developed when hydrogen atoms pair to form the stable higher volume molecule H2. The incidence is increased by increased hydrogen content and plate thickness

Potential defects are:

  • Flake formation
  • Hydrogen induced cracks
  • Fish eyes
  • Blowholes and pinholes
  • Longitudinal surface cracks
  • Excessive unnecessary heat treatments

Hydris measurement can be used

  • To optimize process control:
    • By defining H pickup of different additions
    • Minimizing H pickup by quantifying hydrogen pickup additions
    • Define H level before casting to control H pickup in tundish
  • As a routine instrument:
    • Determining the necessity of an additional degassing step
    • Determine most optimal sulphur content as function of measured H

Hydris: a revolutionary method to control hydrogen has become mature

Deoxidation control at the ladle treatment station

One of the main purposes of ladle metallurgy is to adjust the chemical analysis of the steel in order to have a composition appropriate for the continuous caster. The deoxidation praxis for billet and slab caster must be distinguished, because of the different steel grades.

  • LCAK-steel grades (slab casters):
    • calculation of necessary Al additions to kill the steel and to reach the required Al in almost 1 step
    • minutes per heat can be saved
    • after Al addition and homogenization stir: check final Al before sending ladle to continuous caster
    • control the oxygen in the slag to avoid re-oxidation of the steel
  • Mn-Si-killed steel grades (billet casters):
    • O is controlled by Si and Mn content
    • Upper level: presence of pinholes and blowholes in the billet
    • Lower limit: nozzle clogging: limited max Al content
    • clog due to oxidation of Al by entrapped air in steel stream or reoxidation by slag or ladle refractory material -> increased steel quality

Process Control

The Celox® sensor method, as the world’s standard for oxygen control in liquid steel, enables a lean ladle management in shops running in mixed operation, producing both, concrete and quality Al-killed grades. Significant investment can be saved and operational costs are optimized.

Learn more about process control in continuous billet casting with Celox®

Degasser

Degasser

Products:

Degasser applications for HYDRIS®

Influence of degassing parameters on the final hydrogen content

  • Degassing time: the hydrogen level will decrease with increasing degassing times. However, the reduction in hydrogen will start to slow down as soon as hydrogen levels are being reached of 2 ppm. As soon as this level is reached, other degassing parameters will become more important.
  • Vacuum pressure: agood maintenance of the degassing unit is crucial to ascertain very low hydrogen levels. Final hydrogen contents below 1 ppm can only be achieved with vacuum pressures of below 1mbar. The hydrogen level will not decrease if a working pressure of 100mbar is used.
  • Initial hydrogen level:if only short degassing treatments are applied, it is essential to avoid too high hydrogen levels. Valuable time will be lost to eliminate the superfluous hydrogen. The initial hydrogen level is, however, less critical if longer degassing times are applied.
  • Use of additions: additions at the end of the degassing cycle can spoil the degassing efforts as they can rise the hydrogen pick-up after additions of some alloys shortly before the end of the degassing treatment in an RH.
  • Volume of inert gas blowing: the hydrogen reduction can be maximized by increased argon flow
  • Type of steel grades:Some steel grades require longer degassing times to ascertain very low hydrogen levels.

Summary:

  • Process Control: accurate hydrogen measurements before and after degassing enable the process to be understood and optimized. The potential exists both to reduce treatment cost and also final hydrogen concentration
  • Labeling the product:immediate hydrogen measurement at the end of the degassing cycle provides the steel maker with an improved quality monitor prior sending the ladle to the caster or ingot station. This procedure imposes responsibility to the degassing unit and influences the final quality.

Tundish (continuous casting)

Hydrogen Control

Influence of continuous casting on the final hydrogen concentration Hydris and quality control. A pick-up of hydrogen in the tundish can hardly be avoided.

At the start of a new sequence, special care must be taken to reduce the hydrogen pick-up as much as possible. Despite of the preheating of the tundishes before the start of casting, the moisture deeper in the lining will slowly release hydrogen that gradually will be picked up by the steel. The accuracy of Hydris allows the user to obtain very specific data characterizing the pick-up in the tundish.

Breakout detection

Various workers have confirmed a relation between the hydrogen content in the steel and breakouts on the continuous caster. Related breakouts are of the sticking type and explained by the absorption of hydrogen into the mould lubricant. The gas bubbles cause crystallization of the flux and increase in viscosity. As lubrication deteriorates the tendency to breakouts is increased. The risk of breakouts becomes very critical as soon as the hydrogen level exceeds 9ppm. These types of failures can hardly be detected by pin samples as their reliability drastically decreases for high hydrogen levels.

Thin slab casting

The final product of the thin slab casters is also affected by the hydrogen content in the tundish. Excessive hydrogen contents result in deterioration of the casted quality and should therefore be monitored.

Direct rolling

Directly rolled steel is more sensitive to flake formation, as cooling time is short after casting, decreasing hydrogen removal during cooling as the cast product. A direct hydrogen measurement is essential to inform on the necessaty of additional annealing treatments

Hydris application report

CasTemp Wireless

CasTemp

Achieving enhanced caster performance by utilizing accurate and reliable continuous temperature measurement.

  • The application of an accurate and reliable system for continuous temperature can allow thermal models to be developed and improving in caster productivity and quality.

The maximum casting speed that can be safely obtained for a given superheat depends upon accurate knowledge of superheat, cooling ability of the casting mould, the strength of the slab shell for the given steel chemistry, secondary cooling, and length of containment rolls below the mould.

Implementation at Mittal Steel

  • Maximization of casting speed and throughput of the cast
  • Better control of steel residence time has the opportunity to better control alumina transfer during ladle exchanges
  • Potential for manpower reductions by elimination of most dip probe measurements
  • Avoid break-outs and freezing of the caster
  • Exact temperature of the liquid metal just before the steel reaches the mold

Read more about how the CasTemp implementation in Mittal Steel enabled to optimize the steel making process

Mould (ingot casting)

Casting

Products

Influence of ingot casting on the final hydrogen concentration Process control

Hydrogen pick up in the ingot cannot be avoided. The accuracy of Hydris allows, however, the steel maker, to minimize the hydrogen pickup by optimizing his ingot casting practice.

The accuracy of Hydris ensures the steel maker meeting the required quality standards. The confirmation is independent on the handling practice of the operators.

The measured hydrogen levels will decide which annealing process should be applied after casting.

Hydris application report

Galvanization process product applications

Benefits:

  • Quality: Continuous control of effective aluminium in zinc keeps a constant metallurgical coating process and minimizes dross formation. It enables improved process management and drift analysis
  • Cost: Dross reduction leads to less build-up on rolls and thus enables less frequent roll changes
  • Laboratory aspect: aluminum activity and the temperature in zinc are directly obtained from the sensor.
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