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How to generate ROI with EMG IMPOC?

Online measurement of material properties of ferromagnetic steels

Development of the IMPOC raw value over strip length measured in a hot-dip galvanizing line

Flat steel producers heavily depend on online quality data to maintain the production processes on an optimum level and to avoid costly rework or downgrading of material. As described already in earlier articles, the EMG IMPOC system (Impulse Magnetic Process Online Control) delivers reliable online results for tensile strength and yield strength and allows immediate process interactions.

Today more than 70 EMG IMPOC systems are utilised in HDG, CAL, pickling and tinning lines as well as pressing lines in the automotive industry. 

EMG IMPOC covers a wide material spectrum from IF-steels, Dual Phase steels, TRIP steels and 3rd Generation AHSS Grades with tensile strength values up to 1600 MPa. The system can be applied at production speeds up to 900 m/min for material gauges up to 3 mm and for production speeds up to 600 m/min for thicker material up to 6 mm.

Based on the application scenarios worldwide the major return of investment factors for EMG IMPOC have been clearly identified and analysed: reduction of destructive testing, faster and more accurate coil release, minimising scrap, more efficient and less costly rework, higher yield and tremendous cost reduction in the development phase of new steel grades.

But, why is EMG IMPOC such a powerful tool?

As the reader may already know, EMG IMPOC does not allow a direct measurement of material properties (i.e. tensile strength and yield strength). The direct IMPOC measurement value is the gradient of residual magnetic field strength in A/m² on the top and bottom side of the steel strip (the so-called IMPOC raw value). Based on that raw value, the mechanical parameters of the steel strip (i.e. tensile strength and yield strength) can then be assigned to this gradient via correlations with the destructive testing results and mathematical modelling taking into account the steel group, the strip thickness, the skin-pass rolling and the yield degree either in combination or separately.

But even without mathematical modelling EMG IMPOC delivers valuable data. The IMPOC raw value can be produced over the entire strip length immediately after installation, thereby enabling a relative statement to be made regarding the material behaviour in the coil.

The monetary value of the IMPOC raw data for the development of new steel grades

The image shows a typical curve for the IMPOC measurement raw value over the coil length. 

In this graph the typical bath tub form shows the influence of the different cooling scheme at the beginning and end of the coil due the up-coiling at the exit of the hot mill. The tension leveller degree is unchanged over that period. The variations over strip length in this specific case are in the  range of 10 %. This makes process drifts and even minor deviations visible and allows proper and immediate reactions. Producers do not need to wait for the results of the destructive testing available only hours later and intensive destructive testing can be reduced; an invaluable asset for the development of new materials especially for AHSS (Advanced High Strength Steels).

Process optimisation based on IMPOC measurements in the pickling line 

Another specific application is the use of EMG IMPOC in pickling lines. Pickling lines are the first element in the process chain to detect deviations from the desired material properties. Because destructive testing results aren’t (or in less quantity) available at pickling lines, EMG generated “standard coefficients” for regression models, which can be applied in pickling lines. Long term analysis showed that these “standard coefficients (IMPOC express)” delivered absolute values for the tensile strength which differ from relative changes in full blown models only in the range of +-5 %. In the end the user gets a perfect overview of the relative changes of tensile strength over strip length and a good indication of the absolute values. Immediate reactions with respect to strip release and blocking or alarms concerning cooling problems in the hot mill are therefore a direct consequence of the IMPOC application in pickling lines. Again, for this application no further model development is required and the user gets the results immediately after the system operation starts.

Further return of invest factors result from the model development

In case the user decides to start the development of mathematical models for different steel groups, with or without the support of EMG experts, further ROI factors materialise. Without going into details, they cover the following elements:

  • Full online transparency of the material properties tensile strength and yield strength over strip length and width (absolute values)
  • Possibility of immediate production interventions in case of material properties deviations. Thus, avoiding faulty production and rejections.
  • Drastic reduction of inspection and rework costs
  • Substantial reduction of destructive sampling costs
  • Perfect control of the outgoing material for further processing internally or externally (e.g. at the automotive producer)
  • Fulfillment of the requirements of the end customer 
  • Possibility to transfer the quality records regarding material properties to the end customer; an increasing demand of the automotive industry



Of course, the exact monetary value of the EMG IMPOC application heavily depends on the specific application scenario for the specific production line. EMG offers various ways to support you in the calculation of your own possible ROI by the introduction of EMG IMPOC. This is on the one hand a summary EMG techpaper (IMPOC – HOW TO GENERATE ROI WITH ONLINE MEASUREMENT OF MATERIAL PROPERTIES IN FLAT STEEL PRODUCTION 2021) which goes deeper into that topic, which we provide you on request (just send an email to under the subject IMPOC ROI). On the other hand, we provide direct consultancy and IMPOC ROI workshops using a ROI calculation template for your direct support. In case that you are interested in the latter, just send a  short, informal email to We are happy to support you whenever and wherever you want, digitally or in on-site meetings. 

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