ATAS is an advanced tool based on thermal analysis, intended for use as a resource for controlling and monitoring the melt and treatment processes for gray and ductile iron. ATAS is composed of several systems and add-in modules, making the system easily adaptable to the specific needs of the foundry. ATAS metallurgical process control helps reduce the amount of scrap, increase the yield, reduce costs for alloying material and achieve a high and consistent quality of the castings.

We have chosen a number of applications to visualise the various areas where ATAS can be used. The system can gradually be built out. The foundry can e.g. start with ATAS White for controlling the carbon equivalent in the base iron and then add ATAS Verifier to test the final iron.

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The ATAS system consists of the following products and add-in modules:

• ATAS White
• ATAS Verifier base version 
• Action Editor 
• Risk & Explain 
• Dynamic Inoculation 
• Nodules 
• ATAS Inoculation 
• ATAS Nodules 
• ATAS Research 
• ATAS Curve Viewer
  

50 ways of using ATAS
1. Measure the room temperature
2. Measure the liquidus temperature
3. Measure the liquidus plateau
4. Calculate the active carbon equivalent
5. Measure austenite precipitation
6. Measure the “grey” low eutectic temperature
7. Measure the “white” eutectic temperature
8. Measure the high eutectic temperature
9. Register the recalescence
10. Estimate the amount of dissolved oxygen
11. Measure the under cooling
12. Estimate the risk for chill
13. Measure the average recalescence rate
14. Measure the maximum recalescence rate
15. Evaluate the carbon precipitation during the first part of the solidification
16. Evaluate the carbon precipitation during the later part of the solidification
17. Estimate the risk for macro shrinkage
18. Estimate the risk for micro shrinkage
19. Estimate the risk for inverse chill
20. Control and adjustment of the carbon equivalent for base iron

21. Quality assurance of base iron
22. Quality assurance of final iron
23. ATAS as an “early warning” system
24. Adjustment of the inoculation addition
25. ATAS as a learning tool
26. ATAS as an interactive process control system
27. ATAS as an optimising tool
28. ATAS as a tool to compare quality results between shifts
29. See the combined effect of all carbide stabilising and all graphite stabilising elements
30. Compare different cooling curves
31. Fine-tune the carbon equivalent
32. Compare various inoculants
33. Test the need for inoculation
34. Test the FeSiMg alloys
35. Delivery check of charging and addition material
36. Test the effect of various charge compositions
37. Test the effect of different charging sequences
38. Test the effect of time and temperature
39. Measure the “silicon equivalent”
40. Optimise the addition of copper and tin
41. Quality assurance of the matrix through pearlite estimation
42. Control the pearlite content for “transition iron”
43. Define thermal parameters for the castings
44. Calculating magnesium addition
45. Predicting nodule count
46. Predicting hardness
47. Define limits to be able to cast without feeders
48. Minimize the need for feeding
49. Tool for research and development
50. As a metallurgical knowledge accumulator

1. Measure the room temperature
When a Quik-Cup is placed on the cup holder, the temperature is shown in the status bar at the bottom of the start screen. It might be a good idea to check the room temperature when a new cup is placed on the holder. If the temperature seems totally incorrect, this is an indication of an error either in the cup or in the system connections. Please note that if the cups have been stored in a place where the temperature is different from the room temperature, it can take a minute before correct room temperature is shown on the screen. If there is a constant deviation, the correction can be set in the ”Parameters” screen of ATAS.
If the TwinCup system is used, the difference between the cups should not be larger than 0.3º C.

2. Measure the liquidus temperature
The liquidus temperature for hypo-eutectic alloys is a measure of the active carbon equivalent, see below, and can therefore be used as the first estimation of the behaviour of the alloy during solidification. The liquidus temperature measured by ATAS displays a horizontal plateau, the liquidus plateau, which is partly due to precipitation of primary austenite and partly to precipitation of eutecticum on the walls of the cup. The liquidus temperature can be used for adjusting the active carbon equivalent. If liquidus is higher than the normal maximum then problems with macro shrinkages and even cold laps might occur.

3. Measure the liquidus plateau
Liquidus plateau is defined as the time in seconds when temperature is within liquidus temperature +/- 1º C, which means that the temperature gradient at the thermocouple is actually zero. The gradient is effected by precipitation not only of austenite but also of eutecticum at the walls of the cup, because the cup is cold and initially absorbs energy. The liquidus plateau therefore indicates how the primary solidification takes place.

4. Calculate the active carbon equivalent
By using the values for C, Si and P from chemical analysis a so-called carbon equivalent can usually be calculated as CEL = C + Si/2 + P/4. The carbon equivalent has shown a fairly good correlation to the properties of the iron, even though only three elements are taken into account, while free oxygen and oxides are not considered at all. ATAS calculates the active carbon equivalent of the iron. The active carbon equivalent, ACEL, shows how the iron solidifies under the influence of all basic elements, gases, oxides and other compounds present in the melt that affect the solidification. ACEL shows the integrated effect of all influencing factors! CEL is a rough estimation and ACEL is the correct carbon equivalent.

5. Measure austenite precipitation
From the liquidus temperature down to the low eutectic temperature, there is a precipitation of mainly primary austenite. In ATAS the value of the parameter S1, Surface 1, is calculated and this is a relative value of the amount of primary austenite.

6. Measure the “grey” low eutectic temperature
The ”grey” low eutectic temperature is the lowest temperature registered during the eutectic solidification. A low temperature indicates that the nucleation properties of the melt are bad. A low total oxygen level results in a low eutectic temperature. The grey eutectic temperature is also depending on the chemical composition of the alloy.

7. Measure the “white” eutectic temperature
When Quik-Cups with Tellurium are used, the samples solidify metastable, i.e. all carbon precipitates as cementite, Fe3C. The white eutectic temperature is mainly influenced by the basic elements Si, P Cr and Mo. The temperature shows the combined effect of these elements. What is actually measured is a “silicon-equivalent”. The temperature is not affected by oxides or other compounds. The white eutectic temperature shows only the influence of the basic elements, which means that if the nucleation properties for melts with the same chemical composition vary, then the white eutectic temperature is constant but the grey eutectic temperature can vary considerably.

8. Measure the high eutectic temperature
The high eutectic temperature is dependent on the alloy composition, as well as on the nucleation of eutecticum and therefore on the precipitation of graphite. A high value is usually favourable.

9. Register the recalescence
Recalescence is the difference between the low and the high eutectic temperature. A high recalescence indicates that the melt needed a high undercooling before nucleation took place. The recalescence is therefore a good indicator of of the initial nucleation ability of the melt. Inoculation reduces the recalescence.

10. Estimate the amount of dissolved oxygen
Amount of dissolved oxygen affects the carbon activity. A high amount of oxygen reduces the carbon activity, meaning that the alloy reacts as if the carbon content is lower than it really is. This is registered as a higher liquidus temperature than normal for a given carbon content. The amount of dissolved oxygen is affected by the chemical composition of the alloy and the holding times at different temperatures.

11. Measure the under cooling
The under cooling is the difference between a certain temperature and the ”grey” eutectic temperature. A high under cooling means bad nucleation ability. ATAS calculates the under cooling as the difference between a theoretical grey temperature and the measured temperature.

12. Estimate the risk for chill
Chill is precipitation of primary cementite, especially in areas of high cooling rate. The risk can be estimated by studying the difference between the grey low eutectic temperature and the white eutectic temperature. A big difference is favourable to avoid problems. An increase of Si content increases the grey low eutectic temperature and decreases the white eutectic temperature, which increases the difference in temperature and decreases the risk. Cr works the other way around.

13. Measure the average recalescence rate
The average rate for the temperature increase between low eutectic temperature and high eutectic temperature is measured by ATAS. This gives an estimation of the precipitation rate of eutecticum during the first part of the eutectic solidification.

14. Measure the maximum recalescence rate
ATAS calculates the maximum rate, C/S, during the first part of the eutectic solidification. This gives an estimation of the precipitation of graphite.

15. Evaluate the carbon precipitation during the first part of the solidification
A large amount of energy is released when dissolved carbon precipitates as graphite, which is registered by the cooling curve. Recalescence, recalescence rate, graphite factor 1, and factor S2 are the most important parameters in ATAS to study the precipitation.

16. Evaluate the carbon precipitation during the later part of the solidification
The carbon precipitation during the later part of the solidification is important especially for avoiding micro shrinkage. The factors S3, graphite factor 2 and 3, and the value of the first derivative at the solidus temperature are indicators for this.

17. Estimate the risk for macro shrinkage
Macro shrinkages, i.e. bigger holes most often situated just above heat centres, are formed during the first part of the solidification. Feeding can eliminate this type of defects. By controlling the solidification using thermal analysis the risk (tendency), can be minimised. Important ATAS parameters are the liquidus temperature, S1, the low eutectic temperature and recalescence.

18. Estimate the risk for micro shrinkage
Micro shrinkages are formed during the last part of the solidification in the thermal centre of the casting. Shrinkages occur when the amount of formed graphite and the connected expansion is not enough to compensate for the shrinkage of the austenite. With ATAS the tendency for micro shrinkages can be evaluated. This enables predicting the problem and learning how to melt and treat in order to minimize the risk. Important ATAS parameters are S3, graphite factors 2 and 3, the value of the first derivative at the solidus temperature and the solidus temperature.

19. Estimate the risk for inverse chill
A low solidus temperature compared to the white eutectic temperature indicates a high risk for the formation of cementite in the parts of the casting that solidify last.

20. Control and adjustment of the carbon equivalent for base iron
ATAS calculates the active carbon equivalent ACEL by identifying the liquidus temperature. This is usually done within 60 seconds. By calculating the difference between the desired value of the carbon equivalent and ACEL, a value is directly obtained that indicates how much carbon or silicon should be added to reach the desired value with high precision.

21. Quality assurance of base iron
Two melts with the same chemical composition can behave differently during solidification. This is caused by the fact that the solidification reaction is regulated not only by chemical composition but also by a large number of ceramic particles such as oxides, sulphides, silicates, nitrates etc. and also by dissolved gases. With thermal analysis the effect of all these parameters can be seen. The conclusion is that chemical analysis is not sufficient for quality assurance or verification of a melt.
In ATAS it is possible to define certain parameters that are essential for a certain alloy and a certain type of casting. Maximum and minimum limits can be stored in the database. These limits are used by ATAS to accept a melt. If the values of the melt parameters are outside the limits, the built-in expert system can interpret the situation and warn about the occurrence of possible casting defects.

22. Quality assurance of final iron
The principle for quality assurance of the final iron is the same as for the base iron. In ATAS , limits can be specified even for single castings or for different categories of castings e.g. ”thick wall castings in furan moulds”

23. ATAS as an “early warning” system
The built-in expert system in ATAS warns the operator if the iron is not according to specification. ATAS displays the warning as a big red question mark on the screen and also indicates which type of defect can occur.
Several foundries have used this for reducing the amount of scrapped castings due to shrinkages. If ATAS gives an alarm, the operator can e.g. change mould pattern to a casting that is not sensitive to shrinkages. The point is that the operator gets a warning before it is too late.

24. Adjustment of the inoculation addition
Foundries often use the same amount of inoculant all the time for a certain alloy. In reality the nucleation ability of the melt varies considerably. This cannot be detected by chemical analysis. With ATAS it is possible to get an estimation of the nucleation ability of the iron, by among others studying the low eutectic temperature, the recalescence, the graphite factor 2 and the solidus temperature. The amount of inoculant can be varied according to the condition of the base iron by using the module for ”Dynamic inoculation”. This helps to avoid casting defects such as micro shrinkage and expansion penetration. Some inoculant can also be saved, often up to 30%.

25. ATAS as a learning tool
Since ATAS displays the cooling curve and through the built-in explanation system can judge a sample from a melt, it can be used as an educational tool for metallurgists and floor personnel. The effect of various changes in the process can be visualised.

26. ATAS as an interactive process control system
ATAS measures what really happens during solidification. By defining fixed limits for the different parameters, ATAS can be used as an interactive process control system. Casting results can continuously be followed and correlated against the limits by using the built-in learning function. A rule-based expert system can be used to enter desired corrective actions to certain deviations. Personnel responsible for the metallurgy will thereby obtain an interactive tool for controlling the process. The expert’s knowledge is gradually built into ATAS and becomes available to all operators.

27. ATAS as an optimising tool
ATAS is an ideal tool for optimising melting and treatment processes since it registers the solidification process, calculates and quantifies important parameters. The outcome of steered experiments can directly be controlled and the optimal process thereby found. The steps like charge composition, charge sequence, melting, treatment, inoculation etc. can be fine-tuned.

28. ATAS as a tool to compare quality results between shifts
All measured curves are automatically saved in ATAS together with a time stamp. The different parameters are stored and can be monitored in the SPC section, the statistical process control. This makes it possible to follow certain parameters over time and see the variation in relation to set limits. Comparing different shifts is often a good starting point for discussions regarding quality improvements.

29. See the combined effect of all carbide stabilising and all graphite stabilising elements
By determining the white eutectic temperature, a measure is obtained of the combined effect of elements such as Si and P that decrease it as well as those that increase it, such as Cr and Mo. By determining the white eutectic temperature, the effect of the nucleation ability of the melt is eliminated.

30. Compare different cooling curves
With the ATAS Curve Viewer, up to 10 cooling curves can be input to compare different parts of the curves.

31. Fine-tune the carbon equivalent
ATAS gives a value of the active carbon equivalent after maximum 60 seconds. By calculating the difference relative a desired target value, the required addition of carbon or silicon can directly be calculated with high precision. Note that in this case no chemical analysis is needed!

30. Compare different cooling curves
With the ATAS Curve Viewer, up to 10 cooling curves can be input to compare different parts of the curves.

31. Fine-tune the carbon equivalent
ATAS gives a value of the active carbon equivalent after maximum 60 seconds. By calculating the difference relative a desired target value, the required addition of carbon or silicon can directly be calculated with high precision. Note that in this case no chemical analysis is needed!

32. Compare various inoculants
Various inoculants effect the iron differently. ATAS can be used to test different inoculants and different amounts of additions to see the effect on different parameters. The most common parameters to study when checking inoculation effects are the low eutectic temperature, the recalescence, the graphite factors 1 and 2 and the solidus temperature. Since ATAS displays calculated values for these parameters, it is easy to compare the effect of different inoculants. Tests with increasing amounts of inoculant can be made to determine the optimal amount for a certain inoculant and to study how the low eutectic temperature will increase to a maximum value.

33. Test the need for inoculation
The optimal amount of inoculant for an alloy can be found by making samples with varying amounts. The easiest way to study the inoculation effect is to study the gray eutectic temperature. Inoculation improves the nucleation ability of the iron and that causes the gray eutectic temperature to increase. The temperature is increasing with increased amount of inoculant up to a maximum value. Further increase of inoculant has no effect on the gray eutectic temperature.

34. Test the FeSiMg alloys
The Mg-alloys for ductile iron have an effect not only on the formation of nodules but also on the precipitation process of graphite and therefore also the risk for casting defects. Mg-alloys with almost identical chemical composition but from different suppliers, can have different properties due to varying production processes. ATAS can check samples from testing melts and display the result directly. The important issue is to get a good distribution of nodule size, high nodularity and an even formation of graphite all the way until the solidus temperature has been reached. Important parameters for this are the low eutectic temperature, the recalescence, the recalescence rate, graphite factors 1 and 2 and the first derivative at solidus.

35. Delivery check of charging and addition material
Variations in incoming material e.g. pig iron, steel scrap, FeSi, SiC, FeSiMg and inoculant can cause significant problems in the foundry if not discovered in time. For example the alloying elements of the new micro alloyed steel types now available on the market can effect the solidification conditions. The normal delivery check should be expanded with ATAS samples, which will give a more secure base for judgement.

36. Test the effect of various charge compositions
Properties of final iron are influenced by the charge build-up even with constant chemical composition. For example the use of crystalline graphite as carbonizer has revealed a lower fading in important parameters such as undercooling and graphite precipitation. The optimal composition can be found by making some test melts with different compositions and studying the effects with ATAS. The variation can be achieved by varying the amount of steel, pig iron and type of carbonizer.

37. Test the effect of different charging sequences
The charging sequence, that is the order in which the raw material is put into the electric furnace, may have a big influence on the properties of the melt. The sequence may even have a big influence on the wear of the furnace lining. For example, if the melting is started by the insertion of pig iron and carbonizer, this can result in a very high seering effect in the bottom of the furnace and locally very high carbon content. This can cause an excessive wear in the bottom of the furnace and carbon penetration into the lining material, which increases the risk for shortcuts. If the charging results in high silicon content in the beginning of the melt, this makes it more difficult to dissolve carbon later on. In addition to that, the equilibrium temperature of the melt is increased, which makes the entering of oxygen into the melt harder. ATAS ensures the possibility to optimise the charging sequence from a metallurgical point of view.

38. Test the effect of time and temperature
Time and temperature during melting have a big impact on the properties. The reason for this is the effect on the reaction procedures for oxidation and reduction of the different chemical compounds present in the melt. This is very true for silicon oxide and iron oxide, which effect the nucleation ability. If the melt is held just below the current equilibrium temperature the amount of silicon oxides is increased. If the melt is held some 50º C above the current equilibrium temperature the silicon oxide is reduced and the amount of dissolved oxygen increases. It is therefore very important that the melting is performed according to a specified schedule so that even properties of all melts are achieved. The differences cannot be seen by chemical analysis alone! Thermal analysis easily reveals the differences. Make a number of test melts and document the results with ATAS. Analyse the results and choose the procedure that results in the best properties of the iron.

39. Measure the “silicon equivalent”
The white eutectic temperature is determined mainly by the alloy content of elements like Si, P, Cr and Mo. If the levels of P, Cr and Mo are kept constant, the white eutectic temperature can be used to calculate the Si content. Since the levels of P, Cr and Mo in practice cannot be kept constant, the calculated value displays the combined effect of all these elements, actually a ”silicon equivalent”.

40. Optimise the addition of copper and tin
Copper and tin are most often used In the production of ductile iron castings to regulate the matrix in the iron. Too high amounts are often used in the production of pearlitic iron, to be ”on the safe side”. The formation of pearlite is however even effected by other factors such as the original nucleation ability of graphite etc. The additions of copper and tin can be optimised and costs minimised by using ATAS Pearlite to test the iron.

41. Quality assurance of the matrix through pearlite estimation
The pearlite content of the matrix is normally regulated by additions of Mn, Cu, Sn or Cr. Solidification modulus and other elements such as boron also even effect the formation of pearlite. For example if the boron content exceeds 20 PPM the level of pearlite can be lower than normal. This can happen in furnaces with new lining, where boron acid is added to ease the sintering. Using ATAS Pearlite, these deviations can be seen, which gives a more secure estimation of the pearlite content than traditional spectrometer analysis alone.

42. Control the pearlite content for “transition iron”
When producing castings in different types of ductile iron it can be useful to measure the transition from one quality to another, especially if the iron is kept in a holding or casting furnace.

43. Define thermal parameters for the castings
We are aware that it is not enough to specify a certain chemical composition for quality assurance of castings. ATAS can define values of certain thermal parameters to ensure desired casting quality. The most important parameters are the liquidus temperature, the low eutectic temperature, the recalescence, the graphite factor 2 and the solidus temperature.

44. Calculating magnesium addition
Calculate the ideal amount of magnesium and other additives to be used when treating the iron.

45. Predicting nodule count
The nodularity for ductile iron can be defined using ATAS. Different nucleation ability gives varying amounts of nodules, which results in differences in the graphite precipitation process and in heat conductivity. This is reflected in the cooling curve. ATAS must be calibrated by making samples with varying nodule count.

46. Predicting hardness
The eutectoid transformation between 800º C down to 650º C can be traced using ATAS. Data derived from the pearlite transformation is used to predict the Brinell hardness.

47. Define limits to be able to cast without feeders
Ductile iron castings can be produced without external feeding, provided that the modulus is >2cm and the moult is firm enough, e.g. furan moult with clamps. In addition to this, a sufficient amount of graphite precipitation is needed and also an even distribution of graphite in time, covering the whole solidification process. The alloy should be very close to eutectic or eutectic in composition, and the casting temperature should not exceed 1250º C to minimize shrinkage in liquid state. The metallurgical limits for the thermal parameters can be determined with ATAS and used to verify the melt before casting.

48. Minimize the need for feeding
The need for feed metal during solidification varies depending on the metallurgical condition of the melt. For example: a high amount of dissolved oxygen can lead to increasing amounts of primary austenite and this increases the tendency for shrinkage. Too high recalescence when casting in green sand moulds increases the risk for expansion of the mould, which can initiate shrinkage problems. This leads to many foundries dimensioning their feeders to cope with worst conditions. This results in a situation where, in most practical cases, the feeders are too big. Variations can be reduced if ATAS is used to control the metallurgical quality of the base and the final iron. This decreases the need for feeding metal and the total yield increases.

49. Tool for research and development
The depth and width of ATAS make it a tool for metallurgical and casting technology research and development.

50. As a metallurgical knowledge accumulator
The best experiences expressed in values of thermal parameters and in diagnoses and advice can be stored in ATAS to correct melts. ATAS should be connected to a network, to make production data available to the metallurgists and other interested persons.