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Category Archives: Mold Profilometer

Taper Loss: external deformation cause internal damage?

The link between deformation on the mold external surface and taper loss on its internal faces was unknown. The correlation between those two can only be noticed through a precise measuring equipment, which helps detecting internal anomalies, that happens to be millimetric.

The root cause for mold external surface deformity can be many, such as handling and transport errors and water jacket and screw assembling errors. Even though the copper mold presents a good mechanical resistance for its application, it can experience the consequences of those errors and present deformities. That way, when caused, those defects can lead to some several production problems, because once the taper is compromised, it is not possible to assure the proper steel skin formation.

[Case Study] Water Jacket Assembling Error

Recently a Tozato costumer identified an external surface deformity caused by a water jacket assembling error that ended up seriously damaging the taper on its interior. In this occasion, when proceeding with mold’s assembling in the jacket their screw got uncontrolled thigh up causing a warping on the external surface; As a consequence it constricted the interior face and caused taper loss.

Slag Detector Main Screen

In picture 1, the two areas that were most affected by extreme screw pressing are pointed. It is also perceptible that the warping is extended through the mold following the same direction.

It is worth mentioning that, to a naked eye, the warp caused by the jacket screws did not indicate to have caused a taper damage. Only by utilizing a measuring equipment, it was possible to detect this deformity, which at first would have go unnoticed. That said, the mold’s measurements showed the following results:

Slag Detector Main Screen

In the picture above, a severe warp is identified in the area indicated in the graph, which was most damaged by the assembling error. Besides that, from this point on there is wear that goes all the way to the mold end.

Production Risks

Using out of specifications molds can lead to defects on product’s surface, such as cracks (which have the wrong taper as one of their listed causes), besides the possibility of bleedings and breakouts. With measuring results in hands, it was possible to conclude that this mold was not inside the expected profile; thereafter it could represent a risk to the production if not discarded.

Slag Detector Main Screen

For example, product downgrading is one of the damage provoked by a breakout, as we can see in Picture 3: a thin steel skin that has ruptured during negative strip process due to ferrostatic pressure.

Conclusion

That said, it becomes evident the necessity to create a preventive maintenance culture, that utilizes precise technology like the ones provided by Tozato, aiming to avoid new and old molds improper use, considering the many disadvantage that can occur from the sum of this situation. The preventive maintenance will help to increase the mold’s service life, reduce the product defects, like cracks and breakouts, reduce machine downtime, as well as avoid the premature discard of the mold.

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Cracks due to copper mould meniscus deformation

Recently, a customer hired Tozato Measurements reporting cracks in their product in a particular strand. The cause was unknown, so the work was to investigate the possible problems that would lead to cracks formation.

The procedure consisted in analyzing the internal condition of a 180 mm x 180 mm copper mould which was being used, and checking its conformity to the desired taper and profile.

Measurements and Data Gathering

A mould profilometer system was used to check a 180 mm squared mould profile with a service lifetime of only 50 heats. The readings were performed for both straight and curved face.

Firstly, the data was collected for the straight face and Figure 1 shows a screen from the equipment software which abnormal and deformation is visible in the meniscus region.

Measured graph with deformation at meniscus area

Deformation found in the meniscus area for the straight face.

Secondly, the data was collected for the curved face of the mould, which also presented notorious deformation in the meniscus area. The software screen showing the deformation in the region can be seen in Figure 2.

Measured graph of a curved face with deformation at meniscus area

Deformation found in the meniscus area for the curved face.

Thus, both straight and curved faces of the mould presented accentuated deformation in the meniscus, which can easily explain the cracks on the product. However, some more investigation was needed.

Further Investigation of Cracks Causes

Once found noticeable deformation in the meniscus area of a copper mould with only 50 heats, a concern was raised towards the mould condition previous to the casting moment. Was the mould already worn when first put in operation or was the mechanical conditions of the oscillator that caused the deformation?

Thereby, measurements were done in an identical brand new 180 mm x 180 mm copper mould, with no heats performed, which allowed to collect the data presented in Figure 3 and Figure 4.

Measured graph with no deformation

No deformation found in the straight face of the brand new mould.

Measured graph with no deformation curved face

No deformation found in the curved face of the brand new mould.

Once identified that the straight and curved faces did not present deformation in the meniscus for the brand new mould, the customer started investigating the possible causes for the deformation in the particular region, following the orientations of which would be the most appropriated tool for this purpose.

Upshot

Meniscus deformation is considered a critical abnormality which leads to serious problems in the product quality. The company needs proper tools in order to be able to prevent issues such as prematurely worn moulds or undesired taper for the specific steel grade. Thus, only with the possession of appropriated technologies, it was and it is possible for the customer to identify the real cause of the problem.

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Friction and its Relation with Internal Mold Condition

There is a relation between the mold internal condition and the oscillation friction during the continuous casting process. This relation, however, was only proved after applying both Mold Oscillation Monitoring and Mold Profile Checker simultaneously. Check out the results down below.

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Surface and format defects caused by using wrong mold profile

Surface and format defects as well as breakouts may be caused by wrong mold profile and /or irregularities in the cooper mold profile. Knowing these failures is the very first step to prevent to become the next victim and accumulate losses. When it comes to such important part of steel making process, which is the CCM copper mold, some care and regular maintenance practices are of utmost importance to ensure its proper use.

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Can brand-new copper molds present profile mismatch?

Purchasing new molds for continuous casting machines is a daily basis procedure in the steel plant environment. In most instance, confident on the information provided by the manufacturer, brand-new copper molds without passing through any internal and dimensional taper overhauling process replace outworn ones. However, Tozato technical team performed case studies that testifies the need of checking the mold profile, even in brand-new copper molds.

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Early wear and friction on continuous casting copper molds

The high friction level in continuous casting machine’s mold tubes strongly reduces their service life. A relation that can be proved by using appropriate tools to collect and analyze data.

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Oscillator topographic unleveling and mold service life time

It is rather common to have the copper molds with decreased service life due to early wear. The improper wear, among other reasons, is caused by intense friction between the product and the mold, therefore, resulting in trajectory errors offset caused by an oscillation table topographic unleveling.

After all, is there a straight relation between the oscillation table topographic leveling and the coper molds early wear? The study below will help you to understand how much these two factors are related.

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Trajectory errors and mold wear: the correlation between these factors

During the continuous casting process, many factors may cause surface defects. However, two of them are very common and need special attention: oscillator’s trajectory errors and mold wear.

Nonetheless, it was not always possible to verify and prove the correlation between those two factors. With the advance of technology in oscillation monitoring, and in mold internal faces’ measurements, it was possible to prove this relation successfully. Find out more:

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