TPT March 2022

Improvements for seamless tube The seamless tube industry has gone through certain revolutions process improvements. PQF/FQM mills which replace previous MPM, FMM and Plug mills have been installed across the globe thanks to the successes of their respective manufacturers. However, even with these new mill types, the basics of seamless tube remain the same, and what remains as two critical areas that have been neglected are deoxidation and mandrel bar lubrication. A case for deoxidation improvement Deoxidation remains a critical process within the seamless-tube manufacturing process. When a round billet is pierced, scale formation starts immediately inside the newly formed shell. This scale, if not handled correctly, will cause serious problems throughout the rest of the process. Typically, immediately after piercing, the loose scale is blasted out through the shell via a method referred to as Scale Blowout. Immediately after that, deoxidation powder is blown through. This powder interacts with the scale and turns it into a lubricating liquid. The shell is then transferred to the next process where a graphite-coated mandrel is inserted into the shell and together they are rolled in the rolling process. The amount of powder that is blown has drastic consequences for the final pipe quality: too little powder and the scale is not melted, while the operator risks having significant wall thickness variation and rolled-in scale defects. If too much powder is added, the added mass can cause serious cold bits to form on the mandrel, stopping the process altogether. Therefore, it is critical that the deoxidation powder is properly applied. Design Management Konsulting Oy (DMK) has just delivered the most modern deoxidation system currently known. The system allows for the handling and injection of powder to be located further away from the powder nozzle than ever before. The spray has been optimised using high-level 3D printing techniques. But the most important feature is the dosing accuracy. Where current and previous systems boast an accuracy of ±10 to 20 per cent, the DMK system boasts an accuracy ±6 per cent, which can be further improved, if process conditions allow, to ±1.5 per cent. This improvement not only saves the mill money in deoxidation powder consumption, but permits having a tighter control of the amount of powder being dosed. Having better control of the deoxidant powder allows for the operator to have a tighter control of the entire process and therefore allows the operator to improve product quality, consistency, overall efficiency and savings due to improved prime yield. A case for mandrel-bar lubrication improvement The other significant, and often under-engineered, process in many seamless-tube mills is the Mandrel-Bar Lubrication (MBL) system. After piercing, the shell is transferred to the front of the rolling mill where a coated mandrel is inserted. The mandrel is coated with a graphite lubricant by the MBL

These are applied in the following way: the ScaleFree equipment is installed in a location where scale formation is at its lowest, typically right after casting or descaling. The ScaleFree equipment then sprays the ScaleFree coating onto the hot billet/shell/slab/etc forming a 5-80µm protective layer on the surface. The ScaleFree layer then inhibits the formation of scale by significantly reducing the interaction of oxygen with the steel surface. The ScaleFree coating further reacts only with the existing surface scale to turn it into a lubricating paste. This results in a protective layer being formed on top of the steel so that: • The billet/shell/slab/etc can be reheated with only a limited amount of new scale being formed • Rolling loads are reduced, which then improves tool life • Scale pickup on the rolls is reduced, further improving tool life • Rolled-in scale defects are also minimised, thus improving surface quality • Pickling costs shrink since the method improves pickling efficiency • Sandblast costs are reduced due to improved surface quality The benefits of ScaleFree technology are significant. With a yield improvement of 33 per cent the customer’s plant could save almost €6.5mn annually. With increased pickling efficiency of 25 per cent the customer could save an additional €4.4mn annually. With the average operating cost being €1-4/ton the impact for the customer, not only in direct financial savings but also improved quality, increased efficiency and value-added prime yield, is clear. Investing in ScaleFree technology is both financially and technically sound. ScaleFree technology has been tested with major companies within the steel industry and is currently being implemented in locations around the globe. Design Management Konsulting Oy (DMK), is looking for new locations and interested partners to further implement ScaleFree technology.

Deoxidation system with overhead crane loading and climate control cabinets

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March 2022 TUBE PRODUCTS INTERNATIONAL