Surface Control of High Strength Steel for Galvanization
Lead Research Organisation:
University of Warwick
Department Name: The Warwick Manufacturing Group
Abstract
To be able to develop and produce smarter materials in an environmental and economical way, more flexible technologies are required.
One such a potential breakthrough technology is flexible high-speed Physical Vapour Deposition (PVD). In this process, a vapour is generated in a vacuum and then sprayed onto a strip, thus forming a thin solid film. This technology allows the deposition of a unique selection of coatings onto high quality strip products enabling the optimization of both the substrate and the coating. Motivation to pursue PVD technology not only lies in its future applications, but also in current issues. The automotive industry is pushed to reduce CO2 emissions and improve fuel economy, and one route to achieve this is reducing vehicle weight. Cars can be made lighter by using coated novel Advanced High Strength and Ultra High Strength (UHSS) Steel grades as they deliver the same strength in thinner sections. These steel grades are produced with relatively high alloy levels of Mn, Si and Al. However, such alloying additions influence the coatability for corrosion (typically Zn galvanising), which results in different coating recipes for each steel grade. Some grades are impossible to coat with Hot Dip Galvanizing. Hence, to be able to assist the automotive industry in achieving the future weight saving both steel grade and coating development are essential. The flexible PVD technology will make it possible to coat this range of UHSS and will enable the manufacturing of future substrate/coating systems with an enhanced performance that can presently not be produced.
This PhD project in collaboration with Tata Steel Europe will address the following research questions:
How can the oxide formation and type be controlled during the strip production?
How do different oxides affect the coating performance - adhesion, surface appearance, corrosion?
How can the oxides be removed from the strip before coating - e.g, plasma cleaning?
How does the thickness/stress in the Zn/ZnMg coating layer on top of the substrate influence the overall performance?
One such a potential breakthrough technology is flexible high-speed Physical Vapour Deposition (PVD). In this process, a vapour is generated in a vacuum and then sprayed onto a strip, thus forming a thin solid film. This technology allows the deposition of a unique selection of coatings onto high quality strip products enabling the optimization of both the substrate and the coating. Motivation to pursue PVD technology not only lies in its future applications, but also in current issues. The automotive industry is pushed to reduce CO2 emissions and improve fuel economy, and one route to achieve this is reducing vehicle weight. Cars can be made lighter by using coated novel Advanced High Strength and Ultra High Strength (UHSS) Steel grades as they deliver the same strength in thinner sections. These steel grades are produced with relatively high alloy levels of Mn, Si and Al. However, such alloying additions influence the coatability for corrosion (typically Zn galvanising), which results in different coating recipes for each steel grade. Some grades are impossible to coat with Hot Dip Galvanizing. Hence, to be able to assist the automotive industry in achieving the future weight saving both steel grade and coating development are essential. The flexible PVD technology will make it possible to coat this range of UHSS and will enable the manufacturing of future substrate/coating systems with an enhanced performance that can presently not be produced.
This PhD project in collaboration with Tata Steel Europe will address the following research questions:
How can the oxide formation and type be controlled during the strip production?
How do different oxides affect the coating performance - adhesion, surface appearance, corrosion?
How can the oxides be removed from the strip before coating - e.g, plasma cleaning?
How does the thickness/stress in the Zn/ZnMg coating layer on top of the substrate influence the overall performance?
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/P510695/1 | 01/10/2016 | 31/12/2021 | |||
| 1791922 | Studentship | EP/P510695/1 | 03/10/2016 | 12/09/2021 | Jennifer Rolls |
| Description | We have been working on optimising the analysis of complex surface oxides on steels; this is challenging because these oxides have a thickness and diameter of a few millionths of a mm and vary in distance across the surface. This is still an active project and so research is still taking place towards final findings and discoveries. The main discovery is that we are now able to visualize the occurrence and growth of the oxides on the surface. We also have a better idea on what zinc coating process is best for the grade of steel this project focuses on. |
| Exploitation Route | The current findings of this project could be used in the following ways: Industrial- to optimise the annealing/coating process of various steel grades (this work is in collaboration with Tata Steel), since coating adhesion on the steel is strongly dependent on the presence of oxides. Academic- analytical techniques for thin surface oxides, and how to optimise for the best results. This results in, amongst others, a fundamental understanding of oxide nucleation and growth mechanisms. |
| Sectors | Energy,Manufacturing, including Industrial Biotechology,Transport |
| Description | This project is still in progress and so final findings are hard to comment on. However, a potential benefit has already manifested itself in the area of preparing clean surfaces for coatings to improve corrosion protection of automotive steel grades. This is due to a more thorough understanding of the oxide behaviour throughout the final annealing and coating steps. This project is supported by Tata Steel and so results and findings are reported to them and where possible, used in the surface preparation process. |
| First Year Of Impact | 2018 |
| Sector | Manufacturing, including Industrial Biotechology,Transport |
| Impact Types | Economic |
| Description | Tata Steel Europe (The Netherlands) |
| Organisation | Tata Steel Europe |
| Department | TATA Steel Europe (Netherlands) |
| Country | Netherlands |
| Sector | Private |
| PI Contribution | The research question was set by Tata Steel themselves and so the work being carried out is reported back to Tata to act upon. We, at Warwick are able to spend time researching the oxides and the growth mechanisms of them. We provide the time and the research using Warwick based equipment ready for our regular meetings to discuss progress of the work. It is always an interesting discussion which really allows for the project to progress. |
| Collaborator Contribution | Tata Steel have direct, regular contact with the project and input into the research taking place. Results are reported back to the project supervisors at Tata and discussions take place about the analysis and conclusions of the results. They also provide material and samples needed for the research to take place. Their knowledge of the field of study is invaluable, both in a practical sense and in an intellectual sense. There are talks about me going to their site in the Netherlands to complete some project related work in the future. They have hosted us twice in the Netherlands to allow for face to face meetings, and a big summary of the work, this really allows for indepth discussions and is very beneficial to the project. |
| Impact | As a result of this collaboration, there is a good realtionship between the team in the Netherlands and the research group here at Warwick. The research pertaining to this project is still ongoing and thus the final outcomes are hard to comment on at this present time. Outcomes so far include, the optimisation of oxide analysis on steel surfaces, which is made difficult due to the lateral and vertical size of the oxides. |
| Start Year | 2016 |