Tribological investigations of hot-formning tools

Industrial Partner: Accra Teknik/ Linde+Wiemann Group

Background
Accra Teknik AB/ is a member of the Linde+Wiemann Group and a subcontractor to the automotive industry. They are working with hot forming and hardening of high strength steel components. They have been actively involved in a research project together with the Division of Machine Elements at Luleå University of Technology since 2005 which focuses on high-temperature tribological studies on tool and high strength steels.

 

Introduction
This is a continuation of the earlier project together with Accra Teknik AB.

The form-fixture hardening process is utilised by Accra Teknik AB for hot forming of closed high strength steel profiles. Improving the life of the hot forming tools is a very important objective when looking at the process economy. Since the cost for manufacturing the tools are very high, any improvement in the durability will be highly beneficial for the overall plant economy.

Accra Teknik utilises direct water cooling to quench their hot formed components. They are interested in investigating if there are any differences between water quenched and press quenched boron steel. They are also interested to study how the time above austenitisation temperature affects the dimensions and microstructure of the high strength boron steel.

Purpose and aim
The first part of this project aims at systematic investigations into the failure of hot forming tools with a view to understand the failure (damage) mechanisms.

The results of this project will help in:
- Optimising tool designs to prevent failure induced by the geometry of the tool.
-Selection of most suitable materials and surface treatments/coatings for hot forming tools and
- Finding possible ways of refurbishing the tools

The second part will focus on investigating if there is any difference, in terms of microstructural changes and abrasive wear resistance, between 22MnB5 steel that has been quenched in different ways. The project will look specifically at:
- Does the faster cooling rate with direct water cooling cause cracks in the material?
- How fast can 22MnB5 steel be cooled without causing cracks?
- What happens to the microstructure of 22MnB5 if it is quenched very rapidly?
- Is there any difference in abrasive wear resistance between 22MnB5 steel quenched in different ways (direct water, press-hardened and high quench rate)
- How does the time above austenitisation temperature affect the dimensions and microstructure of the 22MnB5 steel?
- Does the austenitisation temperature affect the microstrucure?

Scope of work
Two different failed hot forming tools will be analysed. High strength boron steel (22MnB5) will be studied at different quenching rates, austenitisation times, material thicknesses and quenching methods. The studies will include abrasive wear tests, microstructural investigations and hardness tests.

Page Editor and Contact: Hans Åhlin

Published: 9 November 2010

Luleå University of Technology