A Review of the 7 th International Tooling Conference

1. A Review of the 7th International Tooling Conference PRESENTED BY: Century Sun Metal Treating, Inc. Mark Baleja, Lab Manager

2. The 7th International Tooling Conference was held in Torino, Italy. May 2-5, 2006 • Bohler, Uddeholm and Schmolz & Bickenbach are the sponsors. • The conference is one of a kind; dedicated to tooling materials and their applications. It is the only conference I know of where there are over 400 tool steel metallurgists. The conference is held every 3-4 years. The next conference is scheduled for the spring of 2009. • Presenters came from many countries including Russia, India, Turkey, China, Japan, the United States, Australia, Brazil, Algeria, and from throughout Europe. • Karlstad University, Uppsala University, University of Torino, Aachen University, Leoben University and Bochum University usually present at every conference.

3. Steel companies from around the world make presentations on new steels they are bringing to the market. • Many European countries' national laboratories present including The Corrosion and Metals Research Institute, Sweden; The Research Center on Tool Materials, France; Institute for Materials Research, Slovakia; etc. • All of the presentations from the 6th Conference can be found at http://www.ingvet.kau.se/mtrl/itc2002.shtml • The 7th Conference had at least 14 presentations that had some relation to die casting. Information was presented on thermal fatigue, modeling thermal fatigue, heat treatment, surface coatings, new hot work steels, and machining hot work steel.

4. Uppsala University discussed the machinability of modern hot work tool steels. They proved that the lower silicon, higher molybdenum grades such as Dievar, TufDie, etc. are more difficult to machine. These steels are tougher with better high temperature compressive strength than normal H13. This results in higher forces and higher temperatures at the cutting zone on the tool. Uddeholm has developed guidelines for machining Dievar steel as have other steel companies with their grades. • Aubalt Duval presented research they are doing on developing new hot work steel grades. They realize that large blocks of H-13 and other hot work grades do not develop the optimum Martensitic microstructure at the center of large blocks. Aubalt Duval has researched different chemistries that will be easier to heat treat, yet still have excellent mechanical properties.

6. Schmolz and Bickenbach gave a presentation on the influence of heat treatment on the properties of hot work steel. They showed that too low of Austenitizing temperature results in a high quantity of carbides and a lower alloy content in the matrix. A low Austenitizing temperature causes low toughness and low strength. Too high of Austenitizing temperature also causes low mechanical properties.

7. Schmolz’s presentation raises some interesting questions on Austenitizing temperatures. Their testing used Austenitizing temperatures higher and lower than the recommended range. What is the optimum Austenitizing temperature? Is it better to use a lower temperature for a longer time or a higher temperature for a shorter time? What provides the best properties and is the most energy efficient? • The University of Torino (Politecnico di Torino) discussed research they are doing on Bainitic hardening. Does a die with a microstructure of tempered lower Bainite perform better than a die with a microstructure of tempered Martensite? Their research showed that Bainite forms much faster near the Martensitic start point. Their data showed that a Bainitic structure may have better temper resistance than Martensite.

8. They achieved an 80% Bainitic (20% Martensitic) microstructure by quenching to 590F and holding for 7 hours. • Questions arise as to how Bainitic hardening could be achieved in a vacuum furnace. The hardening temperature they used was lower than normal. They used H-11 steel. A mixed structure is generally lower in toughness than a uniform structure. If there is an increase in thermal fatigue resistance will it matter if the toughness is somewhat less? • The research into Bainitic hardening is ongoing at the University of Torino. I heard from them yesterday and the project is moving slowly. They have done some thermal fatigue testing but they say they found that the samples that they used were incorrectly manufactured.

9. CROMeP from France gave a presentation on a way to compare all the different thermal fatigue and thermal mechanical tests results from laboratories around the world. I can’t say I understand the equations. They showed that by normalizing the variables between tests, there are two driving forces for thermal fatigue for the same steel tested in different manners. They even can show the relationship between lab testing and actual tools. • CROMeP gave several other presentations on thermal fatigue. They are working on a modeling method that will predict thermal fatigue life without doing testing. • Another CROMeP presentation discussed how thermal fatigue crack initiation and propagation is related not only to the temperature cycles but also environmental affects such as oxidation and corrosion.

10. The University of Torino presented the results of thermal fatigue testing that they have done on common hot work steels and two new steels they are working on. .

11. The Materials Center at Leoben is using a pulsed laser for thermal Fatigue testing. The laser power can be varied during the heat cycle in order to mimic the temperature cycle on die surfaces. • The tests are performed on a temperature controlled plate. The testing is performed in a vacuum chamber to avoid oxidation. The testing conditions are based on numerical simulation that they developed. • They have found that inclusions play a much smaller role in crack initiation since most die steels are very clean. • Most cracks now initiate at grain boundaries or Bainite/Martensite interfaces. • They state that higher strength / higher hardness has only a minor influence on thermal fatigue testing where the thermal fatigue loading is low.

12. The University of Brescia, Italy discussed the affect of long temper times on H-13 at close to maximum hardness. • Aging up to 50 hours shows an increase in fracture toughness. Aging from 50 to 250 hours shows increasing embrittlement. The most likely cause of the embrittlement is the segregation of Phosphorous at the grain boundaries. • For H-11 steel the fracture toughness decreases early in the stages of aging and continues to decrease. The early embrittlement they believe is associated with the increase in carbide size.

13. This is the thermal fatigue test rig at the University of Torino. Two specimens are tested simultaneously. The molten aluminum is 1256 degrees F and the cooling bath is 97 degrees. The specimens pass through metal brushes to remove the aluminum film. The cycle time is about 30 seconds. The surface temperature of ranges between 210 and 970 degrees with every cycle • .

14. See you all at the 8th International Tooling Conference in 2009! • .