Experimental investigation of hot press forming on 22mnb5 boron steel employing response surface methodology (rsm) /
Nuraini Aziz
- Kuantan, Pahang : UMP, 2017
- xii, 82 p. : ill. (some col.) ; 30 cm. + 1 CD-ROM
Faculty of Mechanical Engineering
Thesis (Master of Engineering (Mechanical)) -- Universiti Malaysia Pahang – 2017
Bibliography : p. 70-77
This thesis presents an experimental study on hot press forming of 22MnB5 steel to enhance the mechanical properties. Hot press forming process consists of simultaneous forming and quenching of heated blank. In order to cool down the dies, quenching process requires chilled water flow through cooling channel beneath the die surface at 5°C temperature. However, such water temperature is very expensive to generate. Thus, by increasing water temperature, the production cost can be reduced without compromising the component properties. Research has been focusing on reducing the quenching time as excessive quenching time reduces the production efficiency. The minimum quenching time of 8 seconds was required to obtain a formed sample with high percentage of martensite. These findings contribute to initial design of processing parameters in hot press forming of 22MnB5 steel blanks for automotive component. The aim of this study is to produce high strength 22MnB5 boron steel by hot press forming, with optimised processing parameters for maximum martensite structure area percentage and hardness. The 22MnB5 steel was processed at three different parameter settings: quenching time, water temperature and water flow rate. 22MnB5 was processed using 33 full factorial design of experiment (DOE). The full factorial DOE was designed using three factors namely quenching time, water temperature and water flow rate at three levels. The factors level were quenching time range of 5, 8 and 11 seconds, water temperature; 5, 15 and 27°C and water flow rate; 20, 30 and 40 L/min. The as-received and hot press forming processed steel was characterised for metallographic study and hardness properties. In metallographic study, grain size was determined using inverted optical microscope and JEOL Field Emission Scanning Electron Microscopic (FESEM) while a hardness properties was measured using Matsuzawa MMT-X7 Vickers scale. Obtained results were analysed statistically using ANOVA. Optimization of the processing parameters for 22MnB5 samples was conducted using Response Surface Method (RSM). From the experimental finding, resulted martensite phase area percentage was 52-89% and the hardness properties were enhanced up to 477.0-551.4HV range, which was three times greater than the as-received blank. The equivalent tensile strength was calculated as 1513-1700MPa. The DOE resulted in highest martensite percentage of 85% and hardness of 537.5HV. The significant factors were quenching time and water temperature. Verification test shows experiment yield 551.4HV hardness property while the predicted value was 537.5HV and the error percentage is 2.5%. Based on the optimization solutions, maximum hardness properties was 555.8HV and martensitic percentage was 91.3% resulted in 27 solutions with the highest desirability factor of 0.934 and hot press forming parameters successfully optimized at quenching time of 11 seconds, cooling water temperature 5°C and water flow rate 40 L/min. Main contributions to society industry from these findings are significant to enhance the properties of high strength steel which achieve good product quality and increase production efficiency simultaneously.