A Newly-developed High Wear Resistant Cast Hot-forging Die Steel

Abstract

The alloying design of the cast hot-forging die steels was analyzed. The key property and parameters for the alloying design were selected. The cast hot-forging die steel with high wear resistance was developed through optimizing the parameters. The wear resistance of the newly-developed cast die steel was evaluated in comparison with commercial H13 steels and 3Cr2W8V steel. The wear mechanism is also discussed. The newly-developed cast die steel takes VC as predominant carbide with solid solution strengthening of Cr and Mo. The cast die steel was found to have significantly lower wear rate than normal H13 steel and 3Cr2W8V steel, and almost the same wear rate as high-purified H13 steel. The high wear resistance of the new-developed cast die steel could be attributed to the reasonable alloying design and no sensitivity to detrimental function of S and P. Under the elevated-temperature air at 400°C, the wear for the cast die steels and commercial hot-forging die steels is a typical oxidation wear.KEY WORDS: hot-forging die; cast steel; wear resistance; oxidation wear. 3Cr2W8V steel was austenitized 1 060°C for 1 h and cooled in oil, finally tempered at 620°C or 660°C for 2 h.The wear tests were performed on a uni-directional pinon-disk high-temperature wear tester (MG-2000 type, made by Xuan Hua material testing machine factory of China). The wear test rig used in this study has been described in detail elsewhere.11) All wear tests were carried out at 400°C without lubrication. The test parameters were selected as follows: 100 N for norm load; 1 ms Ϫ1 for sliding speed and 1.8ϫ10 3 m for sliding distance. Pins with dimensions of F6 mmϫ12 mm are made of the studied cast steels and commercial die steels. The disks with dimensions of F70 mmϫ8 mm are made of D2 steel with 58HRC.Before test, pins and disks were polished and degreased. The pin specimens were cleaned with acetone and dried before and after test for weighting wear loss by a balance with an accuracy of 0.01 mg. The wear rates were calculated in term of the formula: WsϭDV/P · d, Where DV is wear volume loss (m 3 ), i.e. wear weight loss divided by density; d is sliding distance (m), P is load (N). All the data were average values for three or five wear experimental results.The morphology, composition and structure of worn surface or wear debris were analyzed with an AMRA-1000B type scanning electron microscope (SEM) coupled with an energy-dipersive X-ray spectroscope (EDS) and a D/Max-2500/pc type X-ray diffractometer (XRD). Thin foil samples for the cast steel were prepared for observing the microstructures using a Hitachi H-800 transmission electron microscope. The hardness and strength were measured with a HRC150 type durometer and a 1 196 type multipurpose tester respectively. Alloying Design for Cast Hot-forging Die Steels Analysis of Alloying DesignGenerally the high toughness was thought to be needed to forbid brittle fracture for application of the cast hot-forging die steels. Thus the improved toughness of the steels was always the basis of the al...

Development Trend in Composition Optimization, Microstructure Manipulation, and Strengthening Methods of Die Steels under Lightweight and Integrated Die Casting

“…Alloying hot-working die steel is an important way to improve its service life. The performance of hot-working die steel can be influenced to varying degrees by different alloying elements and their respective content levels, resulting in either positive or negative effects [ 27 , 59 , 60 , 61 , 62 , 63 , 64 , 65 ]. Table 2 lists the appropriate content ranges of some alloying elements and their functions in hot-working die steels.…”

Brittle Fracture of Hot-Forging Cast Dies

“…The compositions (wt.%) of the new cast die steel are 0.1-0.5C, 3.0-5.0Cr, 1.0-2.0Ni, 1.0-2.0Mo, 0.2-1.0V [5]. The steel was melted in a 250 kg, medium frequency induction furnace in a non-oxidizing environment.…”

“…The site applications of hot-forging cast dies made with a new type of cast steel were carried out in our work [5]. Through failure analysis of the dies and evaluation of properties of the die material, the relationship among brittle fracture and material toughness, strength and manufacturing process was developed.…”