The effect of main alloying elements on thermal wear of cast hot-forging die steels was studied. The wear mechanism was discussed. The results show that alloying elements have significant influences on the thermal wea...The effect of main alloying elements on thermal wear of cast hot-forging die steels was studied. The wear mechanism was discussed. The results show that alloying elements have significant influences on the thermal wear of cast hot-forging die steels. The wear rates decrease with an increase in chromium content from 3% to 4% and molybdenum content from 2% to 3%, respectively. With further increase of chromium and molybdenum contents, chromium slightly reduces the wear resistance and molybdenum severely deteriorates the wear resistance with high wear rate. Lower vanadium/carbon ratio （1.5-2.5） leads to a lower wear resistance with higher wear rate. With an increase in vanadium/carbon ratio, the wear resistance of the cast steel substantially increases. When vanadium/carbon ratio is 3, the wear rate reaches the lowest value. The predominant mechanism of thermal wear of cast hot-forging die steels are oxidation wear and fatigue delamination. The Fe2O3 and Fe3O4 or lumps of brittle wear debris are formed on the wear surface.展开更多
The severely worn position and failure mechanisms of the ring die of a feed pellet machine were investigated.The macroscopic and microscopic morphologies of the failed surface,the chemical composition and mechanical p...The severely worn position and failure mechanisms of the ring die of a feed pellet machine were investigated.The macroscopic and microscopic morphologies of the failed surface,the chemical composition and mechanical properties of the collected samples were analyzed using scanning electron microscopy,energy disperse spectroscopy,optical emission spectrometry,and a universal testing machine.Results show that the dip angle at the entrance of the ring die hole between the roller and ring die was severely worn.The feed powder could not be fully extruded through the dip angle at the entrance of the ring die holes,thus the density of the feed particles produced could not meet the requirements.Therefore,abrasive wear under high stress is the main reason of failure at the entrance of the ring die holes under the action of feeding powder;and cutting and fatigue spalling lead to substantial material loss.In addition,a high damp-heat environment aggravates abrasive wear on the die hole internal surface.展开更多
ERH end-quenching method was used to determine the hardenability of four kinds hot-forging die steels with deep-hardening and hence the order of their hardenability was given.The tempering hardness of the steels was m...ERH end-quenching method was used to determine the hardenability of four kinds hot-forging die steels with deep-hardening and hence the order of their hardenability was given.The tempering hardness of the steels was measured and the tempering resistance was studied.It was approved that ERH method is effective for the determination of hardenability of deep-hardening steel and the beginning of hardness drop in the ERH specimen is caused by bainite occurring.展开更多
Thermal wear of cast hot-forging die steel modified by rare earths（RE） was studied and compared with commercially used die steels. The function of RE and the mechanism of thermal wear of cast steel modified by RE we...Thermal wear of cast hot-forging die steel modified by rare earths（RE） was studied and compared with commercially used die steels. The function of RE and the mechanism of thermal wear of cast steel modified by RE were discussed. The results showed that with increasing content of RE, the wear rate of cast steel reduced at first and then increased. By adding 0.05% （mass fraction） RE, the cast hot-forging die steel with optimum thermal wear resistance was obtained, which was better than that of H13 and 3Cr2WSV. The large amount of coarse inclusions, （RE）2O2S, resulted from excessive RE, which obviously deteriorated thermal wear resistance. The mechanism of thermal wear of the modified cast die steel is oxidation wear and oxide fatigue delamination. The wear debris are lumps of Fe2O3 and Fe3O4.展开更多
We investigated the reasons for frequently appearing early failure of carbide punches in a progressive stamping die when they were used to produce magnetic shielding steel parts. The failure modes of the carbide punch...We investigated the reasons for frequently appearing early failure of carbide punches in a progressive stamping die when they were used to produce magnetic shielding steel parts. The failure modes of the carbide punches were statistically classified. Edge chipping and shoulder fracturing were the two types of failure modes that were found. The composition, hardness, and microstructure of the punches were analyzed. The cobalt content was found to be too low to ensure sufficient toughness. The brittle phase of tungsten carbide （WC）was prone to breaking off during the shear cutting process, and resulted in edge chipping. In addition, the material chips were easily bonded to the punch edge when there was a lack of press oil lubricity. It resulted in an uneven blanking clearance, which caused a lateral force and finally resulted in shoulder fracturing of the punches. Improvement measures were introduced to address the abovementioned issues. By using the carbide punches with greater toughness and shear cutting oil with high lubricity, the early damage problems of the punches are effectively solved, which ensures normal production of the magnetic shielding steel parts.展开更多
The alloying design of cast hot-forging die steels was analyzed. The relationship of the life of cast hot-forging dies with the failure patterns was studied. The thermal wear resistance was believed to be the key prop...The alloying design of cast hot-forging die steels was analyzed. The relationship of the life of cast hot-forging dies with the failure patterns was studied. The thermal wear resistance was believed to be the key property for the alloying design of cast hot-forging die steels. The alloying design parameters were selected and optimized for the cast hot-forging die steel with high wear resistance. The wear resistance of the optimized cast die steel was evaluated in comparison with commercial H13 steels and 3Cr2WSV steel. In the new cast hot-forging die steel, VC is predominant carbide with Cr and Mo as the main solution elements in α-Fe. It is found that the cast die steel has significantly lower wear rate than normal H13 steel and 3Cr2W8V steel, almost the same as that of high purity H13 steel. The high wear resistance of the new cast hot-forging die steel can be attributed to its reasonable alloying design and nonsensibility to the detrimental function of S and P.展开更多
Dry sliding wear tests of a Cr-Mo-V cast hot-forging die steel was carried out within a load range of 50--300 N at 400℃ by a pin-on-disc high temperature wear machine. The effect of heat treatment process on wear res...Dry sliding wear tests of a Cr-Mo-V cast hot-forging die steel was carried out within a load range of 50--300 N at 400℃ by a pin-on-disc high temperature wear machine. The effect of heat treatment process on wear resistance was systematically studied in order to select heat treatment processes of the steel with high wear resistance. The morphology, structure and composition were analyzed using scanning electron microscopy （SEM）, X-ray diffraction （XRD） and energy dispersive spectroscopy （EDS） ; wear mechanism was also discussed. Tribo-oxide layer was found to form on worn surfaces to reduce wear under low loads, but appear inside the matrix to increase wear under high loads. The tribo-oxides were mainly consisted of Fe3O4 and Fe2O3, FeO only appeared under a high load. Oxidative mild wear, transition of mild-severe wear in oxidative wear and extrusive wear took turns to operate with increasing the load. The wear resistance strongly depended on the selection of heat treatment processes or microstructures. It was found that bainite presented a better wear resistance than martensite plus bainite duplex structure, martensite structure was of the poorest wear resistance. The wear resistance increased with increasing austenizing temperature in the range of 920 to 1 120 ℃, then decreased at up to 1 220 ℃. As for tempering temperature and microstructure, the wear resistance increased in following order： 700℃ （tempered sorbite）, 200 ℃ （tempered martensite）, 440 to 650 ℃ （tempered troostite）. An appropriate combination of hardness, toughness, microstructural thermal stability was re- quired for a good wear resistance in high-temperature wear. The optimized heat treatment process was suggested for the cast hot-forging steel to be austenized at 1020 to 1 120 ℃, quenched in oil, then tempered at 440 to 650℃ for 2 h.展开更多
基金Item Sponsored by Early-Term Key Technology of Industrialization and Whole Set Equipment From Plan Committee of China(1999317) ,863 Project of China (2002AA331180) ,and Project of Key Lab of Universities in Jiangsu Province of China(Kjsmcx04004)
文摘The effect of main alloying elements on thermal wear of cast hot-forging die steels was studied. The wear mechanism was discussed. The results show that alloying elements have significant influences on the thermal wear of cast hot-forging die steels. The wear rates decrease with an increase in chromium content from 3% to 4% and molybdenum content from 2% to 3%, respectively. With further increase of chromium and molybdenum contents, chromium slightly reduces the wear resistance and molybdenum severely deteriorates the wear resistance with high wear rate. Lower vanadium/carbon ratio （1.5-2.5） leads to a lower wear resistance with higher wear rate. With an increase in vanadium/carbon ratio, the wear resistance of the cast steel substantially increases. When vanadium/carbon ratio is 3, the wear rate reaches the lowest value. The predominant mechanism of thermal wear of cast hot-forging die steels are oxidation wear and fatigue delamination. The Fe2O3 and Fe3O4 or lumps of brittle wear debris are formed on the wear surface.
基金financially supported by the National Key R&D Program of China(Grant No.:2017YFB0305100)the Teaching Quality and Teaching Reform Project of Guangdong Undergraduate Colleges and Universities:Construction Project of Experiment Demonstration Center(Grant No.:2017002)the Innovation Cultivation Project of Zhuhai College of Jilin University(Grant No.:2018XJCQSQ057)。
文摘The severely worn position and failure mechanisms of the ring die of a feed pellet machine were investigated.The macroscopic and microscopic morphologies of the failed surface,the chemical composition and mechanical properties of the collected samples were analyzed using scanning electron microscopy,energy disperse spectroscopy,optical emission spectrometry,and a universal testing machine.Results show that the dip angle at the entrance of the ring die hole between the roller and ring die was severely worn.The feed powder could not be fully extruded through the dip angle at the entrance of the ring die holes,thus the density of the feed particles produced could not meet the requirements.Therefore,abrasive wear under high stress is the main reason of failure at the entrance of the ring die holes under the action of feeding powder;and cutting and fatigue spalling lead to substantial material loss.In addition,a high damp-heat environment aggravates abrasive wear on the die hole internal surface.
基金Project sponsored by Research Fund for Doctoral Program of Higher Education(9514509)
文摘ERH end-quenching method was used to determine the hardenability of four kinds hot-forging die steels with deep-hardening and hence the order of their hardenability was given.The tempering hardness of the steels was measured and the tempering resistance was studied.It was approved that ERH method is effective for the determination of hardenability of deep-hardening steel and the beginning of hardness drop in the ERH specimen is caused by bainite occurring.
基金Project supported by the Itemof Early-TermKey Technology of Industrialization ,Plan Committee of China (1999317) 863project of China (2002AA331180)
文摘Thermal wear of cast hot-forging die steel modified by rare earths（RE） was studied and compared with commercially used die steels. The function of RE and the mechanism of thermal wear of cast steel modified by RE were discussed. The results showed that with increasing content of RE, the wear rate of cast steel reduced at first and then increased. By adding 0.05% （mass fraction） RE, the cast hot-forging die steel with optimum thermal wear resistance was obtained, which was better than that of H13 and 3Cr2WSV. The large amount of coarse inclusions, （RE）2O2S, resulted from excessive RE, which obviously deteriorated thermal wear resistance. The mechanism of thermal wear of the modified cast die steel is oxidation wear and oxide fatigue delamination. The wear debris are lumps of Fe2O3 and Fe3O4.
文摘We investigated the reasons for frequently appearing early failure of carbide punches in a progressive stamping die when they were used to produce magnetic shielding steel parts. The failure modes of the carbide punches were statistically classified. Edge chipping and shoulder fracturing were the two types of failure modes that were found. The composition, hardness, and microstructure of the punches were analyzed. The cobalt content was found to be too low to ensure sufficient toughness. The brittle phase of tungsten carbide （WC）was prone to breaking off during the shear cutting process, and resulted in edge chipping. In addition, the material chips were easily bonded to the punch edge when there was a lack of press oil lubricity. It resulted in an uneven blanking clearance, which caused a lateral force and finally resulted in shoulder fracturing of the punches. Improvement measures were introduced to address the abovementioned issues. By using the carbide punches with greater toughness and shear cutting oil with high lubricity, the early damage problems of the punches are effectively solved, which ensures normal production of the magnetic shielding steel parts.
基金Item Sponsored by Hi-Tech Research and Development Program of China (2002AA331180)State Key Laboratory of Materials Modification by Laser,Ion and Electron Beams(0708)
文摘The alloying design of cast hot-forging die steels was analyzed. The relationship of the life of cast hot-forging dies with the failure patterns was studied. The thermal wear resistance was believed to be the key property for the alloying design of cast hot-forging die steels. The alloying design parameters were selected and optimized for the cast hot-forging die steel with high wear resistance. The wear resistance of the optimized cast die steel was evaluated in comparison with commercial H13 steels and 3Cr2WSV steel. In the new cast hot-forging die steel, VC is predominant carbide with Cr and Mo as the main solution elements in α-Fe. It is found that the cast die steel has significantly lower wear rate than normal H13 steel and 3Cr2W8V steel, almost the same as that of high purity H13 steel. The high wear resistance of the new cast hot-forging die steel can be attributed to its reasonable alloying design and nonsensibility to the detrimental function of S and P.
基金Item Sponsored by National Nature Science Foundation of China(51071078)
文摘Dry sliding wear tests of a Cr-Mo-V cast hot-forging die steel was carried out within a load range of 50--300 N at 400℃ by a pin-on-disc high temperature wear machine. The effect of heat treatment process on wear resistance was systematically studied in order to select heat treatment processes of the steel with high wear resistance. The morphology, structure and composition were analyzed using scanning electron microscopy （SEM）, X-ray diffraction （XRD） and energy dispersive spectroscopy （EDS） ; wear mechanism was also discussed. Tribo-oxide layer was found to form on worn surfaces to reduce wear under low loads, but appear inside the matrix to increase wear under high loads. The tribo-oxides were mainly consisted of Fe3O4 and Fe2O3, FeO only appeared under a high load. Oxidative mild wear, transition of mild-severe wear in oxidative wear and extrusive wear took turns to operate with increasing the load. The wear resistance strongly depended on the selection of heat treatment processes or microstructures. It was found that bainite presented a better wear resistance than martensite plus bainite duplex structure, martensite structure was of the poorest wear resistance. The wear resistance increased with increasing austenizing temperature in the range of 920 to 1 120 ℃, then decreased at up to 1 220 ℃. As for tempering temperature and microstructure, the wear resistance increased in following order： 700℃ （tempered sorbite）, 200 ℃ （tempered martensite）, 440 to 650 ℃ （tempered troostite）. An appropriate combination of hardness, toughness, microstructural thermal stability was re- quired for a good wear resistance in high-temperature wear. The optimized heat treatment process was suggested for the cast hot-forging steel to be austenized at 1020 to 1 120 ℃, quenched in oil, then tempered at 440 to 650℃ for 2 h.
