Optical microscope, stereomicroscope, scanning electronic microscope （SEM） and mechanical property testing were used to research the effects of different quenching temperatures on the microstructure and mechanical p...Optical microscope, stereomicroscope, scanning electronic microscope （SEM） and mechanical property testing were used to research the effects of different quenching temperatures on the microstructure and mechanical properties of the H13 mandrel steel. The results indicate that following an increase in the quenching ,the degree of alloying is enhanced due to the carbides dissolving gradually in austenite, which improves the hardenability of the specimens, as well as their room and high-temperature strength. At the same time, the fracture toughness increases due to the increment of the martensite number and the interparticle distance of impact toughness. Optimal performance Consequently,the service life of the H13 the carbides. However, extremely coarse grain and martensite can decrease the can be obtained after quenching at 1 060℃ and double tempering at 620℃mandrel steel is extended significantly.展开更多
In this study,the microstructural evolution of H13 mandrel steel during its manufacturing process and the influence of the preheat treatment procedure and the second-step tempering temperature on its microstructural a...In this study,the microstructural evolution of H13 mandrel steel during its manufacturing process and the influence of the preheat treatment procedure and the second-step tempering temperature on its microstructural and mechanical properties were investigated.The experiment results showed that,using an H13 mandrel steel billet in the as-annealed condition produced by Baosteel as a raw material,the preheat treatments of normalization,spheroidization annealing,or normalization plus spheroidization annealing,as described in this paper,had no significant effect on the final mechanical properties after quenching and tempering.H13 mandrel steel met all the mechanical property requirements via quenching and tempering without preheat treatment.In the temperature range from 600 to 680 t,with an increase in the second-step tempering temperature,the strength gradually decreased whereas the plasticity and toughness gradually improved.Using the quenching-plus-first-tempering procedure of 1030℃/l h/oil cooling+600℃/5 h/air cooling,good balance between strength and toughness could be achieved by selecting 650℃ as the second-step tempering temperature.The test results also showed that the holding time of the second tempering played a big role in the mechanical properties.When this holding time was extended from 1 to 2 h,the hardness of the H13 mandrel steel decreased and the extent of this reduction increased with an increase in the second-step tempering temperature.In the temperature range of 1030 to 1090℃,the yield strength,tensile strength,and hardness gradually increased,however,the impact toughness decreased with increases in the quenching temperature.展开更多
The conditions of heating and cooling of piercing mandrels made of 4X5MFS steel of a three-roll screw mill 30-80 in the production of a closed cavity of steel vessels of small volume are determined.It is established t...The conditions of heating and cooling of piercing mandrels made of 4X5MFS steel of a three-roll screw mill 30-80 in the production of a closed cavity of steel vessels of small volume are determined.It is established that multiple cycles of heating up to 600℃ and cooling with water up to 80℃ for about 7 seconds/1 cycle lead to the formation of ridges,shells and cracks on the surface and in the volume of the tool.The loss of structural strength of the material leads to the breakdown of the mandrel during the stitching process.The technique and equipment of magnetic powder control have been developed to establish the dynamics of the growth of internal and external defects of mandrels.An equation is obtained that allows determining the increase in the number of defects in the sewing tool of a screw rolling mill.The technology of non-destructive testing made it possible to develop a rational plan for replacing the sewing mandrels,which allows for predicting the appearance of defects leading to a complex breakdown of the deforming tool at the NPO Pribor machine-building enterprise.展开更多
This study researches the effects of the refining treatment on the microstructure and the mechanical properties of H13 mandrel steel and compares these effects with those of the conventional treatment. The results ind...This study researches the effects of the refining treatment on the microstructure and the mechanical properties of H13 mandrel steel and compares these effects with those of the conventional treatment. The results indicate that both carbide particles and grains were refined, carbide particles were uniformly distributed by the refining treatment, and therefore,the strength and toughness of H13 mandrel steel were improved. Rapid cooling after the solution treatment may inhibit intra-granular precipitation of carbide particles, which is favorable to enhancing toughness. Consequently, high- performance H13 mandrel steel can be produced by proper refining treatment.展开更多
Based on the ABAQUS explicit dynamic simulation platform,the finite element model of single stand mill with restrained mandrel was adopted to research the influence of mandrel - roller velocity ratio (MRVR),mandrel fr...Based on the ABAQUS explicit dynamic simulation platform,the finite element model of single stand mill with restrained mandrel was adopted to research the influence of mandrel - roller velocity ratio (MRVR),mandrel friction and tension between stands on rolling force.The analysis results show that when the MRVR is lower than 1,the rolling force increases obviously with the increase of MRVR and reaches the peak value when the MRVR is about 1.The rolling force increase induced by the MRVR increase is the main reason of the formation of the bulge defect on the tube head and tail at the entering and exiting stage during tube continuous rolling process by full floating mandrel mill,which can be intensified by the increase of mandrel friction coefficient.The rolling force decreases with the increase of tension.As the tension is larger, the rolling force decrease amplitude is larger.The influence of backward tension on rolling force is greater than that of forward tension distinctly.Tension control can be used to decrease the rolling force increase induced by the MRVR increase,which is imposing tension at the same time when the MRVR increases,in order to improve even eliminate the bulge defect,and enhance the tube dimension precision.展开更多
文摘Optical microscope, stereomicroscope, scanning electronic microscope （SEM） and mechanical property testing were used to research the effects of different quenching temperatures on the microstructure and mechanical properties of the H13 mandrel steel. The results indicate that following an increase in the quenching ,the degree of alloying is enhanced due to the carbides dissolving gradually in austenite, which improves the hardenability of the specimens, as well as their room and high-temperature strength. At the same time, the fracture toughness increases due to the increment of the martensite number and the interparticle distance of impact toughness. Optimal performance Consequently,the service life of the H13 the carbides. However, extremely coarse grain and martensite can decrease the can be obtained after quenching at 1 060℃ and double tempering at 620℃mandrel steel is extended significantly.
文摘In this study,the microstructural evolution of H13 mandrel steel during its manufacturing process and the influence of the preheat treatment procedure and the second-step tempering temperature on its microstructural and mechanical properties were investigated.The experiment results showed that,using an H13 mandrel steel billet in the as-annealed condition produced by Baosteel as a raw material,the preheat treatments of normalization,spheroidization annealing,or normalization plus spheroidization annealing,as described in this paper,had no significant effect on the final mechanical properties after quenching and tempering.H13 mandrel steel met all the mechanical property requirements via quenching and tempering without preheat treatment.In the temperature range from 600 to 680 t,with an increase in the second-step tempering temperature,the strength gradually decreased whereas the plasticity and toughness gradually improved.Using the quenching-plus-first-tempering procedure of 1030℃/l h/oil cooling+600℃/5 h/air cooling,good balance between strength and toughness could be achieved by selecting 650℃ as the second-step tempering temperature.The test results also showed that the holding time of the second tempering played a big role in the mechanical properties.When this holding time was extended from 1 to 2 h,the hardness of the H13 mandrel steel decreased and the extent of this reduction increased with an increase in the second-step tempering temperature.In the temperature range of 1030 to 1090℃,the yield strength,tensile strength,and hardness gradually increased,however,the impact toughness decreased with increases in the quenching temperature.
文摘The conditions of heating and cooling of piercing mandrels made of 4X5MFS steel of a three-roll screw mill 30-80 in the production of a closed cavity of steel vessels of small volume are determined.It is established that multiple cycles of heating up to 600℃ and cooling with water up to 80℃ for about 7 seconds/1 cycle lead to the formation of ridges,shells and cracks on the surface and in the volume of the tool.The loss of structural strength of the material leads to the breakdown of the mandrel during the stitching process.The technique and equipment of magnetic powder control have been developed to establish the dynamics of the growth of internal and external defects of mandrels.An equation is obtained that allows determining the increase in the number of defects in the sewing tool of a screw rolling mill.The technology of non-destructive testing made it possible to develop a rational plan for replacing the sewing mandrels,which allows for predicting the appearance of defects leading to a complex breakdown of the deforming tool at the NPO Pribor machine-building enterprise.
文摘This study researches the effects of the refining treatment on the microstructure and the mechanical properties of H13 mandrel steel and compares these effects with those of the conventional treatment. The results indicate that both carbide particles and grains were refined, carbide particles were uniformly distributed by the refining treatment, and therefore,the strength and toughness of H13 mandrel steel were improved. Rapid cooling after the solution treatment may inhibit intra-granular precipitation of carbide particles, which is favorable to enhancing toughness. Consequently, high- performance H13 mandrel steel can be produced by proper refining treatment.
文摘Based on the ABAQUS explicit dynamic simulation platform,the finite element model of single stand mill with restrained mandrel was adopted to research the influence of mandrel - roller velocity ratio (MRVR),mandrel friction and tension between stands on rolling force.The analysis results show that when the MRVR is lower than 1,the rolling force increases obviously with the increase of MRVR and reaches the peak value when the MRVR is about 1.The rolling force increase induced by the MRVR increase is the main reason of the formation of the bulge defect on the tube head and tail at the entering and exiting stage during tube continuous rolling process by full floating mandrel mill,which can be intensified by the increase of mandrel friction coefficient.The rolling force decreases with the increase of tension.As the tension is larger, the rolling force decrease amplitude is larger.The influence of backward tension on rolling force is greater than that of forward tension distinctly.Tension control can be used to decrease the rolling force increase induced by the MRVR increase,which is imposing tension at the same time when the MRVR increases,in order to improve even eliminate the bulge defect,and enhance the tube dimension precision.
