Conventionally manufactured 35CrMo cold heading steel must undergo spheroidization annealing before the cold heading process In this paper, different types of deformation processes with various controlled cooling peri...Conventionally manufactured 35CrMo cold heading steel must undergo spheroidization annealing before the cold heading process In this paper, different types of deformation processes with various controlled cooling periods were operated to achieve on-line spheroidal cementite using the Gleeble-3500 simulation technique. According to the measured dynamic ferrite transformation temperature （Ad3）, the deformation could be divided into two types： low temperature deformation at 810 and 780℃; ＂deformation-induced ferrite transformation＂ （DIFT） deformation at 750 and 720℃. Compared with the low temperature deformation, the DIFT deformation followed by accelerated cooling to 680℃ is beneficial for the formation of spheroidal cementite. Samples subjected to both the low-temperature deformation and DIFT deformation can obtain granular bainite by accelerated cooling to 640℃; the latter may contribute to the formation of a fine dispersion of secondary constituents. Granular bainite can transform into globular pearlite rapidly during subcritical annealing, and the more the disperse phase, the more homogeneously distributed globular cementite can be obtained.展开更多
In order to analyze the evolution of the inclusions in the cold heading steel SWRCH35K during the steelmaking process, a systematic sampling of the steelmaking processes in a steel plant was carried out. Both SEM-EDS ...In order to analyze the evolution of the inclusions in the cold heading steel SWRCH35K during the steelmaking process, a systematic sampling of the steelmaking processes in a steel plant was carried out. Both SEM-EDS and the image processing software Image-Pro-Plus6.0 were employed to analyze the chemical composition, morphology, quantity and size of non-metal inclusions in the steel samples. The results show that from BOF tapping to continuous casting tundish, the composition of inclusions in SWRCH35K steel changes from Al<sub>2</sub>O<sub>3</sub> →MgO·Al<sub>2</sub>O<sub>3</sub> →CaO-MgO-Al<sub>2</sub>O<sub>3</sub>-CaS, and the typical morphology of the inclusions in the steel gradually changes from irregular blocks and clusters to spherical. The number of inclusions in the BOF argon blowing station is the largest, 213#/mm<sup>2</sup>, while the number of inclusions at the end of LF refining is the least, about 12#/mm<sup>2</sup>, and there are basically no inclusions above 5 μm. In addition, LF calcium treatment will adversely affect the size and quantity control of inclusions in steel. In order to effectively reduce the large-size calcium-containing spherical oxide inclusions in cold heading steel, it is necessary to find a technical method that can replace LF calcium treatment to solve the problem of molten steel continuous casting.展开更多
The hip joint femoral head prosthesis was prepared using the Al2O3 material, which was synthesized by high purity alumina micro-powder and Mg- Zr- Y composite addhitives , the cold manufacturing techniques of lathe t...The hip joint femoral head prosthesis was prepared using the Al2O3 material, which was synthesized by high purity alumina micro-powder and Mg- Zr- Y composite addhitives , the cold manufacturing techniques of lathe turning, grade polishing and the matching size correction of the sintered femoral head were studied. The results showed, after being pressed under 200 MPa cold isostatic pressure and being pre-sintered at 1150℃ , the biscuit＇ s strength can meet the demands of lathe turning ; After being grade polished by SiC micro-powder and diamond abrading agent and being size corrected by special instrument, the femoral head prosthesis of Al2O3 ceramic has good surface degree of finish and articulates tightly with femoral handle.展开更多
在精炼进站时采用BaCO_(3)作为示踪剂,对比钢包底吹氩气流量对“120 t BOF→LF→CCM”流程生产的冷镦钢SWRCH35K中DS类夹杂物的影响。结果表明,氩气流量对精炼结束炉渣成分及夹杂物的类型无明显影响;精炼进站到精炼结束采用小氩气和正...在精炼进站时采用BaCO_(3)作为示踪剂,对比钢包底吹氩气流量对“120 t BOF→LF→CCM”流程生产的冷镦钢SWRCH35K中DS类夹杂物的影响。结果表明,氩气流量对精炼结束炉渣成分及夹杂物的类型无明显影响;精炼进站到精炼结束采用小氩气和正常氩气搅拌夹杂物密度分别降低4.5个/mm^(2)和7.1个/mm^(2),精炼结束到中包两种工艺夹杂物变化相差不大,精炼正常氩气搅拌精炼结束、软吹后、中包含Ba的夹杂物比例比小氩气搅拌分别高51.5%、26.1%、39.3%。铸坯中DS夹杂物组成有单相、两相和三相。精炼采用小氩气搅拌和正常氩气搅拌铸坯中检测到含Ba的DS夹杂物占所有DS夹杂物的比例分别为28.6%和39%。所以,控制精炼过程中冶炼的氩气搅拌强度也是控制钢中DS夹杂物的关键。展开更多
Effects of rolling and cooling conditions on microstructure and mechanical properties of low carbon cold heading steel were investigated on a laboratory hot rolling mill. The results have shown that the mechanical pro...Effects of rolling and cooling conditions on microstructure and mechanical properties of low carbon cold heading steel were investigated on a laboratory hot rolling mill. The results have shown that the mechanical proper ties of low carbon steels exceed the standard requirements of ML30, ML35, ML40, and ML45 steel, respectively due to thermomechanical controlled processing （TMCP）. This is attributed to a significant amount of pearlite and the ferrite-grain refinement. Under the condition of relatively low temperature rolling, the mechanical properties exceed standard requirements of ML45 and ML30 steel after water cooling and air cooling, respectively. Fast cooling which leads to more pearlite and finer ferrite grains is more critical than finish rolling temperatures for low carbon cold heading steel. The specimen at high finish rolling temperature exhibits very good mechanical properties due to fast cooling. This result has great significance not only for energy saving and emission reduction, but also for low-carbon economy, because the goals of the replacement of medium-carbon by low-carbon are achieved with TMCP.展开更多
文摘Conventionally manufactured 35CrMo cold heading steel must undergo spheroidization annealing before the cold heading process In this paper, different types of deformation processes with various controlled cooling periods were operated to achieve on-line spheroidal cementite using the Gleeble-3500 simulation technique. According to the measured dynamic ferrite transformation temperature （Ad3）, the deformation could be divided into two types： low temperature deformation at 810 and 780℃; ＂deformation-induced ferrite transformation＂ （DIFT） deformation at 750 and 720℃. Compared with the low temperature deformation, the DIFT deformation followed by accelerated cooling to 680℃ is beneficial for the formation of spheroidal cementite. Samples subjected to both the low-temperature deformation and DIFT deformation can obtain granular bainite by accelerated cooling to 640℃; the latter may contribute to the formation of a fine dispersion of secondary constituents. Granular bainite can transform into globular pearlite rapidly during subcritical annealing, and the more the disperse phase, the more homogeneously distributed globular cementite can be obtained.
文摘In order to analyze the evolution of the inclusions in the cold heading steel SWRCH35K during the steelmaking process, a systematic sampling of the steelmaking processes in a steel plant was carried out. Both SEM-EDS and the image processing software Image-Pro-Plus6.0 were employed to analyze the chemical composition, morphology, quantity and size of non-metal inclusions in the steel samples. The results show that from BOF tapping to continuous casting tundish, the composition of inclusions in SWRCH35K steel changes from Al<sub>2</sub>O<sub>3</sub> →MgO·Al<sub>2</sub>O<sub>3</sub> →CaO-MgO-Al<sub>2</sub>O<sub>3</sub>-CaS, and the typical morphology of the inclusions in the steel gradually changes from irregular blocks and clusters to spherical. The number of inclusions in the BOF argon blowing station is the largest, 213#/mm<sup>2</sup>, while the number of inclusions at the end of LF refining is the least, about 12#/mm<sup>2</sup>, and there are basically no inclusions above 5 μm. In addition, LF calcium treatment will adversely affect the size and quantity control of inclusions in steel. In order to effectively reduce the large-size calcium-containing spherical oxide inclusions in cold heading steel, it is necessary to find a technical method that can replace LF calcium treatment to solve the problem of molten steel continuous casting.
文摘The hip joint femoral head prosthesis was prepared using the Al2O3 material, which was synthesized by high purity alumina micro-powder and Mg- Zr- Y composite addhitives , the cold manufacturing techniques of lathe turning, grade polishing and the matching size correction of the sintered femoral head were studied. The results showed, after being pressed under 200 MPa cold isostatic pressure and being pre-sintered at 1150℃ , the biscuit＇ s strength can meet the demands of lathe turning ; After being grade polished by SiC micro-powder and diamond abrading agent and being size corrected by special instrument, the femoral head prosthesis of Al2O3 ceramic has good surface degree of finish and articulates tightly with femoral handle.
文摘在精炼进站时采用BaCO_(3)作为示踪剂,对比钢包底吹氩气流量对“120 t BOF→LF→CCM”流程生产的冷镦钢SWRCH35K中DS类夹杂物的影响。结果表明,氩气流量对精炼结束炉渣成分及夹杂物的类型无明显影响;精炼进站到精炼结束采用小氩气和正常氩气搅拌夹杂物密度分别降低4.5个/mm^(2)和7.1个/mm^(2),精炼结束到中包两种工艺夹杂物变化相差不大,精炼正常氩气搅拌精炼结束、软吹后、中包含Ba的夹杂物比例比小氩气搅拌分别高51.5%、26.1%、39.3%。铸坯中DS夹杂物组成有单相、两相和三相。精炼采用小氩气搅拌和正常氩气搅拌铸坯中检测到含Ba的DS夹杂物占所有DS夹杂物的比例分别为28.6%和39%。所以,控制精炼过程中冶炼的氩气搅拌强度也是控制钢中DS夹杂物的关键。
基金Item Sponsored by National Natural Science Foundation of China(50334010)
文摘Effects of rolling and cooling conditions on microstructure and mechanical properties of low carbon cold heading steel were investigated on a laboratory hot rolling mill. The results have shown that the mechanical proper ties of low carbon steels exceed the standard requirements of ML30, ML35, ML40, and ML45 steel, respectively due to thermomechanical controlled processing （TMCP）. This is attributed to a significant amount of pearlite and the ferrite-grain refinement. Under the condition of relatively low temperature rolling, the mechanical properties exceed standard requirements of ML45 and ML30 steel after water cooling and air cooling, respectively. Fast cooling which leads to more pearlite and finer ferrite grains is more critical than finish rolling temperatures for low carbon cold heading steel. The specimen at high finish rolling temperature exhibits very good mechanical properties due to fast cooling. This result has great significance not only for energy saving and emission reduction, but also for low-carbon economy, because the goals of the replacement of medium-carbon by low-carbon are achieved with TMCP.
