Effect of controlled rolling and cooling process on the mechanical properties of low carbon cold forging steel was investigated for different processing parameters of a laboratory hot rolling mill. The results show th...Effect of controlled rolling and cooling process on the mechanical properties of low carbon cold forging steel was investigated for different processing parameters of a laboratory hot rolling mill. The results show that the specimens with fast cooling after hot rolling exhibit very good mechanical properties, and the improvement of the mechanical properties can be attributed mainly to the ferrite-grain refinement. The mechanical properties increase with decreasing final cooling temperature within the range from 670 ℃ to 570 ℃ due to the finer interlamellar spacing of pearlite colony. The specimen with fast cooling after low temperature rolling shows the highest values of the mechanical properties. The effect of the ferrite grain size on the mechanical properties was greater than that of pearlite morphology in the present study. The mechanical properties of specimens by controlled rolling and cooling process without thermal treatment were greatly superior to that of the same specimens by the conventional rolling, and their tensile strength reached 490 MPa grade even in the case of low temperature rolling without controlled rolling. It might be expected to realize the substitution medium-carbon by low-carbon for 490 MPa grade cold forging steel with controlled rolling and cooling process.展开更多
The dynamic recrystallization and static recrystallization in a low carbon steel were investigated through single-pass and double-pass experiments. The results indicate that as the deformation temperature increases an...The dynamic recrystallization and static recrystallization in a low carbon steel were investigated through single-pass and double-pass experiments. The results indicate that as the deformation temperature increases and the strain rate decreases, the shape of the stress-strain curve is changed from dynamic recovery shape to dynamic recrystallization shape. The austenite could not recrystallize within a few seconds after deformation at temperature below 900 ℃. According to the change in microstructure during deformation, the controlled rolling of low carbon steel can be divided into four stages: dynamic recrystallization, dynamic recovery, strain-induced ferrite transformation, and rolling in two-phase region. According to the microstructure after deformation, the controlled rolling of low carbon steel can be divided into five regions: non-recrystallized austenite, partly-recrystallized austenite, fully-recrystallized austenite, austenite to ferrite transformation, and dual phase.展开更多
Considering the specialities of the steel plate production, the TMCP study has been carried out with Gleeble 2000 tester to explore the possibility of fine grained ferrite in the low carbon steel plates with the chemi...Considering the specialities of the steel plate production, the TMCP study has been carried out with Gleeble 2000 tester to explore the possibility of fine grained ferrite in the low carbon steel plates with the chemical composition of C 0.13--0.18, Si 0.12-0.18, Mn 0.50-0. 65, P 0. 010-0. 025, and S 0. 005-0. 028. The plates with thickness of 8. 7 mm in which the ferrite grain size is smaller than 8μm have been produced by special de- formation process in the laboratory. Furthermore, the trial production of special plain carbon steel plates of 16-25 mm in thickness and 2 000- 2 800 mm in width with fine grained ferrite has been successfully carried out in the Shougang Steel Plate Rolling Plant. The ferrite grain size is 5.5-7μm in the surface layers and 9.5-15μm in the central layer respectively. The yield strength is 320- 360 MPa, tensile strength is 440-520 MPa and the elongation is 25%- 34 %. It is very important for the rolling plants to improve the low carbon steel plates' mechanical properties. The results show that the ferrite grains in the surface layer can be refined effectively by the appropriate rolling process, and the strength can be also increased.展开更多
Two kinds of Mn-Si-Mo low carbon steels were designed to study the effects of Mn on the microstructures and properties of hot rolled low carbon bainitic steels.To reduce the production cost,a very low Mo content of 0....Two kinds of Mn-Si-Mo low carbon steels were designed to study the effects of Mn on the microstructures and properties of hot rolled low carbon bainitic steels.To reduce the production cost,a very low Mo content of 0.13%was added in both steels.After hot rolling,the mechanical properties of samples were tested.Microstructure was observed and analyzed by optical microscope and transmission electron microscope.The results show that the strength of tested steels increases with the increase in Mn content,while the elongation decreases.When Mn content increases,the bainite microstructure increases.The results can provide a theoretical basis for composition design and industrial production of low cost low carbon bainitic steels.展开更多
Conventionally,direct tensile tests are employed to measure mechanical properties of industrially produced products. In mass production,the cost of sampling and labor is high,which leads to an increase of total produc...Conventionally,direct tensile tests are employed to measure mechanical properties of industrially produced products. In mass production,the cost of sampling and labor is high,which leads to an increase of total production cost and a decrease of production efficiency. The main purpose of this paper is to develop an intelligent program based on artificial neural network(ANN) to predict the mechanical properties of a commercial grade hot rolled low carbon steel strip,SPHC. A neural network model was developed by using 7×5×1 back-propagation(BP)neural network structure to determine the multiple relationships among chemical composition,product process and mechanical properties. Industrial on-line application of the model indicated that prediction results were in good agreement with measured values. It showed that 99.2 % of the products' tensile strength was accurately predicted within an error margin of ±10 %,compared to measured values. Based on the model,the effects of chemical composition and hot rolling process on mechanical properties were derived and the relative importance of each input parameter was evaluated by sensitivity analysis. All the results demonstrate that the developed ANN models are capable of accurate predictions under real-time industrial conditions. The developed model can be used to substitute mechanical property measurement and therefore reduce cost of production. It can also be used to control and optimize mechanical properties of the investigated steel.展开更多
In a typical process, low carbon steel was annealed at two different temperatures (660℃ and 750℃), and then was temper rolled to improve the mechanical properties. Pre-straining and baking treatments were subseque...In a typical process, low carbon steel was annealed at two different temperatures (660℃ and 750℃), and then was temper rolled to improve the mechanical properties. Pre-straining and baking treatments were subsequently carried out to measure the bake-hardening (BH) values. The influences of annealing temperature and temper rolling on the BH behavior of the steel were investigated. The results indicated that the microstructure evolution during temper rolling was related to carbon atoms and dislocations. After an apparent increase, the BH value of the steel significantly decreased when the temper rolling reduction was increased from 0%to 5%. This was attributed to the increase in solute carbon concentration and dislocation density. The maximum BH values of the steel annealed at 660℃ and 750℃ were 80 MPa and 89 MPa at the reductions of 3%and 4%, respectively. Moreover, increasing the annealing temperature from 660 to 750℃ resulted in an ob-vious increase in the BH value due to carbide dissolution.展开更多
Low-carbon steel sheets DC04 used in the automotive industry were subjected to cold rolling for thickness reduction from 20% to 89%. The desired thickness was achieved by successive reductions using a rolling mill. Th...Low-carbon steel sheets DC04 used in the automotive industry were subjected to cold rolling for thickness reduction from 20% to 89%. The desired thickness was achieved by successive reductions using a rolling mill. The influence of thickness reduction on the microstructure was studied by scanning electron microscopy. Microstructure evolution was characterized by the distortion of grains and the occurrence of the oriented grain structure for high cold work. A mechanism of grain restructuring for high cold work was described. The occurrence of voids was discussed in relation with cold work. The evolution of voids at the grain boundaries and inside the grains was also considered. To characterize the grain size, the Feret diameter was measured and the grain size distribution versus cold work was discussed. The chemical homogeneity of the sample was also analyzed.展开更多
A low carbon steel with Cr addition of 0.46wt% combined with trace elements of Mn and Ti was studied. The apparent activation energy of deformation and the hot deformation equation of the steel in the ferritic range w...A low carbon steel with Cr addition of 0.46wt% combined with trace elements of Mn and Ti was studied. The apparent activation energy of deformation and the hot deformation equation of the steel in the ferritic range were determined by means of single hot compression tests. The hot-rolled strip of 3 mm in thickness rolled in the ferritic range was obtained using a laboratory hot rolling mill. The mechanical properties show that the values of yield strength and ultimate tensile strength are 230 and 330 MPa, respectively, and the elongation is 33%. The average r-value is 1.1. Large polygonal ferrite recrystallization grains with about 40 grn in size and the strong { 111 } recrystallization texture can be obtained in the hot-rolled strip.展开更多
Claw poles are a key component of automobile generators.The output power performance of the generator is very dependent on the magnetic properties of its claw poles.Plastic deformation is known to significantly change...Claw poles are a key component of automobile generators.The output power performance of the generator is very dependent on the magnetic properties of its claw poles.Plastic deformation is known to significantly change the magnetic behavior of ferromagnetic materials in claw poles.In this paper,changes in the magnetic properties of low-carbon steel,used for claw pole components due to their plastic deformation,were investigated for different strains and temperatures.Ring-shaped material samples were prepared by machining and their magnetic properties were measured.The surface roughness was first evaluated and a machining process with an arithmetic average of roughness Ra 1.6μm was selected as enabling the lowest measurement error.Hysteresis loops at different applied magnetic fields of the material were obtained for different plastic strains and forming temperatures.The magnetic parameters of magnetic flux density,coercivity,and remanence were obtained and compared with magnetic flux density as the primary focus.Results showed that machining,cold forming,and hot forming all led to lower magnetic flux density,larger coercivity,and smaller remanence.Magnetic flux density showed a sharp decrease at the start of plastic deformation,but as the strain increased,the decreasing trend gradually reached a constant value.The decrease was much larger for cold forming than for hot forming.For example,at 500 A/m,the degradation of magnetic flux density with a reduction percentage of 5%at room temperature was about 50%,while that of hot forming at 1200°C was about 10%.Results of this research may provide a reference for the future process design of hot-forged claw poles.展开更多
Two kinds of low carbon bainitic steels,Nb-free Mo bearing and Nb + Mo addition steels,were cold rolled and annealed to investigate the effect of micro-alloying element Nb on the microstructure and properties of Mo mi...Two kinds of low carbon bainitic steels,Nb-free Mo bearing and Nb + Mo addition steels,were cold rolled and annealed to investigate the effect of micro-alloying element Nb on the microstructure and properties of Mo microalloyed low carbon high strength bainitic steel. No precipitates were observed in Nb-free Mo bearing steel,whereas,two types of precipitates,i.e.,Nb( C,N) and composite( Nb,Mo)( C,N),were observed in the Nb + Mo microalloyed steel,resulting in precipitation strengthening. The strength of Mo bearing steel was improved by addition of Nb under the same annealing conditions. The grain size of Nb addition steel was almost the same as Nb-free steel. Unlike the obvious grain refinement and precipitation strengthening in hot rolling,the increase in yield strength of Nb addition steels in cold rolling and annealing mainly results from the precipitation strengthening,while the effect of grain refinement strengthening can be almost ignored.展开更多
The non-vacuum roll bonding method of nickel plating on the base materials is put forward in accordance with the primary problems existed in the roll bonding of stainless/carbon steel. After nickel plating test on the...The non-vacuum roll bonding method of nickel plating on the base materials is put forward in accordance with the primary problems existed in the roll bonding of stainless/carbon steel. After nickel plating test on the base materials, the microstructure of nickel cladding is observed by scanning electron microscopy (SEM) at high, and room temperature, and the results show that the nickel cladding on base material can be protected from oxidation in the high temperature. Non-vacuum roll bonding tests of nickel plating on base materials are done by the roll bonding equipment, and the roll bonding plates of stainless/carbon steel are obtained. The microstructure and the elements distribution of non-vacuum roll bonding interface are analyzed by optical microscope (OM) and SEM. The results reflect that the nickel plating layer and the base materials bond well.展开更多
Problems encountered in the production of low nickel austenitic stainless steel have been studied. These problems primarily include the changes to the microstructure of the slab during the heating process, the formati...Problems encountered in the production of low nickel austenitic stainless steel have been studied. These problems primarily include the changes to the microstructure of the slab during the heating process, the formation and removal of deformation - induced martensite during cold rolling, and the effects of the annealing process on the surface oxide structure. A reasonable manufacturing process has been proposed on the basis of the research results and high-quality cold-rolled strips of low nickel austenitic stainless steel have been produced.展开更多
Thermomechanical controlled processing (TMCP) of low carbon cold heading steel in different austenite conditions were conducted by a laboratory hot rolling mill. Effect of various processing parameters on the mechan...Thermomechanical controlled processing (TMCP) of low carbon cold heading steel in different austenite conditions were conducted by a laboratory hot rolling mill. Effect of various processing parameters on the mechanical properties of the steel was investigated. The results showed that the mechanical properties of the low carbon cold heading steel could be significantly improved by TMCP without heat treatment. The improvement of mechanical properties can be attributed mainly to the ferrite grain refinement due to low temperature rolling. In the experiments the better ultimate tensile strength and ductility are obtained by lowering finishing cooling temperature within the temperature range from 650 ℃ to 550 ℃ since the interlamellar space in pearlite colonies become smaller. Good mechanical properties can be obtained in a proper austenite condition and thermomechanical processing parameter. The ferrite morphology has a more pronounced effect on the mechanical behavior than refinement of the microstructure. It is possible to realize the replacement of medium-carbon by low-carbon for 490 MPa grade cold heading steel with TMCP.展开更多
In the present paper,controlled rolling and cooling processing was conducted by using a laboratory hot rolling mill.The influence of different processing parameters on the mechanical properties of low carbon cold forg...In the present paper,controlled rolling and cooling processing was conducted by using a laboratory hot rolling mill.The influence of different processing parameters on the mechanical properties of low carbon cold forging steel was investigated.The results show that the faster cooling after the deformation (especially in low temperature rolling conditions) leads to the refinement of the ferrite grain.The specimen exhibits very good mechanical properties owing to the finer ferrite grains.The pearlite morphologies can also affect the mechanical properties of low carbon cold forging steel.The mechanical properties increase with decreasing final cooling temperature within the range from 650℃ to 570 ℃ due to the finer interlamellar spacing of pearlite colony.The mechanical properties of the specimens with fast cooling after the conventional rolling are not only better than those of the specimens with slow cooling after low temperature rolling,but also almost similar to those of the specimens with fast cooling after low temperature rolling.It is suggested that fast cooling after high temperature rolling (the conventional rolling) process would be of important industrial value.展开更多
Al/steel composite plate has a wide application prospect,but great differences in properties between Al and steel are observed.It is difficult to obtain high bonding strength by the traditional cold roll bonding proce...Al/steel composite plate has a wide application prospect,but great differences in properties between Al and steel are observed.It is difficult to obtain high bonding strength by the traditional cold roll bonding process.Al/steel composite plate was thus prepared by cold roll bonding at a reduction rate of 60%after oxidation treatment on the surface to be composited on the steel side.The heat treatment of holding at 400℃ for 1 h and cooling with the furnace was then adopted.The bonding strength,microstructure,and properties of the Al/steel composite plate before and after annealing were analysed and compared through shear test,bending test,tensile test,and micro-characterization.Results show that the shear strengths of the interface before and after annealing are 100 and 80 MPa,respectively.Although the shear strength of the annealed Al/steel composite plate decreases,the bending and overall tensile properties of the composite plate are improved,showing better mechanical properties.展开更多
基金Funded by Shenyang City Application Basic Research Project (No. 1071198-1-00)
文摘Effect of controlled rolling and cooling process on the mechanical properties of low carbon cold forging steel was investigated for different processing parameters of a laboratory hot rolling mill. The results show that the specimens with fast cooling after hot rolling exhibit very good mechanical properties, and the improvement of the mechanical properties can be attributed mainly to the ferrite-grain refinement. The mechanical properties increase with decreasing final cooling temperature within the range from 670 ℃ to 570 ℃ due to the finer interlamellar spacing of pearlite colony. The specimen with fast cooling after low temperature rolling shows the highest values of the mechanical properties. The effect of the ferrite grain size on the mechanical properties was greater than that of pearlite morphology in the present study. The mechanical properties of specimens by controlled rolling and cooling process without thermal treatment were greatly superior to that of the same specimens by the conventional rolling, and their tensile strength reached 490 MPa grade even in the case of low temperature rolling without controlled rolling. It might be expected to realize the substitution medium-carbon by low-carbon for 490 MPa grade cold forging steel with controlled rolling and cooling process.
基金Item Sponsored by High Technology Development Programof China (2001AA332020) and National Natural ScienceFoundation of China (50271015)
文摘The dynamic recrystallization and static recrystallization in a low carbon steel were investigated through single-pass and double-pass experiments. The results indicate that as the deformation temperature increases and the strain rate decreases, the shape of the stress-strain curve is changed from dynamic recovery shape to dynamic recrystallization shape. The austenite could not recrystallize within a few seconds after deformation at temperature below 900 ℃. According to the change in microstructure during deformation, the controlled rolling of low carbon steel can be divided into four stages: dynamic recrystallization, dynamic recovery, strain-induced ferrite transformation, and rolling in two-phase region. According to the microstructure after deformation, the controlled rolling of low carbon steel can be divided into five regions: non-recrystallized austenite, partly-recrystallized austenite, fully-recrystallized austenite, austenite to ferrite transformation, and dual phase.
文摘Considering the specialities of the steel plate production, the TMCP study has been carried out with Gleeble 2000 tester to explore the possibility of fine grained ferrite in the low carbon steel plates with the chemical composition of C 0.13--0.18, Si 0.12-0.18, Mn 0.50-0. 65, P 0. 010-0. 025, and S 0. 005-0. 028. The plates with thickness of 8. 7 mm in which the ferrite grain size is smaller than 8μm have been produced by special de- formation process in the laboratory. Furthermore, the trial production of special plain carbon steel plates of 16-25 mm in thickness and 2 000- 2 800 mm in width with fine grained ferrite has been successfully carried out in the Shougang Steel Plate Rolling Plant. The ferrite grain size is 5.5-7μm in the surface layers and 9.5-15μm in the central layer respectively. The yield strength is 320- 360 MPa, tensile strength is 440-520 MPa and the elongation is 25%- 34 %. It is very important for the rolling plants to improve the low carbon steel plates' mechanical properties. The results show that the ferrite grains in the surface layer can be refined effectively by the appropriate rolling process, and the strength can be also increased.
基金Funded by the National Natural Science Foundation of China(NSFC)(No.51274154)
文摘Two kinds of Mn-Si-Mo low carbon steels were designed to study the effects of Mn on the microstructures and properties of hot rolled low carbon bainitic steels.To reduce the production cost,a very low Mo content of 0.13%was added in both steels.After hot rolling,the mechanical properties of samples were tested.Microstructure was observed and analyzed by optical microscope and transmission electron microscope.The results show that the strength of tested steels increases with the increase in Mn content,while the elongation decreases.When Mn content increases,the bainite microstructure increases.The results can provide a theoretical basis for composition design and industrial production of low cost low carbon bainitic steels.
文摘Conventionally,direct tensile tests are employed to measure mechanical properties of industrially produced products. In mass production,the cost of sampling and labor is high,which leads to an increase of total production cost and a decrease of production efficiency. The main purpose of this paper is to develop an intelligent program based on artificial neural network(ANN) to predict the mechanical properties of a commercial grade hot rolled low carbon steel strip,SPHC. A neural network model was developed by using 7×5×1 back-propagation(BP)neural network structure to determine the multiple relationships among chemical composition,product process and mechanical properties. Industrial on-line application of the model indicated that prediction results were in good agreement with measured values. It showed that 99.2 % of the products' tensile strength was accurately predicted within an error margin of ±10 %,compared to measured values. Based on the model,the effects of chemical composition and hot rolling process on mechanical properties were derived and the relative importance of each input parameter was evaluated by sensitivity analysis. All the results demonstrate that the developed ANN models are capable of accurate predictions under real-time industrial conditions. The developed model can be used to substitute mechanical property measurement and therefore reduce cost of production. It can also be used to control and optimize mechanical properties of the investigated steel.
基金supported by the National Natural Science Foundation of China(51174247)
文摘In a typical process, low carbon steel was annealed at two different temperatures (660℃ and 750℃), and then was temper rolled to improve the mechanical properties. Pre-straining and baking treatments were subsequently carried out to measure the bake-hardening (BH) values. The influences of annealing temperature and temper rolling on the BH behavior of the steel were investigated. The results indicated that the microstructure evolution during temper rolling was related to carbon atoms and dislocations. After an apparent increase, the BH value of the steel significantly decreased when the temper rolling reduction was increased from 0%to 5%. This was attributed to the increase in solute carbon concentration and dislocation density. The maximum BH values of the steel annealed at 660℃ and 750℃ were 80 MPa and 89 MPa at the reductions of 3%and 4%, respectively. Moreover, increasing the annealing temperature from 660 to 750℃ resulted in an ob-vious increase in the BH value due to carbide dissolution.
基金the Romanian Ministry of Education and Research for CNCS Grant, project number PCCE ID100/2010
文摘Low-carbon steel sheets DC04 used in the automotive industry were subjected to cold rolling for thickness reduction from 20% to 89%. The desired thickness was achieved by successive reductions using a rolling mill. The influence of thickness reduction on the microstructure was studied by scanning electron microscopy. Microstructure evolution was characterized by the distortion of grains and the occurrence of the oriented grain structure for high cold work. A mechanism of grain restructuring for high cold work was described. The occurrence of voids was discussed in relation with cold work. The evolution of voids at the grain boundaries and inside the grains was also considered. To characterize the grain size, the Feret diameter was measured and the grain size distribution versus cold work was discussed. The chemical homogeneity of the sample was also analyzed.
基金supported by the Nature Science Foundation of Hebei Province(No.E2007000374)the Scientific Research Plan Project of the Education Department of Hebei Province, China (No.2007147)
文摘A low carbon steel with Cr addition of 0.46wt% combined with trace elements of Mn and Ti was studied. The apparent activation energy of deformation and the hot deformation equation of the steel in the ferritic range were determined by means of single hot compression tests. The hot-rolled strip of 3 mm in thickness rolled in the ferritic range was obtained using a laboratory hot rolling mill. The mechanical properties show that the values of yield strength and ultimate tensile strength are 230 and 330 MPa, respectively, and the elongation is 33%. The average r-value is 1.1. Large polygonal ferrite recrystallization grains with about 40 grn in size and the strong { 111 } recrystallization texture can be obtained in the hot-rolled strip.
基金financially supported by the National Natural Science Foundation of China (No. 51875348)
文摘Claw poles are a key component of automobile generators.The output power performance of the generator is very dependent on the magnetic properties of its claw poles.Plastic deformation is known to significantly change the magnetic behavior of ferromagnetic materials in claw poles.In this paper,changes in the magnetic properties of low-carbon steel,used for claw pole components due to their plastic deformation,were investigated for different strains and temperatures.Ring-shaped material samples were prepared by machining and their magnetic properties were measured.The surface roughness was first evaluated and a machining process with an arithmetic average of roughness Ra 1.6μm was selected as enabling the lowest measurement error.Hysteresis loops at different applied magnetic fields of the material were obtained for different plastic strains and forming temperatures.The magnetic parameters of magnetic flux density,coercivity,and remanence were obtained and compared with magnetic flux density as the primary focus.Results showed that machining,cold forming,and hot forming all led to lower magnetic flux density,larger coercivity,and smaller remanence.Magnetic flux density showed a sharp decrease at the start of plastic deformation,but as the strain increased,the decreasing trend gradually reached a constant value.The decrease was much larger for cold forming than for hot forming.For example,at 500 A/m,the degradation of magnetic flux density with a reduction percentage of 5%at room temperature was about 50%,while that of hot forming at 1200°C was about 10%.Results of this research may provide a reference for the future process design of hot-forged claw poles.
基金Sponsored by the National Natural Science Foundation of China(Grant No.51274154)the National High Technology Research and Development Program of China(Grant No.2012AA03A504)+1 种基金the State Key Laboratory of Development and Application Technology of Automotive Steels(Baosteel Group)Key Project of Hubei Education Committee(Grant No.20121101)
文摘Two kinds of low carbon bainitic steels,Nb-free Mo bearing and Nb + Mo addition steels,were cold rolled and annealed to investigate the effect of micro-alloying element Nb on the microstructure and properties of Mo microalloyed low carbon high strength bainitic steel. No precipitates were observed in Nb-free Mo bearing steel,whereas,two types of precipitates,i.e.,Nb( C,N) and composite( Nb,Mo)( C,N),were observed in the Nb + Mo microalloyed steel,resulting in precipitation strengthening. The strength of Mo bearing steel was improved by addition of Nb under the same annealing conditions. The grain size of Nb addition steel was almost the same as Nb-free steel. Unlike the obvious grain refinement and precipitation strengthening in hot rolling,the increase in yield strength of Nb addition steels in cold rolling and annealing mainly results from the precipitation strengthening,while the effect of grain refinement strengthening can be almost ignored.
文摘The non-vacuum roll bonding method of nickel plating on the base materials is put forward in accordance with the primary problems existed in the roll bonding of stainless/carbon steel. After nickel plating test on the base materials, the microstructure of nickel cladding is observed by scanning electron microscopy (SEM) at high, and room temperature, and the results show that the nickel cladding on base material can be protected from oxidation in the high temperature. Non-vacuum roll bonding tests of nickel plating on base materials are done by the roll bonding equipment, and the roll bonding plates of stainless/carbon steel are obtained. The microstructure and the elements distribution of non-vacuum roll bonding interface are analyzed by optical microscope (OM) and SEM. The results reflect that the nickel plating layer and the base materials bond well.
文摘Problems encountered in the production of low nickel austenitic stainless steel have been studied. These problems primarily include the changes to the microstructure of the slab during the heating process, the formation and removal of deformation - induced martensite during cold rolling, and the effects of the annealing process on the surface oxide structure. A reasonable manufacturing process has been proposed on the basis of the research results and high-quality cold-rolled strips of low nickel austenitic stainless steel have been produced.
基金Sponsored by National Natural Science Foundation of China (50334010)Shenyang City Application Basic Research Project (1071198-1-00)
文摘Thermomechanical controlled processing (TMCP) of low carbon cold heading steel in different austenite conditions were conducted by a laboratory hot rolling mill. Effect of various processing parameters on the mechanical properties of the steel was investigated. The results showed that the mechanical properties of the low carbon cold heading steel could be significantly improved by TMCP without heat treatment. The improvement of mechanical properties can be attributed mainly to the ferrite grain refinement due to low temperature rolling. In the experiments the better ultimate tensile strength and ductility are obtained by lowering finishing cooling temperature within the temperature range from 650 ℃ to 550 ℃ since the interlamellar space in pearlite colonies become smaller. Good mechanical properties can be obtained in a proper austenite condition and thermomechanical processing parameter. The ferrite morphology has a more pronounced effect on the mechanical behavior than refinement of the microstructure. It is possible to realize the replacement of medium-carbon by low-carbon for 490 MPa grade cold heading steel with TMCP.
文摘In the present paper,controlled rolling and cooling processing was conducted by using a laboratory hot rolling mill.The influence of different processing parameters on the mechanical properties of low carbon cold forging steel was investigated.The results show that the faster cooling after the deformation (especially in low temperature rolling conditions) leads to the refinement of the ferrite grain.The specimen exhibits very good mechanical properties owing to the finer ferrite grains.The pearlite morphologies can also affect the mechanical properties of low carbon cold forging steel.The mechanical properties increase with decreasing final cooling temperature within the range from 650℃ to 570 ℃ due to the finer interlamellar spacing of pearlite colony.The mechanical properties of the specimens with fast cooling after the conventional rolling are not only better than those of the specimens with slow cooling after low temperature rolling,but also almost similar to those of the specimens with fast cooling after low temperature rolling.It is suggested that fast cooling after high temperature rolling (the conventional rolling) process would be of important industrial value.
基金the National Key Research and Development Program of China(Grant No.2018YFA0707300)the National Natural Science Foundation of China(Grant Nos.52075472 and 52004242)the National Science Foundation of Hebei Province(Grant No.E2020203001).
文摘Al/steel composite plate has a wide application prospect,but great differences in properties between Al and steel are observed.It is difficult to obtain high bonding strength by the traditional cold roll bonding process.Al/steel composite plate was thus prepared by cold roll bonding at a reduction rate of 60%after oxidation treatment on the surface to be composited on the steel side.The heat treatment of holding at 400℃ for 1 h and cooling with the furnace was then adopted.The bonding strength,microstructure,and properties of the Al/steel composite plate before and after annealing were analysed and compared through shear test,bending test,tensile test,and micro-characterization.Results show that the shear strengths of the interface before and after annealing are 100 and 80 MPa,respectively.Although the shear strength of the annealed Al/steel composite plate decreases,the bending and overall tensile properties of the composite plate are improved,showing better mechanical properties.