In this study, a 600 MPa hot-rolled corrosion-resistant steel plate produced by a specific company is investigated. Edge jagged defects and edge surface defects generated on both sides of the strip during production a...In this study, a 600 MPa hot-rolled corrosion-resistant steel plate produced by a specific company is investigated. Edge jagged defects and edge surface defects generated on both sides of the strip during production are characterized and analyzed. The results indicate that the distribution of reoxidation granules is located underneath the surface peel and that copper-containing granules diffuse along austenite grain boundaries. This phenomenon combined with the chemical composition and production parameters of a strip indicate that copper brittleness leads to edge jagged defects. However,the surface defects should be attributed to inherent defects on the surface of the strip. Measures that prevent surface oxidation and copper segregation at grain boundaries would likely eliminate these two types of edge defects.展开更多
A new kind of high strength, high toughness and high plasticity spring steel has been developed. The strength, the reduction of area and the elongation of the steel are all higher than those of the steel 60Si2CrVA. Th...A new kind of high strength, high toughness and high plasticity spring steel has been developed. The strength, the reduction of area and the elongation of the steel are all higher than those of the steel 60Si2CrVA. The decarburization resistance and the sag resistance are also higher than those of the steel 60Si2CrVA. It has good hardenability, and is suitable for making springs with big cross section. The bogie springs made of this kind of steel have passed 2×106 cycles without broken under the conditions of maximum stress of 906 MPa and the minimum stress of 388 MPa.展开更多
The delayed fracture behavior of medium carbon high strength spring steel containing different amounts of boron （0. 000 5%, 0. 001 6 %） was studied using sustained load delayed fracture test. The results show that d...The delayed fracture behavior of medium carbon high strength spring steel containing different amounts of boron （0. 000 5%, 0. 001 6 %） was studied using sustained load delayed fracture test. The results show that delayed fracture resistance of boron containing steels is higher than that of conventional steel 60Si2MnA at the same strength level and it increases with the increase of boron eontent from 0. 000 5% to 0. 001 6%. The delayed fracture mode is mainly intergranular in the boron containing steels tempered at 350℃, which indicates that the addition of boron does not change the fracture character. However, the increase of boron content enlarges the size of the crack initia tion area. Further study of phase analysis indicates that most boron is in solid solution, and only a very small quantity of boron is in the M3 （C, B） phase.展开更多
Dissimilar material joining of 6008 aluminum alloy to H220 YD galvanized high strength steel was performed by resistance spot welding with especial electrodes that were a flat tip electrode against the steel surface a...Dissimilar material joining of 6008 aluminum alloy to H220 YD galvanized high strength steel was performed by resistance spot welding with especial electrodes that were a flat tip electrode against the steel surface and a domed tip electrode upon the aluminum alloy surface. An intermetallic compound layer composed of Fe2Al5 and FeAl3 was formed at the steel/ aluminum interface in the welded joint. The thickness of the intermetallic compound layer increased with increasing welding current and welding time, and the maximum thickness being 7. 0 μm was obtained at 25 kA and 300 ms. The weld nugget diameter and tensile shear load of the welded joint had increased tendencies first with increasing welding current （ 18 -22 kA） and welding time （ 50 - 300 ms）, then changed little with further increasing welding current （ 22 - 25 kA） and welding time （300 -400 ms）. The maximum tensile shear load reached 5.4 kN at 22 kA and 300 ms. The welded joint fractured through brittle intermetallic compound layer and aluminum alloy nugget.展开更多
The corrosion resistance and evolution of corrosion products in medium-carbon high-strength spring steels were investigated in a neutral salt spray(5 wt% Na Cl solution). A formation model of γ-Fe OOH and a transform...The corrosion resistance and evolution of corrosion products in medium-carbon high-strength spring steels were investigated in a neutral salt spray(5 wt% Na Cl solution). A formation model of γ-Fe OOH and a transformation model describing the conversion of γ-Fe OOH to α-Fe OOH were constructed. The results indicated that, at the initial corrosion stage, the corrosion resistance was gradually improved with the addition of Cr; however, with the addition of alloying element V, the corrosion resistance decreased. These results were attributed mainly to the initial corrosion stage being closely related to the matrix microstructure parameters such as grain-boundary character and dislocation density. After the rust layer was formed at a later corrosion stage, the corrosion resistance was reinforced with the addition of Cr and V because Cr strongly influenced the composition, structure, and morphology of the corrosion products. The results presented herein show that Cr was conducive to the transformation of γ-Fe OOH into α-Fe OOH. Moreover, V and Cr exhibited obvious synergy and were enriched in the inner layer of the corrosion products.展开更多
Resistance spot welding (RSW) is the most common welding method in automotive engineering due to its low cost and high ability of automation. However, physical weldability testing is costly, time consuming and depende...Resistance spot welding (RSW) is the most common welding method in automotive engineering due to its low cost and high ability of automation. However, physical weldability testing is costly, time consuming and dependent of supplies of material and equipment. Finite Element (FE) simulations have been utilized to understand, verify and optimize manufacturing processes more efficiently. The present work aims to verify the capability of FE models for the RSW process by comparing simulation results to physical experiments for materials used in automotive production, with yield strengths from approximately 280 MPa to more than 1500 MPa. Previous research has mainly focused on lower strength materials. The physical weld results were assessed using destructive testing and an analysis of expulsion limits was also carried out. Extensive new determination of material data was carried out. The material data analysis was based on physical testing of material specimens, material simulation and comparison to data from literature. The study showed good agreement between simulations and physical testing. The mean absolute error of weld nugget size was 0.68 mm and the mean absolute error of expulsion limit was 1.10 kA.展开更多
18CrNbTi ferritic stainless steel is a low-cost material mainly used for the fabrication of manifolds, which usually work at temperatures below 950℃. With the development of engine technology, exhaust manifolds tend ...18CrNbTi ferritic stainless steel is a low-cost material mainly used for the fabrication of manifolds, which usually work at temperatures below 950℃. With the development of engine technology, exhaust manifolds tend to work above 1 000 ℃ and this may be even higher in the future. For developing a new kind of steel to satisfy these requirements,the effects of tungsten （W）addition on the high-temperature strength and oxidation resistance of 18CrNbTi ferritic stainless steel are discussed in this study. The test results show that W enhances high-temperature strength at 1 000 ℃ and significantly improves oxidation resistance. However, W addition tends to degrade oxide layer adhesion,causing spalling during alternate hot and cold conditions.展开更多
Exhaust emission regulations of the automotive are enforced in each country to prevent air pollution and global warming,and the restriction standard tends to become severer.Various techniques such as the combustion im...Exhaust emission regulations of the automotive are enforced in each country to prevent air pollution and global warming,and the restriction standard tends to become severer.Various techniques such as the combustion improvement of gasoline,upgrades of the catalyst,and the thermal capacity decreases in the exhaust lines are adopted to suit the regulations,and these lead to an increase of the maximum temperature of the exhaust gas. Recently,ferritic stainless steels are mainly used to parts of exhaust lines,as their thermal expansion coefficient is small,and the cyclic oxidation resistance and the thermal fatigue property are better than austenitic stainless steels. This paper presents newly developed heat-resistant stainless steels from Nisshin Steel for exhaust lines usage,and describes the currents of the steel development that could be envisaged in the future.With regard to improving the high-temperature strength of ferritic stainless steels,the addition of Nb,Mo and Cu is effective in solution hardening and precipitation hardening at 700℃,while the addition of Nb,Mo and W is effective in mainly solution hardening at 900℃.The addition of Cr,Si and Mn suppress the breakaway oxidation in air at 950℃up to 200 h of ferritic stainless steels containing 14%Cr.Especially,the addition of 0.8%or higher Mn would effectively improve the adherence of oxide scale.It is confirmed that ferritic stainless steels,NSSHR-1(14Cr-lMn-0.9Si-Nb) and NSSHR-2(10Cr-0.9Si-Nb-Ti ),is having a superior heat resistance,formability and cost performance compared to conventional Type441 and Type439 respectively.展开更多
Using ABAQUS software and cylindrical ellipsoid and body heat sources with a peak-heat-flux- attenuation function, a finite element model of the temperature field in the laser-arc hybrid welding of 4.5-mm BW300TP wear...Using ABAQUS software and cylindrical ellipsoid and body heat sources with a peak-heat-flux- attenuation function, a finite element model of the temperature field in the laser-arc hybrid welding of 4.5-mm BW300TP wear-resistant steel is proposed. The proposed model considers convection, radiation, molten pool flow, and heat conduction effect on temperature. A comparison of the simulation and actual welding test results confirms the reliability of the model. This welding heat-process model can provide the cooling rate at any position in the heat affected zone （HAZ） and can be used as a reference for the analysis of material properties and for process optimization.展开更多
The dissimilar material resistance spot welding of galvanized high strength steel and aluminum alloy had been conducted. The welded joint exhibited a thin reaction layer composed of Fe2Al5 and Fe4Al13 phases at steel/...The dissimilar material resistance spot welding of galvanized high strength steel and aluminum alloy had been conducted. The welded joint exhibited a thin reaction layer composed of Fe2Al5 and Fe4Al13 phases at steel/aluminum interface. The welded joint presented a tensile shear load of 3.3 kN with an aluminum alloy nugget diameter of 5.7 mm. The interfacial failure mode was observed for the tensile shear specimen and fracture occurred at reaction layer and aluminum alloy fusion zone beside the interface. The reaction layer with compounds was the main reason for reduction of the welded joint mechanical property.展开更多
文摘In this study, a 600 MPa hot-rolled corrosion-resistant steel plate produced by a specific company is investigated. Edge jagged defects and edge surface defects generated on both sides of the strip during production are characterized and analyzed. The results indicate that the distribution of reoxidation granules is located underneath the surface peel and that copper-containing granules diffuse along austenite grain boundaries. This phenomenon combined with the chemical composition and production parameters of a strip indicate that copper brittleness leads to edge jagged defects. However,the surface defects should be attributed to inherent defects on the surface of the strip. Measures that prevent surface oxidation and copper segregation at grain boundaries would likely eliminate these two types of edge defects.
文摘A new kind of high strength, high toughness and high plasticity spring steel has been developed. The strength, the reduction of area and the elongation of the steel are all higher than those of the steel 60Si2CrVA. The decarburization resistance and the sag resistance are also higher than those of the steel 60Si2CrVA. It has good hardenability, and is suitable for making springs with big cross section. The bogie springs made of this kind of steel have passed 2×106 cycles without broken under the conditions of maximum stress of 906 MPa and the minimum stress of 388 MPa.
基金Item Sponsored by National Key Fundamental Research and Development Programme of China (2004CB619104)
文摘The delayed fracture behavior of medium carbon high strength spring steel containing different amounts of boron （0. 000 5%, 0. 001 6 %） was studied using sustained load delayed fracture test. The results show that delayed fracture resistance of boron containing steels is higher than that of conventional steel 60Si2MnA at the same strength level and it increases with the increase of boron eontent from 0. 000 5% to 0. 001 6%. The delayed fracture mode is mainly intergranular in the boron containing steels tempered at 350℃, which indicates that the addition of boron does not change the fracture character. However, the increase of boron content enlarges the size of the crack initia tion area. Further study of phase analysis indicates that most boron is in solid solution, and only a very small quantity of boron is in the M3 （C, B） phase.
文摘Dissimilar material joining of 6008 aluminum alloy to H220 YD galvanized high strength steel was performed by resistance spot welding with especial electrodes that were a flat tip electrode against the steel surface and a domed tip electrode upon the aluminum alloy surface. An intermetallic compound layer composed of Fe2Al5 and FeAl3 was formed at the steel/ aluminum interface in the welded joint. The thickness of the intermetallic compound layer increased with increasing welding current and welding time, and the maximum thickness being 7. 0 μm was obtained at 25 kA and 300 ms. The weld nugget diameter and tensile shear load of the welded joint had increased tendencies first with increasing welding current （ 18 -22 kA） and welding time （ 50 - 300 ms）, then changed little with further increasing welding current （ 22 - 25 kA） and welding time （300 -400 ms）. The maximum tensile shear load reached 5.4 kN at 22 kA and 300 ms. The welded joint fractured through brittle intermetallic compound layer and aluminum alloy nugget.
基金financially supported by the National Natural Science Foundation of China (No.51474031)
文摘The corrosion resistance and evolution of corrosion products in medium-carbon high-strength spring steels were investigated in a neutral salt spray(5 wt% Na Cl solution). A formation model of γ-Fe OOH and a transformation model describing the conversion of γ-Fe OOH to α-Fe OOH were constructed. The results indicated that, at the initial corrosion stage, the corrosion resistance was gradually improved with the addition of Cr; however, with the addition of alloying element V, the corrosion resistance decreased. These results were attributed mainly to the initial corrosion stage being closely related to the matrix microstructure parameters such as grain-boundary character and dislocation density. After the rust layer was formed at a later corrosion stage, the corrosion resistance was reinforced with the addition of Cr and V because Cr strongly influenced the composition, structure, and morphology of the corrosion products. The results presented herein show that Cr was conducive to the transformation of γ-Fe OOH into α-Fe OOH. Moreover, V and Cr exhibited obvious synergy and were enriched in the inner layer of the corrosion products.
文摘Resistance spot welding (RSW) is the most common welding method in automotive engineering due to its low cost and high ability of automation. However, physical weldability testing is costly, time consuming and dependent of supplies of material and equipment. Finite Element (FE) simulations have been utilized to understand, verify and optimize manufacturing processes more efficiently. The present work aims to verify the capability of FE models for the RSW process by comparing simulation results to physical experiments for materials used in automotive production, with yield strengths from approximately 280 MPa to more than 1500 MPa. Previous research has mainly focused on lower strength materials. The physical weld results were assessed using destructive testing and an analysis of expulsion limits was also carried out. Extensive new determination of material data was carried out. The material data analysis was based on physical testing of material specimens, material simulation and comparison to data from literature. The study showed good agreement between simulations and physical testing. The mean absolute error of weld nugget size was 0.68 mm and the mean absolute error of expulsion limit was 1.10 kA.
文摘18CrNbTi ferritic stainless steel is a low-cost material mainly used for the fabrication of manifolds, which usually work at temperatures below 950℃. With the development of engine technology, exhaust manifolds tend to work above 1 000 ℃ and this may be even higher in the future. For developing a new kind of steel to satisfy these requirements,the effects of tungsten （W）addition on the high-temperature strength and oxidation resistance of 18CrNbTi ferritic stainless steel are discussed in this study. The test results show that W enhances high-temperature strength at 1 000 ℃ and significantly improves oxidation resistance. However, W addition tends to degrade oxide layer adhesion,causing spalling during alternate hot and cold conditions.
文摘Exhaust emission regulations of the automotive are enforced in each country to prevent air pollution and global warming,and the restriction standard tends to become severer.Various techniques such as the combustion improvement of gasoline,upgrades of the catalyst,and the thermal capacity decreases in the exhaust lines are adopted to suit the regulations,and these lead to an increase of the maximum temperature of the exhaust gas. Recently,ferritic stainless steels are mainly used to parts of exhaust lines,as their thermal expansion coefficient is small,and the cyclic oxidation resistance and the thermal fatigue property are better than austenitic stainless steels. This paper presents newly developed heat-resistant stainless steels from Nisshin Steel for exhaust lines usage,and describes the currents of the steel development that could be envisaged in the future.With regard to improving the high-temperature strength of ferritic stainless steels,the addition of Nb,Mo and Cu is effective in solution hardening and precipitation hardening at 700℃,while the addition of Nb,Mo and W is effective in mainly solution hardening at 900℃.The addition of Cr,Si and Mn suppress the breakaway oxidation in air at 950℃up to 200 h of ferritic stainless steels containing 14%Cr.Especially,the addition of 0.8%or higher Mn would effectively improve the adherence of oxide scale.It is confirmed that ferritic stainless steels,NSSHR-1(14Cr-lMn-0.9Si-Nb) and NSSHR-2(10Cr-0.9Si-Nb-Ti ),is having a superior heat resistance,formability and cost performance compared to conventional Type441 and Type439 respectively.
文摘Using ABAQUS software and cylindrical ellipsoid and body heat sources with a peak-heat-flux- attenuation function, a finite element model of the temperature field in the laser-arc hybrid welding of 4.5-mm BW300TP wear-resistant steel is proposed. The proposed model considers convection, radiation, molten pool flow, and heat conduction effect on temperature. A comparison of the simulation and actual welding test results confirms the reliability of the model. This welding heat-process model can provide the cooling rate at any position in the heat affected zone （HAZ） and can be used as a reference for the analysis of material properties and for process optimization.
文摘The dissimilar material resistance spot welding of galvanized high strength steel and aluminum alloy had been conducted. The welded joint exhibited a thin reaction layer composed of Fe2Al5 and Fe4Al13 phases at steel/aluminum interface. The welded joint presented a tensile shear load of 3.3 kN with an aluminum alloy nugget diameter of 5.7 mm. The interfacial failure mode was observed for the tensile shear specimen and fracture occurred at reaction layer and aluminum alloy fusion zone beside the interface. The reaction layer with compounds was the main reason for reduction of the welded joint mechanical property.
