This paper proposes a method enabling to compute the prestressing strand resistance using the strain measured on only one core wire. Numerical analysis is conducted considering the pitch length of the strand and the d...This paper proposes a method enabling to compute the prestressing strand resistance using the strain measured on only one core wire. Numerical analysis is conducted considering the pitch length of the strand and the diameters of the core wire and helical wires as parameters. The results verify that the relation between the stresses of the core wire and helical wires can be expressed in terms of the helical angle. Based on this observation, a formula computing directly the prestress force in the strand from the strain measured in the core wire is suggested. Owing to the recently developed measurement method for the core wire strain, the proposed formula can be exploited to determine the prestress of the strand.展开更多
In order to realize the automatic welding of pipes in a complex operation environment,an automatic welding system has been developed by use of all-position self-shielded flux cored wires due to their advantages,such a...In order to realize the automatic welding of pipes in a complex operation environment,an automatic welding system has been developed by use of all-position self-shielded flux cored wires due to their advantages,such as all-position weldability,good detachability,arc's stability,low incomplete fusion,no need for welding protective gas or protection against wind when the wind speed is<8 m/s.This system consists of a welding carrier,a guide rail,an auto-control system,a welding source,a wire feeder,and so on.Welding experiments with this system were performed on the X-80 pipeline steel to determine proper welding parameters.The welding technique comprises root welding,filling welding and cover welding and their welding parameters were obtained from experimental analysis.On this basis,the mechanical properties tests were carried out on welded joints in this case.Results show that this system can help improve the continuity and stability of the whole welding process and the welded joints'inherent quality,appearance shape,and mechanical performance can all meet the welding criteria for X-80 pipeline steel;with no need for windbreak fences,the overall welding cost will be sharply reduced.Meanwhile,more positive proposals were presented herein for the further research and development of this self-shielded flux core wires.展开更多
Cored wires for electric arc spraying of Al/Al 2 O 3 MMC coatings were developed, with Al 2 O 3 powder as the core material and commercial aluminium strip as the retaining sheath. The bond strength, ...Cored wires for electric arc spraying of Al/Al 2 O 3 MMC coatings were developed, with Al 2 O 3 powder as the core material and commercial aluminium strip as the retaining sheath. The bond strength, Al 2 O 3 content, microstructure, micro-hardness and wear resistance of coatings produced by arc spraying of the cored wires were experimentally investigated and were compared with those of pure aluminum coating.展开更多
It is expected that the welding hardfacing of continuous casting rolls has better welding performance and higher wear resistance. A new type of submerged-arc hardfacing flux-cored wire has been developed through nitro...It is expected that the welding hardfacing of continuous casting rolls has better welding performance and higher wear resistance. A new type of submerged-arc hardfacing flux-cored wire has been developed through nitrogen replacing part of carbon and addition of the nitrogen-fixing elements of niobium and titanium. And microstructure, degree of hardness and high-temperature wear resistance of its deposited metal samples were also investigated. It is found that the microstructure is martensite, residual austenite and carbonitride precipitates. As a result, the hardfacing metal with homogeneous distribution of very fine carbonitride particles had high hardness and excellent wear-re- sisting property during high-temperature wear, which could significantly extend the service life of continuous casting rolls.展开更多
In this paper, an artificial neural network method that can predict the chemical composition of deposited weld metal by CO 2 Shielded Flux Cored Wire Surfacing was studied. It is found that artificial neural networ...In this paper, an artificial neural network method that can predict the chemical composition of deposited weld metal by CO 2 Shielded Flux Cored Wire Surfacing was studied. It is found that artificial neural network is a good approach on studying welding metallurgy processes that cannot be described by conventional mathematical methods. In the same time we explored a new way to study the no equilibrium welding metallurgy processes.展开更多
Self-shielded flux-cored wire is a convenient and efficient consumable for pipeline field girth welding because of its self-protection characteristic and high deposition rate, especially for remote construction sites ...Self-shielded flux-cored wire is a convenient and efficient consumable for pipeline field girth welding because of its self-protection characteristic and high deposition rate, especially for remote construction sites in rugged terrain. From the perspective of pipeline safety, the impact toughness of the girth welds is an important factor in pipeline integrity ,which determines the crack arrest behavior in the girth welds. Therefore, improving the girth weld impact toughness is of primary importance in the field of pipeline girth welding. Three self-shielded flux-cored wires comprising different chemical composition systems have been applied to large diameter X80 UOE （U-ing-O- ing-Expanding） pipeline semi-automatic girth welding,and the impact toughness of the welds has been evaluated by girth weld chemical composition analysis and microstructural analysis using scanning electron microscopy （SEM） and energy dispersive spectrometry （EDS） to investigate pipeline girth weld impact toughness and find ways to improve it. This helps in determining the main factors that influence girth weld impact toughness. Pipeline girth weld impact toughness is mainly determined by the final microstructure produced in the solid-state phase transition. In the as-weld state,acicular ferrite （AF） and fine bainite （FB） are a benefit to the impact toughness. For multilayer semiautomatic self-shielded flux-cored wire welding, the normalizing and tempering function of the latter beads to the initial beads plays an important role in the transition of girth weld microstructure, which affects the impact toughness. The original AF and FB and the corresponding heat treatment microstructure of the fine and uniform block ferrite and pearlite result in very good impact toughness. The following two mechanisms are found to promote the production of AF and FB in the girth weld. First, elements promoting the broadening of the austenitic region, such as Ni, C, Cu, and Mn, induce low temperature phase transitions and restrain the opposing function of Al, which is a benefit to the production of AF and FB. Second, dispersed high-melting-point inclusions, especially Al2O3 ,induce the nucleated production of AF. The advantageous function of inclusions is determined by their shape, distribution, and dimension. Dispersed spherical inclusions of small dimension are a benefit to the production of AF, and result in good impact toughness.展开更多
A set of electromagnetic vibration powder feeding apparatus of the flux cored wire production line and its single chip controlling system have been designed in this paper. The parameters of the electromagnatic vibr...A set of electromagnetic vibration powder feeding apparatus of the flux cored wire production line and its single chip controlling system have been designed in this paper. The parameters of the electromagnatic vibration powder feeding apparatus have been tested, the functional relation between powder feeding velocity V L and current I has been made out so that the controlling system can not only automatically make out the quantity of the powder according to the width of the steel belt, powder density, production speed and filling ratio, but also adjust the powder feeding speed according to the real production speed, keeping a stable filling ratio.展开更多
Mg-content cored-wire was used to desulphurize and spheroidize ductile iron melt in industrial experiments. The optimal feeding speed and suitable treatment temperature were determined in the experiments. And cored-wi...Mg-content cored-wire was used to desulphurize and spheroidize ductile iron melt in industrial experiments. The optimal feeding speed and suitable treatment temperature were determined in the experiments. And cored-wire method and pouring method were compared. Conclusions have been drawn that, under these conditions in the experiments, the optimal feeding speed is 15m/min, treatment temperature should be as low as possible, 1400-1450℃ generally; and cored-wire method can act more effective in ductile iron melt desulphurization and spheroid than pouring method.展开更多
A novel Ti cored wire containing Ti B2,Al60 V40 and Ti6 Al4 V mixed powders was developed for wirefeed arc deposition of Ti B/Ti composite coating,to enhance the hardness and wear resistance of Ti alloy.Results showed...A novel Ti cored wire containing Ti B2,Al60 V40 and Ti6 Al4 V mixed powders was developed for wirefeed arc deposition of Ti B/Ti composite coating,to enhance the hardness and wear resistance of Ti alloy.Results showed that after experiencing several chemical reactions,the wire was melted in the arc zone and turned into nonuniform droplets composed of Ti-Al-V-B melt and undecomposed Ti B2 particles.With the increase of welding current,the detachment time of droplet shortened while the transfer frequency accelerated,accompanied by the improvement in coating surface quality.The spatial distribution of Ti B whiskers in coating was governed by welding current.A uniform distribution could be achieved as welding current was sufficient at the expense of elevated dilution ratio,while increasing wire feeding speed could compensate the dilution loss of Ti B whisker to some extent.The decomposition process of Ti B_(2)particles and the microstructure evolution mechanism of coating was discussed in detail.The optimum coating possessed uniform microstructure,relatively low dilution ratio,and high hardness(639.1 HV_(0.5))as compared with Ti6 Al4 V substrate(326 HV_(0.5)).Indentation morphology analysis verified the excellent performance was ascribed to the load-sharing strengthening of Ti B whiskers.This study provides a high-efficiency fabrication method for the ever-developing titanium matrix composites(TMCs)coating.展开更多
The effects of process parameters on the depth-to-width ratio （D/W） of flux-cored wire underwater wet welding with a certain type of homemade .flux-cored wire are studied. It is found that the welding .speed, wire f...The effects of process parameters on the depth-to-width ratio （D/W） of flux-cored wire underwater wet welding with a certain type of homemade .flux-cored wire are studied. It is found that the welding .speed, wire feeding speed and torch oscillating amplitude hare significant effects on the dopth-to-width ratio （D/W） of welds. The D/W ratio of welds increases significantly with the increase of welding speed without the oscillating of welding torch. It increased （from 0. 14 to 0. 26 ） with the increase of wire feeding speed while the torch oscillating. And it decreased linearly with the increase of torch oscillating amplitude. However, the influelwe of oscillating speed, wire extension and welding voltage on the D/W ratio of welds was not obvious.展开更多
This paper puts forward a new method to achieve flux cored wire TIG welding and uses high-speed photography to analyze the droplet transfer behavior and forces acting on the droplet. The droplet transfer forms include...This paper puts forward a new method to achieve flux cored wire TIG welding and uses high-speed photography to analyze the droplet transfer behavior and forces acting on the droplet. The droplet transfer forms include bridging transfer, slag column guided transfer, and non-contact transfer; each of these forms may be observed as the melting position of the welding wire changes. The important role of surface tension in the process of droplet transfer is proposed using static force balance theory and pinch instability theory. The phenomenon of droplet backward swing during welding process could be attributed to the vapor recoil force produced by vapors from the droplet. The welding experiments show that the proposed welding process is stable and that the weld quality produced is good.展开更多
According to the characteristics of electric arc spraying technology and abrasion of boiler piping,a flux cored wire SMD 45 for electric arc spraying is developed The experimental results show that the surface hardn...According to the characteristics of electric arc spraying technology and abrasion of boiler piping,a flux cored wire SMD 45 for electric arc spraying is developed The experimental results show that the surface hardness of the coating reaches 60～65 HR and the adhesive strength between the coating and base is 23～28 MPa The wearability of the coating sprayed by the wire is 5 times than that of ordinary steel pipe Applying the wire to the heated surface,the life of the economizer pipe is doubly increased No local desquamation,rust and abrasion can be examined during more than one year's service.展开更多
In this research, a vermicular graphite cast iron brake drum was produced by cored wire injection in a one-step method. Silica sand and low-density alumina-silicate ceramic were used as molding materials in order to i...In this research, a vermicular graphite cast iron brake drum was produced by cored wire injection in a one-step method. Silica sand and low-density alumina-silicate ceramic were used as molding materials in order to investigate the effect of cooling rate on percentage of vermicular graphite and mechanical properties of the brake drum casting. Several thermocouples were inserted into the casting in the desired positions to measure the temperature change. By means of one-step cored wire injection, the two residual concentrations of Mg and RE were effectively controlled in the ranges of 0.013%-0.017% and 0.019%-0.025%, respectively, which are crucial for the production of vermicular graphite cast iron and the formation of vermicular graphite. In addition, the cooling rate had a significant effect on the vermicular graphite percentage. In the case of the silica mold brake drum casting, there was an obvious difference in the cooling rate with the wall change, leading to a change in vermicular graphite percentage from 70.8% to 90%. In the low-density alumina-silicate ceramic mold casting, no obvious change in temperature was detected by the thermocouples and the percentage of the vermicular graphite was stable at 85%. Therefore, the vermicular graphite cast iron brake drum with a better combination of mechanical properties could be obtained.展开更多
Effects of CeF3 on properties of self-shielded flux cored wire including welding process, inclusions in weld metal and mechanical properties are systematically studied. Welding smoke and spatter are reduced with the a...Effects of CeF3 on properties of self-shielded flux cored wire including welding process, inclusions in weld metal and mechanical properties are systematically studied. Welding smoke and spatter are reduced with the addition of CeF3. The main non-metallic inclusions in weld metal are AlN and Al2O3. CeF3 can refine non-metallic inclusions and reduce the amount of large size inclusions, which is attributed to the inclusion floating behavior during the solidification of weld metal. The low temperature impact toughness is improved by adding suitable amount of CeF3 in the flux.展开更多
The wire was made with foundry tungsten carbide particles as core. Iron-based tungsten carbide wearable composite coatings of different granularity and content on mild steel were prepared by the method of MIG welding....The wire was made with foundry tungsten carbide particles as core. Iron-based tungsten carbide wearable composite coatings of different granularity and content on mild steel were prepared by the method of MIG welding. Microstructure of the welded coating was investigated. Surface hardness and wear resistance to rubber wheel were tested. The results indicate that the small particles dissolved more, which separate out with net on crystal boundary. As a result the hardness and wear resistance of that matrix are relative higher. The big particles dissolved less and tree crystal separates out along particles. The gaps of particles are big and the particles tend to fall off when the coating is worn. So the hardness and wear resistance of the matrix are relative lower. The admixture with 80% big particles and 20% small particles has the best wear resistance and its wear resistance is quintupling of that of quenched 45 steel. With particles content up to 50wt%, the hardness and wear resistance increase.展开更多
The sprayed particles of metallic and cermet wires were collected to analyze the atomization state of the particles in arc spraying forming, the microstructure and properties of metallic and ceramic coatings were inve...The sprayed particles of metallic and cermet wires were collected to analyze the atomization state of the particles in arc spraying forming, the microstructure and properties of metallic and ceramic coatings were investigated and compared. Particle size analyzer was used for quantifying particle size. The XRD, SEM and optical microscope(OM) were used to analyze the phase composition and microstructure of the particles and coatings. From the experimental results, some difference of particle characteristics was established between the spraying metallic and ceramic cored wires, and the microstructure and properties of coatings depend strongly on the particles behaviors. The result shows that Fe-TiB2/Al2O3 composite coating has a high potential for abrasive wear applications.展开更多
Caterpillar construction machines play an important part in many fields such as hydraulic and electric engineering, the construction of highway, for its particular of structure. The walking system of caterpillar const...Caterpillar construction machines play an important part in many fields such as hydraulic and electric engineering, the construction of highway, for its particular of structure. The walking system of caterpillar construction machines is always under the condition of three-body abrasive wear. The abrasive wear of walking system is very severe, which always results in damages of components or structures of walking system of caterpillar construction machines. It is very important to repair the walking system by cladding technique. The abrasive wear properties of four kinds coatings produced by the shielded flux-cored wire surfacing for the repair of the damaged components of walking system of caterpillar construction machines have been studied experimentally on an MLS-23 type wet sand rubber wheel abrasive tester. The surfaces morphologies of the abrasively worn specimens and their microstructures are investigated by transmitting electron microscopy (TEM) after wear testing. Results show that the wear mechanism of cladding metals of the flux-cored wire No.1 and the No.2 is micro-cutting while that of the No.3 and the No.4 is micro-ploughing. The four kinds of flux-cored wire coatings present great potential applications for the repairing of caterpillar construction machines in the Three Gorges Engineering.展开更多
Metal transfer behavior of six kinds of self shielded flux cored wire(SSFCW) is studied using the apparatus of SSFCW high speed photography self made. Six kinds of metal transfer modes of SSFCW were obtained throu...Metal transfer behavior of six kinds of self shielded flux cored wire(SSFCW) is studied using the apparatus of SSFCW high speed photography self made. Six kinds of metal transfer modes of SSFCW were obtained through observation for high speed photograph film and analysis. It is believed that the research is of magnificent for improving operative performance and mechanical properties of SSFCW and dynamics characteristic of welding power.展开更多
文摘This paper proposes a method enabling to compute the prestressing strand resistance using the strain measured on only one core wire. Numerical analysis is conducted considering the pitch length of the strand and the diameters of the core wire and helical wires as parameters. The results verify that the relation between the stresses of the core wire and helical wires can be expressed in terms of the helical angle. Based on this observation, a formula computing directly the prestress force in the strand from the strain measured in the core wire is suggested. Owing to the recently developed measurement method for the core wire strain, the proposed formula can be exploited to determine the prestress of the strand.
文摘In order to realize the automatic welding of pipes in a complex operation environment,an automatic welding system has been developed by use of all-position self-shielded flux cored wires due to their advantages,such as all-position weldability,good detachability,arc's stability,low incomplete fusion,no need for welding protective gas or protection against wind when the wind speed is<8 m/s.This system consists of a welding carrier,a guide rail,an auto-control system,a welding source,a wire feeder,and so on.Welding experiments with this system were performed on the X-80 pipeline steel to determine proper welding parameters.The welding technique comprises root welding,filling welding and cover welding and their welding parameters were obtained from experimental analysis.On this basis,the mechanical properties tests were carried out on welded joints in this case.Results show that this system can help improve the continuity and stability of the whole welding process and the welded joints'inherent quality,appearance shape,and mechanical performance can all meet the welding criteria for X-80 pipeline steel;with no need for windbreak fences,the overall welding cost will be sharply reduced.Meanwhile,more positive proposals were presented herein for the further research and development of this self-shielded flux core wires.
文摘Cored wires for electric arc spraying of Al/Al 2 O 3 MMC coatings were developed, with Al 2 O 3 powder as the core material and commercial aluminium strip as the retaining sheath. The bond strength, Al 2 O 3 content, microstructure, micro-hardness and wear resistance of coatings produced by arc spraying of the cored wires were experimentally investigated and were compared with those of pure aluminum coating.
基金Item Sponsored by National Natural Science Foundation of China (51101050)Fundamental Research Funds for Central Universities of China (2009B30214)Natural Science Foundation of Jiangsu Province of China (BK2011257)
文摘It is expected that the welding hardfacing of continuous casting rolls has better welding performance and higher wear resistance. A new type of submerged-arc hardfacing flux-cored wire has been developed through nitrogen replacing part of carbon and addition of the nitrogen-fixing elements of niobium and titanium. And microstructure, degree of hardness and high-temperature wear resistance of its deposited metal samples were also investigated. It is found that the microstructure is martensite, residual austenite and carbonitride precipitates. As a result, the hardfacing metal with homogeneous distribution of very fine carbonitride particles had high hardness and excellent wear-re- sisting property during high-temperature wear, which could significantly extend the service life of continuous casting rolls.
文摘In this paper, an artificial neural network method that can predict the chemical composition of deposited weld metal by CO 2 Shielded Flux Cored Wire Surfacing was studied. It is found that artificial neural network is a good approach on studying welding metallurgy processes that cannot be described by conventional mathematical methods. In the same time we explored a new way to study the no equilibrium welding metallurgy processes.
文摘Self-shielded flux-cored wire is a convenient and efficient consumable for pipeline field girth welding because of its self-protection characteristic and high deposition rate, especially for remote construction sites in rugged terrain. From the perspective of pipeline safety, the impact toughness of the girth welds is an important factor in pipeline integrity ,which determines the crack arrest behavior in the girth welds. Therefore, improving the girth weld impact toughness is of primary importance in the field of pipeline girth welding. Three self-shielded flux-cored wires comprising different chemical composition systems have been applied to large diameter X80 UOE （U-ing-O- ing-Expanding） pipeline semi-automatic girth welding,and the impact toughness of the welds has been evaluated by girth weld chemical composition analysis and microstructural analysis using scanning electron microscopy （SEM） and energy dispersive spectrometry （EDS） to investigate pipeline girth weld impact toughness and find ways to improve it. This helps in determining the main factors that influence girth weld impact toughness. Pipeline girth weld impact toughness is mainly determined by the final microstructure produced in the solid-state phase transition. In the as-weld state,acicular ferrite （AF） and fine bainite （FB） are a benefit to the impact toughness. For multilayer semiautomatic self-shielded flux-cored wire welding, the normalizing and tempering function of the latter beads to the initial beads plays an important role in the transition of girth weld microstructure, which affects the impact toughness. The original AF and FB and the corresponding heat treatment microstructure of the fine and uniform block ferrite and pearlite result in very good impact toughness. The following two mechanisms are found to promote the production of AF and FB in the girth weld. First, elements promoting the broadening of the austenitic region, such as Ni, C, Cu, and Mn, induce low temperature phase transitions and restrain the opposing function of Al, which is a benefit to the production of AF and FB. Second, dispersed high-melting-point inclusions, especially Al2O3 ,induce the nucleated production of AF. The advantageous function of inclusions is determined by their shape, distribution, and dimension. Dispersed spherical inclusions of small dimension are a benefit to the production of AF, and result in good impact toughness.
文摘A set of electromagnetic vibration powder feeding apparatus of the flux cored wire production line and its single chip controlling system have been designed in this paper. The parameters of the electromagnatic vibration powder feeding apparatus have been tested, the functional relation between powder feeding velocity V L and current I has been made out so that the controlling system can not only automatically make out the quantity of the powder according to the width of the steel belt, powder density, production speed and filling ratio, but also adjust the powder feeding speed according to the real production speed, keeping a stable filling ratio.
基金the High Technology Research and Development Program of China(No.2002A4336072)
文摘Mg-content cored-wire was used to desulphurize and spheroidize ductile iron melt in industrial experiments. The optimal feeding speed and suitable treatment temperature were determined in the experiments. And cored-wire method and pouring method were compared. Conclusions have been drawn that, under these conditions in the experiments, the optimal feeding speed is 15m/min, treatment temperature should be as low as possible, 1400-1450℃ generally; and cored-wire method can act more effective in ductile iron melt desulphurization and spheroid than pouring method.
基金financially supported by Key-Area Research and Development Program of GuangDong Province(2019B010942001)National Key R&D Program of China(No.2017YFB0703100)+1 种基金the National Natural Science Foundation of China[grant numbers 51822103,51731009 and 51671068]the Fundamental Research Funds for the Central Universities[grant number HIT.BRETIV.201902]。
文摘A novel Ti cored wire containing Ti B2,Al60 V40 and Ti6 Al4 V mixed powders was developed for wirefeed arc deposition of Ti B/Ti composite coating,to enhance the hardness and wear resistance of Ti alloy.Results showed that after experiencing several chemical reactions,the wire was melted in the arc zone and turned into nonuniform droplets composed of Ti-Al-V-B melt and undecomposed Ti B2 particles.With the increase of welding current,the detachment time of droplet shortened while the transfer frequency accelerated,accompanied by the improvement in coating surface quality.The spatial distribution of Ti B whiskers in coating was governed by welding current.A uniform distribution could be achieved as welding current was sufficient at the expense of elevated dilution ratio,while increasing wire feeding speed could compensate the dilution loss of Ti B whisker to some extent.The decomposition process of Ti B_(2)particles and the microstructure evolution mechanism of coating was discussed in detail.The optimum coating possessed uniform microstructure,relatively low dilution ratio,and high hardness(639.1 HV_(0.5))as compared with Ti6 Al4 V substrate(326 HV_(0.5)).Indentation morphology analysis verified the excellent performance was ascribed to the load-sharing strengthening of Ti B whiskers.This study provides a high-efficiency fabrication method for the ever-developing titanium matrix composites(TMCs)coating.
文摘The effects of process parameters on the depth-to-width ratio （D/W） of flux-cored wire underwater wet welding with a certain type of homemade .flux-cored wire are studied. It is found that the welding .speed, wire feeding speed and torch oscillating amplitude hare significant effects on the dopth-to-width ratio （D/W） of welds. The D/W ratio of welds increases significantly with the increase of welding speed without the oscillating of welding torch. It increased （from 0. 14 to 0. 26 ） with the increase of wire feeding speed while the torch oscillating. And it decreased linearly with the increase of torch oscillating amplitude. However, the influelwe of oscillating speed, wire extension and welding voltage on the D/W ratio of welds was not obvious.
基金supported by the National Natural Science Foundation of China(No.51175374)the Natural Science Foundation of Tianjin(No.16JCZDJC38700)
文摘This paper puts forward a new method to achieve flux cored wire TIG welding and uses high-speed photography to analyze the droplet transfer behavior and forces acting on the droplet. The droplet transfer forms include bridging transfer, slag column guided transfer, and non-contact transfer; each of these forms may be observed as the melting position of the welding wire changes. The important role of surface tension in the process of droplet transfer is proposed using static force balance theory and pinch instability theory. The phenomenon of droplet backward swing during welding process could be attributed to the vapor recoil force produced by vapors from the droplet. The welding experiments show that the proposed welding process is stable and that the weld quality produced is good.
文摘According to the characteristics of electric arc spraying technology and abrasion of boiler piping,a flux cored wire SMD 45 for electric arc spraying is developed The experimental results show that the surface hardness of the coating reaches 60～65 HR and the adhesive strength between the coating and base is 23～28 MPa The wearability of the coating sprayed by the wire is 5 times than that of ordinary steel pipe Applying the wire to the heated surface,the life of the economizer pipe is doubly increased No local desquamation,rust and abrasion can be examined during more than one year's service.
基金financially supported by the Foundation of Heilongjiang Educational Committee(Grant No.12531116)the Harbin Special Funds for Creative Talents in Science and Technology(Grant No.2013RFQXJ102)
文摘In this research, a vermicular graphite cast iron brake drum was produced by cored wire injection in a one-step method. Silica sand and low-density alumina-silicate ceramic were used as molding materials in order to investigate the effect of cooling rate on percentage of vermicular graphite and mechanical properties of the brake drum casting. Several thermocouples were inserted into the casting in the desired positions to measure the temperature change. By means of one-step cored wire injection, the two residual concentrations of Mg and RE were effectively controlled in the ranges of 0.013%-0.017% and 0.019%-0.025%, respectively, which are crucial for the production of vermicular graphite cast iron and the formation of vermicular graphite. In addition, the cooling rate had a significant effect on the vermicular graphite percentage. In the case of the silica mold brake drum casting, there was an obvious difference in the cooling rate with the wall change, leading to a change in vermicular graphite percentage from 70.8% to 90%. In the low-density alumina-silicate ceramic mold casting, no obvious change in temperature was detected by the thermocouples and the percentage of the vermicular graphite was stable at 85%. Therefore, the vermicular graphite cast iron brake drum with a better combination of mechanical properties could be obtained.
文摘Effects of CeF3 on properties of self-shielded flux cored wire including welding process, inclusions in weld metal and mechanical properties are systematically studied. Welding smoke and spatter are reduced with the addition of CeF3. The main non-metallic inclusions in weld metal are AlN and Al2O3. CeF3 can refine non-metallic inclusions and reduce the amount of large size inclusions, which is attributed to the inclusion floating behavior during the solidification of weld metal. The low temperature impact toughness is improved by adding suitable amount of CeF3 in the flux.
文摘The wire was made with foundry tungsten carbide particles as core. Iron-based tungsten carbide wearable composite coatings of different granularity and content on mild steel were prepared by the method of MIG welding. Microstructure of the welded coating was investigated. Surface hardness and wear resistance to rubber wheel were tested. The results indicate that the small particles dissolved more, which separate out with net on crystal boundary. As a result the hardness and wear resistance of that matrix are relative higher. The big particles dissolved less and tree crystal separates out along particles. The gaps of particles are big and the particles tend to fall off when the coating is worn. So the hardness and wear resistance of the matrix are relative lower. The admixture with 80% big particles and 20% small particles has the best wear resistance and its wear resistance is quintupling of that of quenched 45 steel. With particles content up to 50wt%, the hardness and wear resistance increase.
基金Project(50375004) supported by the National Natural Science Foundation of ChinaProject(2062005) supported by the Natural Science Foundation of Beijing City, China
文摘The sprayed particles of metallic and cermet wires were collected to analyze the atomization state of the particles in arc spraying forming, the microstructure and properties of metallic and ceramic coatings were investigated and compared. Particle size analyzer was used for quantifying particle size. The XRD, SEM and optical microscope(OM) were used to analyze the phase composition and microstructure of the particles and coatings. From the experimental results, some difference of particle characteristics was established between the spraying metallic and ceramic cored wires, and the microstructure and properties of coatings depend strongly on the particles behaviors. The result shows that Fe-TiB2/Al2O3 composite coating has a high potential for abrasive wear applications.
文摘Caterpillar construction machines play an important part in many fields such as hydraulic and electric engineering, the construction of highway, for its particular of structure. The walking system of caterpillar construction machines is always under the condition of three-body abrasive wear. The abrasive wear of walking system is very severe, which always results in damages of components or structures of walking system of caterpillar construction machines. It is very important to repair the walking system by cladding technique. The abrasive wear properties of four kinds coatings produced by the shielded flux-cored wire surfacing for the repair of the damaged components of walking system of caterpillar construction machines have been studied experimentally on an MLS-23 type wet sand rubber wheel abrasive tester. The surfaces morphologies of the abrasively worn specimens and their microstructures are investigated by transmitting electron microscopy (TEM) after wear testing. Results show that the wear mechanism of cladding metals of the flux-cored wire No.1 and the No.2 is micro-cutting while that of the No.3 and the No.4 is micro-ploughing. The four kinds of flux-cored wire coatings present great potential applications for the repairing of caterpillar construction machines in the Three Gorges Engineering.
文摘Metal transfer behavior of six kinds of self shielded flux cored wire(SSFCW) is studied using the apparatus of SSFCW high speed photography self made. Six kinds of metal transfer modes of SSFCW were obtained through observation for high speed photograph film and analysis. It is believed that the research is of magnificent for improving operative performance and mechanical properties of SSFCW and dynamics characteristic of welding power.
