One of the key problems by diffusion-rolling bonding with small reduction for carbon steel plates is the bonding assistant coat. Abonding assitant coat used below 850℃ was developed. It contained copper as basic elem...One of the key problems by diffusion-rolling bonding with small reduction for carbon steel plates is the bonding assistant coat. Abonding assitant coat used below 850℃ was developed. It contained copper as basic element and zinc as main alloy element. Other small elements and rear metals were added to decrease the melting point and to obtain a better clouding and bigh plasticity. Based on the theory of brazing and transient liquid diffusion welding, two carbon steel plates were rolled with small reduction by using self-made bonding assistant coat. Temperature, pressure and holding time are the main technology parameters for controlling the process of diffusion-rolling. The results show that the bonding strength is the greatest when the bonding temperature is 830℃, holding time is 3 min and the reduction rate is 9%.展开更多
CO2 sorption and diffusion in coal are closely related to the occurrence of coal and gas outburst,geological sequestration of CO2 in coalbeds,and enhancing coalbed methane recovery by injecting CO2.Hence,it is signifi...CO2 sorption and diffusion in coal are closely related to the occurrence of coal and gas outburst,geological sequestration of CO2 in coalbeds,and enhancing coalbed methane recovery by injecting CO2.Hence,it is significant to investigate the sorption properties and diffusion models of CO2 in coal.Here we used a newly designed experimental apparatus at Peking University to investigate the sorption and diffusion properties of CO2 in natural coal samples from Dashucun Mine and Wutongzhuang Mine in Handan city,Hebei province,and Jinhuagong Mine in Datong city,Shanxi province,and obtained CO2 sorption isotherms and diffusivity models.The results indicate that,in a certain pressure range,CO2 sorption isotherms for the coal samples are consistent with the Langmuir model,which assumes that monolayer sorption occurs at the interface between coal matrix and CO2 molecules,and the sorption isotherms feature nonstandard hyperbolas in mathematics.At the same pressure and temperature,as the vitrinite content increases,coal adsorbs more CO2 molecules.The relation between the sorption capacity and the coal rank may be described as a "U-type" trend,and medium rank coal has the least sorption capacity.The bulk diffusivity of CO2 in coal is not constant;in the range of CO2 mass fraction greater than 1%,it increases roughly linearly with increasing mass fraction of CO2 adsorbed(or CO2 partial pressure) in coal.CO2 diffusivity in coal is approximately 10-4 to 10-2 mm2/s in magnitudes,and the diffusivity ranges in coal samples are 3×10-4 to 8×10-3 mm2/s from Dashucun Mine,2×10-4 to 4×10-3 mm2/s from Wutongzhuang Mine,and 2×10-4 to 4×10-3 mm2/s from Jinhuagong Mine.The results of the CO2 sorption and diffusion study can be applied to help predict and prevent coal and gas outburst as well as to evaluate the feasibility in geological sequestration of CO2 and to enhance coalbed methane recovery.展开更多
文摘One of the key problems by diffusion-rolling bonding with small reduction for carbon steel plates is the bonding assistant coat. Abonding assitant coat used below 850℃ was developed. It contained copper as basic element and zinc as main alloy element. Other small elements and rear metals were added to decrease the melting point and to obtain a better clouding and bigh plasticity. Based on the theory of brazing and transient liquid diffusion welding, two carbon steel plates were rolled with small reduction by using self-made bonding assistant coat. Temperature, pressure and holding time are the main technology parameters for controlling the process of diffusion-rolling. The results show that the bonding strength is the greatest when the bonding temperature is 830℃, holding time is 3 min and the reduction rate is 9%.
基金supported by Peking University (985 Program by Chinese Ministry of Education)the National Natural Science Foundation of China (Grant No.40640420141)
文摘CO2 sorption and diffusion in coal are closely related to the occurrence of coal and gas outburst,geological sequestration of CO2 in coalbeds,and enhancing coalbed methane recovery by injecting CO2.Hence,it is significant to investigate the sorption properties and diffusion models of CO2 in coal.Here we used a newly designed experimental apparatus at Peking University to investigate the sorption and diffusion properties of CO2 in natural coal samples from Dashucun Mine and Wutongzhuang Mine in Handan city,Hebei province,and Jinhuagong Mine in Datong city,Shanxi province,and obtained CO2 sorption isotherms and diffusivity models.The results indicate that,in a certain pressure range,CO2 sorption isotherms for the coal samples are consistent with the Langmuir model,which assumes that monolayer sorption occurs at the interface between coal matrix and CO2 molecules,and the sorption isotherms feature nonstandard hyperbolas in mathematics.At the same pressure and temperature,as the vitrinite content increases,coal adsorbs more CO2 molecules.The relation between the sorption capacity and the coal rank may be described as a "U-type" trend,and medium rank coal has the least sorption capacity.The bulk diffusivity of CO2 in coal is not constant;in the range of CO2 mass fraction greater than 1%,it increases roughly linearly with increasing mass fraction of CO2 adsorbed(or CO2 partial pressure) in coal.CO2 diffusivity in coal is approximately 10-4 to 10-2 mm2/s in magnitudes,and the diffusivity ranges in coal samples are 3×10-4 to 8×10-3 mm2/s from Dashucun Mine,2×10-4 to 4×10-3 mm2/s from Wutongzhuang Mine,and 2×10-4 to 4×10-3 mm2/s from Jinhuagong Mine.The results of the CO2 sorption and diffusion study can be applied to help predict and prevent coal and gas outburst as well as to evaluate the feasibility in geological sequestration of CO2 and to enhance coalbed methane recovery.
