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Superplastic Solid State Welding of Cr12MoV Steel Under Electric Field

Author: YueYun
Tutor: ZhangKeKe
School: Henan University of Science and Technology
Course: Materials Processing Engineering
Keywords: Of Cr12MoV 40Cr steel Electric field Superplastic Compression Superplastic solid-state welding
CLC: TG457.11
Type: Master's thesis
Year: 2010
Downloads: 36
Quote: 3
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Abstract

Containing a large volume fraction of carbide steel superplasticity and superplastic and solid-state welding test applied electric field is conducive to material facts presented electroluminescent superplastic welding new ideas, enrich and development of materials, the solid-state welding theoretical basis and find it difficult welding the development of the material, including the solid-state welding molding process open new avenues. In this paper, as the research object in Cr12MoV and 40Cr steel, determination of the mechanical properties of hot-rolled annealed under the influence of an electric field of Cr12MoV superplastic observe and analyze the impact of the electric field on its microstructure, provide a reference for the electric field of plastic welding data; ultra-fine processing on the basis of the hot-rolled 40Cr, Cr12MoV/40Cr electroluminescent Superplastic solid-state welding experiment of the electric field strength and polarity of the welding parameters before welding organization of the state Cr12MoV / 40Cr Superplastic solid-state welding quality through the welded joint area microstructure, fracture morphology, microhardness detected and analyzed, discussed the formation mechanism of the of plastic welding head under the influence of an electric field. Experimental results show that in the initial strain rate (1.5 × 10 ^{-5 : Cr12MoV steel ^{1 .5 × 10 ^{-3 ) s ^{- 1 , temperature (760 ^{8 20) ° C, the electric field strength (1 ^{5 ) kV / cm under the conditions of a one-way compression true stress-true strain curve showing typical superplastic compression rheological characteristics of the electric field to yield limit reduced to varying degrees, to shorten the non-steady-state plastic deformation stage, the steady state flow stress is reduced. Sample then negative electric field strength 2kV/cm the greatest impact, a 7% reduction in the steady-state flow stress, strain rate sensitivity index increased from 0.21 to 0.24, the superplastic deformation activation energy is reduced by the 241kJ/mol to 224kJ / mol, change the polarity of the electric field is not obvious; superplastic compression in the presence or absence of electric field conditions, steady-state flow stress decreases with increasing temperature and initial strain rate decreases; compared with no electric field, Cr12MoV steel in 800 ° C, 1.5 × 10 ^{-4 s ^{-1 and the 2kV/cm electric field is applied superplastic compressive deformation, the ferrite grains grew slightly still remained shaft-like and improved axial compression deformation process does not appear in the new phase; Cr12MoV steel and the salt bath circulation quenching ultrafine pretreatment 40Cr steel, pre-stress 62.2MPa, insulation 20min, welding temperature (760 ^{8 00) ℃, initial strain rate (0.75 × 10 ^{-4 ^{3 × 10 ^{-4 s ^{-1 , the electric field strength of (0 ^{4 ) kV / cm, welding time (0 ^{1 0) min under the conditions of Superplastic Welding with no electric field the electric field Cr12MoV side swell rate slightly larger; electric field can significantly shorten the welding time and increase the tensile strength of welded joints, the sample then negative electric field strength the greatest impact 2kV/cm, welding joint tensile strength of 690MPa, reaching more than 95% of the 40Cr base material; atomic diffusion welding process in the joint area, and depleted carbon layer is formed in the 40Cr side Cr12MoV side formed by carbon layer, and with the extension of the welding time and temperature increases, the the depleted carbon layer and increase the carbon layer width increases; field welding could significantly promote the diffusion of the atoms of the linker region, the diffusion layer on both sides of the connector are widened mouth metallurgically bonded area ratio increases after welding joint tensile breaking; Compared with hot-rolled, salt bath circulation 40Cr steel after quenching Pretreatment for ultra-fine, easy to implement high-quality and Cr12MoV steel Superplastic solid-state welding.}}}}}}}}}}}}}}}

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Welding, metal cutting and metal bonding > Welding process > Welding of a variety of metal materials and components > Welding of metallic materials > Steel
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