Effect of Solidification Pressure on Interfacial Heat Transfer and Solidification Structure of 19Cr14Mn0.9N High Nitrogen Steel

Abstract

The effect of solidification pressure (0.5, 0.85 and 1.2 MPa) on heat transfer between ingot and mould was investigated with the measurement of cooling curves and calculation of heat transfer coefficient. Combined with cooling rate, temperature gradient and local solidification time (LST), the influence of pressure on solidification structure of 19Cr14Mn0.9N was revealed by macrostructure observation. The calculation results of heat transfer coefficient, obtained by the Beck-Nonlinear estimation technique, indicate that increasing solidification pressure obviously enhances heat transfer at the ingot/mould interface. And higher solidification pressure is benefit to increase cooling rate and temperature gradient of ingot. Meanwhile, increasing solidification pressure considerably suppresses nitrogen gas pore, and reduces the whole area of dispersing porosity and shrinkage, which is favorable to obtain a sound ingot. With the solidification pressure increasing from 0.5 to 1.2 MPa, the columnar zone is lengthened, the columnar-toequiaxed transition (CET) position gradually moves to the ingot center, and both dendritic arm spacing (λ 1 and λ 2 ) and local solidification time (LST) gradually decrease. The solidification structure is significantly refined and compressed under higher solidification pressure.

Effect of Single Power Two Circuits Electroslag Remelting Process on the Ingot Solidification Quality

“…Local solidification time ( LST ) is a decisive factor for the solidification structure during the ESR process, and it can be calculated by Equation where X M is the distance between solidus and liquidus, v l is the local solidification velocity and perpendicular to the solidus carve, v s is the velocity of withdrawing and can be obtained by calculating the remelting rate and θ is the angle for solidification front and axial.…”

Effect of Pressure on Dendrite Structure and Characteristics of Carbides during Solidification Process of H13 Die Steel Ingot

“…The increment of pressure can speed up the reaction rate, improve the cooling rate, refine the solidification structure and eliminate the solidification defects, etc. [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29] In addition, increasing pressure can effectively refine carbides to alleviate the negative effect. Li 16) increases pressure and higher solidification pressure is beneficial to reduce the volume fraction of M 6 C. Therefore, it is worth exploring a new method to improve quality of H13 ingot using the pressurized metallurgy technology.…”

“…It is well established that the relation between dendrite arm spacing and cooling rate is crucial to investigate the effect of pressure on dendrite structure. 17) The relation between the SDAS λ 2 and cooling rate R can be written as follow: 32,33) where n and M, mainly depending on alloy compositions, can be regarded as constant. 32,33) Curves represented the quantitative correlation between λ 2 and R (the cooling rate is between 0.5 and 3 K/s) were fitted as shown in Fig.…”

Effects of Nitrogen Gas Pressure on the Solidification Parameters and As-cast Microstructure Revolution during Pressurized Electroslag Remelting AISI 304 Stainless Steel

“…8,9) In addition, pressure also affects the solidification process. 10) On the one hand, increasing pressure could decrease the heat resistance at ingot/mould interface and enhance the cooling rate of ingots, providing a fine solidification structure. [11][12][13][14] On the other hand, increasing pressure could affect the thermodynamic and kinetic parameters, and change the solidification mode.…”

“…Meanwhile, the Q loss increases with an increase in pressure because increasing pressure could decrease the air gap. [10][11][12][13][14] However, the pool depth increased from 28 to 34 mm. This indicated that there was also an increase in the heat transfer rate at the slag/pool interface.…”