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A method for solidification of fine grains by low-frequency pulsed magnetic field using electromagnetic force-induced melt oscillation

A low-frequency pulse and electromagnetic force technology, used in the field of low-frequency pulse magnetic field solidification of fine crystals, can solve the problems of high equipment cost, easy blockage of nozzles, and difficulty in floating of inclusions, reducing power consumption, obvious skin effect, and avoiding skin effect of effect

Active Publication Date: 2017-02-08
BAOSHAN IRON & STEEL CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Practice has proved that the equiaxed grain ratio of the metal can be significantly increased only when the pouring superheat is below 15°C, and the low superheat will make the fluidity of molten steel worse, causing nozzles to be easily blocked, inclusions difficult to float, and many other problems
The use of electromagnetic stirring technology can properly increase the superheat range of pouring, but the practical application faces the following problems: 1. The limitation of the electromagnetic force makes the ratio of equiaxed crystals not high and unstable; 2. The existence of the skin effect makes the use of electric energy 3. Using electromagnetic stirring technology in the secondary cooling section, there are problems such as negative segregation and V-shaped segregation in the billet; 4. The equipment costs a lot and the later maintenance is complicated
The principle is that in the early stage of solidification, when the solidification shell has not yet formed, the low-voltage pulsed magnetic field is used to promote the free crystal nuclei to fall off from the mold wall, but when the solidification shell exists, the free crystals formed on the mold wall due to supercooling disappear. Magnetic field cannot obtain good thinning effect
This principle has certain problems in the application of many continuous casting processes, such as the continuous casting process of steel. According to the principle of this method, the excitation coil should be installed at the upper end of the crystallizer. The free crystal nuclei will be melted and installed in the lower part of the crystallizer. At this time, the solidification shell of the cast slab is formed, which cannot provide free crystal nuclei
In addition, the refinement effect of this method for large-size billets is not yet clear

Method used

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  • A method for solidification of fine grains by low-frequency pulsed magnetic field using electromagnetic force-induced melt oscillation
  • A method for solidification of fine grains by low-frequency pulsed magnetic field using electromagnetic force-induced melt oscillation
  • A method for solidification of fine grains by low-frequency pulsed magnetic field using electromagnetic force-induced melt oscillation

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Embodiment 1

[0034] The Sn-20%Pb alloy was selected for the experiment, and the non-magnetic austenitic stainless steel crucible was selected as the mold. During the experiment, the Sn-20%Pb alloy ingot was remelted in a resistance furnace, and the wire mesh was placed in the melt. Insulate at 800ºC for 30 minutes, then pour into a graphite crucible with an inner diameter of about 40 mm and a height of about 100 mm. During the experiment, the magnetic field strength at the center of the fixed mold was 0.07T, and the spiral, rotary, and traveling wave electromagnetic stirring and low-frequency pulsed magnetic fields were applied respectively. The parameters of the low-frequency pulsed magnetic field are: the pulse discharge frequency is 1-10Hz, the pulse waveform frequency is 10-50Hz, and the pulse discharge voltage is 500v. After the solidification experiment, at the same position of the melt sample, use a metallographic microscope to observe the microstructure of the sample, as shown in ...

Embodiment 2

[0040] 304 austenitic stainless steel no longer undergoes δ→γ phase transformation during solidification. During the grain growth process, there is no phase transformation that hinders the columnar crystals, resulting in relatively developed columnar crystals and a low proportion of equiaxed crystals. In addition, vibration marks will be formed on the surface of 304 austenitic stainless steel during the continuous casting process. In the subsequent treatment, it needs to be removed after processing, which significantly affects the yield of the product.

[0041] During the implementation, for the 160*160mm billet continuous casting machine, the pulse excitation coil is placed between the No. 1 and No. 2 sections of the secondary cooling zone, and the casting billet is placed in the middle of the coil. The size of the coil is: outer diameter 400mm, inner diameter 280mm, height 500mm, insulation between coils. The coil is made of copper material. Since the Joule heat will be gene...

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Abstract

The invention relates to a metal material preparative technology, in particular to a low frequency pulsed magnet field fine-grain solidification method for causing melt oscillation through electromagnetic force. A low frequency pulsed magnet field exciting coil is mounted outside a casting mold, when metal melt enters the casting mold through pouring equipment, a low frequency pulsed power supply is started, a pulse current generated by the low frequency pulsed power supply can generate a low frequency pulsed magnet field through the exciting coil, and the low frequency pulsed magnet field acts on the metal melt in the casting mold. The pulse discharge frequency fT is 1-25 Hz, the pulse waveform frequency fw is 1-50 Hz, and the pulse voltage Um is 0-500 V. The instantaneous magnetic field intensity of the low frequency pulsed magnet field technology is large, electromagnetic oscillation force with the direction varied in a reciprocating mode in the melt enables dendritic crystals to be broken more easily, no contact with the metal melt is achieved, pollution can be avoided, and the method can be applied to the solidification process of metal large-sized casting blank.

Description

technical field [0001] The invention relates to a metal material preparation technology, in particular to a low-frequency pulsed magnetic field solidification fine-grain method using electromagnetic force to induce melt oscillation. Background technique [0002] The increase of the equiaxed grain ratio of the metal slab is beneficial to the improvement of the rolling performance of the slab and the reduction of structural defects such as internal cracks and center segregation of the slab. At present, the general method in metallurgical process production is to reduce the pouring superheat and put into use the electromagnetic stirring technology. Practice has proved that the equiaxed crystal ratio of the metal can be significantly increased when the pouring superheat is below 15°C, but the low superheat will make the fluidity of molten steel worse, causing nozzles to be easily blocked, inclusions difficult to float and many other problems. The use of electromagnetic stirring...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): B22D27/02
Inventor 华骏山张永杰
Owner BAOSHAN IRON & STEEL CO LTD
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