Molten waste molten steel modifier as well as preparation method and application thereof

The invention discloses a molten steel scrap modifier as well as a preparation method and application thereof. The modifier comprises the following raw materials in percentage by weight: 55-75% of low-cost silicon-aluminum-calcium-carbon alloy, 10-20% of sintered calcium aluminate, 5-15% of industrial sodium carbonate and 5-15% of fluorite. By introducing a low-cost silicon-aluminum-calcium-carbon alloy and high-content Si, Al, Ca and C alloy elements into the modifier, the supplement of the alloy elements in the molten iron and the deep deoxidation of the molten iron are realized, meanwhile, the reduction modification of the top slag of the molten iron is completed, the thermodynamic conditions of the molten iron desulfurization reaction are improved, the efficient desulfurization of the molten iron of the Ca alloy element is also realized, and the molten iron desulfurization efficiency is improved. MgS in the desulfurization slag is converted into CaS, so that the stability of sulfide in the desulfurization