EP2039788A1

EP2039788A1 - Dephosphorization method in the process of smelting ni-cr pig iron from a nickel oxide ore

Info

Publication number: EP2039788A1
Application number: EP06775350A
Authority: EP
Inventors: Guanghuo Liu; Shenjie Liu
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-07-12
Filing date: 2006-08-11
Publication date: 2009-03-25
Also published as: EP2039788A4; CN101020943A; WO2008009178A1

Abstract

A dephosphorization method in the process of smelting Ni-Cr pig iron from a nickel oxide ore compi basicity oft lica, then adding limestorses the following steps: adjusting the heraw ore to 0.4-0.7 by adding limestone or si ne and coke powder, sintering to obtain sintered ore with abasicity of 0.5-0.7, and smelting the sintered ore to obtain Ni-Cr pig iron, in which the amount of the coke powderin the sintering process is 9-17% based on total weight, P content of the coke is not greater than 0.016%, P content of the limestone is not greater than 0.008%, P content of the raw ore is not greater than 0.012%.The P content could be reduced to lessthan 0.035% in one pass and in low cost without contamination by using the method.

Description

Technical Field:

This invention regards the field of metallurgy , and in particular the dephosphorization method in the process of smelting Ni-Cr pig iron from a nickel oxide ore,.

Background Art:

At present, the requirement about content of phosphorus (P) in the blast furnace process is not high: pig iron for steelmaking containing 0.15 P and foundry pig iron containing 0.06 P are rated as high quality goods; while the P content requirement for stainless steel products is relatively higher: below 0.035 for 304 series stainless steel, below 0.05 for 200 series stainless steel. To meet these requirements, the "Triple Dephosphorising" machine for dephosphorization is required for the large blast furnace, which is costly and can not keep the chromium (Cr) metal in the raw ore. The machine causes waste of raw material. Also it is not economic for medium and small blast furnace to invest a lot of money for dephosphorization. In prior art, there are also some other dephosphorization methods. For example, the Chinese patent CN85101003A disclosed a method of jet metallurgy which can reduce the P content to below 0.005 by spraying alkali metals or alkaline-earth metals or their alloy powder into steel ladle. But this method is not applicable for mass-production for its high cost. Chinese patent CN03808054.0 disclosed an oxygen top-blowing pre-dephosphorising device for dephosphorization which needs special device and thus increases the cost for smelting. CN200410021379 disclosed a reducing and dephosphorising agent for stainless steel used in vacuum induction furnace; this agent is mainly made up of Ca, Mg, which will be added into the liquid steel, adding a dephosphorising process.

Summary of invention:

The invention aims to overcome the shortcomings of prior art to provide a dephosphorization method in the process of smelting Ni-Cr pig iron from a nickel oxide ore.
The purpose of the invention is achieved through the following technical solution: a dephosphorization method in the process of smelting Ni-Cr pig iron from a nickel oxide ore, adjusting the binary basicity to 0.4-0.7 by adding limestone or silica to the raw ore, then adding limestones and coke powder for sintering to obtain sintered ore with a binary basicity of 0.5-0.8, and further smelting the sintered ore to obtain Ni-Cr pig iron.
When adjusting the binary basicity, the amount of the limestones to be added into the raw ore is 12% (percentage by weight, similarly hereinafter); when sintering, the amount of limestones to be added is 10-12% and that of coke powder is 9-17%.
CaO content in the limestones shall not be less that 80%.
The limestones can be replaced by quicklime.
The P content of the coke in raw material shall not be greater than 0.016%; P content of the limestone shall not be greater than 0.008%; P content of the raw ore not greater than 0.012%.
The sintering charge to be input into furnace contains: Fe: 6-46%; P: 0.019%; SiO_2: 18-41%; MgO: 16-21%; CaO: 16-24%; Ni: 1-3%; Cr: 1-3%.
The method offered in the invention is actually to adjust and prepare the variety and mixture ratio to be input into the fusing agent in the smelting process to get a proper binary basicity for direct dephosphorization and reduction of P in the smelting process, without adding any special equipment or preparing any special dephosphorising agent, which is applicable for smelting with many types of furnace such as blast furnace, electric furnace etc. The P content could be reduced to less than 0.035% in one pass and in low cost without contamination by using the method.

Detailed description of the invention:

In combination with the embodiments, a further description of the invention is given below. The following embodiments shall not be considered to limit the protection scope of the invention; any alteration and adjustment based on the idea of this invention belongs to the protection scope of the invention.

example I:

Composition of the raw ore:

with crystal water: 35%; Fe: 30%; P: 0.010%, SiO_2: 38.62%; CaO: 6.42%; Al₂O₃: 1.80%; MgO: 18.44%; MnO: 0.52%; Ni: 1.2-1.8%; Cr: 1-1.5%.

Mix the raw ore and limestones containing CaO of 80%, wherein the limestones occupy 12% in percentage by weight; and then it is dried in the sun, 14-16% coke powder (containing carbon: 78-80%) is added, and add limestone of 10-12% containing CaO of 84% for sintering, with the composition of sintered ore of: Fe 25.38%, P 0.019%, SiO₂ 21.5%, CaO 20.29%, MgO 15.17%, F1-3%, Cr 0.7-1.5%, Ni 1.2-1.8%;
Smelt the sintered ore. The sinter reduces the basicity to between 0.5-0.8 by the equilibrating action among Si, Mg and F, and makes the phosphorus get into the liquid slag in large quantities. During the process of slag tapping, as the discharge of the slag, the composition of the Chromel pig iron obtained are as follows: P below 0.035%, S below 0.08%, Fe 69%-92%, Ni 3-16%, Cr 2-7%, Mn 0.5%, Si 1.0-2.4%, C 1-4%.

Claims

A dephosphorization method in the process of smelting Ni-Cr pig iron from a nickel oxide ore, characterized in that adjusting the binary basicity to 0.4-0.7 by adding limestone or silica in the raw ore, sintering after adding the limestone and coke powder to obtain sintered ore with a basicity of 0.5-0.8, further smelting the sintered ore to obtain Ni-Cr pig iron.
A dephosphorization method in the process of smelting Ni-Cr pig iron from a nickel oxide ore according to claim 1 characterized in that: to calculate by the percentage of mass, the amount of the limestone added when adjusting the binary basicity of the raw ore is 12%, the amount of the limestone added when sintering is 10-12%, coke powder 9-17%.
A dephosphorization method in the process of smelting Ni-Cr pig iron from a nickel oxide ore according to claim 1 or 2, characterized in that: to calculate by the percentage of mass, the contents of CaO of the limestone is not less than 80%.
A dephosphorization method in the process of smelting Ni-Cr pig iron from a nickel oxide ore according to claim 1 or 2, characterized in that: the limestone shall be replaced by quicklime.
A dephosphorization method in the process of smelting Ni-Cr pig iron from a nickel oxide ore according to claim 1 or 2, characterized in that: to calculate by the percentage of mass, the contents of P in the coke powder is not greater than 0.016%, the contents of P in the limestone is not greater than 0.008%, the contents of P in the raw ore is not greater than 0.012%.
A dephosphorization method in the process of smelting Ni-Cr pig iron from a nickel oxide ore according to claim 1 or 2, characterized in that: to calculate by the percentage of mass, the sintering charges include Mg 12-30%, Si 15-40%, Ca 12-30%, F 0.3-4%.
A dephosphorization method in the process of smelting Ni-Cr pig iron from a nickel oxide ore according to claim 6, characterized in that: to calculate by the percentage of mass, the sintering charges include Fe 6-46%, P 0.019%, SiO₂ 18-41%, MgO 16-21%, CaO 16-24%, Ni 1-3%, Cr 1-3%.