CN112553411A - Method for trace accurate nitrogen increase of cold-rolled deep-drawing steel through RH vacuum decarburization - Google Patents

Abstract

The invention discloses a method for trace accurate nitrogen increase of cold-rolled deep-drawing steel by RH vacuum decarburization, which comprises the following steps: after the cold-rolled deep-drawing steel reaches the RH process: step 1), RH is vacuumized to the ultimate vacuum degree of 60-70Pa, then the decarburization stage is carried out, and pure degassing is carried out for 15-18min under the pressure; step 2), RH adopts the whole circulation nitrogen blowing mode; step 3), after the air is broken, the circulation nitrogen blowing pressure is kept at 3-3.2Kpa, and the speed of increasing nitrogen of 1.8ppm/min in the molten steel can be realized; step 4), keeping the circulation time for 39-41 min. The invention realizes the ultralow carbon and short-time nitrogen increase in steel to 60-90 ppm; effectively reduces the cost of the nitrogen alloy, effectively eliminates the influence of temperature drop of the steel ladle and is difficult to control the nitrogen increasing amplitude.

Description

Method for trace accurate nitrogen increase of cold-rolled deep-drawing steel through RH vacuum decarburization

Technical Field

The invention belongs to the technical field of metallurgical steelmaking, and particularly relates to a method for trace accurate nitrogen increase of cold-rolled deep-drawing steel through RH vacuum decarburization.

Background

The method is used for theoretically analyzing the decarburization of the RH vacuum, then the nitrogen can be increased in the steel by circulating nitrogen blowing, and for the condition that the trace accurate nitrogen increase is needed in the cold-rolled deep-drawing steel, the purposes of accurate decarburization, pressure control and full-process nitrogen blowing in the RH process are achieved.

Under the condition of ultra-low carbon, part of cold-rolled deep-drawing steel also has the requirement of trace nitrogen content (60-90ppm), thus needing to be subjected to RH vacuum treatment, and then carrying out nitrogen increase on the basis of decarburization, wherein nitrogen alloy is generally added in the process, nitrogen is blown from the bottom of a steel ladle or nitrogen is circulated in a specific stage of an RH procedure, and the like, but the methods increase the alloy cost, influence the temperature drop of the steel ladle and are difficult to control the nitrogen increase amplitude.

Disclosure of Invention

The invention aims to provide a method for trace accurate nitrogen increase of cold-rolled deep-drawing steel by RH vacuum decarburization, which realizes the ultra-low carbon and short-time nitrogen increase to 60-90ppm in the steel; effectively reduces the cost of the nitrogen alloy, effectively eliminates the influence of temperature drop of the steel ladle and is difficult to control the nitrogen increasing amplitude.

The technical scheme adopted by the invention for solving the technical problems is as follows: a method for trace accurate nitrogen increase of cold-rolled deep-drawing steel by RH vacuum decarburization comprises the following steps: after the cold-rolled deep-drawing steel reaches the RH process:

step 1), RH is vacuumized to the ultimate vacuum degree of 60-70Pa, then the decarburization stage is carried out, and pure degassing is carried out for 15-18min under the pressure;

step 2), RH adopts the whole circulation nitrogen blowing mode;

step 3), after the air is broken, the circulation nitrogen blowing pressure is kept at 3-3.2Kpa, and the speed of increasing nitrogen of 1.8ppm/min in the molten steel can be realized;

step 4), keeping the circulation time for 39-41 min.

The invention has the following beneficial effects: the invention relates to a method for trace accurate nitrogen increase of cold-rolled deep-drawing steel by RH vacuum decarburization, which realizes the ultra-low carbon and short-time nitrogen increase to 60-90ppm in the steel; effectively reduces the cost of the nitrogen alloy, effectively eliminates the influence of temperature drop of the steel ladle and is difficult to control the nitrogen increasing amplitude.

Detailed Description

Example 1:

the heat 1917543, the mark TC1, the temperature 1652 ℃ after the molten steel reaches RH, the oxygen content 587ppm, the nitrogen content 42ppm, and the carbon content before arrival 0.04%.

Step 1), RH vacuum pumping is carried out for 4min and 35sec till the ultimate vacuum degree is 61 Pa;

step 2), RH adopts the whole circulation nitrogen blowing mode; a

Step 3), keeping the circulation pressure at 3-3.2 Kpa;

and 4) pure degassing for 18min, and performing air breaking treatment for about 40min of circulation time. The carbon content of the steel is 0.0027 percent, the nitrogen content is 79ppm, and the nitrogen content of the molten steel is increased by 1.8 ppm/min.

Claims (1)

1. A method for trace accurate nitrogen increase of cold-rolled deep-drawing steel by RH vacuum decarburization is characterized by comprising the following steps: after the cold-rolled deep-drawing steel reaches the RH process:

step 1), RH is vacuumized to the ultimate vacuum degree of 60-70Pa, then the decarburization stage is carried out, and pure degassing is carried out for 15-18min under the pressure;

step 2), RH adopts the whole circulation nitrogen blowing mode;

step 3), after the air is broken, the circulation nitrogen blowing pressure is kept at 3-3.2Kpa, and the speed of increasing nitrogen of 1.8ppm/min in the molten steel can be realized;

step 4), keeping the circulation time for 39-41 min.