阅读说明：本技术 一种大型真空钢锭的浇注方法 (Pouring method of large vacuum steel ingot ) 是由 杨海石 王志刚 朱伟伟 高峰 王紫林 乔麟淞 于 2020-06-30 设计创作，主要内容包括：本发明的一种大型真空钢锭的浇注方法,在精炼结束前采用钢包底吹氮,当吹氮结束后,控制温度比浇注温度高30～40℃,出钢准备浇注,并在浇注完成后破坏真空。采用本发明制造方法制造的大型真空钢锭,钢水纯净度大幅提升,C类夹杂物含量由以往1～1.5级降低至0.5～1级,其余几类夹杂物含量由0.5～1级降低直0～0.5级,部分板类件产品,探伤合格率由以往不足70％提升至95％以上。(According to the method for pouring the large vacuum steel ingot, the ladle bottom is used for blowing nitrogen before refining is finished, after the nitrogen blowing is finished, the temperature is controlled to be 30-40 ℃ higher than the pouring temperature, tapping is carried out for pouring, and vacuum is broken after pouring is finished. The purity of the molten steel of the large vacuum steel ingot manufactured by the manufacturing method is greatly improved, the content of C-type inclusions is reduced to 0.5-1 grade from the previous 1-1.5 grade, the content of the rest types of inclusions is reduced to 0-0.5 grade from 0.5-1 grade, and the flaw detection qualification rate of partial plate products is improved to more than 95 percent from the previous less than 70 percent.)

1. A pouring method of large vacuum steel ingots is characterized by comprising the following steps: and (3) blowing nitrogen at the bottom of the ladle before refining is finished, controlling the temperature to be 30-40 ℃ higher than the pouring temperature after the nitrogen blowing is finished, tapping for preparing pouring, and breaking vacuum after pouring is finished.

2. A pouring method of large vacuum ingots according to claim 1, characterized by comprising the following steps:

s100, pre-blowing nitrogen, wherein nitrogen is blown from the bottom of a ladle before refining is finished;

s200, pouring, wherein argon is blown through a water gap or a plug rod in the pouring process, and the initial argon blowing pressure is greater than 0.6 Mpa;

and S300, breaking the vacuum, and breaking the vacuum after the pouring is finished.

3. A method of casting a large vacuum ingot according to claim 2, wherein: in the step S100, the nitrogen blowing flow rate is controlled to be 200L/min, and when the product has a nitrogen content requirement, the nitrogen blowing flow rate is controlled to be: [ N ]% + 100-120 ppm, wherein N is a target value; when the product has no nitrogen content requirement, controlling the nitrogen blowing amount to be 160-200 ppm; when the nitrogen content required by the product is less than 70ppm, the nitrogen blowing amount is controlled to be 140-460 ppm.

4. A method of casting a large vacuum ingot according to claim 2, wherein: in step S200, the vacuum chamber pressure is controlled to be kept lower than 65Pa during the casting process.

5. A method of casting a large vacuum ingot according to claim 2, wherein: in the step S200, in the casting process, the initial argon blowing pressure is required to be greater than 0.6 MPa.

6. A method of casting a large vacuum ingot according to claim 2, wherein: in the step S200, in the casting process, the casting speed is controlled to be 3t/min, and is limited after 2 minutes.

7. A method of casting a large vacuum ingot according to claim 2, wherein: in the step S300, the first batch of heating agent is added within 1 minute after the end of casting, the second batch of heating agent is added after 5 minutes, and the carbonized rice husk is added as a covering agent.

8. A casting method of a large vacuum ingot according to claim 7, characterized in that: the amount of the first batch of the heat generating agent is 0.5kg per ton of steel, and the amount of the second batch of the heat generating agent is 2.5kg per ton of steel.

9. A method of casting a large vacuum ingot according to any one of claims 2 to 8, wherein: the diameter of the water gap is 60 mm.

Technical Field

The invention belongs to the technical field of steel ingot pouring, and particularly relates to a pouring method of a large vacuum steel ingot.

Background

Some large vacuum steel ingots cannot adopt a Vacuum Carbon Deoxidation (VCD) casting process due to limited components (Si, Al and the like are required to be added), a vacuum trickle (MSD) casting process is usually adopted, molten steel has poor flow dispersion in the casting process, the effect of trickle casting cannot be achieved, even if a stopper rod or a sliding plate argon blowing technology is adopted, the liquid drops of the molten steel are relatively large and flaky, and the effects of degassing and removing impurities are not obvious. Moreover, due to the limitation of equipment, the argon blowing strength can not be very high, and particularly in the later period of pouring, the flow dispersing effect is worse. The purity of the large steel ingot is seriously influenced, particularly after the large-forging ratio forging, C-type and Ds-type inclusions are easily expanded and enlarged, so that the defect equivalent exceeds the standard, and the qualified rate of the forged piece is relatively low.

Disclosure of Invention

1. Technical problem to be solved by the invention

The invention aims to solve the problems that in the casting process of the existing large vacuum steel ingot process, molten steel is poor in flow dispersion, the dripping casting effect cannot be achieved, the defect equivalent exceeds the standard, and the qualified rate of forgings is relatively low.

2. Technical scheme

In order to achieve the purpose, the technical scheme provided by the invention is as follows:

according to the method for pouring the large vacuum steel ingot, the ladle bottom is used for blowing nitrogen before refining is finished, after the nitrogen blowing is finished, the temperature is controlled to be 30-40 ℃ higher than the pouring temperature, tapping is carried out for pouring, and vacuum is broken after pouring is finished.

Preferably, the method specifically comprises the following steps:

s100, pre-blowing nitrogen, wherein nitrogen is blown from the bottom of a ladle before refining is finished;

s200, pouring, wherein argon is blown through a water gap or a plug rod in the pouring process, and the initial argon blowing pressure is greater than 0.6 Mpa;

and S300, breaking the vacuum, and breaking the vacuum after the pouring is finished.

Preferably, in the step S100, the nitrogen blowing flow rate is controlled to be 200L/min, and when the product has a nitrogen content requirement, the nitrogen blowing flow rate is controlled to be: [ N ]% + 100-120 ppm, wherein N is a target value; when the product has no nitrogen content requirement, controlling the nitrogen blowing amount to be 160-200 ppm; when the nitrogen content required by the product is less than 70ppm, the nitrogen blowing amount is controlled to be 140-460 ppm.

Preferably, in step S200, the vacuum chamber pressure is controlled to be kept below 65Pa during the casting process.

Preferably, in the step S200, during the casting process, the initial pressure of argon blowing is greater than 0.6 Mpa.

Preferably, in step S200, the casting speed is controlled to be 3t/min during the casting process, and is limited after 2 minutes.

Preferably, in the step S300, the first batch of heat generating agent is added within 1 minute after the end of casting, the second batch of heat generating agent is added after 5 minutes, and the carbonized rice husk is added as a covering agent.

Preferably, the amount of the first batch of the heat generating agent is 0.5kg per ton of steel, and the amount of the second batch of the heat generating agent is 2.5kg per ton of steel.

Preferably, the nozzle has a diameter of 60 mm.

3. Advantageous effects

Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:

according to the method for pouring the large vacuum steel ingot, the ladle bottom is used for blowing nitrogen before refining is finished, after the nitrogen blowing is finished, the temperature is controlled to be 30-40 ℃ higher than the pouring temperature, tapping is carried out for pouring, and vacuum is broken after pouring is finished. The purity of the molten steel of the large vacuum steel ingot manufactured by the manufacturing method is greatly improved, the content of C-type inclusions is reduced to 0.5-1 grade from the previous 1-1.5 grade, the content of the rest types of inclusions is reduced to 0-0.5 grade from 0.5-1 grade, and the flaw detection qualification rate of partial plate products is improved to more than 95 percent from the previous less than 70 percent.

Drawings

FIG. 1 is a flow chart of a method for casting a large vacuum ingot according to the present invention.

Detailed Description

In order to facilitate an understanding of the invention, the invention will now be described more fully hereinafter with reference to the accompanying drawings, in which several embodiments of the invention are shown, but which may be embodied in many different forms and are not limited to the embodiments described herein, but rather are provided for the purpose of providing a more thorough disclosure of the invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs; the terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention; as used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.