CN100451135C - Process of producing high quality carbon steel ingot with aluminium and RE added for high grade forging - Google Patents

Abstract

The invention discloses a process for producing high-quality carbon steel ingots by adding aluminum and rare earth to improve the flaw detection level of forgings. While adopting the original high-quality carbon steel ingot production process, aluminum and rare earth are used as deoxidizers for final deoxidation. Add aluminum (0.5-0.9) Kg/t steel and smelt for 10-15 minutes, then add rare earth (0.5-0.8) kg/t steel, pour into the ingot mold after melting, and demould when it reaches 7-9 times the solidification time. When the carbon steel ingot produced by this process is used for forgings, the quality is excellent, and the flaw detection level reaches the national standard level two or above.

Description

The process of producing high-quality carbon steel ingots by adding aluminum and rare earth to improve the flaw detection level of forgings

technical field

The invention relates to iron and steel smelting technology, in particular to a production process for adding aluminum and rare earth to high-quality carbon steel ingots to improve the flaw detection level of forgings.

Background technique

At present, the production method of high-quality carbon steel ingots is to smelt solid raw materials into molten steel in an electric furnace, refine them with refining slag during the reduction period, and finally add trace amounts of aluminum or rare earth, silicon aluminum calcium barium and other strong deoxidizers to deoxidize and then pour them into Cooling in the ingot mould. Although such a process is better than deoxidizing without a strong deoxidizer, the structure of the steel ingot is coarse and the segregation is serious. When the steel ingot is used for forging products, it cannot guarantee that the flaw detection of the steel ingot after forging can reach the national standard level 3 or above.

Contents of the invention

In order to solve the above problems, the present invention provides a process for producing high-quality carbon steel ingots by adding aluminum and rare earth to improve the flaw detection level of forgings.

The technical solution is to use the original high-quality carbon steel ingot production process, and use aluminum and rare earth as deoxidizers for final deoxidation, first add aluminum (0.5-0.9) Kg/t steel to smelt for 10-15 minutes, and then add rare earth ( 0.5-0.8) Kg/t steel, pour into the ingot mold after smelting, demould when it reaches 7-9 times of the solidification time, pass the inspection after air cooling and put into storage.

The invention overcomes the disadvantages that simply using a certain deoxidizer for deoxidation causes the smelted steel ingot to have a coarse structure, which is not conducive to forging high-quality forgings, and improves the flaw detection level of the forgings.

According to the above process for final deoxidation, the Al _S content in the steel can be controlled at 0.015% to 0.030%. When the Al _S content is controlled at 0.015%, the oxygen content in the steel does not decrease significantly with the increase of the Al _S content in the steel; and When the Al _S content is controlled at 0.030%, with the increase of the Al _S content in the steel, the oxygen content in the steel basically does not change; when the Al _S (acid-soluble aluminum) ≥ 0.020%, it also has a strong grain refinement effect ; In order to ensure the content of acid-soluble aluminum, it needs to be used in conjunction with rare earth, a two-pronged approach. Sulfur, oxygen, etc. in the steel react with the added rare earth to form spherical rare earth sulfide (RE ₂ S ₃ ) or sulfur oxide (RE ₂ O ₂ S),

Instead of elongated manganese sulfide (MnS) inclusions, the sulfide morphology is controlled, thereby improving the toughness and plasticity of the steel, especially the transverse impact performance, and improving the anisotropy of the steel. In addition, rare earths transform the angular high-hardness alumina inclusions into spherical rare earth oxysulfides and rare earth aluminates (REAlO ₃ ), which is beneficial to improve the fatigue performance of steel. As long as the amount of rare earth added is appropriate, rare earth elements can not only denature the inclusions, but also reduce the number of inclusions and make them finer, providing good conditions for ingot forging. With the increase of rare earth addition, rich rare earth will be dissolved in steel after deoxidation, desulfurization and metamorphic inclusion, and its solid solution amount can reach the order of 10 ^-5 ~ 10 ^-4 , and this part of rare earth will play the role of alloying role. Rare earth microalloying has the effect of purifying grain boundaries and solid solution strengthening, and at the same time can improve the as-cast structure, shorten columnar grains, and reduce dendrite segregation. Rare earth increases the amount of ferrite, improves the band structure, refines the grains, and inhibits grain growth and grain boundary corrosion at high temperature.

Due to the interaction between rare earth and acid-soluble aluminum, it plays a role of dispersion strengthening in the steel ingot, greatly refines the grains, and the content of inclusions is extremely low, and the phenomenon of grain growth does not occur when the steel ingot is forged and heated. Forging provides excellent conditions, making the forging structure more dense and uniform, and improving the flaw detection level.

Detailed ways

The present invention will be further described below in conjunction with embodiment.

Example 1:

For 12 pieces of 45# high-quality steel ingot 9.42T type, the final deoxidation is adopted. First, 0.5Kg/t of aluminum is added to the steel for smelting for 10 minutes, and then 0.5Kg/t of rare earth is added to the steel for re-smelting, and injected into the ingot mold to reach 7-9 times the solidification time After the steel ingot is forged into a shaft, the flaw detection is carried out on the forging, and the flaw detection grades all meet the second level of the national standard.

Example 2:

35# high-quality steel ingot 9.0T type 16 adopts final deoxidation, first add aluminum 0.9Kg/t steel for smelting for 15 minutes, then add rare earth 0.8Kg/t steel for re-smelting, inject into the ingot mold, reach 7-9 times of solidification time When the mold is demoulded, after forging into a shaft, the forgings are tested for flaws, and the flaw detection grades all meet the national standard level two.

Claims (2)

1. A process for producing high-quality carbon steel ingots by adding aluminum and rare earth to improve the flaw detection level of forgings, using the original high-quality carbon steel ingot production process, characterized in that aluminum and rare earth are used as deoxidizers for final deoxidation, and firstly added Aluminum (0.5-0.9) Kg/t steel is smelted for 10-15 minutes and then rare earth (0.5-0.8) Kg/t steel is added. 2. A process for producing high-quality carbon steel ingots by adding aluminum and rare earths to improve the flaw detection level of forgings according to claim 1, which is characterized in that when the melted steel is injected into the ingot mold to reach 7-9 times the solidification time demoulding.