澆注歷程當中注流卷吸空氣是鋼液二次氧化的緊張緣故。鋼液二次氧化不但會形成無益的氧化物同化導致鍛件報廢，并且還會使鋼錠中的氣體（H 、O 、N）含量增高。而氣體含量高又是導致超大型鍛件缺陷的要緊緣故之一。為了幸免鋼液的二次氧化，在模仿冶金行業履歷的底子上，開發了長水口保護澆注手藝，有效地幸免了鋼液的二次氧化。
In order to improve the symmetry and purity of large and super large free forging steel ingots, China has integrated a series of smelting and ingot casting techniques.
(1) Low silicon controlled aluminum steel smelting technology.
In order to reduce the assimilation and obtain the intrinsic fine grain steel, a low silicon controlled aluminum steel production technique was invented. It not only improves the purity of the molten steel, but also obtains the intrinsic fine-grain steel. It also effectively controls the segregation of the composition of the super-large steel ingot, and the assimilation and good body content in the ingot. The use of low-silicon controlled aluminum steel smelting and casting techniques has produced high-quality forgings with well-balanced components and few assimilates.
(2) Protection pouring.
1) New tundish.
In order to reduce the steel slag involved in the ingot casting process, imitating the history of the “retaining wall” and “blocking dam” in the continuous casting process of the metallurgical industry, the invention of the new middle with “retaining wall” and “blocking dam” package. Numerical simulations and engineering have proved that the assimilates in the ultra-large steel ingots cast by the new tundish are greatly reduced compared to the ancient round tundish.
2) Long nozzle protection pouring.
The injection of air in the pouring process is the tension of the secondary oxidation of molten steel. The secondary oxidation of molten steel not only causes undesired oxide assimilation, but also causes the forgings to be scrapped, and also increases the content of gases (H, O, N) in the ingots. The high gas content is one of the reasons for the defects of ultra-large forgings. In order to survive the secondary oxidation of molten steel, in the imitation of the metallurgical industry resume, the development of the long nozzle protection casting technology, effectively spared the secondary oxidation of molten steel.
3) Secondary filling.
Segregation is the inevitable consequence of the selection of crystallization of steel and the agglomeration of steel ingots. The larger the steel ingot, the more tight the defects such as segregation and shrinkage. When China developed a support roll with a 459t steel ingot with a balanced C content of 0.62%, it broke at the roll body near the riser end. After explaining the macroscopic morphology of the fracture site, it was found that the second shrinkage cavity was tight, and the C content in the lower part of the riser was as high as 1.16%, which was close to twice the scale value. In order to inquire about this difficulty, the steel ingot secondary refilling technique was invented, and the C content in the lower part of the riser was reduced to 0.8%, and the ultra-large steel ingot for the 5m and 5.5m support rolls was successfully produced.