APL Annealing Steel Pickling Line Continuous Push-Pull Type 550000t/Year

Steel strip pickling line continuous&push-pull type

Deep-type pickling lines consist of deep working tanks where the acid solution presents an extremely slow flow motion. Shallow-type pickling lines rely on a different tank design, which guarantees a higher pickling effect on the bottom surface of the strip with respect to conventional deep-type lines, even with slow motion of acid flow. Unfortunately, some sealing problems characterize this kind of line

Usually, the scale thickness is 10 to 20 μm. Its so-called scale structure is not uniform, but mainly consists of a layer of wustite (FeO). According to the descaling model described by Frisch and Thiele (see Gruchot et al., 2001), the acid penetrates the scale structure, thus reaching the free metal surface. The reaction occurring between acid and free metal generates a local current flowing from the scale-free metal portion, acting as an anode, to the conductive wustite layer, playing the role of a cathode

Coil to Coil Pickling lines are a part of the finishing process of flat rolled steel in which oxides and scale are removed from the surface of the strip by dissolution in acid. Generally HCL is used for carbon steel applications and hydrofluoric or nitric acids are used for stainless steel.

Push-pull pickling lines primarily handle coils and do not have welders at the entry sections nor storage areas for the strips. Therefore, each coil is threaded through the process line separately.

The pickling tanks of a push-pull line are generally shorter than those of a continuous line because the line speed during pickling (from about 150 to 660 fpm) is usually slower than that of a continuous line. Other operating procedures of a push-pull line are similar to those of a continuous line. The pickle “liquor” is usually maintained at 180 °F or higher by external heat exchangers. A rinse section follows the pickling section to remove acid residue from the strip surface with fresh water. Pickled coils can be then coated on both side of the strip with a rust preventative oil or lubricant for later downstream processes like stamping or ship out dry for parts to be later rollformed and painted for example

The push-pull pickling line

Process Flow

Main equipments according to processflow in turn are as follows:

Manually loading → entry skid→ coil loading trolley → pre-decoiling (floor roller) → decoiling scraper →3-roller pinch straightener → anti-bend roller → pay off reel → decoiling pinchroll → vertical guide roller → 5-roller pinch straightener → transverse shearer→ vertical guide roller → acid pickling trough → washing trough → edge blowingdevice → hot air dryer → accumulator pinch roll → pit type accumulator →vertical guide roller → pinch centering machine → circle shearer → waste edgerecoiler → 3-roller tension bridle roll → transverse shearer → vertical guideroller → exit pinch roll → recoiler (EPC) → coil unloading trolley → rear partpressure roller → exit skid → manually unloading

Continuous Acid Pickling Line

Process Flow

Main equipments according to processflow in turn are as follows:

Manually loading → entry skid→ coil loading trolley I# &II# → pay off reel I#&II# → decoiling scraper I# &II# →5-roller pinch straightener I# &II# → transverse shearerI#&II# → vertical guide roller → welder → crescentshearer → pinch roll → entry accumulator → scale breaker → tension bridle roll →vertical guide roller → acid pickling trough → washing trough → edge blowingdevice → vertical guide roller → hot air dryer → tension bridle roll → exit accumulator→ tension bridle roll → transverse shearer → exit pinch roll → recoiler (EPC) →coil unloading trolley → exit skid → manually unloading