Metal treatment – Process of modifying or maintaining internal physical... – Heating or cooling of solid metal
Patent
1990-06-13
1993-01-26
Wyszomierski, George
Metal treatment
Process of modifying or maintaining internal physical...
Heating or cooling of solid metal
148287, 723662, C21D 802
Patent
active
051819708
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for the production of ferritic stainless steel or martensitic stainless steel thin strips and sheets. More particularly, the present invention relates to a process for producing stainless steel sheets having a good surface gloss and high rusting resistance or superior grindability by controlling rusting origins. Especially, the present invention relates to slab heating conditions and hot rolling conditions, and methods of mechanical descaling and cold rolling.
BACKGROUND ART
As the stainless steel thin sheet products, there can be mentioned the 2B product, BA product and polished product specified by JIS. The commercial values of these stainless steel sheet products are determined by surface characteristics such as the gloss, rusting resistance, presence or absence or degree of flaws called "gold dust", peculiar to BA products, and the grindability, and accordingly, there is a need to improve these characteristics.
To satisfy this demand, there have heretofore been adopted a process in which a hot-rolled strip before cold rolling is annealed and pickled and the surfaces then ground to remove flaws (called "coil grinding"), a double rolling/annealing method, and a method in which heat streaks are formed at the cold-rolling step, but satisfactory results cannot be always obtained according to these methods.
The inventors carried out research with a view to developing a production process for obtaining stainless steel thin sheets having superior surface characteristics and clarified the causes of the forming of concavities and convexities on the surface of the product under various conditions, including slab-heating conditions and hot-rolling conditions, while omitting the coil grinding step of removing surface flaws by grinding the surfaces of a strip and searched for a means of eliminating these causes.
The technical problem concerning the surface characteristics of a stainless steel product is how to produce a product having a good gloss, high rusting resistance and superior grindability, and free of flaw called "gold dust". Our research found that the main causes of the degrading of these characteristics are "overlap" defects present on the surface of a cold-rolled material.
These "overlap" defects are caused by the following surface unevennesses or pitting before cold-rolling.
i) A concavity formed by intergranular corrosion caused at the pickling of a hot-rolled strip.
ii) An undulation present on the surface of a pickled material, which is generally called "surface roughness". iii) A grind grain left at the grinding of the surfaces of a pickled material.
Of these surface unevennesses or pitting, the concavity i) by intergranular corrosion can be prevented by the method of preventing the sensitization of the material or by the selection of appropriate composition for the pickling solution. In connection with the grind grain iii) left after the grinding, desirably the grind grain is made finer, but to prevent a formation of this unevenness, the coil grinding step should be omitted so that no grind grain is present.
The surface unevenness ii) called "surface roughness" has a large influence, because a large surface roughness results in a degradation of the surface properties of the product. As the means for reducing the surface roughness of the pickled material, there have been known a method in which the hardness of the material is increased at the mechanical descaling of the material (Japanese Examined Patent Publication No. 60-56768) and a method in which the surface roughness is reduced at the pickling step, as disclosed in Japanese Examined Patent Publication No. 61-38270 and Japanese Examined Patent Publication No. 49-16698.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a production process in which stainless steel sheet products having surface characteristics can be obtained even if the coil grinding step is omitted, and another object of the present invention is to provide a process in which a stainles
Fujiwara Shigeru
Iura Teruo
Tsuchinaga Masamitsu
Ueda Masanori
Nippon Steel Corporation
Wyszomierski George
LandOfFree
Process for production of stainless steel thin strip and sheet h does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for production of stainless steel thin strip and sheet h, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for production of stainless steel thin strip and sheet h will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1410756