Cold Rolled Low Carbon Steel Coil and Steel Plate
In the trade, processing, procurement, pledge of the steel industry chain, there are often some materials with long inventory time, buyers shall be careful of the steel property change through time, such as DC51D+Z produced in year 2015 and DC03 produced in year 2014. These steel coil products usually have an advantage in price, while people tend to ignore the impact of inventory time on the value of the material used.
Steel Coil Product has Expiration Date
Take DC03 cold-rolled steel coil and sheet product as an example. After 2 years of stock, the state of steel property must have changed compared with the newly produced.
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Corrosion Risk:
There may be variations in surface quality such as rust, steel coil deformation, etc. Take Baosteel Q/BQB 408 2014 as an example. Under normal oiling conditions, the conventional storage and transportation guarantees no rust for 6 month; but the risk of corrosion increases greatly when the inventory is 2 years. -
Mechanical Property Change:
In addition, there will be changes in mechanical properties, that is, the aging phenomenon we often say, resulting in higher material strength, poorer shape, and higher scrap rate when processing products. -
Surface Quality Change:
The change in surface quality is visible to the naked eye and is well distinguished. The change in performance is invisible and can only be inferred through the factory time of the warranty book, that is, the inventory time.
Steel Grade and Manufacturer Influence on Quality
The aging phenomenon caused by long inventory time is different in different steel mills or steel grades. In addition to managing inventory time, steel grades and steel mills should be treated differently.
The difference between different steel grades is very large
For example, low-alloy high-strength steel grade HC340LA and IF steel grade DC06 are also stored for one year. The former may have stamped orange peel, which may not change much when used.
It is important to note that advanced high-strength steel products (eg, HC780/980DP) rarely mention the issue of aging. It is not that they have no aging, but because their strength is too high, the effect of aging is nothing.
The large difference between the steel coils manufactured by different steel mills.
If it is still DC01, there is a big difference between the products of large steel mills and private small factories. It is possible that the DC01 coil produced by a large steel mill has not changed much in one year, but a small private factory has a problem for three months.
There are two main reasons for this phenomenon: First, most private small factories do not have their own steel production lines, raw materials of hot-rolled steel coil are purchased from second-tier steel mills, and the ingredients cannot be effectively controlled; second, the private small steel mills has lower quality management system, and the cold rolling process cannot carry out fine quality control.
