About CRC(2)

The raw materials of cold rolled is HRC. In order to obtain high quality cold rolled coils, the inner grains of HRC?are required to be uniform and orderly, and the size is appropriate. To achieve this , the temperature of hot finishing rolling and coiling should be controlled effectively,It is hoped that the final rolling temperature of hot finishing rolling is 800 ~ 900℃ and the coiling temperature is 500 ~ 700℃

There will be scale on the surface of HRC, so HRC must be pickled before cold rolling.

The way to remove the scale is:bending the HRC for many times, which cause the breach of the scale and then start pickling which the acid will comes into the breach of scale to solvent the scale.

The composition of scale on the HRC:

1 FeO(Wustite)

2 Fe3O4(Magnetite)

3 Fe2O3(Hematite)

The surface states of CRC has direct influence to the application, if there is scratches, even very little, the CRC can be used as car side panel, if there is tiny hole on HRC, there not able to produce bear cans, if the brightness is not good enough, then can not be used in decoration parts.

The main defects of CRC

1,Iron scarp: The scale on the HRC is not cleaned 100%, there will be still scale on the HRC surface, after cold rolling, caused Iron scarp.

2,Scratch: The pit on surface, which shows parallelly.

three reasons to cause :

1 Oiling is not good, coiling speed is no good.

2 Unwind the coil, there is loose condition

3 There is hard things stick to the surface of guide roll

3,Cross breaks:When the bending stress born by the CRC is larger than the yield point.

Several reasons to cause:

1 strip shape is not good

???? 2 The outside diameter of coil cylinder is too short, not match

with the thickness of CRC

???? 3 skin rolling speed is too slow

???? 4 reduction ratio is not enough?

4 Cross breaks at the side of coil:Reduction too much on the side of coils, which cause the wave shape on the side of coil.

The surface finish of CRC?depends on the surface state of the roll?cylinder, which can be divided into rough surface and smooth surface

The advantages of rough surface

1, Not easy to cause defect on the surface in future operation

2, The surface can save more oil in the pressing process.

3, The adhesive ability of the coating is better when operating coating process.

Sumec steel is top 5 steel exporter in China, if you have the need for steel material, please contact me

Phil: [email protected]

Whatsapp: 0086 17821275251