Difference between JSH270CN and JSC270CC

What is Commercial Quality Cold Rolled Steel? 

The commercial quality cold rolled steel is a type of steel that can be used commercially for forming purposes that can also include shearing of a metallic sheet. Common operations that can be done on such steels are: Bending, Curling, De-cambering, Blanking, Shaping, Lancing, Piercing, Notching.

Cold rolled Steel: – Metal bar is passed through high tension rollers below the re-crystallization temperature of the steel. The roller does not only decrease the thickness of the sheets but also refines the grain structure and hardens the steels. After the cold rolling process there are some
additive processes like annealing, and then skin passing to make a complete SPCC material with bright finish.

What are Ageing & Non ageing properties in steel material. 

Non-Ageing 

It mean, material will meet the requirement specified in applicable standard for TS, Proof Stress, and Elongation after 12 month of manufacturing. Also no occurrence of stretcher strain for 12 months after steel manufacturing.

Delayed ageing

It mean specified steel shall have no occurrence of stretcher strain for at least 3 months after manufacturing, when stored at room temperature.

Therefore it is desirable delayed ageing steel sheet be used as promptly as possible after the steel sheets arrival within the time period.
After warranty sheet should not be used, if used there may happen age hardening for less than 3 months in case if any manufacturing done.

Engineering materials used in Industries

Types of steel:-

1. Carbon Steel 
2. Alloy Steel  
3. Stainless Steel 
4. Tool Steel {Its nothing but High carbon steel}

Large numbers of variety of steel is used for machine components. Generally steel can be specified by symbol Fe followed by T/S. Example FeE250, which mean 250 is Tensile strength.

Further designation of some steel types is explained as following:-

20C8   [ Carbon%= 0.2 and Manganese%= 0.8]

Here in plain carbon steel symbol (20C8), first 2 words before C are 100 times of average % of carbon and after C is 10 times of average % of manganese. Rest will be Fe (Iron).

25C12S14 [Carbon%= 0.25, Manganese%= 1.2% and Sulphur%= 0.14]

Here in free cutting steel symbol (25C12S14, 20C12Pb15) first 2 words before C are 100 times of average % of carbon, after C is 10 times of average % of manganese and last 2 words after S or Pb are 100 times of Sulphur /Lead percentage. Rest will be Fe (Iron).

25Cr4Mo2 [Carbon%= 0.25, Chromium%= 1 and Molybdenum%= 0.2]

Here in alloyed steel symbol (25Cr4Mo2) first 2 words before Cr is 100 times of average % of carbon, Before Mo divide number by 4 gives you average percentage of Chromium and divide number which is after Mo by 2 will give you average percentage of Molybdenum.

Note:- If any steel which contains more than 10% of alloy elements will be consider high alloy steel.

Effects of alloying elements on steel

1. Silicon:-  Silicon is presence almost in every steel. It increase hardness and strength without decreasing ductility of steel.

2. Manganese:-  It act as deoxidizing agent in steel material, which increase hardness and strength of material. Since Manganese is deoxidizing agent, which help material to prevent from rust.

3. Nickel:-  It increase the roughness by limiting grain growth during heat treatment process. It also increase strength hardness without effecting ductility.

4. Chromium:-  It is added to prevent material from corrosion, it is best corrosion resistance element. Chromium increases hardness and wear resistance. Material with chromium retains hardness and strength at elevated temperature.

5. Molybdenum:-  It increase hardness and wear resistance of material also it resist softening of material during tempering and heating.

6. Tungsten:-  It has same effect as Molybdenum.

7. Sulphur:-  It is added to increase the machinability of material.

Mechanical properties of a metal