Most of the professional mold buyers would specify the mold structure design, as well as the mold steel used, mold steel is one of the most critical factors to affect the mold quality, proper steel selection is the guarantee that the mold would run as long as expectancy.

Types of mold steel used in China
There are many different steel options for plastic injection molds. Here is list of the steel frequently used by China mold makers.
1050C:
P20
1.2311/1.2312
1.2344/1.2343
S136
H13
Alloy
Be-copper

Each of them has certain hardness and property, China local suppliers can make them all and the quality of them is different, the price is different too. Question is how to choose right steel?

How to choose mold steel?
To choose right mold steel, we need to start with the factors related to mold steel.

Molds Life
Mold life refers to the running life of the plastic injection mold work under normal operation.
High quality mold steel can withstand hundreds of thousands injection pressure without being deformed or broken, the price of the high quality is usually 4-5 times of the normal steel. What steel to be used, it depends on how many shots are required and expected from the mold, the principle is suitable is the best.

In order to choose right mold steel material, we divided the mold life into five classes as following.
Class- A molds, 1,000,000 shots
Class-B molds. 500,000-1,000,000
Class-C molds. 500,000 shots
Class-D molds. 100,000 shots
Class-E molds. 500 shots

Class-A molds, the hardness of core and cavity steel have to be up to 52-54 HRC, options you have 1.2344, 1.2343, H11, H13, 1.2767, 2083, S136. SKD11 or SKD61 are for angle pin or lifter.

Class-B molds, the hardness of core and cavity has to be up to 48-52 HRC, you can choose 1.2344, H13 mold steel. For slider and life, you can use 1.2344 or SKD11 or 61.

Class C Mold. The hardness of core and cavity has to be no less than 30 HRC. You can use 1.2738, 1.2738H. If the plastic material is of corrosion. You have to do nitride for the steel.

Class D mold. The hardness of core and cavity has to be no less than 22HRC. You can use P20, 1050C etc.

Class E mold. The hardness of core and cavity has to be over 22HRC. You could choose aluminum alloy, 1050C, P20.

Plastic Materials
Some plastic material can corrode the steel, you have to choose the corrosion resistance steel such as 1.2344, 1.2343, 2083 etc.

Finished requirement
Class A and Class B mold with mirror polishing, 1.2344, 1.2343 even S136 will be used. Class C and Class D mold with high glossary polishing, 1.2312, 1.2311, 1.2738 and 1.2738H would be used. Injection mold steel has to be nitride to enhance the surface, tiny damage on the surface would just destroy the injection mold.