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Pellet Die Materials

Typically there are 2 main material used to manufacture pellet dies. These are:
• X46Cr13 (commonly known as ‘stainless steel’ or ‘chrome-steel’)
• 20MnCr5 (commonly known as ‘alloy’)

These materials have different characteristics and each are suitable for different applications: 

 

X46Cr13

Known as 4Cr13 in China, and 40KH13 in Russia,
The X46Cr13 steel dies are vacuum / through hardened, the thermal treatment achieving a 53-55 HRc hardness on the surface and in the core. The high content of chrome makes it corrosion resistant.

Although the cost is higher for that of normal alloy, X46Cr13 is by far the most common material used throughout the feed milling industry. 

20MnCr5

The dies made with 20MnCr5 steel, on the other hand, are alloys. The added Nickel content acts to strengthen the die, while the added maganese acts to improve the resistance to wears and shocks. The amount of chrome will affect how well the material it's mechanical properties (resistance and hardness) and the physical ones (resistance to corrosion and oxidisation)

Dies made with 20MnCr5 are generally treated by case hardening, giving a 60-62 HRc hardness for approximately 0.8-1.2 mm. Under the case hardened layer, the steel remains malleable and therefore less brittle. The dies made with this steel are more resistant during the pelleting of extremely difficult fibre-rich products such as: beet pulp, alfalfa, straw and hay.

JUS	Č.4321
DIN 17210	20MnCr5
BS	-
GOST	-
AISI  SAE	5120
UNI 7846	20MnCr5
NF A35-551-86	20MC5

Chemical composition (cast analysis)

Chemical elements	C	Si max	Mn	P max.	S	Cr
%, by mass	0,17-0,22	0,40	1,10-1,40	0,035	≤ 0,035	1,00-1,30
Permissible deviation	±  0,02	+ 0,03	± 0,05	+ 0,005	+ 0,005	± 0,05

18NiCrMo5

Another material that is use is alloy 18NiCrMo5, which is similiar to the above 20MnCr5 steel but with a higher alloy content.
18NiCrMo5 chemical composition in weight %: 0.19% C, 0.81% Mn, 0.32% Si, 0.75% Cr, 0.17% Mo, 1.25% Ni.