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In pellet production, the ring die is a major part of pellet production, and it is also a vulnerable part of the ring die pellet machine, and its quality will directly affect the quality and output of the pellets.

Force analysis of ring die of pellet machine

When the ring die pellet machine is working, the direction of the pressing force of the pressing roller on the ring die is from the inside to the outside along the diameter of the ring die. The inner ring surface of the ring die receives the friction force of the pressing roller, and the direction of the pressing roller of the material to the ring die is along the diameter of the ring die. From the inside to the outside, the side pressure of the raw material on the die hole wall, the inner ring surface of the ring die is subjected to the squeezing friction force of the material; and in the pressure roller area, the ring die will be subjected to the static friction force brought by gravity and the material.

The ring die carries the material in the die hole to make a rotary motion, which will be subjected to the squeeze friction of the pressure roller and the material. The normal failure mode of the ring die is the excessive wear of the discharge hole, the inner ring working surface or the ring die cracking.

The quality of the ring die and the length of its life span are largely related to the quality of the raw materials, in addition to the design, manufacturing, and heat treatment. Due to the high cost of ring dies, we will compromise on wear resistance, corrosion resistance and toughness when choosing ring dies.
Ring die materials on the market generally use alloy steel and stainless steel, so today Bao Shell will focus on alloy steel ring die, stainless steel ring die and the difference between the two.


Alloy steel ring die

Alloy steel: In addition to iron and carbon, other alloying elements are added to the steel. The iron-carbon alloy formed by adding an appropriate amount of one or more alloying elements on the basis of ordinary carbon steel increases the surface hardness of the ring die; the core material has low carbon content, is softer, and has high impact resistance Ability, not easy to crack; but poor corrosion resistance; after the hardened layer of the surface is worn, it wears more quickly in the later stage of use.

The main material of alloy steel ring die is *0CrMnTi low-carbon carburized alloy steel. The processing hardness is above HRC*0 and has good comprehensive mechanical properties. The ring die made of this type of material has high strength and toughness, and good hardenability, but the disadvantages are The corrosion resistance is not good.

Stainless steel ring die

Stainless steel (Stainless Steel) is the abbreviation of stainless and acid-resistant steel. Steels that are resistant to weak corrosive media such as air, steam, and water, or are stainless steel are called stainless steel. It contains 0.4%~0.5% carbon and *2%~*4% chromium. It has strong corrosion resistance. The hardness from the surface of the ring die to the core is more uniform, but the wear resistance and toughness are worse than that of alloy steel.

Stainless steel ring die materials include German stainless steel X*6Cr*3, domestic stainless steel 4Cr*3, etc. These materials have good stiffness and toughness. The heat treatment is overall quenching, the hardness is greater than HRC*0, and it has good wear resistance and corrosion resistance, and has a long service life. The cost of ring die for ton material is lowest.


The difference between alloy steel ring die and stainless steel ring die


1. The corrosion resistance of alloy steel ring die is worse than that of stainless steel ring die
2. The wear resistance and toughness of alloy steel ring die are better than stainless steel ring die
3. The cost of alloy steel ring die is lower than that of stainless steel ring die

How to correctly choose the material of ring die


When selecting the ring die, we should choose it reasonably according to the pressing material, the precision of the ring die, the working intensity and the economic benefits of the enterprise.

1. The corrosiveness of materials: chemical additives, salt and other corrosive media in raw materials such as aquatic livestock and poultry feed, fertilizers, etc., have a greater corrosive effect on the ring die. The stainless steel ring die can perform better than the alloy steel ring die. ,increase output.
2. The hardness of the pressed material: Because the raw materials such as sawdust, sawn wood and straw contain more impurities, the raw material has high hardness, and the carbon content in alloy steel is lower, and it is soft, has higher impact toughness, and has higher abrasion resistance than stainless steel. Good, the use of alloy steel ring die is not easy to cause the ring die to crack.
3. Working strength of ring die: The greater the strength of the ring die, the smaller the opening rate. The opening rate of the forage, straw, wood chips and other materials with high extrusion force is smaller than that of the feed ring die. Alloys can be selected. Steel ring die; and stainless steel ring die is recommended for high precision, small ring die hole and deep hardened layer.
4. Ring die price: The price of stainless steel ring die with the same compression ratio and caliber is much higher than that of alloy steel ring die. However, the quality assurance time and the service life of the stainless steel ring die are unmatched by the alloy steel ring die, and the overall operating cost is lower than that of the alloy steel ring die.

When choosing a ring die, we also need to pay attention that frequent replacement of the die will affect the use time of the ring die and the production output of the pellet machine. Only by choosing the ring die reasonably, and through correct use and effective maintenance, can the production efficiency be improved and the production cost reduced.