Grinding Rolls/Rollers/Tyres and Table Liners/ Bull Ring Segments have evolved over the past many years. Some of the technologies present in the market, are:
- Weld Over lay Rolls/Table Liners
- Hi-Cr Rolls/Table liners
However, they have not been able to keep up with the developments in the product, and failed to give advantage to the customer in terms of higher productivity, and cost per running hour.
SBIPL manufactures and supplies Ni-Hard grinding rollers and Bull ring segments in the below specification. The combination of Ni-Hard rolls and High Chrome table liners is still holding a significant market share as the cheaper cast iron core is easier to machine. BIPL manufactures the same through the bi-metallic technology in the below grade.
Specification of Ni-Hard
|Elements||NiLCr 30/500||NiLCr 34/550|
|Carbon||2.7 % – 3.3 %||3.2 % – 3.6 %|
|Silicon||0.3 % – 0.6 %||0.3 % – 0.6 %|
|Manganese||0.3 % – 0.6 %||0.3 % – 0.6 %|
|Nickel||3.0 %– 5.5 %||3.0 % – 5.5 %|
|Chromium||1.5 % – 2.5 %||1.5 % – 2.5 %|
|Molybdenum||0.5 % Max.||0.5 % Max.|
|Sulphur||0.15 % Max.||0.15 % Max.|
|Phosphorus||0.3 % Max.||0.3 % Max.|
|Hardness||500 BHN Min.||550 BHN Min.|
Over the years, we have studied the pattern of changing coal quality in thermal plants in India, and with it, the reducing life of mill internals, and associated difficulties. In order to overcome the same, we have after continuous R&D, developed the 3rd generation of High Performance Grinding Rolls and High Performance Bull Ring Segments. Please see below the salient features of this latest, High Performance Grinding Rolls and High Performance Bull Ring Segments HIGH PERFORMANCE GRINDING ROLLS The High Performance Grinding Rolls have hard carbide tips which are mechanically fixed to roll mould, with more than adequate strength in such a fashion that these remain in location, through out its life cycle. The Carbide tips are first separately cast with an alumina grain cake inside the tip body. These tips are then arranged in a suitable pattern to the roll mould (metallic or sand) and further bound by a parent body of SG Iron metal. The intermittent gap maintained between adjacent tips, ensure gripping of coal particles and avoid material slippage. This ensures excellent grinding efficiency throughout the life cycle of the rolls. Mechanical Properties:- They are suitably heat treated to achieve high hardness (in the range of 59-66 HRc) and offer excellent wear resistance. Photo and sketch of above HIGH PERFORMANCE BULL RING SEGMENTS The bull Ring Segment metallurgy is specially developed to give excellent physical, mechanical and metallurgical properties. It is formed by casting a similar alumina grains cake in a high chromium material. Heat treatment is done to achieve microstructure of chromium carbides in matrix of tempered martensite. Special heat treatment controls Retained Austenite below 5%, giving hardness in the range of 59-66 HRc. This allows Bull Ring Segments to be used even up to 45 mm wear without losing of grinding efficiency, maintaining consistently high mill out put and coal fineness. Salient Advantages of High Performance Grinding Rolls and High Performance Bull Ring Segments
- Stability of Product: Even if there are cracks in the tips, to achieve the high hardness, the same do not propagate owing to the deign and the intermittent SG iron body.
- Higher life of Mill Internals (High Performance Grinding Rolls and High Performance Bull Ring Segments), due to high hardness, unique design, differential surface formed due to differential wear rate of 3 elements, the alumina grains, the carbide tip and the main SG Iron body.
- Precise machining of the bore helping in proper fitment, less wear of other mill components.
- Less shut downs due to higher life, leading to less maintenance costs.
- Consistency and increment of output: Our unique design of Carbide Tip Rolls and Bull Ring Segments, overcome the problem of coal slippage (which comes in Ni-Hard and Weld Over Lay Grinding Rolls and Bull Ring Segments) as the quantum of rough surface (owing to it’s unique design and differential wear pattern of alumina grains, carbide material and parent SG Iron body) results in virtually zero slippage of coal and results in consistent output of the mill with virtually zero mill rejects.
- Low collar formation and non-interference with wear area: It also results in uniform wear on the entire wearing face, without formation of wrinkles or wave on the wearing surface and the collar is virtually non existent. The Bull Ring Segments are such designed, that the collar so formed complements the space in Bull Ring Segments. As a result of this, the fineness of the coal ground is uniformly maintained at desired at more than 80% passing through 200 mesh sieve.