HOW TO PRODUCE STEEL GRITS?
Simple Introduction of Steel Grits
Steel shots are non-polluting steel blasting media used extensively in the blasting and cleaning industry to remove paint, rust, mill scale and other surface contaminants from steel, concrete and other surfaces prior to coating. Steel shot abrasives are also used to remove surface contaminations from castings after removal from the mould and also for shot peening operations on metal components which are exposed to severe stress in automobile and construction machinery industries.
Steel grit is angular in shape and is produced by crushing oversize steel shots and subsequently heat treated by tempering to get the required hardness and microstructure. These intrinsic characteristics of the product enormously enhance the performance of the blasting for heavy descaling, deep descaling and surface preparations. The angular shape and relative hardness of steel grit ensures rapid cleaning rates and excellent recyclability. With variations in hardness and size, steel grit can also be used for cutting granite and stones.
Three standard levels of hardness for high carbon steel grits range from:
GP steel grit: 42 – 50 HRC
GL steel grit: 56 – 60 HRC
GH steel grit: 63 – 66 HRC
Introduction about Production Method of Steel Grits
Steel grits are produced by crushing steel shots and subsequently heat treatment. To learn about the production method of steel grits, we firstly talk about production methods of steel shots.
There are three production methods of steel shots: Air Injection method, Water Jet Impact method, and Centrifugal Atomization method.
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The centrifugal atomization process was originally developed by Pratt& Whitney Aircraft Manufacturing Company. Due to its unique grain size distribution, grain shape, cleanliness and cost-effectiveness, people pay more attention to it. Now it is the main method for producing cast steel shot in the industry.
Let us talk about the centrifugal atomization used in the production of steel shots and steel grits. The centrifugal atomization method uses centrifugal force to separate molten steel. The molten liquid is thrown out of a series of small holes at the edge of the rotary wheels and falls into the cooling medium, and cure to shape. Then the semi-products follow a series of thermal and mechanical treatments in order to attain martensite microstructure.
Production of GH Steel Grits
Detailed procedures are:
First step: raw material.
Steel scraps are the most widely used raw material. The steel scrap price the factor which mostly affect the steel shot market.
Second step: melting.
Steel scraps become steel liquid in this step.
Third step: atomizing.
The molten steel liquid is thrown out of the rotary wheel by centrifugal force and falls down into the cooling medium, and then steel shots are shaped.
Fourth step: drying.
Fifth step: first-round sieving.
The steel shots fall into rough categories according to their diameters, ready for the fine sieving later.
Sixth step: refining shape.
Roundness of the final product is determined by the refining machine.
Seventh step: quenching.
Change the metallographic structure of steel shots and increase the hardness of steel abrasives.
Eighth Step: crushing.
Steel shots are crushed into steel grits. Steel grits are just the semi-product now.
Ninth step: second-round sieving.
Steel grits will be roughly classified into several ranges according to their sizes.
Tenth step: final sieving
Steel grits will be strictly classified into specific grit sizes (from G12 to G120) after this step.
Eleventh step: packaging.
Twelfth step: quality check.
Chemical composition (including C, Mn, Si, S, and P) and physical characteristics (including density, size distribution, structure and hardness) are tested in the typical quality inspection process.
Production of GP GL Steel Grits
Detailed procedures are:
First step: raw material.
Steel scraps are the most widely used raw material. The steel scrap price the factor which mostly affect the steel shot market.
Second step: melting.
Steel scraps become steel liquid in this step.
Third step: atomizing.
The molten steel liquid is thrown out of the rotary wheel by centrifugal force and falls down into the cooling medium, and then steel shots are shaped.
Fourth step: drying.
Fifth step: first-round sieving.
The steel shots fall into rough categories according to their diameters, ready for the fine sieving later.
Sixth step: refining shape.
Roundness of the final product is determined by the refining machine.
Seventh step: quenching.
Change the metallographic structure of steel shots and increase the hardness of steel abrasives.
Eighth Step: crushing.
Steel shots are crushed into steel grits. Steel grits are just the semi-product now.
Ninth step: second-round sieving.
Steel grits will be roughly classified into several ranges according to their sizes.
Tenth Step: low backfire.
Improve the toughness of steel grits and increase the durability of steel abrasives.
Eleventh step: final sieving
Steel grits will be strictly classified into specific grit sizes (from G12 to G120) after this step.
Twelfth step: packaging.
Thirteenth step: quality check.
Chemical composition (including C, Mn, Si, S, and P) and physical characteristics (including density, size distribution, structure and hardness) are tested in the typical quality inspection process.