The nine-tooth sprocket, i.e. the sprocket with nine teeth, is also known as the nine-angle sprocket and nine-angle wheel. A wheel-shaped mechanical part with teeth that engages with a chain is called a “sprocket”.
The shape of the chain wheel teeth must ensure that the chain can enter and exit the engagement smoothly and freely, minimise the impact and contact stress of the chain links during engagement, and be easy to process. It is composed of three circular arcs and one straight section, referred to as the three-arc-straight tooth profile. The tooth shape is processed with a standard tool, and it is not necessary to draw the end face tooth shape on the working diagram of the sprocket wheel, only to indicate on the diagram that “the tooth shape is manufactured according to 3RGB1244-85”, but the shaft face tooth shape of the sprocket wheel should be drawn.
Small diameter chain wheels are generally made into integral type, medium diameter chain wheels are mostly made into spoke plate type, and holes are opened in the spoke plate for easy handling, card loading and weight reduction, and large diameter chain wheels can be made into combined type, where the tooth ring and core can be made of different materials such as C45, stainless steel, etc.
The material of the sprocket wheel in steel and cast steel should ensure that the teeth of the wheel have sufficient strength and wear resistance, so the teeth of the sprocket wheel are generally heat-treated to make them reach a certain hardness.
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Sprocket specifications:4 angle sprocket|Pentagonal sprocket|Hexagonal sprocket|Seven angle sprocket|Eight angle sprocket|Nine angle sprocket|Eleven angle sprocket|Twelve angle sprocket|Thirteen tooth sprocket|Fifteen tooth sprocket|Sixteen tooth sprocket| . Bore 45mm|50mm|55mm|57mm|75mm|100mm|120mm|140mm| .
Nine tooth sprocket with outer diameter of 230mm and inner diameter of 50mm-75mm is used to match the sprocket for ring chain slagging machine.
Anchor chain sprocket is a reel with a deep groove for engagement with the chain ring of the anchor chain. They are divided into type A and type B according to the number of teeth: type A is a five-tooth anchor sprocket and type B is a six-tooth anchor sprocket. The anchor chain wheel is the main part of the anchoring machinery and its manufacturing quality directly affects the effectiveness of anchoring and anchoring, which is essential to ensure the safe navigation of the ship. The anchor chain wheel and the anchor chain’s engagement part – the chain ring bearing nest – is made up of the bottom of the bearing nest and the side of the wheel teeth, which is subject to torsion, traction and impact from all directions.
The anchor chain wheel is the main component of the anchoring machinery and its manufacturing quality directly affects the effectiveness of anchoring and anchoring, which is essential to ensure the safe navigation of the ship. The anchor chain sheave is made from the bottom surface of the chain ring and the sides of the teeth, and is subjected to torsion, traction and impact from all directions. However, after repeated research on the process design of this product, combined with the use of advanced MAGMA simulation software, by increasing the external cooling iron with the shape, increasing the amount of correction, Sprocket Rim Suppliers setting the tensioning bar, etc., finally the performance of this batch of products all qualified at one time, and the feedback from customers after use is very good.
1 Product structure and process
1.1 Product structure analysis
The casting product belongs to the marine class, is a thin-walled high-strength castings, relatively complex structure, special shape, uneven wall thickness, basically streamlined, the flange inside is very easy to open mouth deformation, easy to crack and sticky sand phenomenon in the groove.
1.2 Analysis of process characteristics
The anchor chain wheel is thick at the central axis, and the upper and lower layers are open back-to-back basins, and the bottom of the basin is a pentagram-shaped change in the surface. The wall is thinnest at the borders of the upper and lower parts of the whole casting, so the complementary shrinkage channel breaks off at the centre, and shrinkage holes and cracks are easily formed. The roughness of the outer surface is high and the tolerances marked on the casting meet the m-level in GB/T1804 and the K-level in GB1184-96. The gap between the upper and lower parts is the key part of the blank, which is required to be within 3 mm and needs to be controlled by a special finished product inspection sample. The internal requirements of the intermediate shaft bore are high and the process design needs to focus on ensuring this. The steel is refined and purified before it is discharged. In addition, the heat treatment must be supported by a smooth pad to prevent deformation.
1.3 Product process solutions
For the structural characteristics and quality requirements of this type of castings, taking into account the production operation and economic factors such as comprehensive analysis, the use of a box of one, horizontal parting, horizontal pouring process. The flange end face is used as the parting surface, and the moulding scheme of solid sample lifting tires is adopted to ensure stable control of dimensional accuracy. Resin self-hardening sand is used, quartz sand is used for the face sand, chromite sand is used at the rounded corners 50 mm ~ 80 mm thick, and chromite sand is covered at the thick lower part 80 mm ~ 100 mm to meet the solidification requirements and prevent cracking when shrinking at the hot joints.
1) Determination of shrinkage rate
The casting is a structural part with uneven wall thickness and many ribbed plates, and the shrinkage is severely hindered. For the whole casting, shrinkage is unevenly hindered shrinkage, choose a different shrinkage rate, 1.4% in the radial direction and 1.8% in the height direction.
2) Machining allowance
Machining allowance is to ensure the accuracy of the castings machining surface size and parts. According to JB/T5000.6-1998, according to the casting machining allowance requirements selected above 18 mm, below, the side of 14 mm, hole selected 18 mm.
(3) process correction amount
Process correction amount is to compensate for the casting shrinkage rate and the actual discrepancy or casting deformation caused by the wall thickness of the castings after processing can not meet the requirements and set the amount of correction. Due to the special structure of the casting, it is seriously obstructed during shrinkage, so 5 mm is added between the two major surfaces for correction to ensure the size and strength requirements. In addition, in the internal cavity of the non-assembly surface using the curve method to design the amount of correction, as a substitute for subsidies, not only can reduce the amount of steel, but also do not need to remove the subsidies, can avoid the use of gas cutting to remove the subsidies brought casting defects.
(4) Tension bar setting
In the process of solidification and shrinkage under the product, it is very easy to have uneven stress and the opening becomes bigger. In order to prevent the deformation from causing the size to exceed the difference, multiple tension bars are set at the gap in order to increase the strength.
(5) The riser and allowance setting
Through the casting simulation, determine the location of its hot joints, and basically determine the number of risers. The design of the riser is based on the cross-sectional dimensions of the casting, the temperature of the steel and the alloy composition, etc. to calculate the effective subsidence distance of the riser and the range of subsidence. The central rim is subsidised using the rolling method to increase the shrinkage channel and thus eliminate the lower hot section out of the shrinkage hole. In order to improve the ability of the riser shrinkage, the use of insulation riser set, pouring after the end of the liquid surface in the riser to arrange a sufficient amount of thickness of the insulation covering agent, and to ensure uniform coverage, reduce the cooling rate of the steel in the riser, so that the riser than the casting is subject to shrinkage part of the delayed solidification, in order to make the metal liquid in the riser shrinkage casting, so that the casting is more dense.
(6) external cold iron setting
Due to the special characteristics of the structure of the anchor chain wheel, various measures must be taken to ensure its sequential solidification and ensure that the internal organization is dense. The middle section of the anchor chain wheel has a thin and long wall, so if no measures are taken, shrinkage is bound to occur. The design of the external cooling iron with the shaped hanging sand, the adjustment of the complementary shrinkage area, the improvement of the temperature field, the local forced solidification, but also to prevent structural sticky sand.
A reasonable heat treatment process gives the casting the desired mechanical properties and effectively controls thermal deformation. The castings are insulated for 20 d after pouring for sand removal. The recesses are faced with chromite sand, which is easy to clean. The casting is soft annealed after sand cleaning and the riser is hot cut at 350°C after discharge. When cutting the riser all parts should be well padded and flattened, immediately after cutting the riser for normalising and tempering. Temper at a holding temperature of (900± 10). The austenite recrystallisation is used to evenly refine the organisation. Air cooling is used during normalising to ensure good grain refinement, thus improving the strength and toughness of the casting, giving full play to the strength potential of the material and making the properties more homogeneous and stable.
2 Results
After the casting is cleared of sand, the surface is smooth and clean, and there are no defects such as sticky sand cracks, shrinkage holes, etc. The mechanical properties of the product, the appearance of the dimensions, the implementation of the above process scheme makes the trial production of the anchor chain wheel received good results, the finished product produced without cracks, deformation, etc. lead to scrap, to meet customer requirements.
3 Conclusion
(1) The anchor chain wheel series is the first product produced by the company. In view of the deformation, slagging, cracking and other casting defects that occur in this type of structural parts, the process measures such as risers, subsidies and cold iron are optimised, and the defect prediction of castings by MAGMA saves costs and shortens the delivery period.
(2) Through practical verification, the product quality is good and has been approved by many classification societies, and has accumulated rich experience for the subsequent development of anchor chain wheels of similar structure.