Production Process of Cast Iron Gates

As a key equipment in water conservancy projects, sewage treatment and other fields, the production process of cast iron gates integrates various technologies such as precision casting, mechanical processing and quality control. The following will detail its complete production process.

Raw Material Selection and Melting

The first step in production is to strictly screen raw materials, mainly using gray cast iron or ductile iron. These two materials have high strength, corrosion resistance and good fluidity, which can meet the needs of gates working underwater for a long time. After the raw materials enter the workshop, they need to undergo composition testing to ensure that the contents of carbon, silicon, manganese and other elements meet the standards. Qualified cast iron blocks are sent to the medium - frequency induction furnace for melting, and the furnace temperature is controlled at 1400 - 1450℃. During this period, the composition of the molten iron is monitored in real - time by a spectrum analyzer. After the composition reaches the standard, it is left standing for 30 minutes to remove impurities, laying the foundation for subsequent casting.

Mold Design and Casting

According to the specification parameters of the gate (such as size, bearing capacity, etc.), engineers use CAD software to design a 3D model of the mold. The model needs to accurately calculate the stress points of the gate and the radian of the sealing surface. The mold is made of resin sand, which has good air permeability and collapsibility, and can reduce the porosity defects of castings. During casting, the high - temperature molten iron is slowly injected into the mold along the runner, and the injection speed is controlled at 5 - 8kg/s to avoid mold damage due to excessive impact. After the molten iron is cooled to below 200℃, the mold is removed to take out the casting, which is called a "blank" at this time, and there may be burrs and risers on the surface.

Mechanical Processing

The blank first enters the lathe for end face processing to ensure that the parallelism error of the upper and lower planes of the gate does not exceed 0.05mm/m. Then it is transferred to the milling machine to mill the sealing groove of the gate plate. The depth and width of the sealing groove must strictly follow the drawing requirements. Usually, the depth is 8 - 12mm, and the width error is controlled within ±0.1mm. For the guide rail surface of the gate, a grinder is used for precision grinding to make the surface roughness reach Ra1.6μm, so as to ensure the smoothness of the gate when it is lifted and lowered. During the processing, each process is equipped with a coordinate measuring machine for real - time detection to prevent unqualified workpieces from flowing into the next process.

Surface Treatment and Anti - corrosion

The processed gate needs to be surface treated. First, the surface oxide scale and oil stains are removed by sandblasting. The sandblasting pressure is set at 0.4 - 0.6MPa to form a uniform rough surface on the surface and enhance the coating adhesion. Then, the epoxy zinc - rich primer is sprayed, and the dry film thickness is controlled at 60 - 80μm. After the primer is cured, the polyurethane topcoat is applied, with a dry film thickness of 80 - 100μm. The two coatings together form an anti - corrosion system, which can make the service life of the gate in fresh water environment reach more than 15 years.

Assembly and Commissioning

The gate plate with qualified surface treatment is assembled with the door frame, hoist and other components. During assembly, the gap between the gate plate and the door frame needs to be adjusted to ensure that the gap around is uniform, and the maximum gap does not exceed 0.3mm, so as to ensure the sealing performance. After assembly, a hydrostatic test is carried out. The gate is immersed in water, a water pressure of 0.1MPa is applied, and it is kept for 30 minutes to observe whether there is leakage on the sealing surface. The leakage amount must be controlled within 0.1L/(m·h). At the same time, the operation status of the hoist is tested to ensure that the gate is lifted and lowered stably without jamming, and the operation noise does not exceed 75 decibels.

Finished Product Inspection and Delivery

Finally, quality inspectors conduct a comprehensive inspection on the dimensional accuracy, coating quality, sealing performance of the gate, and all indicators must meet the requirements of the "Code for Manufacture, Installation and Acceptance of Steel Gates in Water Conservancy and Hydropower Projects" (DL/T 5018). Qualified products are attached with quality certificates, user manuals and other documents, packaged and delivered. The packaging adopts a wooden frame to ensure that the gate is not damaged during transportation.