Casting Process for Steel Casting of Steam Turbine Intermediate Pressure Inner Cylinder

A steam turbine is an external combustion rotary machine that can convert steam heat energy into mechanical energy. After entering the turbine, steam from the boiler passes through a series of annular nozzles and moving blades to convert the heat energy of the steam into mechanical energy for the rotation of the turbine rotor. Its cylinder is in a high-temperature and high-pressure working environment, with harsh conditions, which require extremely high performance of steel castings.

The surface of the cast steel body of the intermediate pressure inner cylinder of the steam turbine has many laps, and the large flange on the back of the cast steel makes the bottom hot spot larger, making it difficult to feed; Complex parts such as the inner steam inlet chamber are prone to casting defects such as slag inclusion, cracks, and eccentric core, so it is difficult to design the casting process for this steel casting. In view of the above casting difficulties, the author discussed and analyzed the gating system, molding scheme, riser design, and solidification simulation based on the structure of steel castings.

0.09~0.14≤ 0.300.4~0.7≤ 0.020≤ 0.02010.0~11.01.00~1.300.04~0.080.03~0.070.2~0.3≤ 0.010Allowance

The product is a steam turbine intermediate pressure inner cylinder. The upper half of the cylinder is made of steel, as shown in the figure. The weight of the single half is about 11.2 t, and the maximum overall dimension is 2221 mm × 2 290 mm × 1090 mm, maximum wall thickness 360 mm, minimum wall thickness 120 mm. The material is ZG12Cr10Mo1NiWVNbN. The specific chemical composition is shown in Table 1, and the mechanical properties are shown in Table 2. NDT requires 100% UT2 and MT2 level testing of the steel casting body. The steel casting is welded, and the welds are accepted according to UT inspection level I.

Tensile strength/MPaYield strength/MPaElongation (%)Reduction of area (%)Hardness (HBW)
≥ 690≥ 490≥ 11.0≥ 35220~260