Medium-pressure heavy-section outer-cylinder iron casting gating system of steam turbine

Abstract

The invention discloses a gating system of a large-section iron casting for an medium pressure external cylinder in a steam turbine; the gating system comprises a weighing ladle, a sprue, a runner and an ingate, the runner consists of an upper runner and a lower runner, a refractory ceramic filter is arranged between the upper runner and the lower runner, the minimum sectional area ratio of the sprue, the runner, a transition sprue, a transition runner and the ingate is 1.2:1.34:1:1.07:1.24; the sprue, the upper runner and the lower runner are arranged at the middle part of the casting, and the ingate of an ingate is arranged at the inner wall of an axle hole of the casting; and the gating system of the structure mainly plays a role in buffering, decompressing and steady entry of melted iron, the molding sand in the scour cast is avoided, the casting is heated evenly, with the advantages of being not easy to be mingled with impurities, carry sand, produce air gaps and cracks.

Description

Technical field: [0001] The invention relates to a pouring system for large-scale iron castings, in particular to a pouring system for large-section iron castings of medium-pressure outer cylinders of steam turbines. Background technique: [0002] With the advancement of science and technology and the needs of industrial development, more and more large and super-large machines are being researched and manufactured in China. Recently, the applicant unit has accepted the casting task of large-section iron castings for medium-pressure outer cylinders of large-scale steam turbines. The castings as a whole The single weight is more than 80 tons, the shape is 6075mm long, 4320mm wide, and 4380mm high. It also puts forward the inherent quality requirements that there should be no shrinkage cavity, shrinkage porosity, inclusions, air gaps, cracks and other defects in the casting that affect the use. To complete such large and heavy castings, the design of the gating system is parti...

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Problems solved by technology

Although the patent application improves the structure of the traditional gating system, it controls the filling method of the molten metal, so that the molten metal is in a full state in the gating system, no gas and oxide film are involved in the molten metal, and the air gap in the casting is reduced. , cracks, porosity and inclusions, but the sprue cup of this gating system is set as an eccentric structure, which is generally only suitable for small tonnage castings, and its filling speed is 0.5M / s-1.0M / s, and it cannot satisfy large The filling speed requirements for large tonnage castings. It can be seen that the structure and filling speed of the gating system are the best for large steam turbine medium pressure outer cylinder large section iron castings with large body, weight and irregular casting shape. It is very inapplicable, therefore, it is necessary to open another channel to design a gating system that is more suitable for the large-section cast iron parts of the medium-pressure outer cylinder of a large steam turbine

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