Casting technique for low-temperature high-tenacity nodular cast iron butterfly valve body

Abstract

The invention relates to a casting technique for a low-temperature high-tenacity nodular cast iron butterfly valve body. The casting technique for the low-temperature high-tenacity nodular cast iron butterfly valve body comprises the first procedure of smelting, the second procedure of nodularization and inoculation, the third procedure of pouring and pulling out of a box, and the fourth procedure of heat treatment. The procedure of smelling comprises the first step of material preparation and the second step of smelling. According to the casting technique, strict material proportioning is conducted, material feeding for fusion is conducted in batches by two times, silicon carbide is added in the time interval between the two times of material feeding, and a traditional melting process is changed; a nodulizing agent is protected by combining a dam type nodulizing bag and a compacted nucleating agent, so that the nodulizing time and the nodulizing way are controlled; in addition, nodulization is conducted in batches, then mixing is conducted, and thus an ideal nodulizing effect is achieved; the chemical elements of a final product discharged out of a furnace are ideal, the metallography detection index is excellent, the mechanical property is excellent, and the requirement for operation of a valve in a low-temperature environment is completely met.

Description

technical field

[0001] The invention belongs to the technical field of casting technology, and in particular relates to a casting technology of a low-temperature high-toughness ductile iron butterfly valve body. Background technique

[0002] The material of butterfly valve body is QT400-18L (GB1348-2009); foreign standard: EN-GJS-400-18LT (DIN-EN1563-2012); material requirements: 1. Tensile strength ≥ 400MPa; 2. Elongation ≥ 18 %; 3. The average impact energy of 3 samples at -20°C ≥ 14J and the single experimental value is not less than 12J (the last type of body sampling); 4. The inside of the valve body is required to have no casting defects such as shrinkage and porosity, "X" light The inspection shall not exceed level 3.

[0003] It is especially used in the field of fluid (water, gas, oil) pipeline transportation system and chemical and pharmaceutical fields to control the flow rate and cut-off butterfly valve. Because the working environment is more used in low tempe...