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

A technology of ductile cast iron and casting process, which is applied in the field of casting process of low-temperature and high-toughness ductile iron butterfly valve body, which can solve the problems of easy shrinkage, unqualified material, unstable process, etc., and achieve outstanding mechanical performance and metallographic detection. Excellent index and ideal chemical composition

Active Publication Date: 2016-03-09
HEBEI YULONG CASTING
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0004] However, at present, when many production plants produce this type of casting, the process is unstable, and it is prone to unqualified materials such as unqualified tensile strength and low-temperature impact energy, and internal defects such as shrinkage and porosity, which cannot meet the requirements of the standard, resulting in batches of waste products.
Failure to meet customer requirements, resulting in claims and other losses

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0065] A casting process for a low-temperature high-toughness ductile iron butterfly valve body, comprising the following steps:

[0066] 1) Melting process

[0067] 1. Prepare materials

[0068] Weigh each material according to the following mass percentage ratio: 400kg of pig iron, 775kg of carbon steel, 785kg of returned charge, 33kg of recarburizer, 5kg of silicon carbide, and 2kg of molten iron pretreatment agent;

[0069] Among them, raw material selection:

[0070] Pig iron: high-quality ductile iron pig iron Q10:

[0071] Chemical composition: one class one group:

[0072]C>3.4%, Si0.5-1%, Mn<0.1%, S≤0.02%, P≤0.03%, Ti≤0.03%,

[0073] The sum of impurity elements Cr, V, Pb, Bi, As, B, Al, Mo, Sn≤0.085%

[0074] Surface quality: the surface is clean, no slag, no sand, no rust, uniform lumpiness;

[0075] Carbon steel: no rust, no impurities, minimum thickness not less than 5mm;

[0076] Return material: Use 400-18 return material, which needs to be shot blasted; ...

Embodiment 2

[0112] The difference from Example 1 is:

[0113] In step 1) 1, each material is weighed according to the weight ratio when preparing materials: 380kg of pig iron, 787kg of carbon steel, 797kg of furnace charge, 20kg of recarburizer, 4kg of silicon carbide, and 2kg of molten iron pretreatment agent;

[0114] In step 2) 3, when the temperature of molten iron is 1520°C, the molten iron in step 1) 2, 4) is poured into 60% of the total amount of molten iron in the furnace from the electric furnace to the spheroidizing ladle, and poured into the bottom of the spheroidizing ladle for another On one side, pour the remaining molten iron in the electric furnace after the spheroidization reaction time is reached after pouring;

[0115] In four) 1. After the blank is loaded into the heat treatment furnace, the temperature is controlled to rise by 85°C per hour, and the temperature is raised to 755°C.

Embodiment 3

[0116] Embodiment 3 differs from Embodiment 1 in that:

[0117] A casting process for a low-temperature high-toughness ductile iron butterfly valve body, comprising the following steps:

[0118] 1) Melting process

[0119] 1. Prepare materials

[0120] Weigh each material according to the following mass percentage ratio: 380kg of pig iron, 787kg of carbon steel, 797kg of returned charge, 20kg of recarburizer, 4kg of silicon carbide, and 2kg of molten iron pretreatment agent;

[0121] 2. Melting

[0122] 1) Put pig iron, recarburizer and carbon steel into an intermediate frequency induction furnace in turn for melting, the amount of pig iron added is 1 / 3 of the total amount of pig iron described in step 1) 1, and the addition of the recarburizer The amount is the full amount of the carburizing agent described in step 1) 1, and the addition of the carbon steel is 1 / 2 of the full amount of the carbon steel described in step 1) 1;

[0123] 2) 2 minutes after melting, put the r...

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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...

Claims

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Application Information

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IPC IPC(8): C21C1/10B22D1/00
CPCB22D1/00C21C1/10Y02P10/20
Inventor 张连会
Owner HEBEI YULONG CASTING
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