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Structure and casting process of cast steel lower valve body:
Cast steel lower valve body is an important control part of hot air and gas in metallurgical blast furnace valve system. xinyuanzhu group uses the material ZG230-450, with high internal and external quality requirements.
1 lower valve body casting structureLower valve body casting structure, casting single weight of 2.5 t, the maximum external dimensions of 2 680 mm × 2 930 mm × 735 mm. casting body absolutely does not allow cracks, shrinkage, porosity, porosity, trachoma, slag and cold compartment defects, flange and stop inside and outside the work surface machining to be magnetic particle flaw inspection, the entire casting does not allow any casting defects affecting the quality of the existence. Casting dimensional accuracy required to achieve CT6 ~ CT8, casting internal surface roughness requirements to achieve Ra ≤ 12.5 μm .
2 Casting process
2.1 Casting process analysis of the casting
The main wall thickness of the valve body in the range of 30 ~ 40 mm, because it belongs to the box structure, how to eliminate shrinkage and cracking is the key to the casting process is difficult. If the casting process does not take the appropriate measures, it will bring great trouble to the later process. Cracks cause casting scrap, shrinkage or shrinkage must be repaired by gas dissection, welding, grinding, which will cause a waste of manpower and material resources.
2.2 Determine the pouring position and parting surface
From the consideration of the order of solidification and shrinkage, according to the pouring position shown in Figure 2, the use of three-box modeling, the entire casting in the middle box, the riser in the upper box, the core head in the lower box. In this way, it is convenient for the core and box operation, but also convenient for the casting size and wall thickness detection. The main structural parts of the casting are controlled in the middle box, which is conducive to ensuring the casting size.
2.3 Casting system
Adopt layered pouring, straight sprue is introduced along the center of 2# sand core and 1# sand core, and there are two layers of inner sprue (each layer has four channels evenly distributed). The first layer is the bottom pouring channel which is taken from the bottom of the casting, and the other layer is introduced along the circumferential tangent line in the position of the stop and the outer skin. Such a continuous pouring system fills the mold smoothly, fills the cavity for a reasonable time, regulates the temperature distribution in the mold, avoids the phenomenon of local overheating at the gate, reduces the casting stress, and prevents defects such as deformation and cracks in the casting; the straight sprue and the inner sprue take Φ70 mm and Φ40 mm refractory porcelain tubes respectively, which effectively avoid the occurrence of sand flushing and can obtain complete and clear castings.
2.4 Design of riser
In order to ensure that the heart of the casting without shrinkage or shrinkage, the riser should have a large enough shrinkage capacity to ensure a smooth shrinkage channel. To this end, the choice of insulation riser, slowing down the condensation of the steel, improve the effect of shrinkage.
In the casting flange top surface placed four insulation open mouth, the size of 160 mm × 240 mm × 300 mm.
The casting thermal section modulus (hollow cylinder): M = a/2 (b > 5a), (where the height of the section b = 250 mm; the thickness of the section a = 40 mm = 4 cm).
Then: M pieces = 4 / 2 = 2 (cm).
Modulus of insulated riser (160 × 240 × 300): M insulated riser = V/A = [(160 × 240 × 300) / [2 × (160 × 240) + 2 × (160 × 300) + 2 × (240 × 300)] = 3.64 (cm).
According to M sand bubble = 1.4 M keep bubble (M keep bubble - insulation bubble modulus; M sand bubble - ordinary sand type bubble modulus)
Then: M sand bubble = 1.4 × 3.64 = 5.1 (cm).
Then M sand bubble / M pieces = 5.1/2 = 2.55 ≥ 1.2, you can achieve the final solidification of the casting to fill the shrinkage. After verification, the effective shrinkage distance and the amount of steel required for shrinkage of the inner ring set 2 heat preservation riser are sufficient, the size and number of riser is suitable.
2.5 Design of sand core
1# sand core (the lower part is left with positioning core head, the upper part is left with 2# sand core positioning core head seat) is left with two hanging rings of moderate height not exceeding the top surface of the sand core, and welded together with the core iron, which is properly dug out when the core is made to reveal the recess for lifting. The core iron is made of steel pipe (Φ10 mm hole is made on the outer wall for exhausting). In the center of the core, put Φ70 mm porcelain pipe as a straight sprue and 4 Φ40 mm porcelain pipes in the lower part of the inner sprue (mark the position in the core box). Put chromite sand, about 80 mm thick, in the lower part of the stopper at the bend neck A (in order to play a cooling effect).
In the center of 2# sand core, Φ70 mm refractory porcelain pipe is placed as a straight sprue (positioned correctly) and connected with the inner sprue Φ40 mm refractory porcelain pipe; a hanging ring is left at the top.
3# sand core (using chrome iron ore sand) does not leave the core head at both ends of the round core, and adopts the middle square core head for positioning (core iron winding exhaust rope leads from the core head).
4# sand core is pre-buried core, core head is left at the top and both sides of sand core and core iron is protruded along the core head, so that the sand core is fixed in the sand.
Xinyuanzhu Group specializes in the production of Ductile iron castings, Pig iron gray iron casting, Steel casting, Brass Casting, Malleable Iron Casting, and undertakes batch casting processing of castings. Welcome guests to cooperate with pictures or samples.
