CN111250664A - A method for preventing cracks in castings of low-pound and large-diameter check valve bodies - Google Patents

Abstract

The invention relates to the technical field of valve body casting, in particular to a method for preventing cracks of a valve body casting of a low-pound-grade large-caliber check valve, which comprises the following steps of uniformly placing foam plates at a neck part, a seat part, a first parting surface rear part, a second parting surface rear part and a third parting surface rear part of a valve body core box flange; arranging anti-cracking ribs between the four open risers and the five open risers of the outer mold seat part, and placing chillers at positions corresponding to the anti-cracking ribs of the sand cores; two thermal pitch circles are arranged at the four positions of the open riser and the five positions of the open riser, and a supplement channel is arranged between the two thermal pitch circles; the pouring speed, temperature and molten steel melting property are strictly controlled. According to the invention, the chill is placed at the position corresponding to the sand core anti-cracking rib, the chill improves the temperature field of the casting to enable the casting to tend to be sequentially solidified, the supplement channels are arranged between the two thermal pitch circles, and when the casting liquid in the film is short, the supplement channels supplement the casting, so that the casting is prevented from generating cracks, and the casting cannot generate cracks during casting.

Description

A method for preventing cracks in castings of low-pound and large-diameter check valve bodies

technical field

The invention relates to the technical field of valve body casting, in particular to a method for preventing cracks in a valve body casting of a low-pound and large-diameter check valve.

Background technique

Valves are an important component of industrial pipelines. They are the basic structural parts of mechanical products with movable mechanisms. With the continuous advancement of technology, the quality requirements for valves are bound to become higher and higher, and the quality of valves is closely related to the quality of valve castings. Relatedly, there is no good valve without good castings; among them, the impact of cracks on castings is the most prominent, and the existing large-diameter check valve body castings are prone to cracks during pouring.

SUMMARY OF THE INVENTION

The purpose of the present invention is to propose a method for preventing cracks in the casting of a low-pound large-diameter check valve body in order to solve the disadvantage that cracks are easily generated during pouring in the prior art.

In order to achieve the above object, the present invention adopts the following technical solutions:

A method for preventing cracks in the valve body casting of a low-pound and large-diameter check valve is designed, including the following steps;

S1: Concealed riser 1, concealed riser 2, concealed riser 3, concealed riser 4, concealed riser 5 and concealed riser 6 on the valve body adopt symmetrical design;

S2: Design clear riser one, clear riser two and clear riser three at the core heads of the three flanges;

S3: Place foam boards evenly on the neck, seat, rear part of the parting surface, rear part 2 of the parting surface and three parts behind the parting surface of the valve body core box flange, and the sand core adopts two half molds A whole core is formed, and a semicircular gap is artificially drawn out on the parting surface of the sand core;

S4: Set up anti-crack ribs between the exposed riser 4 and the exposed riser 5 of the outer mold base, and place cold iron at the corresponding position of the sand core anti-crack ribs. Place chromite sand at the seat of the sand core;

S5: Two hot nodal circles are set at the fourth and fifth places of the open riser, and a supplementary channel is opened between the two hot nodal circles;

S6: Strictly control the pouring speed, temperature and chemical properties of molten steel.

Preferably, the size of the foam board in S3 is 100*30*20 mm, the distance between the foam and the surface of the sand core is no more than 30 mm, and the distance between the foams is 30-40 mm.

Preferably, the thickness of the chromite sand in the S4 is 15-20mm.

Preferably, after the pouring starts in S6, it must be injected into the mold cavity quickly and smoothly, and at the end of the pouring, the speed must be slowed down.

Preferably, the pouring temperature of molten steel in the S6 is controlled at 1550-1580°C.

The invention proposes a method for preventing cracks in the valve body castings of a low-pound and large-diameter check valve, and the beneficial effects are as follows:

By placing cold iron at the position corresponding to the anti-cracking ribs of the sand core, the cold iron improves the temperature field of the casting and makes the casting tend to solidify sequentially. The two thermal nodal circles are set to avoid excessive heat loss, and there are supplementary channels between the two thermal nodal circles. When the casting liquid in the film is lacking, the supplementary channels are used to avoid cracks in the casting, and no cracks will appear in the casting. .

Description of drawings

FIG. 1 is a schematic structural diagram of a method for preventing cracks in the valve body casting of a low-pound and large-diameter check valve proposed by the present invention.

In the picture: dark riser one 1, bright riser one 2, dark riser two 3, dark riser three 4, dark riser four 5, bright riser two 6, bright riser three 7, dark riser five 8 , dark riser six 9, open riser four 10, open riser five 11, runner 12, sprue 13, anti-cracking rib 14, hot pitch circle 15, supplementary 16, neck 17, seat 18 , The rear part of the parting surface is 19, the rear part of the parting surface is 20, and the rear part of the parting surface is 21.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments.

Example 1

Referring to Fig. 1, a method for preventing cracks in the valve body casting of a low-pound large-diameter check valve includes the following steps:

S1: Dark riser 1, dark riser 2, 3, dark riser 3, 4, 4, 5, 5, 8, and 6 9 on the valve body are symmetrically designed, with runners 12 is connected to the sprue 13, and the runner 12 enters the molten steel into the runner flange through the hidden riser 58 and the hidden riser 69, which reduces the risk of molten steel entering the middle flange and neck cracks, and reduces the casting cost of the casting. stress;

S2: Design the exposed riser 1 2, the exposed riser 2 6 and the exposed riser 3 7 at the core heads of the three flanges, and leave the exhaust holes connected to the outside at the three-end core heads to strengthen the exhaust. Fully dry the sand mold and sand core before placing the core to reduce the amount of gas generated;

S3: Put foam boards evenly on the neck 17, seat 18, rear part 19 of parting surface, rear part 2 20 of parting surface and rear part 3 21 of parting surface of the valve body core box flange. The size of the board is 100*30*20 mm, the distance between the foam and the surface of the sand core is 20 mm, and the interval between the foam is 30 mm. The foam board enhances the concession of the sand core. Take out a semi-circular gap, and leave a certain gap between the contact surfaces of the two half-cores when assembling, and artificially create the sand core concession space, which maximizes the sand core concession;

S4: Set up anti-crack rib 14 between the exposed riser 4 10 and the exposed riser 5 11 of the outer mold base, and place cold iron at the position corresponding to the crack-proof rib of the sand core. Chromite sand is placed at the seat of anti-cracking ribs and sand core. The thickness of chromite sand is 15mm. Chromite sand reduces the solidification time of this part. Cold iron improves the temperature field of the casting and makes the casting tend to solidify sequentially. , there is a certain solidification sequence, and there is enough replenishment ability to eliminate the great stress generated by the overall shrinkage;

S5: Two hot nodal circles 15 are arranged at the four 10 and five 11 positions of the open riser. The hot nodal circles 15 avoid excessive heat loss. A supplementary channel 16 is opened between the two hot nodal circles 15. When the casting liquid in the film is lacking, it is supplemented by the supplementary channel 16 to avoid cracks in the casting;

S6: Strictly control the pouring speed, temperature and the chemical properties of the molten steel, reasonably control the pouring speed and pouring temperature, the tapping temperature is 1620 ° C, sedation for 3 minutes, pouring at 1550 ° C, it must be injected into the mold cavity quickly and steadily, and at the end of the pouring stage , The speed must be slowed down to avoid false filling, control the sand falling time, and unpack the sand after cooling for 8 hours.

Example 2

Referring to Fig. 1, a method for preventing cracks in the valve body casting of a low-pound large-diameter check valve includes the following steps:

S1: Dark riser 1, dark riser 2, 3, dark riser 3, 4, 4, 5, 5, 8, and 6 9 on the valve body are symmetrically designed, with runners 12 is connected to the sprue 13, and the runner 12 enters the molten steel into the runner flange through the hidden riser 58 and the hidden riser 69, which reduces the risk of molten steel entering the middle flange and neck cracks, and reduces the casting cost of the casting. stress;

S2: Design the exposed riser 1 2, the exposed riser 2 6 and the exposed riser 3 7 at the core heads of the three flanges, and leave the exhaust holes connected to the outside at the three-end core heads to strengthen the exhaust. Fully dry the sand mold and sand core before placing the core to reduce the amount of gas generated;

S3: Put foam boards evenly on the neck 17, seat 18, rear part 19 of parting surface, rear part 2 20 of parting surface and rear part 3 21 of parting surface of the valve body core box flange. The size of the board is 100*30*20 mm, the distance between the foam and the surface of the sand core is 25mm, and the interval between the foams is 35mm. Take out a semi-circular gap, and leave a certain gap between the contact surfaces of the two half-cores when assembling, and artificially create the sand core concession space, which maximizes the sand core concession;

S4: Set up anti-crack rib 14 between the exposed riser 4 10 and the exposed riser 5 11 of the outer mold base, and place cold iron at the position corresponding to the crack-proof rib of the sand core. Chromite sand is placed at the seat of anti-cracking ribs and sand core. The thickness of chromite sand is 17mm. Chromite sand reduces the solidification time of this part. Cold iron improves the temperature field of the casting and makes the casting tend to solidify sequentially. , there is a certain solidification sequence, and there is enough replenishment ability to eliminate the great stress generated by the overall shrinkage;

S5: Two hot nodal circles 15 are arranged at the four 10 and five 11 positions of the open riser. The hot nodal circles 15 avoid excessive heat loss. A supplementary channel 16 is opened between the two hot nodal circles 15. When the casting liquid in the film is lacking, it is supplemented by the supplementary channel 16 to avoid cracks in the casting;

S6: Strictly control the pouring speed, temperature and the chemical properties of the molten steel, reasonably control the pouring speed and pouring temperature, the tapping temperature is about 1620 °C, sedated for 4 minutes, poured at 1565 °C, it must be quickly and steadily injected into the mold cavity, pouring In the last stage, the speed must be slowed down to avoid false filling, control the sand falling time, and unpack the sand after 8 hours of cooling.

Example 3

Referring to Fig. 1, a method for preventing cracks in the valve body casting of a low-pound large-diameter check valve includes the following steps:

S1: Concealed riser 1, concealed riser 2, 3, concealed riser 3, concealed riser 4, concealed riser 4, 5, concealed riser 5, and concealed riser 6, 9 on the valve body are of symmetrical design. The top of 12 is connected to the sprue 13, and the runner 12 enters the molten steel into the runner flange through the hidden riser 58 and the hidden riser 69, which reduces the risk of molten steel entering the middle flange and neck cracks, and reduces the casting cost of the casting. stress;

S2: Design the exposed riser 1 2, the exposed riser 2 6 and the exposed riser 3 7 at the core heads of the three flanges, and leave the exhaust holes connected to the outside at the three-end core heads to strengthen the exhaust. Fully dry the sand mold and sand core before placing the core to reduce the amount of gas generated;

S3: Put foam boards evenly on the neck 17, seat 18, rear part 19 of parting surface, rear part 2 20 of parting surface and rear part 3 21 of parting surface of the valve body core box flange. The size of the board is 100*30*20 mm, the distance between the foam and the surface of the sand core is 30mm, and the foam interval is 40mm. The foam board enhances the retreat of the sand core. Take out a semi-circular gap, and leave a certain gap between the contact surfaces of the two half-cores when assembling, and artificially create the sand core concession space, which maximizes the sand core concession;

S4: Set up anti-crack rib 14 between the exposed riser 4 10 and the exposed riser 5 11 of the outer mold base, and place cold iron at the position corresponding to the crack-proof rib of the sand core. Chromite sand is placed at the seat of the anti-cracking ribs and sand core. The thickness of chromite sand is 20mm. The chromite sand reduces the solidification time of this part. The cold iron improves the temperature field of the casting and makes the casting tend to solidify sequentially , there is a certain solidification sequence, and there is enough replenishment ability to eliminate the great stress generated by the overall shrinkage;

S5: Two hot nodal circles 15 are arranged at the four 10 and five 11 positions of the open riser. The hot nodal circles 15 avoid excessive heat loss. A supplementary channel 16 is opened between the two hot nodal circles 15. When the casting liquid in the film is lacking, it is supplemented by the supplementary channel 16 to avoid cracks in the casting;

S6: Strictly control the pouring speed, temperature and the chemical properties of the molten steel, reasonably control the pouring speed and pouring temperature, the tapping temperature is about 1620 ° C, sedation for 5 minutes, pouring at 1580 ° C, must be quickly and smoothly injected into the mold cavity, pouring In the last stage, the speed must be slowed down to avoid false filling, control the sand falling time, and unpack the sand after 8 hours of cooling.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. The equivalent replacement or change of the inventive concept thereof shall be included within the protection scope of the present invention.

Claims (5)

1. The method for preventing the cracks of the valve body casting of the low-pound-grade large-caliber check valve is characterized by comprising the following steps of:

s1: a first blind riser (1), a second blind riser (3), a third blind riser (4), a fourth blind riser (5), a fifth blind riser (8) and a sixth blind riser (9) on the valve body are designed in a symmetrical mode;

s2: open risers I (2), open risers II (6) and open risers III (7) are designed at the core heads of the three flanges;

s3: uniformly placing foam plates at a neck (17), a seat (18), a first parting surface rear part (19), a second parting surface rear part (20) and a third parting surface rear part (21) of a valve body core box flange, wherein a sand core adopts two half dies to form a whole core, and a semicircular gap is artificially drawn at the parting surface of the sand core;

s4: an anti-cracking rib (14) is arranged between the four (10) of the open riser and the five (11) of the open riser of the seat of the outer die, a chill is placed at the position corresponding to the anti-cracking rib of the sand core, and chromite sand is placed at the neck of the flange of the outer die and the sand core, the anti-cracking rib and the seat of the sand core;

s5: two thermal pitch circles (15) are arranged at the four (10) and five (11) positions of the open riser, and a supplement channel (16) is arranged between the two thermal pitch circles (15);

s6: the pouring speed, temperature and molten steel melting property are strictly controlled.

2. The method of claim 1, wherein the foam sheet size in S3 is 100 x 30 x 20mm, the foam is no more than 30mm from the sand core surface, and the foam spacing is 30-40 mm.

3. The method for preventing the valve body casting cracks of the low-pound-grade large-caliber check valve according to claim 1, wherein the thickness of the ferrochrome sand in the S4 is 15-20 mm.

4. The method of claim 1, wherein the casting is performed in a manner such that the casting is performed smoothly and quickly after the start of the casting in S6, and the casting is slowed down at the end of the casting.

5. The method for preventing the valve body casting cracks of the low-pound-grade large-caliber check valve as claimed in claim 1, wherein the casting temperature of the molten steel in the S6 is controlled at 1550-.

Images