CN108044073B - A kind of cold iron with exhaust layer, its preparation method, and the preparation method of casting - Google Patents

Abstract

The invention relates to a cold iron with an exhaust layer, a preparation method thereof, and a preparation method of a casting, belonging to the technical field of casting. The chilled iron with venting layer of the present invention includes chilled iron, and the surface of the chilled iron used to be in contact with the casting is provided with a venting layer, and the venting layer includes an inner layer, a middle layer, and an outer layer; The inner layer is a varnish layer, the middle layer is a sand layer, and the outer layer is a graphite paint layer. In the chilled iron with exhaust layer of the present invention, an exhaust layer is attached to the surface of the chilled iron in contact with the casting, which prevents the chilled iron from clinging to the casting, prevents bubbles from being trapped in the chilled layer due to too fast solidification of the molten metal, and improves Exhaust the cooling layer of castings, reduce the occurrence of pore defects in castings, improve the internal and surface quality of castings, reduce segregation, and improve the strength and mechanical properties of castings.

Description

A kind of cold iron with exhaust layer, its preparation method, and the preparation method of casting

technical field

The invention relates to a cold iron with an exhaust layer, a preparation method thereof, and a preparation method of a casting, belonging to the technical field of casting.

Background technique

Due to the characteristics of low density, low cost and good performance of aluminum alloy, aluminum alloy castings have been widely used in the field of aerospace. Along with the special-shaped structure of new products and the characteristics of integral molding, it is increasingly required that the parts are integrally cast, and the inner cavity is not processed, and the wall thickness is thinner.

Extensive technical and manufacturing research by the foundry industry on large thin-walled aluminum alloy structures has shown that porosity defects are the most common problem in production casting. There are many causes and complex types of porosity defects, which seriously affect product quality. Therefore, it is necessary to study the process that can improve the venting of castings.

After research, it can be found that most of the causes of pore defects are: when the molten metal is poured into the model, the molten metal on the chilled surface begins to solidify due to the chilling effect. Due to the fast solidification time, the gas in the molten metal there Lack of sufficient escape time causes many bubbles to remain in the chilled layer, thereby forming pore defects.

The Chinese invention patent with application publication number CN102430737A discloses a chill iron with coated sand, which includes a three-layer structure, the base layer is chill iron, the middle layer is a furan resin layer, and the upper layer is a coated sand layer. The surface quality and internal quality of the casting obtained by using the cold iron disclosed in this patent cannot be guaranteed, and the mechanical properties are not good.

Contents of the invention

The object of the present invention is to provide a cold iron with a venting layer, and the casting obtained by using the cold iron has good quality and excellent mechanical properties.

The second object of the present invention is to provide a method for preparing the above-mentioned cold iron with an exhaust layer.

The third object of the present invention is to provide a casting method.

A chilled iron with a venting layer, comprising chilled iron, a venting layer is arranged on the surface of the chilling iron used to be in contact with a casting, and the venting layer includes an inner layer, a middle layer and an outer layer; the inner layer The first layer is a varnish layer, the middle layer is a sand layer, and the outer layer is a graphite paint layer.

The above-mentioned cold iron with the exhaust layer can be used for casting thin-walled aluminum alloy castings.

In the cold iron with exhaust layer of the present invention, an exhaust layer is arranged on the surface of the cold iron that is used to contact the casting, so as to prevent the cold iron from being close to the casting and prevent the molten metal in contact with the cold iron from solidifying too quickly so that the internal gas is not exhausted. Enough time to escape and stay in the chilling layer, which affects the quality of the casting; the existence of the exhaust layer can also provide a channel for the escape of internal gas, improve the exhaust of the chilling layer of the casting, reduce the occurrence of pore defects in the casting, and improve the quality of the casting inside. And surface quality, reduce segregation, improve the strength and mechanical properties of castings.

The sand layer is a fine sand layer.

The thickness ratio of the varnish layer, sand layer and graphite paint layer is 1:4:2.

The thickness of the varnish layer is 0.1-0.3mm. The firm bond of the sand layer to the cold iron is achieved through the varnish layer.

The thickness of the graphite coating layer is 0.2-0.6 mm. Graphite coating has good thermal conductivity, which can prevent the molten metal from wrapping the cold iron while reducing the temperature, reduce the cleaning workload of the cold iron on the casting, and further ensure the quality of the obtained casting. In addition, during the casting process, the gap between the chilled iron and the sand core can be filled with graphite paint, and the gap between the chilled iron and the sand core can be filled and sealed to prevent the molten metal from entering the gap and wrapping the chilled iron after pouring, reducing the friction of the chilled iron. The cleaning workload is beneficial to the reuse of cold iron.

The thickness of the sand layer is 0.4-1.2mm. The sand layer can provide a channel for the escape of gas inside the molten metal.

The thickness of the above-mentioned sand layer is preferably 0.8 mm.

The particle size of the sand in the sand layer is 70-100 mesh.

The preparation method of the graphite coating comprises the following steps: uniformly mixing rosin, phenolic resin, graphite, and ethanol; the mass ratio of the rosin, phenolic resin, graphite, and ethanol is 1:3:2:4.

The preparation method of the chilled iron with the above-mentioned band exhaust layer may further comprise the steps:

Brush varnish on the surface of the cold iron to form a varnish layer, then lay sand on the surface of the varnish layer to form a sand layer, then brush graphite paint on the surface of the sand layer to form a graphite paint layer, and dry it.

The above-mentioned cold irons are polished and rust-removed before the varnish is applied to ensure the cleanness and brightness of the cold iron surfaces.

After the above-mentioned sand layer is formed, blow off the floating sand after the varnish is dry.

The drying includes keeping the temperature at 120-160° C. for 2-4 hours. The above-mentioned heat preservation at 120-160° C. for 2-4 hours is carried out in a trolley furnace. The heat preservation at 120-160° C. for 2-4 hours can remove the gas and moisture adsorbed in the graphite coating layer and the sand layer, and further reduce the pores and shrinkage defects inside the casting.

Place the above-mentioned at 120-160°C for 1-2 hours before keeping warm, and then keep warm at 120-160°C for 2-4 hours after the graphite coating is dry.

The above-mentioned cold iron after being kept at 120-160° C. for 2-4 hours is assembled into a mold for use after the temperature drops below 50° C. If the temperature is too high, the mold will explode during the pouring process, choke on fire, and the casting will have pores and other problems.

The invention discloses a method for preparing castings, comprising the following steps: putting the above-mentioned chilled iron with a vent layer into a sand mold or on the surface of a pattern, closing the box, pouring, and demoulding.

When using the above-mentioned casting method to cast thin-walled aluminum alloy castings, the pouring temperature of the aluminum alloy melt is 690°C.

In the chilled iron with venting layer of the present invention, the venting layer is provided on the surface of the chilled iron that is in contact with the casting, so as to prevent the chilled iron from clinging to the casting and prevent bubbles from being trapped in the chilling layer due to the rapid solidification of molten metal , improve the exhaust of the chilled layer of the casting, reduce the occurrence of pore defects in the casting, improve the internal and surface quality of the casting, reduce segregation, and improve the strength and mechanical properties of the casting.

The preparation method of the cold iron with the exhaust layer of the present invention is simple, feasible, low in cost and suitable for mass production.

The preparation method of the casting of the present invention utilizes the cooling iron with the exhaust layer of the present invention, and the obtained casting has a high pass rate, good surface quality and internal quality, and excellent mechanical properties, and at the same time, the cleaning time of the cooling iron on the casting after casting can also be shortened. Zoom out by a factor of 1.

Detailed ways

Example 1

The cold iron with venting layer of the present embodiment comprises cold iron, and the surface that cold iron is used for contacting with casting is provided with venting layer, and venting layer is made of inner layer, middle layer, outer layer; Wherein inner layer is The varnish layer has a thickness of 0.2mm; the middle layer is a fine sand layer with a thickness of 0.8mm; the outer layer is a graphite coating layer with a thickness of 0.4mm; wherein the preparation method of the graphite coating comprises: adding 1 part of rosin and 3 parts of phenolic resin 4 parts of ethanol and mix evenly, then add 2 parts of graphite and mix evenly to obtain.

The preparation method of the cold iron with vent layer of the present embodiment may further comprise the steps:

1) After the cold iron is polished and derusted, use a fine brush to evenly paint the varnish on the surface in contact with the cold iron and the casting to form a varnish layer with a thickness of 0.2mm;

2) Immediately afterwards, evenly sprinkle 100-mesh fine sand on the surface of the varnish layer, and blow off the floating sand after the varnish is dry to form a fine sand layer with a thickness of 0.8 mm;

3) Use a fine brush to evenly coat the graphite coating on the surface of the fine sand layer to form a graphite coating layer with a thickness of 0.4 mm, and place it for 1 hour. After the graphite coating is dry, place it in a trolley furnace and bake at 120°C for 3 hours. Take it out of the oven and wait for the temperature to drop below 50°C.

The preparation method of the casting of the present embodiment comprises the following steps:

Place the chilled iron with venting layer obtained above into the sand mold, close the box, pour and demould.

Example 2

The cold iron with venting layer of the present embodiment comprises cold iron, and the surface that cold iron is used for contacting with casting is provided with venting layer, and venting layer is made of inner layer, middle layer, outer layer; Wherein inner layer is The varnish layer has a thickness of 0.2mm; the middle layer is a fine sand layer with a thickness of 0.8mm; the outer layer is a graphite coating layer with a thickness of 0.4mm; wherein the preparation method of the graphite coating comprises: adding 1 part of rosin and 3 parts of phenolic resin 4 parts of ethanol and mix evenly, then add 2 parts of graphite and mix evenly to obtain.

The preparation method of the cold iron with vent layer of the present embodiment may further comprise the steps:

1) After the cold iron is polished and derusted, apply the varnish evenly on the contact surface between the cold iron and the casting with a fine brush to form a varnish layer with a thickness of 0.2mm;

2) Immediately afterwards, evenly sprinkle 80-mesh fine sand on the surface of the varnish layer, and blow off the floating sand after the varnish is dry to form a fine sand layer with a thickness of 0.8mm;

3) Use a fine brush to evenly coat the graphite coating on the surface of the fine sand layer to form a graphite coating layer with a thickness of 0.4mm, and place it for 2 hours. After the graphite coating is dry, place it in a trolley furnace and bake at 140°C for 2 hours Take it out of the oven and wait for the temperature to drop below 50°C.

The preparation method of the casting of the present embodiment comprises the following steps:

Place the chilled iron with venting layer obtained above into the sand mold, close the box, pour and demould.

Example 3

The cold iron with venting layer of the present embodiment comprises cold iron, and the surface that cold iron is used for contacting with casting is provided with venting layer, and venting layer is made of inner layer, middle layer, outer layer; Wherein inner layer is The varnish layer has a thickness of 0.2mm; the middle layer is a fine sand layer with a thickness of 0.8mm; the outer layer is a graphite coating layer with a thickness of 0.4mm; wherein the preparation method of the graphite coating comprises: adding 1 part of rosin and 3 parts of phenolic resin 4 parts of ethanol and mix evenly, then add 2 parts of graphite and mix evenly to obtain.

The preparation method of the cold iron with vent layer of the present embodiment may further comprise the steps:

1) After the cold iron is polished and derusted, apply the varnish evenly on the contact surface between the cold iron and the casting with a fine brush to form a varnish layer with a thickness of 0.2mm;

2) Immediately afterwards, evenly sprinkle 70-mesh fine sand on the surface of the varnish layer, and blow off the floating sand after the varnish dries to form a fine sand layer with a thickness of 0.8mm;

3) Use a fine brush to evenly coat the graphite coating on the surface of the fine sand layer to form a graphite coating layer with a thickness of 0.4 mm, and place it for 1.5 hours. After the graphite coating is dry, place it in a trolley furnace and bake at 160 ° C Take it out of the oven after 2 hours, and wait for the temperature to drop below 50°C.

The preparation method of the casting of the present embodiment comprises the following steps:

Place the chilled iron with venting layer obtained above into the sand mold, close the box, pour and demould.

Example 4

The cold iron with venting layer of the present embodiment comprises cold iron, and the surface that cold iron is used for contacting with casting is provided with venting layer, and venting layer is made of inner layer, middle layer, outer layer; Wherein inner layer is The varnish layer has a thickness of 0.1mm; the middle layer is a fine sand layer with a thickness of 0.4mm; the outer layer is a graphite coating layer with a thickness of 0.2mm; wherein the preparation method of the graphite coating comprises: adding 1 part of rosin and 3 parts of phenolic resin 4 parts of ethanol and mix evenly, then add 2 parts of graphite and mix evenly to obtain.

The preparation method of the cold iron with vent layer of the present embodiment may further comprise the steps:

1) After the cold iron is polished and derusted, use a fine brush to evenly paint the varnish on the contact surface between the cold iron and the casting to form a varnish layer with a thickness of 0.1mm;

2) Immediately afterwards, evenly sprinkle 100-mesh fine sand on the surface of the varnish layer, and blow off the floating sand after the varnish is dry to form a fine sand layer with a thickness of 0.4mm;

3) Use a fine brush to evenly coat the graphite coating on the surface of the fine sand layer to form a graphite coating layer with a thickness of 0.2mm, and place it for 2 hours. After the graphite coating is dry, place it in a trolley furnace and bake it at 130°C for 2 hours Take it out of the oven and wait for the temperature to drop below 50°C.

The preparation method of the casting of the present embodiment comprises the following steps:

Place the chilled iron with venting layer obtained above on the surface of the pattern, close the box, pour and demould.

Example 5

The cold iron with venting layer of the present embodiment comprises cold iron, and the surface that cold iron is used for contacting with casting is provided with venting layer, and venting layer is made of inner layer, middle layer, outer layer; Wherein inner layer is The varnish layer has a thickness of 0.3mm; the middle layer is a fine sand layer with a thickness of 1.2mm; the outer layer is a graphite coating layer with a thickness of 0.6mm; wherein the preparation method of the graphite coating comprises: adding 1 part of rosin and 3 parts of phenolic resin 4 parts of ethanol and mix evenly, then add 2 parts of graphite and mix evenly to obtain.

The preparation method of the cold iron with vent layer of the present embodiment may further comprise the steps:

1) After grinding and derusting the cold iron, use a fine brush to evenly paint the varnish on the contact surface between the cold iron and the casting to form a varnish layer with a thickness of 0.3mm;

2) Immediately afterwards, evenly sprinkle 70-mesh fine sand on the surface of the varnish layer, and blow off the floating sand after the varnish is dry to form a fine sand layer with a thickness of 1.2 mm;

3) Use a fine brush to evenly coat the graphite coating on the surface of the fine sand layer to form a graphite coating layer with a thickness of 0.6 mm, and place it for 1.5 hours. After the graphite coating is dry, place it in a trolley furnace and bake at 160 ° C Take it out of the oven after 2 hours, and wait for the temperature to drop below 50°C.

The preparation method of the casting of the present embodiment comprises the following steps:

Place the chilled iron with venting layer obtained above on the surface of the pattern, close the box, pour and demould.

comparative example

The cold iron of this comparative example includes a three-layer structure, the base layer is cold iron, the middle layer is a furan resin layer, and the upper layer is a coated sand layer.

The preparation method of the casting of this comparative example includes the following steps: placing the above-mentioned cold iron in a sand mold, closing the box, pouring, and demoulding.

Experimental example

Thin-walled aluminum alloy components were cast using the casting preparation methods of Examples 1-3 and Comparative Examples, wherein the aluminum alloy melt used was ZL104 prepared according to the composition standard of GB/T 1173-2013 "Casting Aluminum Alloys"; The temperature of the melt was 690°C. The obtained thin-walled aluminum alloy member is a cylindrical thin-walled aluminum alloy member. The upper and lower ends of the member are thick parts, the wall thickness is ≤4mm, the external dimension is ≥φ1000mm, and the middle is a circumferential rib and a longitudinal rib. Each piece weighs about 150kg.

1) The mechanical properties of the thin-walled aluminum alloy components obtained by the methods of Examples 1-3 and Comparative Examples were tested. The testing method was based on GBT 228-2010 "Metal Materials Tensile Test Method at Room Temperature". The testing results are shown in Table 1.

The mechanical property test result of the thin-walled aluminum alloy component that table 1 embodiment 1～3 and comparative example make

project Example 1 Example 2 Example 3 comparative example Tensile strength/MPa 320 280 300 220 Elongation/% 7 5 6 1.5

It can be seen from the contents of Table 1 that the tensile strength of the thin-walled aluminum alloy member obtained by the method of Examples 1-3 is 180-320MPa, which is much higher than that of the comparative example and much higher than the national standard (not less than 130MPa); the elongation It is 5-7%, far higher than the standard requirement (not less than 2%).

2) Measure the surface roughness and basic dimensions of the thin-walled aluminum alloy components of Examples 1-3 and Comparative Example respectively, and calculate the tolerance level of the components according to the basic dimensions (refer to GB/T6414 "Casting Dimensional Tolerance and Machining Allowance") , the results are shown in Table 2.

Table 2 Tolerance grades and surface roughness of thin-walled aluminum alloy components of Examples 1 to 3 and Comparative Examples

project Example 1 Example 2 Example 3 comparative example Tolerance class CT7 CT8 CT7 CT10 Surface roughness 6.3 6.3 6.3 12.5

3) The surface quality of the thin-walled aluminum alloy components of Examples 1-3 and Comparative Example was detected by fluorescence, and the detection results are shown in Table 3.

Table 3 The surface quality of the thin-walled aluminum alloy components of Examples 1 to 3 and Comparative Examples

project Example 1 Example 2 Example 3 comparative example Pinhole Class I Class I Class I Class III

The test results show that the components obtained by the method of Examples 1-3 meet the requirements of GB/T 9438-2013 "Aluminum Alloy Castings" Class I castings, and compared with GB/T 1173-2013 "Casting Aluminum Alloys", the surface quality of the product is improved by 40% .

4) The thin-walled aluminum alloy components obtained by the methods of Examples 1-3 and the comparative example were respectively measured for X-ray flaw detection, and the test results are shown in Table 4.

Table 4 The internal quality of the thin-walled aluminum alloy components of Examples 1 to 3 and Comparative Examples

project Example 1 Example 2 Example 3 comparative example Shrinkage level Class I Class I Class I Class III

The results show that the shrinkage level of the internal quality of the components in Examples 1-3 meets the requirements of GB/T 9438-2013 "Aluminum Alloy Castings" Class I castings, and compared with GB/T 1173-2013 "Casting Aluminum Alloys", the internal quality of the product is qualified rate increased by 30%.

In summary, compared with the components obtained by the method of the comparative example, the components obtained by the methods of Examples 1-3 not only have good mechanical properties, but also have good surface quality and internal quality.

Claims (7)

1. a chilled iron with venting layer, comprising chilled iron, it is characterized in that, described chilled iron is used for being provided with venting layer on the surface that contacts with casting, and described venting layer comprises inner layer, middle layer, Outer layer; the inner layer is a varnish layer, the middle layer is a sand layer, and the outer layer is a graphite coating layer; the sand layer is a fine sand layer, and the particle size of the sand in the sand layer is 70 to 100 mesh The preparation method of the graphite coating comprises the following steps: mixing rosin, phenolic resin, graphite, and ethanol to get final product; the mass ratio of the rosin, phenolic resin, graphite, and ethanol is 1:3:2:4; The thickness ratio of varnish layer, sand layer and graphite paint layer is 1:4:2. 2. The cold iron with exhaust layer according to claim 1, characterized in that, the thickness of the varnish layer is 0.1 ~ 0.3mm. 3. The cold iron with exhaust layer according to claim 1, characterized in that, the thickness of the graphite coating layer is 0.2 ~ 0.6 mm. 4. The cold iron with exhaust layer according to claim 1, characterized in that, the thickness of the sand layer is 0.4-1.2mm. 5. a preparation method of the cold iron with exhaust layer as claimed in claim 1, is characterized in that, comprises the following steps: Brush varnish on the surface of cold iron to form a varnish layer, then lay sand on the surface of the varnish layer to form a sand layer, then brush graphite paint on the surface of the sand layer to form a graphite paint layer, and dry it. 6 . The method for preparing chilled iron with an exhaust layer according to claim 5 , wherein the drying includes keeping the temperature at 120-160°C for 2-4 hours. 7. A method for preparing a casting, characterized in that it comprises the following steps: putting the chilled iron with vent layer according to claim 1 into the sand mold or on the surface of the pattern, closing the case, pouring, and demoulding.