The utility model belongs to the casting technology, in particular to a composite graphite cold cast iron, which aims to eliminate the phenomenon of "hot junction" and "hot junction transfer".

Background technique:

In casting technology, cold iron refers to placing metal objects or other chilling objects on the sand mold, sand core surface, or cavity to increase the local cooling rate of the casting. It is a common method in casting technology and casting production to adjust the temperature field during the solidification process of castings by using chilled iron, increase the cooling rate of castings at the chilled iron part, and prevent casting defects such as shrinkage cavities and shrinkage cavities. The commonly used materials for making cold hardware are cast iron and graphite. That is to say, the commonly used cold hardware includes cast iron cold hardware and graphite cold hardware.

When cold iron is used in actual production, such problems will be encountered. Because the chilling effect of the cold iron is too strong, the phenomenon of "hot junction transfer" is formed. The so-called hot spot refers to the node or local area in the casting whose solidification rate is slower than that of the surrounding metal during the solidification process of casting. It is due to the structural factors of the casting, such as different wall thicknesses, or different heat dissipation rates, which cause more heat to be dissipated in some areas of the casting than the surroundings, and the temperature is higher during solidification, so a thermal junction is formed in this area. It can also be said that the main purpose of placing chilled iron on the casting is to eliminate hot knots through better heat absorption and heat transfer of the chilled iron. However, if the cold soldering iron placed is too large and the effect of the cold soldering iron is too strong, although the hot spot is eliminated, the temperature of the surrounding part of the cold iron soldering iron may be significantly higher than that of the cold iron soldering iron, because the cooling rate of the part of the casting where the cold iron is placed is too high Faster, the temperature is higher, and new hot nodes appear in these parts where the temperature is higher, that is, the phenomenon of "hot node transfer" occurs. After the casting is solidified, casting defects such as shrinkage cavity and shrinkage porosity may be formed at the transferred hot joint. In the production of high-end ductile iron castings such as wind power castings, due to the strict requirements on casting shrinkage and shrinkage defects, the problem caused by hot spot transfer is even more serious. In principle, heat transfer can be avoided by reducing the chilling capacity of the cold iron by thinning the cold iron. However, the thinning of cold iron is limited, and it cannot be thinned arbitrarily. When the chilled iron is small to a certain extent, for cast iron chilled iron, due to its low melting point, it may fuse with the casting and affect the surface quality of the casting; for graphite chilled iron, although its melting point is high, its strength is low. Breakage may be found during use, which affects the use of cold iron.

Technical realization elements:

The technical problem to be solved and the technical task proposed by the utility model is to overcome the defect that the existing chilled cast iron is easy to produce hot joints and provide a composite graphite chilled cast iron.

To achieve the above object, the composite graphite cold iron of the present invention is characterized in that: a layer of refractory thin plate is compounded on one side of the graphite flat iron as the cold iron working surface.

As the preferred technical means of the composite graphite cold iron of the utility model: the thickness of the thin plate of the refractory product is 10-15mm.

As the preferred technical means of the composite graphite the cold iron of the present invention: the thickness of the graphite cold iron is 20-.

As the preferred technical means of the composite graphite chilled cast iron of the utility model: the graphite chilled cast iron and the refractory thin plate are bonded together through a water glass bonding layer.

The utility model uses one side of the flat graphite cold iron as the cold iron working surface to compound a layer of flat refractory products, and the composite graphite cold iron is made of low thermal conductivity refractory clay and graphite. The composite graphite chill iron reduces the chilling ability of the composite graphite chill iron, effectively avoiding the heat transfer phenomenon.

Drawing Description

Fig. 1 is a kind of structural representation of composite graphite chilled cast the iron of the present invention;

Explanation of symbols in the figure: 1-refractory thin plate, 2-water glass bonding layer, 3-graphite cold soldering iron.

detailed method

Below in conjunction with the accompanying drawing, the utility model is further described.

The composite graphite chilled cast iron shown in Figure 1 is a flat refractory thin plate compounded on one side of the graphite flat chilled cast iron as the chilled cast iron working face. The thickness of the refractory product sheet is 10-15mm. The thickness of the graphite chill iron is 20-. Graphite chilled cast iron and refractory products are bonded together through the water-glass bonding layer between the two. The water glass adhesive layer adopts water glass with a modulus of 2.5-3.5 as the adhesive.

Example 1

(1) the clay (refractory clay clinker) refractory product sheet 1 a thickness is 10mm is cut into the same size as graphite chilled iron 3 a thickness is 20mm;

(2) Water glass with a modulus of 2.5 is used as a binding agent, coated on one side of the refractory product sheet to form a water glass bonding layer 2, and the refractory product sheet is bonded on the working surface of the graphite cold soldering iron. For neatness, get a composite board;

(3) Dry the composite board at a temperature of 110±10°C to solidify the water glass, and bond the refractory product sheet 1 and graphite chilled iron 3 together to form a refractory product sheet, that is, the composite graphite chilled iron on a cold iron work surface.

The thermal conductivity of the prepared composite graphite cold iron is about 85W/(m•K); while at room temperature, the thermal conductivity of the ordinary graphite plate is about 110-140W/(m•K).

Example 2

(1) the clay (refractory clay clinker) refractory product sheet 1 a thickness is 10mm is cut into the same size as graphite chilled iron 3 a thickness is 50mm;

(2) Water glass with a modulus of 2.5 is used as a binding agent, coated on one side of the refractory product sheet to form a water glass bonding layer 2, and the refractory product sheet is bonded on the working surface of the graphite cold soldering iron. For neatness, get a composite board;

(3) Dry the composite board at a temperature of 110±10°C to solidify the water glass, and bond the refractory product sheet 1 and graphite chilled iron 3 together to form a refractory product sheet, that is, the composite graphite chilled iron on a cold iron work surface.

The thermal conductivity of the prepared composite graphite cold iron is about 80W/(m•K); while at room temperature, the thermal conductivity of the ordinary graphite plate is about 110-140W/(m•K).

Example 3

(1) the clay (refractory clay clinker) refractory product sheet that a thickness is 12mm is cut into the same size as the graphite cold iron with a thickness is 60mm;

(2) Use water glass with a modulus of 3.0 as a binder, apply it on one side of the refractory product sheet to form a water glass bonding layer, and bond the refractory product sheet to the working surface of the graphite cold soldering iron. Arranging to get the composite board;

(3) The composite board is dried at a temperature of 150±10°C to solidify the water glass, and the refractory product sheet is bonded with the graphite cold iron to form a refractory product sheet as a composite graphite cold iron for the cold iron working surface.

The thermal conductivity of the prepared composite graphite cold iron is about 35W/(m•K); while at room temperature, the thermal conductivity of the ordinary graphite plate is about 110-140W/(m•K).

Example 4

(1) The 15mm thick clay (refractory clay clinker) refractory product sheet is cut into the same size as the 80mm thick graphite cold iron;

(2) Use water glass with a modulus of 3.5 as a binding agent, apply it on one side of the refractory product sheet to form a water glass bonding layer, and bond the refractory product sheet to the working surface of the graphite cold soldering iron. Arranging to get the composite board;

(3) Dry the composite plate at a temperature of 190±10°C to solidify the water glass, and bond the refractory product sheet with the graphite chill iron to form a refractory product sheet as a composite graphite chill iron for the cold iron working surface.

The thermal conductivity of the prepared composite graphite cold iron is about 15W/(m•K); while at room temperature, the thermal conductivity of the ordinary graphite plate is about 110-140W/(m•K).

Example 5

(1) the clay (refractory clay clinker) refractory product sheet that a thickness is 15mm is cut into the same size as the graphite cold iron with a thickness is 15mm;

(2) Use water glass with a modulus of 3.5 as a binding agent, apply it on one side of the refractory product sheet to form a water glass bonding layer, and bond the refractory product sheet to the working surface of the graphite cold soldering iron. Arranging to get the composite board;

(3) Dry the composite plate at a temperature of 190±10°C to solidify the water glass, and bond the refractory product sheet with the graphite chill iron to form a refractory product sheet as a composite graphite chill iron for the cold iron working surface.

The thermal conductivity of the prepared composite graphite cold iron is about 10W/(m•K); while at room temperature, the thermal conductivity of the ordinary graphite plate is about 110-140W/(m•K).

The graphite chill used in foundry production is mostly the flat graphite chill of the working surface (the contact surface of the chill and the casting), so the composite graphite chill of the present invention is suitable as this chill.

Usually, graphite material is used to make cold iron because graphite has a relatively high thermal conductivity. Therefore, the utility model makes composite graphite cold iron by compounding refractory clay and graphite with lower thermal conductivity, to reduce the thermal conductivity of the cold iron, thereby reducing the chilling ability of the cold iron.