CN108080602A - A kind of part blank nature cracking technology - Google Patents

Abstract

The invention discloses a natural cracking process of parts blanks. Firstly, the magnesium foil is processed into thin slices, put into a mold according to a preset cracking position and fixed, and the mold is divided into two cavities; secondly, the mold is pre-processed. The molten metal is melted into two streams and flowed into two cavities respectively; after the molten metal is cooled, the casting is taken out of the mold, and the surface is cleaned; then the expansion hole is processed at the preset cracking position of the casting , and set up a cracking groove at the intersection of the expansion hole and the pre-designed cracking interface; finally load the expansion casting at the location of the expansion hole. The present invention enables the parts to be brittle and split along the preset interface when they are cracked, and ensures that the two fractured surfaces have good meshing properties and strength, provides a positioning reference for the subsequent reassembly of the split body, breaks through the cracking technology and provides a practical technology for material limitations , with greater economic benefits.

Description

A natural pyrolysis process for parts blanks

technical field

The invention relates to a process for accelerating cracking and improving cracking quality, in particular to a natural cracking process for parts blanks.

Background technique

Cracking technology is the most advanced high-precision machining technology for manufacturing dissected parts, and it has been widely used in the fields of engine connecting rods, crankcase end covers, etc. Cracking technology has strict requirements on material selection. On the premise of ensuring the comprehensive mechanical properties of the connecting rod, the toughness index of the connecting rod is limited, and the material used is required to have brittle fracture characteristics at room temperature, and the formed fracture surface must have sufficient strength. The available pyrolysis materials are greatly limited. At present, the types of cracking materials that can be used in engineering are relatively limited. The selection of cracking connecting rods is concentrated in high-carbon steel, powder metallurgy materials, malleable cast iron, etc., while ordinary steel, aluminum alloy, titanium alloy and other tough materials are generally not applicable. cracking technology. At present, the mature pyrolysis material preparation technology is complex and the material composition control requirements are high, which directly restricts the application and promotion of pyrolysis technology. On the other hand, there are many problems in the cracking process of commonly used cracking materials: such as cracking deformation, cracking surface dislocation, cracking plane offset, bifurcation, unilateral tearing, bursting, etc. In response to this "bottleneck" problem, domestic and foreign explorations on microalloying to improve material properties, development of new cracking equipment, and optimization of cracking parameters have failed to break through the limitations of cracking technology on material selection.

Contents of the invention

The technical problem to be solved by the present invention is to provide a natural pyrolysis process for part blanks in view of the defects involved in the background technology.

The present invention adopts the following technical solutions to solve the above-mentioned technical problems

A natural pyrolysis process for parts blanks, comprising the following steps:

Step 1), the magnesium foil is processed into thin slices, put into the mold according to the preset cracking position and fixed, and the mold is divided into two cavities;

Step 2), preheating the mold;

Step 3), melt the molten metal into two streams and flow into the two cavities respectively, and the inflow directions are opposite, so that they reach both sides of the magnesium foil at the same time and fill the two cavities smoothly;

Step 4), after the molten metal is cooled, the casting is taken out from the mold, and the surface is cleaned;

Step 5), processing the expansion hole at the preset cracking position of the casting, and opening a cracking groove at the intersection of the expansion hole and the pre-designed cracking interface;

Step 6), load the burst casting at the position of the burst hole.

As a further optimization scheme of the natural cracking process of a part blank in the present invention, the cracking tank in step 5) is a V-shaped cracking tank.

As a further optimization scheme of the natural pyrolysis process of a part blank in the present invention, the opening width of the V-shaped pyrolysis groove is 1.5 mm, and the depth is 1 mm.

As a further optimization scheme of the natural cracking process of a part blank in the present invention, the magnesium foil material is an AZ31 sheet with a thickness of 0.12mm.

Compared with the prior art, the present invention adopts the above technical scheme and has the following technical effects:

1. The present invention enables the part added with magnesium foil to start cracking along the root of the cracking tank, and the fracture crack expands along the preset interface layer. The formed section is smooth, without plastic deformation, the fracture color is dark, the required bursting load is small, and the cracking is separated. Easy, no cracks, slag falling, fracture surface deformation and other problems, realizing low-energy brittle fracture;

2. The fracture surface produced by the present invention has the following characteristics in its fracture morphology: the fracture presents brittleness, has intergranular fracture characteristics, and has flaky fracture characteristics; The plasticity of the cracking zone, the fracture surface is smooth, and the cracks have no bifurcation or offset;

3. The invention enables the parts to be brittle and split along the preset interface when they are cracked, and ensures that the two fractured surfaces have good meshing properties and strength, and provides a positioning reference for the subsequent reassembly of the split body, breaking through the limitations of the cracking technology for materials. Practical technology, with greater economic benefits.

Description of drawings

Fig. 1 is a schematic diagram of the mold used in the present invention;

Fig. 2 is a schematic diagram of cracking tank processing position in the technical solution of the present invention;

Fig. 3 is a schematic diagram of the cracking effect of the present invention;

In the figure, 1-mold, 2-magnesium foil, 3-mold cavity, 4-processing position of cracking tank, 5-casting before cracking, 6-joint surface of casting, 7-casting after cracking.

Detailed ways

Below in conjunction with accompanying drawing, technical scheme of the present invention is described in further detail:

This invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, components are exaggerated for clarity.

The invention discloses a natural cracking process of a part blank, which comprises the following steps:

Step 1), the magnesium foil is processed into thin slices, put into the mold according to the preset cracking position and fixed, and the mold is divided into two cavities;

Step 2), preheating the mold;

Step 3), melt the molten metal into two streams and flow into the two cavities respectively, and the inflow directions are opposite, so that they reach both sides of the magnesium foil at the same time and fill the two cavities smoothly;

Step 4), after the molten metal is cooled, the casting is taken out from the mold, and the surface is cleaned;

Step 5), processing the expansion hole at the preset cracking position of the casting, and opening a cracking groove at the intersection of the expansion hole and the pre-designed cracking interface;

Step 6), load the burst casting at the position of the burst hole.

The cracking tank in step 5) is preferably a V-shaped cracking tank. The opening width of the V-shaped cracking groove is 1.5 mm, and the depth is 1 mm.

The magnesium foil is preferably AZ31 sheet with a thickness of 0.12mm.

The whole process of the formation mechanism of the cracking surface of the present invention is as follows: two relatively flowing molten metals in the mold are overlapped on both sides of the magnesium foil material, the magnesium foil material is violently oxidized in the high-temperature liquid and the metal film at the front of the metal liquid flows forms an interface. When forming a low-melting-point melt layer inside the alloy, the low-melting-point liquid phase moves to the edge of the grain boundary as the growing crystals move. Due to the shrinkage of the interface liquid film, intergranular feeding cannot be carried out smoothly. Micro-shrinkage cavities are formed, and the joint action finally forms a natural cracking interface.

Beneficial effect of the present invention can be illustrated by following experiments:

The mold for testing the method of the present invention is shown in Figure 1. The runner adopts the form of single gate and double runner, that is, a main runner and two runners are symmetrically distributed, and the molten metal is guided into two streams to flow into the cavity relatively and reach the mold cavity at the same time. Both sides of the sheet metal fill the two cavities smoothly. The demoulding ejector pin is set at the bottom of the cavity to realize the smooth demoulding of the casting. In order to facilitate the clamping of the magnesium foil on the mold, a convex-concave structure that cooperates with each other is set in the vertical parting surface of the mold.

The experimental material is LD10 alloy with a melting point of 660°C as the connecting rod material, and the magnesium foil is AZ31 sheet with a thickness of 0.12mm, and its melting point is 649°C. The casting is cut by wire cutting to take a rectangular sample, the size is 40mm×30mm×20mm, a φ14mm round hole is opened at the preset cracking position, and the width is 1.5mm, and the depth is 1.5mm at the intersection of the expansion hole and the pre-designed cracking interface. 1mm V-shaped cracking groove, and then a bursting load is applied in the circular hole to make it fracture along the brittle interface, as shown in Figure 2.

The castings prepared under the above conditions were split and dissected by the expansion fracture method. Under the action of the expansion fracture load, the sample cracked along the interface, as shown in Figure 3. The macroscopic fracture characteristics: flat section and small deformation in the plastic zone. Under the same conditions, the base metal casting without magnesium foil was dissected and dissected. Compared with the former, there are obvious differences in the fracture of the two, mainly in:

(1) The location of the crack initiation point of the cracking. The sample added with magnesium foil cracks along the root of the cracking tank, and the fracture crack propagates along the preset interface layer. The formed section is flat and has no plastic deformation. It is random, and the plasticity of the section is large;

(2) Fracture color, the color of the fracture of the magnesium foil is dark, while the color of the base material is bright;

(3) Fracture deformation. The expansion load required for the sample added with magnesium foil is small, the cracking and separation are easy, and there are no problems such as cracking, slag falling, and fracture surface deformation, etc., and low-energy brittle fracture is realized. , the fracture surface is uneven, the deformation of the fracture surface is large, and the required bursting load is large.

Those skilled in the art can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this invention belongs. It should also be understood that terms such as those defined in commonly used dictionaries should be understood to have a meaning consistent with the meaning in the context of the prior art, and unless defined as herein, are not to be interpreted in an idealized or overly formal sense explain.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (4)

1. A natural pyrolysis process for parts blank, is characterized in that, comprises the following steps: Step 1), the magnesium foil is processed into thin slices, put into the mold according to the preset cracking position and fixed, and the mold is divided into two cavities; Step 2), preheating the mold; Step 3), melt the molten metal into two streams and flow into the two cavities respectively, and the inflow directions are opposite, so that they reach both sides of the magnesium foil at the same time and fill the two cavities smoothly; Step 4), after the molten metal is cooled, the casting is taken out from the mold, and the surface is cleaned; Step 5), processing the expansion hole at the preset cracking position of the casting, and opening a cracking groove at the intersection of the expansion hole and the pre-designed cracking interface; Step 6), load the burst casting at the position of the burst hole. 2. The natural cracking process for parts blanks according to claim 1, characterized in that the cracking tank in step 5) is a V-shaped cracking tank. 3. The natural cracking process for parts blanks according to claim 1, characterized in that, the opening width of the V-shaped cracking groove is 1.5 mm, and the depth is 1 mm. 4. The natural pyrolysis process for parts blanks according to claim 1, characterized in that the magnesium foil material is AZ31 sheet with a thickness of 0.12mm.