WO2020052528A1

WO2020052528A1 - Method for producing high-strength near-net-shaped metal part

Info

Publication number: WO2020052528A1
Application number: PCT/CN2019/105001
Authority: WO
Inventors: 杨云峰
Original assignee: 佛山峰合精密喷射成形科技有限公司
Priority date: 2018-09-10
Filing date: 2019-09-10
Publication date: 2020-03-19
Also published as: CN109290543A

Abstract

Disclosed is a method for producing a high-strength metal complex-shaped near-net-shaped metal blank, comprising the following steps: manufacturing a metal ingot blank using a metal spray forming process; heating the metal ingot blank to a semi-solid temperature; and molding a semi-solid metal ingot blank to a near-net-shaped metal part using processes such as extrusion. The method uses the characteristic that the spray-forming ultra-high-speed coagulation can directly create a fine and uniform spheroidal texture that has a better semi-solid thixoforging characteristic than a material manufactured by means of a traditional method, and is directly used to produce a semi-solid formed high-strength and complex near-net-shaped part, with the advantages of low costs for equipment and the production process, a high efficiency and more stable and reliable quality.

Description

Method for producing high-strength near-net-shape metal parts

Technical field

The invention relates to the field of processing near-net-shape parts, in particular to a method for producing high-strength near-net-shape metal parts.

Background technique

Many complex-shaped metals, such as aluminum alloys, are formed by casting aluminum alloys by die casting. However, this method is limited by the type and process of the alloy. The strength of traditional die-casting parts is low, most of which are in the range of 100-300 MPa. Moreover, the die-casting parts are prone to pores or loose internal structures, and it is difficult to meet the requirements of high-end parts. Figure shown in Figure 1.

The metal spray forming technology appeared in the 1970s, but the metal liquid condenses at a high speed of the order of 10,000 degrees per second. It can prepare fine and uniform high-alloy materials that are difficult to produce by traditional pressing technology. -The strength of the aluminum alloy is 800 MPa, and its metallographic diagram is shown in Figure 2. However, it is precisely because of the high strength of the material produced by the metal injection molding technology that its plasticity is poor. In the field, metal injection molding technology has been used to directly produce part blanks, and then the final parts are formed by cutting and grinding processes. For complex parts, although the spray forming technology can achieve precise forming, the more complex and precise the part structure, the smaller the layer thickness and the longer the forming time.

Moreover, if these metal injection-molded part blanks are remelted and die-cast, their structures and properties will return to a very poor level. The metallographic diagram is shown in Figure 3.

Semi-solid forming technology is also a new metal forming technology invented in the 1970s. The dendritic crystals (as shown in Figure 1) generated during the solidification of the metal are transformed into pellets by various processes and have semi-solid thixotropic properties and rheological filling ability under pressure. Compared with traditional die-casting, semi-solid formed products have the advantages of high strength and density, low shrinkage, so that the size and shape of near-net-shape parts are more accurate, and the forming temperature is lower, which improves the life of the mold. The semi-solid temperature is the temperature in the solid-liquid temperature range. The near-net shape part means that after the part is formed, only a small amount of processing or no processing is required.

At present, there are mainly two methods for preparing semi-solid forming metal raw materials: 1) The ultrasonic vibration method is used during the solidification process, and the metallographic diagram is shown in Figure 4; 5 shown. But their processes are complex, costly and inefficient. However, those skilled in the art spend a lot of time and energy to solve the problem of how to make dendritic crystals better, more uniform, and faster.

The metal spray forming strength is high, but the structure and properties after remelting will be significantly deteriorated, and the casting process performance is poor. In the process of semi-solid forming, the material must be re-melted. Therefore, metal spray forming and semi-solid forming are both emerging and parallel technologies. Because the two processes have conflicts, the There are advantages and disadvantages. For the forming of complex parts, the forming speed of semi-solid forming is high, but the strength is low. The processing time of metal injection molding is long, but the strength is high.

The research direction of metal spray forming process to make high-strength near-net-shape metal parts is to accelerate the formation of each layer thickness, and the research direction of semi-solid forming is how to effectively and quickly dendrites are broken to increase their strength. The research directions of the two are completely different.

Summary of the Invention

The technical problem to be solved by the present invention is to provide a method for producing a high-strength near-net-shape metal part.

The solution to the technical problem of the present invention is:

A method for producing a high-strength near-net-shape metal part includes the following steps:

Step a) making a metal ingot by a metal spray forming process;

Step c) heating the metal ingot to a semi-solid temperature;

Step d) forming the metal ingot having a semi-solid temperature into a near-net shape metal part by an extrusion process.

As a further improvement of the foregoing solution, a step c1) is further provided between step c) and step d): the metal ingot is held for 5 seconds to 30 seconds.

As a further improvement of the above solution, in step c), the metal ingot is heated by using an electromagnetic inductor.

As a further improvement of the above solution, in step d), the forming process of the near-net-shape metal part is as follows: the mold includes an upper mold and a lower mold, and the upper mold and the lower mold are each provided with successively connected feeding port sections, flows, The channel section, cavity section, upper and lower mold inlets, runners, and cavity sections are assembled into successively connected inlets, runners, and cavities, and the metal ingots at a semi-solid temperature are placed. Into the feed inlet, the metal ingot is extruded with a pressing rod that is suitable for the shape and size of the inlet. The press rod passes the metal ingot at a semi-solid temperature from the mold inlet through the narrow flow channel to the The cavity of the mold is filled and filled to form a near-net shape metal part.

As a further improvement of the above solution, the cross-sectional area of the flow channel is not greater than one-tenth of the cross-sectional area of the pressing rod.

As a further improvement of the above solution, in step d), the volume of the metal ingot> the volume of the cavity + the volume of the runner, and the pressure of the pressing rod to press the metal ingot is called the first pressure. After completing the cavity of the mold After filling, the pressure stick uses a second pressure to hold the near-net shape metal part.

As a further improvement of the above solution, the second pressure is generally greater than the first pressure, and the holding time is not less than 3 seconds

As a further improvement of the above solution, the forming process of step d) of a near-net shape metal part is such that the mold is a forging mold, the mold includes an upper mold and a lower mold, and a metal ingot is placed on the upper mold and the lower mold. In between, the upper and lower dies are closed with a die forging device to form a near-net shape metal part.

As a further improvement of the above solution, a step b) is further provided between step a) and step c): the metal ingot is processed into a metal ingot with a single cross-section by a pressing process.

As a further improvement of the above solution, the pressure processing process described in step b) includes any one of hot extrusion and hot rolling.

The beneficial effect of the present invention is that since the metal ingot of the present invention is made by a metal spray forming process, its internal structure is very fine and uniform, and there is no dendrite. Heating such a metal ingot to a semi-solid temperature will not produce crystallites, and the fluidity is good. Therefore, the metal ingot is pressure-formed and used directly to produce semi-solid formed high-strength complex near-net-shaped parts. It has equipment and Low cost, high efficiency, more stable and reliable quality. The invention utilizes the ultra-high condensing speed of metal spray forming to obtain the metal characteristics of a small round metallographic structure, and directly uses it as a semi-solid forming blank to produce high-strength near-net-shape metal parts, instead of the traditional technology of preparing the semi-solid forming blank, which is a cumbersome process such as traditional stirring. It has the advantages of short process flow, high quality, and comprehensive technical and economic benefits. The invention is used for forming metal parts.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to explain the technical solution in the embodiments of the present invention more clearly, the drawings used in the description of the embodiments will be briefly described below. Obviously, the drawings described are only a part of the embodiments of the present invention, but not all the embodiments. Those skilled in the art can also obtain other designs and drawings according to these drawings without creative efforts.

Figure 1 is a metallographic diagram of a cast A390 aluminum alloy;

Figure 2 is a metallographic diagram of the spray-formed A390 aluminum alloy;

3 is a metallographic diagram of the metal injection-molded A390 aluminum alloy after re-melting and cooling;

4 is a metallographic diagram of a metal ingot blank prepared by an ultrasonic vibration method of an A390 aluminum alloy liquid;

5 is a metallographic diagram of a metal ingot blank prepared by the hot-mix method of A390 aluminum alloy liquid;

6 is a metallographic diagram of a near-net shape metal part prepared by the A390 aluminum alloy using the present invention.

detailed description

In the following, the concept, specific structure, and technical effects of the present invention will be clearly and completely described in combination with the embodiments and the drawings to fully understand the objects, features, and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all the embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative efforts belong to The scope of the invention. In addition, all the connection / connection relationships mentioned in the article are not directly connected by a single-finger member, but mean that a better connection structure can be formed by adding or reducing connection accessories according to the specific implementation situation. Various technical features in the present invention can be combined and interacted on the premise of not conflicting with each other.

Referring to FIG. 6, this is an embodiment of the present invention applied to A390 aluminum alloy, specifically:

Step a) making a metal ingot by a metal spray forming process;

Step c) heating the metal ingot to a semi-solid temperature;

Step d) forming the metal ingot with a semi-solid temperature into a near-net-shape metal part by using a die pressure forming.

The method of the present invention can directly produce a semi-solid forming raw material with a fine and uniform pellet-like structure by using ultra-high-speed solidification of spray forming. It is used to produce semi-solid formed near-net-shape parts with high strength and complex shapes. It has the characteristics of low equipment and process flow, high efficiency, and more stable and reliable quality. Comparing FIG. 2 and FIG. 6, it can be known that the present invention not only can make the internal component structure of the near-net-shape metal part denser, but also basically maintains the fine spherical grain structure of the spray-formed metal, and has high semi-solid thixotropy and flow filling. Ability to achieve the compression molding of parts with complex shapes, and the structure is more dense, so the invention can still retain the high strength characteristics of metal injection molding, while strength and plasticity itself are a pair of contradictions, but through the present invention is exactly These two contradictions are combined. That is, the semi-solid forming process of the present invention avoids re-melting the spray-formed metal material, maintains its superior structure and performance, and then forms a complex-shaped high-strength near-net-shape part. The traditional process of transforming the crystal grains of semi-solid forming raw materials into spherical shapes is realized under stirring and vibration. The semi-solid forming raw material of the present invention directly generates better quality through ultra-high-speed solidification by spray forming, which greatly simplifies the process flow, reduces costs, and provides part performance.

A step b) is further provided between steps a) and c) of this embodiment: a metal ingot blank is processed into a metal ingot blank with a single cross-section by a pressure processing process. This facilitates accurate segmentation of the metal ingot, and each segment of the metal ingot is used as the metal ingot in step c).

In step b) of this embodiment, the metal ingot is compacted into a rod shape. In actual production and processing, the cooled rod-shaped metal ingot can be cut into sections, and then the cut metal rod can be subjected to step c).

The processes such as pressure processing described in step b) include any one of hot extrusion and hot rolling. In this way, the plasticity of the metal ingot can be improved, the pores in the metal ingot can be eliminated well, and the semi-solid forming raw material blank with a suitable shape and weight can be prepared.

A small amount (about 1% by volume) of pores in the metal ingot blank formed by metal spraying can be effectively eliminated after steps b) and d), and the strength of the metal near-net-shape parts can be effectively guaranteed.

In order to make the inner and outer temperature of the metal ingot more consistent, step c1) is further provided between step c) and step d): the metal ingot is kept warm for 5 seconds to 30 seconds.

In step c) of this embodiment, the metal ingot is heated by using an electromagnetic inductor, so that the entire metal can be heated at the same time by adjusting the frequency and power, avoiding the traditional external heating method to allow the outside of the metal ingot to be heated first. The heat can even be melted to reach the semi-solid temperature inside, which can effectively reduce the heating time and achieve a good overall temperature control. At the same time, no dendrites will appear inside and outside the metal ingot. Under the premise of ensuring production efficiency Therefore, the problem of "remelting and injection molding of spray-formed material, and its structure and performance will return to a very poor level" described in the background art of the present invention is avoided.

In step d), the forming process of the near-net-shape metal part is as follows: the mold includes an upper mold and a lower mold, and the upper mold and the lower mold are provided with a feeding inlet section, a flow channel section and a cavity section which are sequentially connected, The upper, lower, and lower mold inlets, runners, and cavities are combined into successively connected inlets, runners, and cavities. Metal ingots at a semi-solid temperature are placed in the inlets. The shape and size of the feeding port are adapted to press the metal ingot. The pressing rod will pass the metal ingot at the semi-solid temperature from the mold inlet through the narrow flow channel into the mold cavity and carry out Fill to form a near-net shape metal part. Because the cross-sectional area of the flow channel is small, the pressure of the metal ingot in the flow channel during the filling process will be very large, which can make the internal structure of the near-net-shape metal parts more dense. The shapes and sizes of the feed inlet, the pressing rod, and the metal ingot in this embodiment are all the same, so that gas can be prevented from entering the interior of the near-net-shape metal part to the maximum, and the surface of the metal ingot can be prevented from being plastically deformed and wrapped. Gas, which brings the gas into the interior of the near-net-shape metal part.

The cross-sectional area of the flow channel is usually set to not more than one tenth of the cross-sectional area of the press stick. The small cross-sectional area of the flow channel can increase the effect of grain fusion and rounding.

In step d), the volume of the metal ingot> the volume of the cavity + the volume of the runner. The pressure of the press rod on the metal ingot is called the first pressure. After the cavity of the mold is filled, the second pressure is used for the press rod. Hold pressure on near-net-shape metal parts to avoid gas precipitation and formation of porosity. In this embodiment, the second pressure is greater than the first pressure, and the holding time is not less than 3 seconds. Due to the setting of the holding pressure, the density of the near-net-shaped metal part can be well guaranteed.

Of course, in step b), the metal ingot can be pressed into a near-net-shape metal part by a pressing process, and then the following step b) is performed.

Step d) the mold is a forging mold, the mold includes an upper mold and a lower mold, a metal ingot is placed between the upper mold and the lower mold, and the upper mold and the lower mold are closed by a forging equipment, thereby forming Near-net-shape metal parts.

After the processing of the near-net-shape part blank is completed, further machining can be performed to remove burrs and runner material, and further heat treatment can be performed.

The preferred embodiments of the present invention have been specifically described above, but the present invention is not limited to the embodiments. Those skilled in the art can make various equivalent modifications or replacements without departing from the spirit of the present invention. Equivalent variations or substitutions are included in the scope defined by the claims of the present application.

Claims

A method for producing a high-strength near-net-shape metal part, which is characterized by comprising the following steps:

Step a) making a metal ingot by a metal spray forming process;

Step c) heating the metal ingot to a semi-solid temperature;

Step d) forming the metal ingot having a semi-solid temperature into a near-net-shape metal part by using a die pressure forming method.
The method for producing a high-strength near-net-shape metal part according to claim 1, further comprising a step c1) between step c) and step d): holding the metal ingot blank for 5 seconds to 30 seconds.
The method for producing a high-strength near-net-shape metal part according to claim 1, wherein in step c), the metal ingot is heated by an electromagnetic inductor.
The method for producing a high-strength near-net-shape metal part according to claim 1, wherein in step d), the forming process of the near-net-shape metal part is as follows: the mold includes an upper mold, a lower mold, and an upper mold; Both the die and the lower die are provided with a feeding inlet section, a runner section and a cavity section which are connected in sequence. The upper and lower die inlet sections, the runner section and the cavity section are connected into a sequentially connected inlet. , Runner, cavity, put the metal ingot at the semi-solid temperature into the feeding port, and press the metal ingot with the pressing rod that matches the shape and size of the feeding port. The pressing rod will be at the semi-solid temperature. The metal ingot enters the cavity of the mold through the narrow flow channel from the feeding port of the mold and is filled, thereby forming a near-net shape metal part.
The method for producing a high-strength near-net-shape metal part according to claim 4, wherein the cross-sectional area of the flow channel is not more than one-tenth of the cross-sectional area of the pressing rod.
The method for producing a high-strength near-net-shape metal part according to claim 4, characterized in that in step d), the volume of the metal ingot blank> the volume of the cavity + the volume of the flow channel, and the pressing rod is used for the metal ingot The pressure of the blank press forming is called the first pressure. After the cavity filling of the mold is completed, the pressure stick uses the second pressure to maintain the near-net shape metal parts.
The method for producing a high-strength near-net-shape metal part according to claim 4, wherein the second pressure is generally greater than the first pressure, and the holding time is not less than 3 seconds
The method for producing a high-strength near-net-shape metal part according to claim 1, characterized in that: the step d) the forming process of the near-net-shape metal part is such that the mold is a forging mold, and the mold includes The upper mold and the lower mold, the metal ingot blank is placed between the upper mold and the lower mold, and the upper mold and the lower mold are closed by a forging device, thereby forming a near-net shape metal part.
The method for producing a high-strength near-net-shape metal part according to claim 1, wherein step b) is further provided between step a) and step c): the metal ingot is processed into Metal ingots.
The method for producing a high-strength near-net-shape metal part according to claim 9, characterized in that the press working process in step b) comprises any one of hot extrusion and hot rolling.