阅读说明：本技术 一种减少基材-增材体界面残余应力的方法 (Method for reducing residual stress of substrate-additive body interface ) 是由 虞文军 王大为 王少阳 荣鹏 唐维之 于 2021-08-23 设计创作，主要内容包括：本发明公开了一种减少基材-增材体界面残余应力的方法,涉及激光送粉增材制造技术领域,包括以下步骤：步骤S1：在基材制备阶段,将基材-增材体界面周边的基材材料去除,在界面上形成凸台结构；步骤S2：使增材体在凸台结构上进行生长,并将增材体底部与基材界面的过渡区设计成圆角过渡结构,再开展增材制造；步骤S3：对基材-增材体制件进行机械加工,本发明具有可减小激光增材制造过程基材-增材体界面的残余应力,从而减少制件的变形、开裂趋势的优点。(The invention discloses a method for reducing residual stress of a substrate-additive interface, which relates to the technical field of laser powder feeding additive manufacturing and comprises the following steps: step S1: in the preparation stage of the base material, the base material at the periphery of the interface of the base material and the additive body is removed, and a boss structure is formed on the interface; step S2: growing the additive body on the boss structure, designing a transition area between the bottom of the additive body and the interface of the base material into a fillet transition structure, and then performing additive manufacturing; step S3: the method has the advantages that the residual stress of the interface of the substrate and the additive body in the laser additive manufacturing process can be reduced, so that the deformation and cracking tendency of the workpiece is reduced.)

1. A method of reducing substrate-additive body interface residual stress, comprising the steps of:

step S1: in the preparation stage of the base material, the base material at the periphery of the interface of the base material and the additive body is removed, and a boss structure is formed on the interface;

step S2: growing the additive body on the boss structure, designing a transition area between the bottom of the additive body and the interface of the base material into a fillet transition structure, and then performing additive manufacturing;

step S3: the substrate-additive body article is machined.

2. The method according to claim 1, wherein the step S1 specifically comprises:

step S11: selecting a corresponding dimension specification of the base material according to the structure of the part to be processed, and determining the processing allowance H on the base material;

step S12: determining the projection size X of the additive body according to the characteristics, the shape and the size of the additive body of the part;

step S13: and removing the substrate material with the thickness H locally or on the whole plane outside the determined substrate position and projection size X range, and enabling H to be less than H to form a boss structure with the cross section size of X X H.

3. The method of claim 2, wherein in step S12, the projection dimension X comprises a width of the part itself, an additive machining allowance, and a transition fillet radius of the substrate-additive body.

4. The method for reducing the residual stress at the interface between the substrate and the additive body according to claim 2 or 3, wherein the step S2 specifically comprises:

step S21: designing the outline structure of the additive body on the base material according to the determined dimension and outline of the additive body of the part, and designing a transition area between the base material and the additive body into a fillet transition structure;

step S22: designing a three-dimensional digital model of the additive body, guiding the three-dimensional digital model of the additive body into a slicing software slice, compiling an additive manufacturing program, guiding the additive manufacturing program into laser coaxial powder feeding additive manufacturing equipment, and carrying out additive manufacturing.

5. The method of claim 4, wherein in step S22, the three-dimensional software used in designing the three-dimensional simulation of the additive body is CATIA.

6. The method of reducing the substrate-additive body interface residual stress of claim 2, wherein in step S12, said part is a rolled plate or a forging.

Technical Field

The invention relates to the technical field of laser powder feeding additive manufacturing, in particular to a method for reducing residual stress of a substrate-additive body interface.

Background

Laser synchronous powder feeding additive manufacturing (also called laser three-dimensional forming) is a flexible manufacturing technology which can be used for rapid forming and damage repair. The metal powder is sprayed to the surface of the metal base material, the base material and the metal powder particles are melted by laser at the same time, layer-by-layer accumulation is realized, and the shape of the accumulation is controlled by a computer program to form a part blank with a specific shape. Compared with the traditional manufacturing technology, the laser coaxial feeding additive manufacturing technology does not need to manufacture a die additionally, and the forming speed is higher than that of a selective laser melting (SL) technology. The laser synchronous powder feeding additive manufacturing is combined with the traditional rolling and forging manufacturing process, the additional micro structure of the part is manufactured in an additive mode on the basis of the plate and the forge piece, the excellent mechanical properties of the base materials of the plate and the forge piece can be fully utilized, and meanwhile the material utilization rate and the production efficiency of a blank of the part are improved by combining the flexibility of the laser synchronous powder feeding additive manufacturing.

However, the interface between the substrate and the additive body is melted, accumulated and solidified after being scanned by the laser beam, and generates a significant temperature gradient with the substrate, so that a great residual stress is inevitably formed, the substrate is deformed and even the interface is cracked, and the deformation caused by stress release in the process of processing parts is also caused. In the prior art, mainly the residual stress of an additive body is reduced, for example, an invention patent with the application number of "CN 202010238130.4" discloses a "repair path optimization method based on an in-situ stress release model", and the like, the control of the residual stress of a substrate-additive body interface is still lack of further measures, which causes defects that a workpiece is easy to deform and crack.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a method for reducing the residual stress of the interface of a base material and an additive body, so that the residual stress of the interface of the base material and the additive body in the laser additive manufacturing process can be reduced, and the deformation and cracking tendency of a workpiece can be reduced.

In order to solve the technical problems, the invention adopts the following technical scheme:

a method of reducing substrate-additive body interface residual stress comprising the steps of:

step S1: in the preparation stage of the base material, the base material at the periphery of the interface of the base material and the additive body is removed, and a boss structure is formed on the interface;

step S2: growing the additive body on the boss structure, designing a transition area between the bottom of the additive body and the interface of the base material into a fillet transition structure, and then performing additive manufacturing;

step S3: the substrate-additive body article is machined.

Preferably, the step S1 specifically includes:

step S11: selecting a corresponding dimension specification of the base material according to the structure of the part to be processed, and determining the processing allowance H on the base material;

step S12: determining the projection size X of the additive body according to the characteristics, the shape and the size of the additive body of the part;

step S13: and removing the substrate material with the thickness H locally or on the whole plane outside the determined substrate position and projection size X range, and enabling H to be less than H to form a boss structure with the cross section size of X X H.

Preferably, in step S12, the projection dimension X includes the width of the part itself, the additive body machining allowance, and the base material-additive body transition fillet radius.

Preferably, the step S2 specifically includes:

step S21: designing the outline structure of the additive body on the base material according to the determined dimension and outline of the additive body of the part, and designing a transition area between the base material and the additive body into a fillet transition structure;

step S22: designing a three-dimensional digital model of the additive body, guiding the three-dimensional digital model of the additive body into a slicing software slice, compiling an additive manufacturing program, guiding the additive manufacturing program into laser coaxial powder feeding additive manufacturing equipment, and carrying out additive manufacturing.

Preferably, in step S22, when designing the additive volume three-dimensional digital-analog, the three-dimensional software used is CATIA.

Preferably, in step S12, the part is a rolled plate or forging.

The invention has the beneficial effects that:

1. according to the invention, a boss structure without constraint on the periphery is constructed on the base material corresponding to the additive manufacturing area, so that the extrusion and stretching effects of peripheral materials on the surface of the base material in the laser scanning thermal expansion and cooling shrinkage processes are reduced, meanwhile, the transition area between the bottom of the additive body and the interface of the base material is changed from a right angle to a fillet transition structure, the stress concentration of the base material-additive body transition area is reduced, the residual stress of the interface is further reduced, and the residual stress of the base material-additive body interface in the laser additive manufacturing process can be greatly reduced through the synergistic effect of the boss structure and the fillet transition structure, so that the deformation and cracking tendency of a workpiece is reduced.

2. Based on the method, the manufacturing thickness of the additive body in the traditional additive manufacturing composite component is improved, so that the volume ratio of the traditional manufactured plate and the traditional manufactured forging is reduced, and the material utilization rate is improved; in the post-treatment process of the workpiece, because the residual stress level is reduced, the time required for eliminating the residual stress annealing can be reduced, and the energy is saved; meanwhile, the deformation control scheme of subsequent machining can be simplified, and the production efficiency is improved; still can save equipment repacking expense, to the coaxial powder feeding vibration material disk equipment that does not possess the substrate heating function, can reach the similar reduction interfacial stress effect of heating the substrate through adopting the transition structure that this boss and fillet combine.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.

FIG. 1 is a schematic representation of a substrate-additive body structure in accordance with the present invention;

FIG. 2 is a schematic illustration of the present invention in determining the machining allowance H;

FIG. 3 is a schematic representation of the present invention in determining additive body projection dimension X;

FIG. 4 is a schematic view of the present invention when designing a machined boss structure;

FIG. 5 is a schematic view of the present invention as it is being additively manufactured;

FIG. 6 is a diagram illustrating a dimensional correspondence in an exemplary embodiment of the invention;

FIG. 7 is a schematic diagram of a sample structure for residual stress testing using different substrate-additive body structure test pieces.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

Example 1

As shown in fig. 1-6, the present embodiment provides a method for reducing the residual stress at the interface of a substrate and an additive body, comprising the following steps:

step S1: in the preparation stage of the base material, the base material at the periphery of the interface of the base material and the additive body is removed, and a boss structure is formed on the interface;

step S2: growing the additive body on the boss structure, designing a transition area between the bottom of the additive body and the interface of the base material into a fillet transition structure, and then performing additive manufacturing;

step S3: the substrate-additive body article is machined.

In this embodiment, through establish an unconstrained boss structure around on the substrate that the vibration material disk region corresponds, thereby reduce the substrate surface and be heated the expansion in laser scanning, the extrusion of cooling shrink in-process peripheral material, tensile effect, change the transition region at vibration material disk bottom and substrate interface into fillet transition structure from the right angle simultaneously, reduce the stress concentration of substrate-vibration material disk transition region, further reduce the residual stress at interface, through boss structure and fillet transition structure's synergism, can reduce the residual stress at laser vibration material disk process substrate-vibration material disk interface greatly, thereby reduce the deformation of finished piece, the fracture trend.

Specifically, the step S1 specifically includes:

step S11: selecting a corresponding dimension specification of the base material according to the structure of the part to be processed, and determining the processing allowance H on the base material;

step S12: determining the projection size X of the additive body according to the characteristics, the shape and the size of the additive body of the part;

step S13: and removing the substrate material with the thickness H locally or on the whole plane outside the determined substrate position and projection size X range, and enabling H to be less than H to form a boss structure with the cross section size of X X H.

Specifically, in step S12, the projection dimension X includes the width of the part itself, the additive machining allowance, and the base material-additive transition fillet radius.

By specifically providing a design scheme of the boss structure, the manufactured boss structure is more standardized, scientific and efficient, has certain guiding significance, and lays a core foundation for subsequently reducing the residual stress of the substrate-additive interface.

Specifically, the step S2 specifically includes:

step S21: designing the outline structure of the additive body on the base material according to the determined dimension and outline of the additive body of the part, and designing a transition area between the base material and the additive body into a fillet transition structure;

step S22: designing a three-dimensional digital model of the additive body, guiding the three-dimensional digital model of the additive body into a slicing software slice, compiling an additive manufacturing program, guiding the additive manufacturing program into laser coaxial powder feeding additive manufacturing equipment, and carrying out additive manufacturing.

The additive manufacturing is carried out through the designed additive body three-dimensional digital analogy, the manufacturing process is more standardized, and the high-precision process requirement can be ensured.

Specifically, in step S22, when designing the three-dimensional numerical model of the additive body, the three-dimensional software adopted is CATIA, which is convenient and fast to operate and improves efficiency.

Specifically, in step S12, the part is a rolled plate or forging.

It should be noted that, the present invention can be combined with the invention patent with application number "CN 202010238130.4" to "a repair path optimization method based on in-situ stress relief model", which can greatly reduce the residual stress of the interface, and its economic benefit is reflected in:

(1) the manufacturing thickness of the additive body in the traditional additive manufacturing composite component is improved, so that the volume ratio of the traditional manufactured plate and the traditional manufactured forged piece is reduced, and the material utilization rate is improved;

(2) in the post-treatment process of the workpiece, because the residual stress level is reduced, the time required for eliminating the residual stress annealing can be reduced, and the energy is saved;

(3) the deformation control scheme of subsequent machining can be simplified, and the production efficiency is improved;

(4) the equipment refitting cost can be saved, and the transition structure combining the boss and the fillet can achieve the effect of reducing the interface stress similar to that of heating the base material for the laser coaxial powder feeding additive manufacturing equipment without the base material heating function.

Example 2

As shown in fig. 1-6, this example is based on the specific example of example 1, and provides a method for reducing the residual stress at the interface between the substrate and the additive body, comprising the following steps:

step 1: designing a main stress part of the part in a forge piece or plate area, selecting the specification and the size of a rolled plate and a forge piece base material according to the main structure of the part, and determining the machining allowance H on the base material to be 10 mm;

step 2: the part lug is processed by adopting an additive body, the lug width A is 50mm, the processing allowance W of the side surface of the additive body is 6mm, the transition fillet radius R of the base material-additive body is 5mm, and the projection size X of the additive body is 5mm +6mm +50mm +6mm +5mm is 72 mm;

and step 3: outside the central line of the lug +/-36 mm, removing base material with the thickness h of 5mm on the whole plane to ensure the sufficient ultrasonic flaw detection allowance and the machinability of the part and form a boss structure with the cross section size of 72 x 5 mm;

and 4, step 4: and designing a three-dimensional digital-analog of the additive body on the substrate in the CATIA, and designing the transition part of the substrate and the additive body into a 5mm round corner structure. Guiding the designed three-dimensional digital analogy of the additive body into a slicing software slice, and programming an additive manufacturing program to be guided into laser coaxial powder feeding additive manufacturing equipment to finish additive manufacturing;

and 5: and machining the workpiece.

Testing and detecting:

the titanium alloy forging TC4 is used as a base material, the laser scanning power of the additive body is 1.6KW, the diameter of a light spot and the scanning speed are respectively 6mm +800mm/min and 3mm +1100mm/min, the base material-additive body interface is respectively in right-angle transition, boss transition and fillet transition structure, the solid structure of a test sample with the three transition structures is respectively shown as A, B, C in figure 7, the solid structure of the test sample with the boss + fillet transition structure is shown as D in figure 7, the residual stress of the base material-additive body interface of the corresponding transition structure is measured by an X-ray method, and the test result is shown as the following table 1:

table 1 table of interface residual stress test results

As can be seen from table 1, under the same conditions of the substrate, the profile of the additive body, the pretreatment and the post-treatment of the workpiece, the residual stress of the interface can be significantly reduced under different laser scanning parameters by adopting the substrate-additive body interface boss transition structure; as shown in fig. 7, by combining the boss and fillet transition structure, the residual stress of the interface can be greatly reduced, thereby reducing the deformation and cracking tendency of the product and obviously reducing the defects of the produced product.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention, and they should be construed as being included in the following claims and description.