A heat treatment method for a fan ring metal piece

Abstract

The application belongs to the field of metal processing, and particularly relates to a heat treatment method of a fan ring metal piece, which comprises the following steps: providing a plurality of blanks, the blank being a closed ring, the blank comprising a plurality of workpieces and connecting ribs for fixedly connecting adjacent workpieces, and the profile of the workpiece being a fan ring; performing heat treatment on the blank; and cutting all the connecting ribs to obtain a plurality of independent workpieces. The application has the effect of heat treating non-complete ring workpieces without deformation.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of metal processing, in particular to a heat treatment method of a sector ring metal piece. BACKGROUND

[0002] In the metal processing industry, heat treatment technology is a basic and critical process, widely used to improve the mechanical properties of metal materials, such as hardness, strength, toughness and wear resistance. By heating, holding and timely cooling of metal materials, heat treatment process can control the microstructure of metal, so as to achieve the purpose of improving the performance.

[0003] Common heat treatment methods include annealing, normalizing, quenching and tempering, etc. Each method is suitable for different industrial needs and material properties according to its specific temperature control and cooling rate, so as to ensure that the metal parts can achieve the best performance in practical application.

[0004] However, although heat treatment has achieved remarkable results in the manufacture of whole ring metal pieces, it effectively controls the mechanical properties and dimensional stability of finished products by whole heating and uniform cooling. However, in the heat treatment process of half ring or sector ring metal pieces, due to the opening in the structure of these parts, the lack of sufficient geometric constraints often leads to an unacceptable deformation problem after heat treatment. Specifically, due to the free edge at the gap that cannot be effectively constrained, the uneven shrinkage and expansion of the material during cooling and heating exacerbates the deformation of the part, which not only affects the dimensional accuracy of the part, but also reduces its application reliability and performance. Therefore, there is an urgent need for a process that can heat treat non-complete ring workpieces without deformation. SUMMARY

[0005] In order to solve the above problems and make the non-complete ring retain its original shape after heat treatment, in a first aspect, the present application provides a heat treatment method of a sector ring metal piece.

[0006] The heat treatment method of a sector ring metal piece provided by the present application adopts the following technical scheme:

[0007] A heat treatment method of a sector ring metal piece, comprising the following steps:

[0008] providing a plurality of blanks, the blank being a closed ring, the blank comprising a plurality of workpieces and connecting ribs for fixedly connecting adjacent workpieces, the profile of the workpiece being a sector ring, heat treating the blank; and cutting all the connecting ribs to obtain a plurality of independent workpieces.

[0009] By adopting the technical scheme, the loss of constraint at the opening of the two ends of the workpiece is compensated, the stress conditions of the two ends and the middle section of the workpiece are similar, the stability of the entire blank during the heat treatment process is significantly enhanced, and the deformation caused by the heat treatment is effectively prevented, especially in high-temperature operation, the design of the closed ring helps to uniformly distribute the thermal stress, and the product after heat treatment has higher dimensional accuracy and structural consistency.

[0010] Optionally, the step of providing a plurality of blanks comprises: providing a plurality of workpieces and connecting ribs, and alternately arranging the workpieces and the connecting ribs into a ring shape; welding adjacent workpieces and connecting ribs, so that the two ends of each workpiece are connected to two connecting ribs, and the two ends of each connecting rib are connected to two workpieces; the heat source for welding moves along the circumferential direction of the ring, and the length of the molten pool on both sides of the weld is greater than or equal to twice the width of the weld.

[0011] By adopting the technical scheme, the metal liquid in the molten pool has a direction-determined temperature gradient under the influence of the movement of the heat source, and the liquid metal has the largest growth driving force in the direction of the temperature gradient, so that the long-axis crystal with the same direction as the reinforcing rib is preferentially grown in the molten pool.

[0012] Optionally, the material of the blank is FN0208 steel, and the step of heat treating the blank comprises: quenching the blank, the quenching temperature range is 850-870℃, the heating time is 55 minutes, and the cooling time is 5 minutes; and tempering the blank, the tempering temperature is 180℃, and the tempering time range is 90-120 minutes.

[0013] By adopting the technical scheme, a small amount of elements doped in the blank can have the effects of solid solution strengthening and second phase strengthening on the workpiece, and the performance of the workpiece is enhanced. Precise control of the heat treatment conditions ensures that the metal material reaches the expected hardness, toughness and wear resistance. Specifically, quenching enhances the hardness of the workpiece, and tempering reduces unnecessary internal stress and increases the service life of the product.

[0014] Optionally, the workpiece is a semicircular ring, and the workpiece and the connecting rib are integrally formed.

[0015] By adopting the technical scheme, integrally forming increases the production efficiency of the blank, especially in the production process of small blanks, a plurality of workpieces can be formed in one pressing.

[0016] Optionally, in the step of cutting all the connecting ribs to obtain a plurality of independent workpieces, the cutting method is gas cutting or die stamping.

[0017] By adopting the technical scheme, the gas cutting removes the connecting rib while keeping the cutting surface neat and accurate, which is helpful for subsequent processing and assembly; and the stamping whole cutting keeps high productivity in batch production with low surface accuracy requirement.

[0018] Optionally, the step of providing the plurality of blanks comprises: making a mold according to a process design drawing; putting metal powder into the mold and pressurizing to obtain a green compact; and sintering the green compact to obtain the blank.

[0019] By adopting the technical scheme, the connecting rib in the green compact is integrally formed with the workpiece, and the connection is more firm.

[0020] Optionally, the step of sintering the green compact to obtain the blank comprises: applying heat to the green compact along the circumference of the closed ring to gradually sinter and form along the circumference.

[0021] By adopting the technical scheme, the crystal phase structure in the green compact is a long axis crystal extending along the circumference of the closed ring, which makes the connecting rib and the workpiece more difficult to separate.

[0022] Optionally, an end point of the heat application is set at a point in the connecting rib.

[0023] By adopting the technical scheme, impurity elements enriched before sintering and forming are deposited in the connecting rib and removed in subsequent processes, so as not to affect the quality of the workpiece.

[0024] Optionally, at any time, the central angle of the closed ring corresponding to the green compact reaching the sintering temperature is less than or equal to 90°.

[0025] By adopting the technical scheme, the green compact has a more obvious temperature gradient along its circumference during the forming process, so that the long axis crystal is more stable during forming.

[0026] In a second aspect, the application provides a heat treatment method of a fan ring metal piece.

[0027] The metal finished piece provided by the application adopts the following technical scheme:

[0028] A heat treatment method of a metal finished piece is made after the heat treatment method of the fan ring metal piece.

[0029] By adopting the technical scheme, a metal finished piece with higher dimensional accuracy is provided.

[0030] In summary, the application includes at least one of the following beneficial technical effects:

[0031] 1. By arranging connecting ribs between multiple fan-shaped metal workpieces and joining them into a closed ring structure, the technical solution provided by the present application significantly improves the stability and deformation resistance of the non-complete ring during heat treatment. The connecting ribs serve as fixed links between the workpieces, not only physically connecting the individual workpieces into a whole, but also playing a restraining role during heat treatment, limiting uneven deformation caused by thermal expansion and contraction. In addition, the closed ring geometry further enhances the overall rigidity and symmetry, effectively dispersing various residual stresses and reducing the risk of deformation caused by local overheating or uneven cooling. Therefore, not only is the effectiveness of heat treatment optimized, but also the accuracy and performance of the finished product are improved.

[0032] 2. Using a sintering method that gradually applies heat along the circumference of the closed ring, the heat distribution during sintering can be uniformly controlled, allowing the metal powder of the green body to preferentially grow along the circumference under the guidance of the heat gradient after melting and sintering. The final product has higher structural strength in the circumferential direction. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a flowchart of embodiment 1 of the present application;

[0034] Figure 2 is a general structure diagram of the green body of embodiment 1 of the present application;

[0035] Figure 3 is a top view of the green body of embodiment 1 of the present application;

[0036] Figure 4 is a cross-sectional view along Figure 3 line A-A in FIG. 1;

[0037] Figure 5 is a cross-sectional view along Figure 3 line B-B in FIG. 1.

[0038] REFERENCE SIGNS: 1, workpiece; 2, connecting rib. DETAILED DESCRIPTION

[0039] The present application will be further described in detail below in conjunction with the accompanying drawings. Figures 1-5

[0040] In the metal processing industry, heat treatment technology is an important link in improving the performance of metal products. According to the phase change curve of the metal material itself, it is heated to a certain temperature and maintained for a proper time, and then cooled in different ways to change its microstructure and physical and chemical properties.

[0041] ​Common heat treatment methods include annealing, normalizing, quenching, and tempering. Among them, annealing is to reduce hardness and eliminate internal stress by slow cooling after heating, so that the material is easier to process or prepare for other heat treatment processes. Normalizing is to cool in air after heating to a suitable temperature, aiming to refine grains, homogenize structure and improve mechanical properties. Quenching involves rapidly cooling the metal after heating to a higher temperature to enhance hardness and strength, but usually needs to be combined with tempering to reduce the brittleness caused by quenching. The tempering process is to reheat to a temperature below the critical point after quenching, and then cool down, in order to enhance toughness, reduce brittleness and stabilize size. Each heat treatment method has its specific temperature control and cooling rate to meet the needs of different industrial applications and adapt to different material properties, so as to ensure that the metal parts can achieve the best performance in actual application.

[0042] However, during the heating and cooling of the metal, it is difficult to uniformly heat the entire workpiece unless it is a thin-walled part. Generally, when the surface of the workpiece has cooled to the non-plastic deformation stage, the interior is still in the plastic deformation state, and when the interior of the workpiece undergoes non-plastic deformation, the surface of the workpiece has been completely defined. Therefore, residual thermal stress is generated in the interior of the workpiece, causing the size of the workpiece to deviate from the design standard. In standard parts with regular shapes, this overall shrinkage can be solved by means such as pre-quantity and secondary annealing, but in the production of non-closed ring-shaped workpieces, this deformation is due to the loss of constraint at the open ring, and the deformation is not simply a size shrinkage, but also a complex twist. Therefore, the size parameter control of non-closed ring-shaped workpieces such as water power dynamometers is a problem that needs to be solved in this technical field.

[0043] The embodiments of the present application disclose a heat treatment method of a fan ring metal piece.

[0044] Embodiment 1

[0045] Reference Figure 1 The heat treatment method of the fan ring metal piece comprises the following steps:

[0046] B1, reference Figure 2 , Figure 3 , a plurality of blanks are provided, the blank comprises a plurality of workpieces 1 and connecting ribs 2 for fixedly connecting adjacent workpieces 1, the profile of the workpiece 1 is a fan ring, and all the workpieces 1 and the connecting ribs 2 are spliced into a closed ring.

[0047] Please refer to Figure 4 , Figure 5 , for example, the blank comprises two connecting ribs 2 and two workpieces 1, each workpiece 1 is a semicircular ring, and the two semicircular rings are oppositely arranged, and the connecting line of the centers of the two semicircular rings is parallel to the axis of the connecting rib 2.

[0048] Specifically, step B1 comprises:

[0049] The workpiece 1 is obtained by powder metallurgy or casting, forging, additive manufacturing, and the shape of the workpiece 1 is a semicircular ring;

[0050] The connecting ribs 2 are provided, and the workpieces 1 and the connecting ribs 2 are alternately arranged into a ring shape;

[0051] The adjacent workpieces 1 and the connecting ribs 2 are connected, so that two connecting ribs 2 are connected at two ends of each workpiece 1, and two workpieces 1 are connected at two ends of each connecting rib 2.

[0052] Preferably, the connection mode is welding, the heat source used for welding moves along the circumferential direction of the ring formed by the alternately arranged workpieces 1 and connecting ribs 2, and the length of the molten pool on both sides of the weld is greater than twice the width of the weld.

[0053] It should be noted that when the heat source moves along the circumferential direction across the weld, the size difference between the reinforcing rib and the workpiece 1 needs to be controlled within a certain range. If the production conditions cannot be met, the above-mentioned movement along the circumferential direction can be modified to movement perpendicular to the weld along the surface of the blank.

[0054] Optionally, the material of the workpiece 1 is FN0208 steel, wherein the mass percentage of iron is 91.6%-98.4%, the mass percentage of nickel is 1.0%-3.0%, the mass percentage of carbon is 0.6%-0.9%, and the mass percentage of copper is 0.0%-2.5%.

[0055] It should be noted that the present application only selects two semicircular ring workpieces 1 as an example. In fact, more sector ring workpieces 1 whose sum of central angles is less than or equal to 360° can also achieve the technical effects of the present embodiment.

[0056] Alternatively, the blank provided in step B1 is integrally formed, and the workpiece 1 and the connecting rib 2 are directly obtained by powder metallurgy or casting, forging, additive manufacturing to form an integral closed ring.

[0057] B2, heat treating the blank.

[0058] The heat treatment can be one or more of normalizing, tempering, quenching, and annealing. For example, the heat treatment includes quenching and tempering processes.

[0059] Specifically, step B2 comprises:

[0060] First, quenching the blank, the quenching temperature is 850-870℃, the heating time is 55 minutes, and the cooling time is 5 minutes;

[0061] Then, tempering the blank, the tempering temperature is 180℃, and the tempering time is 90-120 minutes.

[0062] B3, cutting all the connecting ribs 2 to obtain a plurality of independent workpieces 1.

[0063] For example, the cutting position is at the joint of the connecting rib 2 and the workpiece 1, and the cutting position should be a certain distance away from the joint of the workpiece 1 and the connecting rib 2 considering the loss in the cutting process.

[0064] Optionally, the cutting method is gas cutting, and an example is oxyacetylene cutting.

[0065] Alternatively, the connecting rib 2 and the workpiece 1 are integrally cut by a die, and a gas gun is used to clean the connecting rib 2 and other impurities to improve product quality; if there is an appearance requirement or the joint has assembly sliding, etc., the fracture is polished.

[0066] The implementation principle of embodiment 1 is as follows:

[0067] As described above, for a non-closed ring workpiece 1, when it expands or shrinks due to thermal stress caused by heat treatment, because its two ends are not constrained, the stress state is quite different from that of the middle section, which will cause the deformation of the two ends of the workpiece 1 to be out of sync with that of the middle section during the heat treatment process, and the final shaped workpiece 1 is not in the same proportion as the shape before heat treatment, which is difficult to correct in actual production.

[0068] In this embodiment, the non-closed ring workpiece 1 is spliced into a whole closed ring, so that when the workpiece 1 deforms during heat treatment, the two ends of the workpiece 1 are restricted by the opposite workpiece 1, and the stress state of the two ends of the workpiece 1 is the same as that of the middle section of the workpiece 1. Therefore, the whole workpiece 1 expands and shrinks synchronously, and the shape and size change little. Moreover, even if there is a size change that cannot be ignored, the final size parameter change can be predicted, so as to in turn adjust the blanking amount and size of the blank in advance.

[0069] In addition, for the convenience of illustration, the workpiece 1 is provided as a semicircular ring, and the axis of the connecting rib 2 is a straight line. In a further preferred embodiment, the workpiece 1 is a fan ring, and the sum of the central angles of the fan ring is less than 360°. The connecting rib 2 is also provided as a fan ring, and the blank formed by splicing all the connecting ribs 2 and the workpiece 1 is a circular ring, so that the stress condition is more uniform, and after heat treatment and as much as possible to eliminate internal stress, it can be approximately regarded as not deformed.

[0070] In the preferred embodiment, the moving direction of the welding heat source controls the microstructure of the metal in the molten pool. The material of the blank in this embodiment is FN0208 steel, in which the main microstructure is similar to that of pure iron, and the small amount of other elements play the role of strengthening performance through solid solution strengthening or second phase strengthening. Under the guidance of the moving heat source, the liquid metal in the molten pool has a directionally determined temperature gradient, and the liquid metal has the maximum growth driving force in the direction of the temperature gradient, so that the long axis crystal which is unified with the direction of the reinforcing rib is preferentially grown in the molten pool, so that the blank has strong physical properties in the circumferential direction, avoiding the loss of constraint caused by the breakage of the welding point.

[0071] Embodiment 2

[0072] The difference between this embodiment and embodiment 1 is that:

[0073] Step B1 includes:

[0074] According to the process design drawing, a mold is made; metal powder is placed in the mold and pressure is applied to obtain a green body; and the green body is sintered to obtain a blank.

[0075] Specifically, the process of sintering the green body to obtain the blank includes: applying heat to the green body along the circumferential direction of the closed ring formed by the workpiece 1 and the connecting rib 2, so that the green body is gradually sintered along the circumferential direction.

[0076] Preferably, the starting point and the ending point of the sintering heat application are located in one of the connecting ribs 2.

[0077] Preferably, at any time, the volume of the green body that reaches the sintering temperature accounts for less than or equal to one fourth of the total volume of the green body.

[0078] The implementation principle of embodiment 2 is:

[0079] In this embodiment, during the forming of the workpiece 1 and the connecting rib 2, they are already an integral structure, and the microstructure from the inside to the outside is the long axis crystal distributed along the circumferential direction. The forming principle of the long axis crystal is referred to embodiment 1, the difference is that embodiment 1 connects the workpiece 1 and the connecting rib 2 by welding after the workpiece 1 is formed, and the long axis crystal only exists in the surface area of the blank covered by the molten pool; this embodiment is the long axis crystal extending in the circumferential direction from the inside to the outside, which makes the entire green body have stronger physical properties in the circumferential direction, especially the tensile strength, and during the entire heat treatment process, the connecting rib 2 can realize its function with a smaller volume ratio and a more slender size.

[0080] In addition, during the movement of the heat source, the main structure of the metal forming is the long axis crystal formed by iron element and solid solution element, some elements exceeding the solid solution limit and the second phase are enriched at the grain boundary of the long axis crystal, most of which are fixed in the following forming process, and some are continuously pushed to the front of the forming and finally stay in the front of the forming terminal. The concentration of some elements in the workpiece 1 caused by this enrichment can be compensated by targeted doping during batching, but the enrichment at the final forming front is difficult to eliminate. In the embodiment, the start and end of the sintering heat are located in one of the connecting ribs 2, so the enrichment is eliminated with the removal of the connecting rib 2 and does not affect the quality of the workpiece 1.

[0081] And the proportion of the volume of the green body reaching the sintering temperature at any time to the total volume of the green body is less than or equal to one fourth, which can ensure a more definite temperature gradient in the circumference of the green body, making the generation of long axis crystal more stable.

[0082] The above are preferred embodiments of the present application, which do not limit the protection scope of the present application, therefore: any equivalent changes made on the structure, shape, principle of the present application should be covered within the protection scope of the present application.

Claims

1. A heat treatment method for a fan-shaped metal part, characterized in that, Includes the following steps: Multiple blanks are provided, each blank being a closed ring. Each blank includes multiple workpieces (1) and connecting ribs (2) that fix adjacent workpieces (1) together. The outline of each workpiece (1) is a fan ring. The steps of providing multiple blanks include: Molds are made according to the process design drawings; Metal powder is placed inside the mold and pressure is applied to obtain a preform. Heat is applied to the blank along the circumference of the closed ring, causing it to be sintered and formed gradually along the circumference. The endpoint of the heat application is set at a point within the connecting rib (2); The billet is heat-treated, and All the connecting ribs (2) are cut off to obtain multiple independent workpieces (1).

2. The heat treatment method for the fan-shaped metal part according to claim 1, characterized in that, The material of the provided billet is FN0208 steel.

3. The heat treatment method for the fan-shaped metal part according to claim 1, characterized in that, The steps of heat treating the billet include: The blank is subjected to quenching treatment at a temperature range of 850℃-870℃ for 55 minutes and a cooling time of 5 minutes. The blank is subjected to tempering treatment at a temperature of 180°C for a duration of 90-120 minutes.

4. The heat treatment method for the fan-shaped metal part according to claim 1, characterized in that, The workpiece (1) is a semi-circular ring, and the workpiece (1) and the connecting rib (2) are integrally sintered.

5. The heat treatment method for the fan-shaped metal part according to claim 1, characterized in that, In the step of cutting all the connecting ribs (2) to obtain multiple independent workpieces (1), the cutting method is gas cutting or die stamping.

6. The heat treatment method for the fan-shaped metal part according to claim 1, characterized in that, At any given moment, the central angle of the closed ring corresponding to the preform that has reached the sintering temperature is less than or equal to 90°.

7. A finished metal part, characterized in that, It is manufactured by heat treatment of the fan ring metal part as described in any one of claims 1-6.

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