Groove pin and quenching method thereof

Abstract

The invention relates to the field of textile equipment, in particular to a groove pin and a quenching method thereof.The method comprises the following steps that (S.1) the groove pin is heated to the critical temperature or above, so that the groove pin is wholly or partially austenitized; (S.2) providing an asymmetric temperature field, wherein the asymmetric temperature field has a preset temperature difference; and (S.3) the heated groove pin is placed in the temperature field and makes contact with the temperature field, so that the two sides of the groove pin are rapidly cooled under the condition of different cooling rates, and martensite transformation and quenching are completed. Through active regulation and control of an asymmetric cooling field, thermal stress and structural stress in the quenching process are remarkably inhibited, the deformation amount of the groove pin is extremely controlled, the high-precision geometric dimension of the groove pin is effectively guaranteed, synchronous cooling and phase change of different parts of the groove pin are achieved on the basis of the temperature difference compensation principle in the City, and the service life of the groove pin is prolonged. And the uniformity of hardness distribution and the compactness of a microscopic structure are greatly improved, so that the wear resistance is enhanced, and the overall service life is prolonged.

Description

Technical Field

[0001] This invention relates to the field of textile equipment, and more particularly to a grooved needle and its quenching method. Background Technology

[0002] In the field of textile machinery manufacturing, the grooved needle, as a critical and highly precise specialized component, directly impacts the operating efficiency and product quality of textile equipment. The grooved needle is characterized by its unique flat geometry and extremely thin cross-sectional thickness, while one side in the thickness direction typically requires the machining of an extremely fine groove structure. This design results in extremely thin walls in the groove area, significantly reducing the overall structural rigidity of the component. To meet the stringent requirements for wear resistance and fatigue strength in high-speed textile operations, the grooved needle must undergo quenching treatment to obtain a high-hardness martensitic structure. However, it is precisely these special structural and performance requirements that have presented a long-standing and unresolved challenge to the heat treatment process of the grooved needle.

[0003] The conventional quenching method commonly used in the industry involves directly immersing the austenitized heating pin into quenching oil for cooling. This method has revealed two significant technical drawbacks in practice. First, the pin experiences a violent impact from the liquid medium upon immersion, making it highly susceptible to plastic deformation such as bending or twisting due to its delicate structure and insufficient rigidity. Second, because different parts of the pin do not contact the cooling medium simultaneously, a significant time difference exists. This asynchronous cooling leads to asynchronous phase transformations in different areas of the part, resulting in uneven stress distribution and varying degrees of martensitic transformation, ultimately manifesting as uneven hardness distribution and residual stress concentration. Even with subsequent corrective treatment, this not only increases production costs but may also cause internal damage.

[0004] To address the shortcomings of oil quenching, some advanced processes have attempted to employ clamping cooling devices, utilizing symmetrically arranged cooling blocks for contact cooling of the workpiece. While this method mitigates mechanical deformation caused by media impact to some extent and provides mechanical constraint through clamping, it does not fundamentally solve the core problem. Due to the inherent structural asymmetry of the grooved pin—one side has a groove while the other is a solid structure—even if the temperature and cooling capacity of the cooling blocks on both sides are identical, differences in mass distribution and heat dissipation conditions will lead to different cooling rates on the grooved side and the solid side. This uneven cooling phenomenon caused by structural asymmetry still creates uneven thermal and structural stresses within the workpiece, resulting in uncontrollable micro-deformation and performance fluctuations. In particular, the root region of the groove is prone to performance degradation due to stress concentration. Currently, no fundamental solution has been found to effectively reconcile this contradiction between structural asymmetry and the heat treatment process, which has become a technical bottleneck restricting the improvement of quality and production yield of high-end grooved pin products.

[0005] Therefore, the textile machinery manufacturing industry urgently needs an innovative quenching method that can effectively suppress heat treatment deformation and ensure uniform microstructure properties while ensuring high hardness and wear resistance of the grooved needles. In particular, it needs to address the problem of uneven cooling caused by the special structure of the needle grooves. This would allow the method to meet the stringent requirements of precision parts while simultaneously meeting the efficiency and economic needs of industrial production. Summary of the Invention

[0006] The present invention aims to overcome the problems of easy deformation and uneven hardness distribution of grooved needles in the existing quenching methods, and thus provides a grooved needle and its quenching method to overcome the above-mentioned shortcomings.

[0007] To achieve the above-mentioned objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides a quenching method for grooved needles, comprising the following steps: (S.1) Heat the slotted needle to above the critical temperature to make it all or part austenitized; (S.2) Provide an asymmetric temperature field, the asymmetric temperature field having a preset temperature difference; (S.3) The heated grooved needle is placed in the temperature field and brought into contact with it, so that the two sides of the grooved needle are cooled rapidly under different cooling rates, thereby completing the martensitic transformation and quenching.

[0008] As described in the background section, in the field of textile machinery, the deformation control of grooved needles, as extremely precise flat, thin-walled components, during heat treatment has always been a challenging problem. Traditionally, when using oil quenching, the grooved needles face a double challenge the moment they are immersed in the quenching oil: on the one hand, the intense impact of the liquid flow easily causes the thin needle body, lacking rigidity, to bend or twist; on the other hand, because different parts of the needle body are not cooled synchronously, the area that first comes into contact with the oil will undergo martensitic transformation first. This asynchronous phase transformation process generates uneven structural stress within the workpiece, ultimately leading to uneven hardness distribution and difficulty in meeting shape accuracy requirements. Although a clamping quenching technique using symmetrical cooling blocks later emerged, which suppressed deformation caused by mechanical impact to some extent through physical constraints, this method ignores a fundamental problem: the grooved needle itself has an inherent structural asymmetry due to the grooves on one side. This geometric asymmetry means that even under perfectly symmetrical cooling conditions, the actual heat dissipation rate and phase change behavior of the groove side and the solid side will differ. The internal stress caused by uneven cooling will still cause the part to warp slightly towards the solid side. For precision groove pins that require extremely high flatness, this slight deformation is still unacceptable.

[0009] This application recognizes that the root cause of the aforementioned technical bottleneck lies in the inherent contradiction between "structural asymmetry" and "traditional cooling symmetry." Therefore, it abandons the traditional thinking framework of pursuing idealized uniform cooling and proposes a new solution: instead of trying to eliminate the non-uniformity of cooling, it actively utilizes a controlled non-uniformity to counteract another inherent non-uniformity.

[0010] Therefore, the core of this application lies in the "asymmetric temperature field" created in steps (S.2) and (S.3). Unlike existing technologies that aim for uniform cooling medium temperatures on both sides, this application intentionally creates a preset temperature difference in the cooling environment on both sides of the slotted needle. This temperature difference is set based on the structural characteristics of the slotted needle. Due to the small mass and large specific surface area of ​​the slotted needle's groove side, its cooling rate is naturally faster than that of the solid side under the same cooling conditions. Therefore, by setting a cooling source with a temperature difference, a precise thermal compensation mechanism is formed. From the perspective of the entire slotted needle, the cooling rates of both the groove and the solid part are slightly lower than those under a symmetrical temperature field. Therefore, under an asymmetric temperature field, the difference in cooling rates between the groove and the solid part also decreases relatively, allowing the cooling process on the groove side to match the cooling process on the solid side. This offsets the natural cooling differences caused by structural asymmetry, promoting the martensitic phase transformation on both sides of the slotted needle to occur as synchronously as possible.

[0011] The reverse-thinking approach presented in this application yields unexpected technical results. The most significant improvement lies in the extreme control over quenching deformation. Because the phase transformation process becomes more synchronized, the tensile stress generated within the workpiece due to asynchronous phase transformation is effectively balanced, significantly reducing the internal driving force that causes warping (especially on the groove side). Combined with the mechanical stabilizing effect of contact cooling, the quenching deformation of the grooved pin is significantly reduced, enabling it to achieve extremely high shape accuracy immediately after quenching, reducing or even eliminating the need for subsequent tedious correction processes. Simultaneously, the uniformity of hardness is also greatly improved. The entire grooved pin, from the solid part to the thin-walled part with the groove, undergoes a more coordinated cooling process, resulting in more uniform hardness and a finer martensitic structure from the core to the surface. This not only directly improves the product's wear resistance but also extends its service life due to its uniform mechanical properties. Most importantly, the method in this application also optimizes the residual stress distribution inside the workpiece, especially in areas with geometric abrupt changes such as the root of the needle groove where stress concentration is prone to occur. Harmful tensile stress is effectively suppressed, which is crucial for preventing the generation of quenching microcracks and improving the fatigue strength of the parts.

[0012] Therefore, in summary, the slotted needle quenching method in this application, for the first time, successfully transforms the unfavorable factor of workpiece structural asymmetry into a controllable variable that can be compensated for by process parameters by actively introducing a controllable asymmetric temperature field. This core idea of ​​"using asymmetry to cure asymmetry" solves the long-standing technical problem of quenching deformation in precision asymmetric parts, while also effectively improving deformation control, performance uniformity, and stress state optimization.

[0013] Preferably, in step (S.1), the slotted pin is heated to a temperature above Ac1 or Ac3 and held at that temperature to austenitize it.

[0014] Preferably, a gradient heating method is used to heat the groove needle to 30°C-50°C above Ac1 or Ac3.

[0015] Preferably, the gradient heating includes keeping the groove needle in the temperature ranges of 600℃-630℃, 680℃-720℃, 720℃-780℃, 780℃-810℃, 800℃-820℃, and 810℃-820℃ for 10-20 seconds respectively.

[0016] Preferably, the asymmetric temperature field in (S.2) is composed of two cooling blocks with different temperatures. During the cooling process, the heated slotted needle is clamped and contacted by the cooling blocks to achieve cooling and quenching of the slotted needle.

[0017] This application employs two cooling blocks with a preset temperature difference to physically clamp the slotted needle. This solution simultaneously addresses two key issues: precise control of heat conduction and suppression of mechanical deformation. The cooling blocks at different temperatures actively create a directional heat flow environment, precisely compensating for the inherent heat dissipation differences caused by the slotted needle's structure, thus promoting synchronized martensitic transformation. The clamping contact not only ensures efficient heat transfer but also provides crucial rigid constraints, directly resisting deformation tendencies caused by thermal stress and phase transformation stress during quenching. This dual mechanism of "thermal management through physical temperature difference" and "morphological stability through mechanical clamping" works synergistically to ensure that the slotted needle achieves high hardness while maintaining extremely high dimensional accuracy.

[0018] Preferably, in step (S.2), the contact time between the slot pin and the cooling block is no more than 10 seconds, and the slot pin is cooled to below 150°C.

[0019] Preferably, the preset temperature difference between the two cooling blocks with different temperatures ranges from 40°C to 70°C.

[0020] Preferably, the cooling block is made of ceramic material.

[0021] Secondly, the present invention also provides a grooved needle, which is obtained by quenching as described above.

[0022] Preferably, the quenching deformation of the grooved needle is less than 0.08 mm, and its overall hardness uniformity deviation does not exceed 40 HV.

[0023] Therefore, this application has the following beneficial effects: (1) By actively controlling the asymmetric cooling field, the thermal stress and structural stress during the quenching process are significantly suppressed, so that the deformation of the groove needle is controlled to the extreme, and its high-precision geometric dimensions are effectively guaranteed. (2) Based on the principle of temperature difference compensation, the synchronous cooling and phase transformation of different parts of the groove needle are realized, which greatly improves the uniformity of hardness distribution and the density of microstructure, thereby enhancing wear resistance and overall service life. (3) The use of contact clamping cooling instead of traditional liquid quenching avoids media impact and improves process stability and reproducibility. At the same time, it helps to reduce subsequent processing steps and reduce production costs. Attached Figure Description

[0024] Figure 1 This is a comparison diagram of the state of the grooved needles obtained after quenching in Example 1 and Comparative Example 1. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0026] Example 1 A quenching method for grooved needles includes the following steps: (S.1) Austenitizing heating: The slotted needle made of 95Cr1 high carbon steel is placed in a controlled atmosphere furnace and subjected to gradient heating. First, it is held at 610℃ for 15 seconds, then at 700℃ for 15 seconds, then at 750℃ for 15 seconds, then at 795℃ for 15 seconds, and finally at 810℃ for 20 seconds to achieve complete austenitization. (S.2) Provide an asymmetric temperature field: Prepare two cooling blocks made of alumina ceramic. Through an independent temperature control system, precisely control the temperature of the first cooling block at 30°C and the temperature of the second cooling block at 70°C, thereby creating a preset temperature difference of 40°C between the two; (S.3) Cooling and quenching: The heated slotted needle is quickly transferred between the two cooling blocks, so that both sides are tightly clamped and in contact with the cooling blocks. The contact and clamping time is 5 seconds. During this process, the slotted needle is rapidly cooled to about 85°C, which is far below its martensitic transformation termination point (Mf), thereby completing the martensitic transformation.

[0027] Example 2 A quenching method for grooved needles includes the following steps: (S.1) Austenitizing heating: The slot needle made of 95Cr1 high carbon steel is placed in a controlled atmosphere furnace and subjected to gradient heating. First, it is held at 630℃ for 18 seconds, then at 720℃ for 18 seconds, then at 780℃ for 18 seconds, then at 810℃ for 18 seconds, and finally at 850℃ for 25 seconds to achieve complete austenitization. (S.2) Provide an asymmetric temperature field: Prepare two cooling blocks made of silicon nitride ceramic. Through an independent temperature control system, precisely control the temperature of the first cooling block at 30°C and the temperature of the second cooling block at 80°C, thereby creating a preset temperature difference of 50°C between the two; (S.3) Cooling and quenching: The heated slotted needle is quickly transferred between the two cooling blocks, ensuring that both sides are tightly clamped and in contact with the cooling blocks. The contact and clamping time is 8 seconds. During this process, the slotted needle is rapidly cooled to approximately 120°C, thereby completing the martensitic transformation.

[0028] Example 3 A quenching method for grooved needles includes the following steps: (S.1) Austenitizing heating: The slotted needle made of 95Cr1 high carbon steel is placed in a controlled atmosphere furnace and subjected to gradient heating. First, it is held at 600℃ for 10 seconds, then at 680℃ for 10 seconds, then at 720℃ for 10 seconds, then at 780℃ for 10 seconds, and finally at 800℃ for 10 seconds, so as to partially austenitize it; (S.2) Provide an asymmetric temperature field: Prepare two cooling blocks made of zirconia ceramic. Using an independent temperature control system, control the temperature of the first cooling block at 20°C and the temperature of the second cooling block (in contact with the needle groove side) at 80°C, thereby creating a preset temperature difference of 60°C between the two; (S.3) Cooling and quenching: The heated slotted needle is quickly transferred between the two cooling blocks, so that both sides are tightly clamped and in contact with the cooling blocks. The contact and clamping time is 10 seconds. During this process, the slotted needle is rapidly cooled to about 100°C, thereby completing the martensitic transformation.

[0029] Example 4 A quenching method for grooved needles includes the following steps: (S.1) Austenitizing heating: The slot needle made of 95Cr1 high carbon steel is placed in a controlled atmosphere furnace and subjected to gradient heating. First, it is held at 600℃ for 20 seconds, then at 680℃ for 20 seconds, then at 720℃ for 20 seconds, then at 780℃ for 20 seconds, and finally at 810℃ for 20 seconds to achieve complete austenitization. (S.2) Provide an asymmetric temperature field: Prepare two cooling blocks made of zirconia ceramic. Using an independent temperature control system, control the temperature of the first cooling block at 20°C and the temperature of the second cooling block (in contact with the needle groove side) at 90°C, thereby creating a preset temperature difference of 70°C between the two; (S.3) Cooling and quenching: The heated slotted needle is quickly transferred between the two cooling blocks, so that both sides are tightly clamped and in contact with the cooling blocks. The contact and clamping time is 7 seconds. During this process, the slotted needle is rapidly cooled to about 70°C, thereby completing the martensitic transformation.

[0030] Comparative Example 1 Comparative Example 1 uses a traditional quenching method. 95Cr1 high-carbon steel is fully austenitized at 810℃ and then rapidly immersed in quenching oil at 20℃ for uniform cooling.

[0031] Comparative Example 2 Comparative Example 2 uses a similar apparatus to Example 1 of the present invention, but omits the temperature difference. A 95Cr1 high-carbon steel groove needle is heated to 810°C using the same gradient heating process as in Example 1. It is then placed between two alumina ceramic cooling blocks, both at 20°C, for cooling, with a contact time of 5 seconds.

[0032] The grooved pins obtained after quenching in Examples 1-4 and Comparative Examples 1-2 were tested, and the test results are shown in Table 1 below: Table 1 project Quenching deformation amount / 50 pieces Hardness uniformity deviation Example 1 -0.03mm to -0.10mm 34 HV Example 2 -0.03mm to -0.08mm 32 HV Example 3 -0.04mm to -0.08mm 27 HV Example 4 -0.03mm to -0.08mm 32 HV Comparative Example 1 -0.11mm to +0.14mm 68 HV Comparative Example 2 -0.04mm to -0.12mm 37 HV [Performance Analysis] As can be seen from the results in the table above, the quenching method described in this application can effectively reduce the deformation of the grooved needle during the quenching process. Specifically, comparing Example 1 with Comparative Example 1, we can see that when the oil quenching method used in the conventional method is applied to a grooved needle with an extremely thin, flat geometric structure, the deformation of the grooved needle increases significantly, making it difficult to use in subsequent applications. Figure 1 The figures show a comparison between the grooved needles obtained by quenching using the method described in Example 1 of this application and by quenching using the conventional method described in Comparative Example 1. As can be seen from the figures, the grooved needle obtained by quenching using the method described in Example 1 of this application is smoother. While the deformation amount of the symmetrically arranged cooling blocks used in Comparative Example 2 is significantly lower than that of Comparative Example 1, it is still higher than that of Examples 1-4 of this application.

[0033] Therefore, in summary, this application, through the active regulation of the asymmetric cooling field, significantly suppresses thermal and structural stresses during the quenching process, thereby achieving extreme control over the deformation of the slotted pin and effectively ensuring its high-precision geometric dimensions. Simultaneously, based on this temperature difference compensation principle, synchronized cooling and phase transformation are achieved at different parts of the slotted pin, greatly improving the uniformity of hardness distribution, thus enhancing wear resistance and overall service life. Finally, as described in this application, the use of contact clamping cooling instead of traditional liquid quenching avoids media impact and improves process stability and reproducibility, while also reducing subsequent processing steps, thereby effectively lowering production costs.

[0034] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A quenching method of a slot needle, characterized by, The method comprises the following steps: (S.1) heating the slot needle to a temperature above the critical temperature so that it is fully or partially austenitized; (S.2) providing an asymmetric temperature field with a preset temperature difference; (S.3) placing the heated slot needle in the temperature field and contacting it, so that both sides of the slot needle are cooled at different cooling rates to complete the martensitic transformation and quenching.

2. The quenching method of the slot needle according to claim 1, wherein in the step (S.1), the slot needle is heated to a temperature above Ac1 or Ac3 and is kept at the temperature to be austenitized.

3. The quenching method of the slot needle according to claim 2, wherein the slot needle is heated to a temperature above Ac1 or Ac3 by 30-50℃ by gradient heating.

4. The quenching method of the slot needle according to claim 3, wherein the gradient heating comprises sequentially keeping the slot needle at temperature intervals of 600-630℃, 680-720℃, 720-780℃, 780-810℃, 800-820℃ and 810-820℃ for 10-20s.

5. The quenching method of the slot needle according to claim 1, wherein the asymmetric temperature field in the step (S.2) is composed of two cooling blocks with different temperatures, and the heated slot needle is clamped and contacted by the cooling blocks during the cooling process to achieve the cooling and quenching of the slot needle.

6. The quenching method of the slot needle according to claim 5, wherein the contact time between the slot needle and the cooling blocks in the step (S.2) is not more than 10s, and the slot needle is cooled to below 150℃.

7. The quenching method of the slot needle according to claim 5, wherein the preset temperature difference between the two cooling blocks with different temperatures ranges from 40℃ to 70℃.

8. The quenching method of the slot needle according to claim 1 or 5, wherein the cooling blocks are made of ceramic material.

9. A slot needle obtained by the method according to any one of claims 1-8.

10. The slot needle according to claim 9, wherein the quenching deformation of the slot needle is less than 0.08mm, and the overall hardness uniformity deviation of the slot needle is not more than 40HV. ​ ​ ​ ​ ​ 9. A slot needle characterized by, ​ ​ ​

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