A quenching and shape control method for the outer ring of a double-row tapered bearing

Abstract

The present invention discloses a quenching shape control method for the outer ring of a double-row tapered bearing, which is realized by using a press bed with a quenching shape control die. The press bed includes an upper die, a lower die, a base, a guide seat, a disc spring, a plurality of demoulding limit bolts and a press; the shape control method includes: Step 1, select the thickness and height of the disc spring; Step 2, first calculate the theoretical downward pressing height H1 of the upper die in the cooling state, and then calculate the actual downward pressing height H1' of the upper die in the cooling state; Step 3, first put the heated outer ring on the lower die of the die, and then the press drives the upper die to press down until the top surface of the upper die reaches the top surface of the base at H1'; Step 4, fill the quenching shape control die with coolant to cool and quench the outer ring; Step 5, after cooling is completed, the press applies a downward pressure to the upper die again, so that a plurality of demoulding limit bolts jack up the outer ring to realize the separation of the outer ring and the quenching shape control die. The present invention effectively solves the deformation problem of the outer ring during the quenching and cooling process.

Description

Technical Field

[0001] The present invention relates to a quenching shape control method for the outer ring of a double-row tapered bearing. Background Art

[0002] The outer ring of a double-row tapered roller bearing used on railways is a sleeve with two conical raceways and is quenched in a press containing a quenching shape control die. During the cooling process of the product, due to the shrinkage of the product, the quenching shape control die cannot be effectively fitted with the product, resulting in not only ineffective shape control of the product, but also problems such as poor ovality (more than 0.3 mm) of the product raceway, perpendicularity difference of the outer diameter (more than 0.2 mm), and out-of-tolerance concentricity of the raceway. If the deformation is too large and the margin is insufficient, it is easy to cause waste products after quenching. Currently, many bearing manufacturing enterprises still use multiple cylindrical compression springs as the cooling method for the quenching shape control die to fit the cooling shrinkage of the product. The disadvantages are often that the elastic forces of multiple cylindrical compression springs are uneven, resulting in uneven forces at each point when the quenching shape control die rebounds, and the service life and fatigue strength of the cylindrical compression springs are poor, requiring frequent replacement. The most core point is that the elastic forces of the compression springs are uneven, and the height of each outer ring is different after heating. If the pressing height of the upper die of the quenching shape control die is controlled, it will cause the compression springs to be flattened by products with out-of-tolerance heights, reducing the rebound performance of the compression springs and significantly increasing the dimensional dispersion of the products after quenching. Therefore, generally, bearing manufacturing enterprises do not fully control the height of the product before quenching and cooling. Summary of the Invention

[0003] The purpose of the present invention is to overcome the defects of the prior art and provide a quenching shape control method for the outer ring of a double-row tapered bearing, which effectively solves the deformation problem of the bearing outer ring during the quenching and cooling process.

[0004] The purpose of the present invention is achieved as follows: A quenching shape control method for the outer ring of a double-row tapered bearing is realized by using a press containing a quenching shape control die. The press includes an upper die, a lower die, a base, a guide seat, a disc spring, several demoulding limit bolts, and a press; the upper die and the lower die are clamped between the two end faces of the bearing outer ring; the guide seat is installed on the base; the lower die is slidably sleeved on the guide seat; the disc spring is sleeved on the guide seat with the large head facing up and is elastically supported between the lower die and the base; several demoulding limit bolts are respectively installed in several limit holes uniformly opened on the base; the ram of the press is connected to the top surface of the upper die by screws;

[0005] The quenching shape control method includes the following steps:

[0006] Step 1, selection of the disc spring. First, calculate the compression amount ΔH of the disc spring by the following formula (1),

[0007] ΔH = h2 - h1 - (0.03% - 0.05%)×h1 (1)

[0008] In formula (1), h1 is the minimum height value after cooling in the free state of all bearing outer rings; h2 is the maximum height value after quenching and heating of all bearing outer rings;

[0009] Then, select the thickness of the disc spring to be 3.0 mm - 5.0 mm according to the compression amount ΔH of the disc spring, and then obtain the height h4 of the disc spring from the third series of Appendix A of the national standard GB / T1972 - 2005 according to the thickness of the disc spring;

[0010] Step two, calculate the downward pressing height of the upper die of the quenching shape - controlling die. Calculate the theoretical downward pressing height H1 of the upper die in the cooling state through the following formula (2), that is, when quenching and cooling, press the top surface of the upper die down to a position H1 from the top surface of the base;

[0011] H1 = h1 + h3 + h4 (2)

[0012] In formula (2), h1 is the minimum height value after cooling in the free state of all bearing outer rings; h3 is the height of the quenching shape - controlling die itself; h4 is the height of the disc spring;

[0013] Calculate the actual downward pressing height H1' of the upper die in the quenching and cooling state through the following formula (3),

[0014] H1' = H1 - (0.03% - 0.05%)×h1 (3)

[0015] Step three, first put the heated bearing outer ring on the lower die of the quenching shape - controlling die, then the press drives the upper die to press down through the punch until the top surface of the upper die reaches the top surface of the base at H1'. The bearing outer ring moves downward with the downward pressure of the upper die. The bearing outer ring pushes the lower die to squeeze the disc spring below, and the disc spring undergoes elastic deformation under extrusion, so that the upper die and the lower die fit with the upper end surface and the lower end surface of the bearing outer ring one by one;

[0016] Step four, fill the quenching shape - controlling die with coolant to cool and quench the bearing outer ring. The coolant is sprayed on the surface of the bearing outer ring, and control the pressure - maintaining time of the press to be 130 - 250 seconds;

[0017] Step five, after cooling is completed, the press applies a downward pressure on the upper die again, so that the upper die continues to descend by 0.20 - 0.50 mm, and several demoulding limit bolts jack up the bearing outer ring to separate the bearing outer ring from the quenching shape - controlling die, completing the quenching and cooling process of the bearing outer ring.

[0018] The above-mentioned quenching shape control method for the outer ring of a double-row tapered bearing. When performing Step 5, the holding pressure time is determined according to the surface temperature of the bearing outer ring. When the surface temperature of the bearing outer ring is lower than 50 °C, the holding pressure ends.

[0019] The quenching shape control method for the outer ring of a double-row tapered bearing of the present invention has the following characteristics:

[0020] 1) By using a disc spring in the quenching shape control die, the pressure transmitted by the press can be evenly distributed on the surface of the disc spring. The surface where the disc spring deforms directly contacts the lower die. When the disc spring rebounds, it can fit the shrinkage of the bearing outer ring and release elastic force, eliminating the situation that the bearing outer ring will shake due to cooling; and the disc spring is placed with the large end facing up, which can increase its force-bearing area, enable the pressure of the lower die to be better transmitted to the surface of the disc spring, and ensure that the deformation area of the disc spring directly contacts the lower die, and can effectively fit the different pressures transmitted at different positions of the lower die for elastic deformation, increasing the stability of its rebound;

[0021] 2) By positioning the downward pressing height of the upper die of the quenching shape control die, when the bearing outer ring cools and shrinks, the lower die of the quenching shape control die is always under force, so that the upper die and the lower die are tightly attached to the two end faces of the bearing outer ring in a one-to-one correspondence;

[0022] 3) The shape control method of the present invention effectively solves the deformation problem of the bearing outer ring during the quenching and cooling process, thereby controlling the straightness and perpendicularity difference of the outer diameter of the bearing outer ring, as well as the concentricity of the upper and lower raceways. Description of the Drawings

[0023] Figure 1 is the axial sectional view of the quenching shape control die used in the quenching shape control method for the outer ring of a double-row tapered bearing of the present invention;

[0024] Figure 2 is the axial sectional view of the disc spring in the quenching shape control die used in the present invention;

[0025] Figure 3a is the first schematic diagram when performing Step 2 of the quenching shape control method of the present invention;

[0026] Figure 3b is the second schematic diagram when performing Step 2 of the quenching shape control method of the present invention. Detailed Embodiments

[0027] The present invention will be further described below in conjunction with the drawings.

[0028] Please refer to Figures 1 to 3b, The quenching shape control method for the outer ring of the double-row tapered roller bearing of the present invention is realized by using a press with a quenching shape control die. The press includes an upper die 1, a lower die 2, a base 3, a guide seat 4, a disc spring 5, several demolding limit bolts 6 and a press; among them, the upper die 1 and the lower die 2 are clamped between the two end faces of the bearing outer ring 8; the guide seat 4 is installed on the base 3; the lower die 2 is slidably sleeved on the guide seat 3; the disc spring 5 is sleeved on the guide seat 3 with the large head facing up and elastically supports between the lower die 2 and the base 3; several demolding limit bolts 6 are correspondingly installed in several limit holes uniformly opened on the base 3; the press head 7 of the press is connected to the top surface of the upper die 1 by screws (see Figure 1 ).

[0029] The quenching shape control method for the outer ring of the double-row tapered roller bearing of the present invention includes the following steps:

[0030] Step 1, selection of the disc spring. First, calculate the compression amount ΔH of the disc spring through the following formula (1),

[0031] ΔH = h2 - h1 - (0.03% - 0.05%) × h1 (1)

[0032] In formula (1), h1 is the maximum height value after cooling in the free state of all bearing outer rings (see Figure 3a ); h2 is the minimum height value after quenching and heating of all bearing outer rings (see Figure 3b );

[0033] Then, select the thickness B of the disc spring to be 3.0 mm - 5.0 mm according to the compression amount ΔH of the disc spring. Then, according to the thickness of the disc spring, check the height h4 of the disc spring, the inner diameter Φ1 of the disc spring, and the outer diameter Φ2 of the disc spring from the third series of Appendix A of the national standard GB / T1972 - 2005 (see Figure 2 );

[0034] Step 2, calculate the downward pressure height of the upper die of the quenching shape control die. Calculate the theoretical downward pressure height H1 of the upper die in the cooling state through the following formula (2), that is, when quenching and cooling, press the top surface of the upper die down to a position H1 from the top surface of the base;

[0035] H1 = h1 + h3 + h4 (2)

[0036] In formula (2), h1 is the minimum height value after cooling in the free state of all bearing outer rings; h3 is the height of the quenching shape control die itself, h3 = 2 × h0, and h0 is the protruding height of the upper die 1 or the protruding height of the lower die 2 (see Figure 1 ); h4 is the height of the disc spring;

[0037] Calculate the actual downward pressure height H1' of the upper die in the quenching and cooling state through the following formula (3),

[0038] H1’ = H1 - (0.03% - 0.05%) × h1 (3)

[0039] Step 3: First, put the heated bearing outer ring 8 on the lower die 2 of the quenching control die. Then, the press drives the upper die 1 to press down through the pressure head 7 until the top surface of the upper die 1 reaches the top surface H1’ of the base 3. The bearing outer ring 8 moves downward with the downward pressure of the upper die 1. The bearing outer ring 8 pushes the lower die 2 to squeeze the lower butterfly spring 5. The butterfly spring 5 is elastically deformed under the extrusion, so that the upper die 1 and the lower die 2 are in one-to-one correspondence with the upper end surface and the lower end surface of the bearing outer ring 8 respectively;

[0040] Step 4: Fill the quenching control die with coolant to cool and quench the bearing outer ring. The coolant is sprayed on the surface of the bearing outer ring. Control the pressure holding time of the press to be 130 - 250 seconds. The pressure holding time is determined according to the surface temperature of the bearing outer ring after cooling. When the surface temperature of the bearing outer ring is lower than 50°C, the pressure holding ends; the size of the bearing outer ring begins to contract due to the influence of thermal stress; at this time, the butterfly spring begins to release the elastic force formed by the previous extrusion and slowly rebounds following the contraction of the bearing outer ring;

[0041] Step 5: After cooling, the press applies a downward pressure on the upper die 1 again, so that the upper die 1 continues to descend by 0.20 - 0.50 mm, and several demolding limit bolts 6 lift the bearing outer ring 8, realizing the separation of the bearing outer ring and the quenching control die, and completing the quenching and cooling process of the bearing outer ring.

[0042] Now, taking a batch of bearing outer rings with the raw material grade of 2CrNi2MoA as an example, the present invention will be specifically described.

[0043] The material of the butterfly spring in the quenching control die is 60Mn or 65Mn; the pressure of the press is 4 - 8 Mpa;

[0044] The height value of the bearing outer rings of the same batch before quenching: 161.4 - 161.6 mm;

[0045] The height value of the bearing outer rings of the same batch after quenching and heating: 161.8 - 162.3 mm, and h2 is taken as 162.3 mm;

[0046] The height value of the bearing outer rings of the same batch after cooling in the free state: 161.3 - 161.6 mm, and h1 is taken as 161.3 mm;

[0047] The height h3 of the quenching control die itself = h0 × 2 = 22 × 2 = 44 mm;

[0048] Step 1: Calculate the compression amount ΔH of the butterfly spring through the following formula (1),

[0049] ΔH = h2 - h1 - 0.03%×h1 = 162.3 - 161.3 - 0.03%×161.3 = 0.95

[0050] Select the thickness B = 4.5 mm of the conical spring according to the compression amount ΔH of the conical spring, and then obtain the height h4 = 17 mm of the conical spring from the third series of Appendix A of the national standard GB / T1972 - 2005 according to the thickness B = 4.5 mm of the conical spring; the inner diameter Φ1 = 142 mm of the conical spring; the outer diameter Φ2 = 202 mm of the conical spring;

[0051] Step two, calculate the theoretical downward pressure height H1 of the upper die in the cooling state through the following formula (2),

[0052] H1 = h1 + h3 + h4 = 161.3 + 44 + 17 = 222.3 mm;

[0053] Calculate the actual downward pressure height H1' of the upper die in the cooling state through the following formula (3),

[0054] H1' = H1 - 0.03%×h1 = 222.3 = 222.25 mm;

[0055] Step three, first put the bearing outer ring 8 after heating on the lower die 2 of the quenching shape control die, and then the press drives the upper die 1 to press down through the pressure head 7 until the top surface of the upper die 1 reaches the top surface of the base 3 at H1' = 222.25 mm. The bearing outer ring 8 moves downward with the downward pressure of the upper die 1. The bearing outer ring 8 pushes the lower die 2 to squeeze the conical spring 5 below. After being squeezed, the conical spring 5 generates elastic deformation, so that the upper die 1 and the lower die 2 are in one-to-one correspondence with the upper end surface and the lower end surface of the bearing outer ring 8 and fit;

[0056] Step four, fill the quenching shape control die with coolant to cool and quench the bearing outer ring. The coolant is sprayed on the surface of the bearing outer ring, and the pressure holding time of the press is controlled to be 130 - 250 seconds;

[0057] Step five, after cooling, the press applies a downward pressure to the upper die 1 again, so that the upper die 1 continues to descend by 0.20 - 0.50 mm, and several demoulding limit bolts 6 jack up the bearing outer ring 8 to realize the separation of the bearing outer ring 8 and the quenching shape control die, and complete the quenching and cooling process of the bearing outer ring.

[0058] The quenching shape control method for the double-row tapered bearing outer ring of the present invention has the following characteristics:

[0059] 1) The significance and purpose of calculating the theoretical downward pressure height H1 of the upper die in the cooling state

[0060] During the quenching and cooling process of the entire batch of bearing outer rings, due to the pre-tightening force of the disc springs and the pressure caused by the thermal expansion of the bearing outer rings, the lower die of the quenching shape control die is always under force, so that the upper die and the lower die are in one-to-one correspondence and fit on the upper and lower end faces of the bearing outer ring.

[0061] Due to the irregular expansion of the bearing outer ring in the heated state, there are individual local areas of the bearing outer ring where the height after heating is the same as the height after cooling, that is, there is no thermal expansion. In order to ensure that the upper and lower dies are in one-to-one correspondence and fit on the upper and lower end faces of the bearing outer ring, a certain interference amount is required between the upper and lower dies to restrain the two end faces of the bearing outer ring. If the upper and lower dies are not tightly attached to the upper and lower end faces of the bearing outer ring in one-to-one correspondence, during the coolant spraying process, due to the gaps between the upper and lower dies and the upper and lower end faces of the bearing outer ring in one-to-one correspondence, the bearing outer ring will be shaken by the cold. Therefore, in the actual production process, the pressure of the press should cause the upper and lower ends of the bearing outer ring in the free cooling state to be stressed, that is, the disc spring should have a certain amount of pre-tightening force. The magnitude of this pre-tightening force is controlled by the downward pressing height of the upper die, and it is necessary to increase the upper die by 0.03% - 0.05% of h1 based on the theoretical downward pressing height H1;

[0062] Therefore, the actual downward pressing and positioning height H1' of the upper die = H1 + (0.03% - 0.05%) × h1.

[0063] 2) Purpose and significance of calculating the compression amount ΔH of the disc spring:

[0064] The only influencing factor for the height change of the quenching shape control die is: the thermal stress generated during the quenching and cooling process of the entire product, that is, the height value h2 of the product after heating and the height value h1 of the product after cooling. The change amount ΔH between them is the change amount of the height of the quenching shape control die during the cooling process.

[0065] The purpose and significance of calculating this height change amount is to provide a technical basis for the design and selection of the disc spring in the quenching shape control die.

[0066] The purpose of measuring the height value h1 of the product after cooling is to calculate the height of the position where the upper die is pressed down by the press during product shape control for positioning. The purpose of measuring the height value h2 of the product after heating is to calculate the maximum deformation amount of the disc spring.

[0067] When calculating the deformation amount ΔH of the disc spring, take the height value of all bearing outer rings in the same batch after heating as h2, and take the height value of all bearing outer rings in the same batch after free state cooling as h1; the deformation amount ΔH of the disc spring = h2 - h1. This ΔH is a collection, and the maximum value in the deformation amount ΔH of the disc spring should be taken as ΔH';

[0068] 3) When the conical spring is installed at the bottom of the mold, it should be placed with the large end facing up.

[0069] When the conical spring is placed with the large end facing up, when the mold is pressed down, the contact area between the conical spring and the lower mold becomes larger. The pressure transmitted by the press can be evenly distributed on the surface of the conical spring. The surface where the conical spring deforms is directly in contact with the lower mold. When the conical spring rebounds, it can fit and contract with the outer ring of the bearing, releasing elastic force.

[0070] If the conical spring is placed with the small end facing up, when the mold is pressed down, the contact area between the conical spring and the lower mold does not change. The changing area is the contact area between the conical spring and the base. The pressure is evenly distributed elastically, so that when the mold is pressed down and rebounds, the lower mold cannot ensure that the two end faces of the outer ring of the bearing always fit with the upper mold and the lower mold one by one according to the actual shrinkage deformation of each part of the end face of the outer ring of the bearing.

[0071] 4) There are two purposes for transmitting the pressure of the press through the outer ring of the bearing: one is that during the heating process of the outer ring of the bearing, there are differences in the expansion amounts at various parts of its end face. By transmitting the pressure of the upper mold of the quenching shape control mold to the lower mold through the outer ring of the bearing, the different expansion amount differences at various parts of the end face of the outer ring of the bearing can also be transmitted to the conical spring below the lower mold; the other is that it is easier to achieve the pressure interference between the upper and lower molds during the entire quenching and cooling process by transmitting the pressure through the outer ring of the bearing.

[0072] For the quenching shape control method of the outer ring of the double-row tapered bearing of the present invention, conical springs of different sizes and specifications are used for quenching and cooling the outer ring of the bearing. The shape control effect is shown in the following table; the deformation amount in the following table is the ovality of the outer ring of the bearing; the service life in the following table is the service duration before the conical spring fails. Since the heat treatment process is discontinuous batch processing, the service duration of the conical spring cannot be recorded by time, and only the number of products processed before failure can be used to evaluate the service life of the conical spring;

[0073]

[0074] The above embodiments are only for illustrating the present invention, rather than limiting the present invention. Those skilled in the relevant technical fields can also make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also belong to the scope of the present invention and should be defined by each claim.

Claims

1. A quenching and shape control method for the outer ring of a double-row tapered bearing, which is realized by using a press with a quenching and shape control die. The press includes an upper die, a lower die, a base, a guide seat, a disc spring, several demoulding limit bolts and a press; the upper die and the lower die are clamped between the two end faces of the bearing outer ring; the guide seat is installed on the base; the lower die is slidably sleeved on the guide seat; the disc spring is sleeved on the guide seat with its large head facing up and elastically supported between the lower die and the base; several demoulding limit bolts are respectively installed in several limit holes evenly opened on the base; the press head of the press is connected to the top surface of the upper die by screws; It is characterized in that The quenching and shape control method includes the following steps: Step 1, selection of the disc spring. First, calculate the compression amount ΔH of the disc spring by the following formula (1), ΔH = h2 - h1 - (0.03% - 0.05%) × h1 (1) In formula (1), h1 is the minimum height value after cooling in the free state of all bearing outer rings; h2 is the maximum height value after quenching heating of all bearing outer rings; Then, select the disc spring with a thickness of 3.0 mm - 5.0 mm according to the compression amount ΔH of the disc spring, and then obtain the height h4 of the disc spring from the third series of Appendix A of the national standard GB / T1972-2005 according to the thickness of the disc spring; Step 2, calculate the downward pressing height of the upper die of the quenching and shape control die. Calculate the theoretical downward pressing height H1 of the upper die in the cooling state by the following formula (2), that is, when quenching and cooling, press the top surface of the upper die down to a position H1 from the top surface of the base; H1 = h1 + h3 + h4 (2) In formula (2), h1 is the minimum height value after cooling in the free state of all bearing outer rings; h3 is the height of the quenching and shape control die itself; h4 is the height of the disc spring; Calculate the actual downward pressing height H1' of the upper die in the quenching and cooling state by the following formula (3), H1' = H1 - (0.03% - 0.05%) × h1 (3) Step 3, first put the heated bearing outer ring on the lower die of the quenching and shape control die, and then the press drives the upper die to press down through the press head until the top surface of the upper die reaches the top surface of the base at H1'. The bearing outer ring moves downward with the downward pressure of the upper die, and the bearing outer ring pushes the lower die to squeeze the disc spring below. The disc spring is squeezed to produce elastic deformation, so that the upper die and the lower die are respectively attached to the upper end face and the lower end face of the bearing outer ring; Step 4, fill the quenching and shape control die with coolant to cool and quench the bearing outer ring. The coolant is sprayed on the surface of the bearing outer ring, and control the pressure holding time of the press to be 130 - 250 seconds; Step 5, after cooling, the press applies a downward pressure to the upper die again, so that the upper die continues to descend by 0.20 - 0.50 mm, and several demoulding limit bolts lift the bearing outer ring to realize the separation of the bearing outer ring and the quenching and shape control die, and complete the quenching and cooling process of the bearing outer ring.

2. The quenching and shape control method for the outer ring of a double-row tapered roller bearing according to claim 1, characterized in that, When performing Step 5, the pressure holding time is determined according to the surface temperature of the bearing outer ring. When the surface temperature of the bearing outer ring is lower than 50 °C, the pressure holding ends.

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