Process method for controlling size of impeller by utilizing difference of thermal expansion coefficients

Abstract

The invention belongs to the field of impeller manufacturing, and particularly relates to a technological method for controlling the size of an impeller through thermal expansion coefficient differences. According to the method, different linear expansion coefficients of materials are utilized, the difference value between the outlet size of the impeller and the design is combined, the heights of different adjusting tools are calculated, the installation mode of the adjusting tools and the impeller is determined, and after the impeller and the adjusting tools are assembled, the impeller and the adjusting tools jointly enter a furnace to be heated integrally for size adjustment. Repairing adjustment is carried out through the adjusting tool and the technological method, the situation that the impeller outlet width does not meet the design requirement due to impeller deformation or cracking can be repaired, the qualified rate of the impeller is increased, and the unit efficiency problem caused by the fact that the critical size outlet width does not meet the design requirement is avoided.

Description

Technical Field

[0001] The invention relates to a process method for controlling the size of an impeller, and in particular to a process method for controlling the size of an impeller by utilizing a difference in thermal expansion coefficients. Background Art

[0002] The centrifugal impeller is the core component of the centrifugal compressor. Its design and manufacturing quality directly affect the overall performance and efficiency of the compressor. The closed impeller is the mainstream impeller structure of the centrifugal compressor. The manufacturing of the centrifugal impeller determines its different molding methods due to its structural characteristics. Including plug welding molding, fillet welding molding, integral milling, brazing molding, electric spark machining and many other different molding methods. Each molding method has its unique advantages and limitations. Choosing a suitable molding method requires comprehensive consideration of the impeller's structural characteristics, performance requirements, cost-effectiveness and manufacturing feasibility.

[0003] At present, among the forming and manufacturing methods of centrifugal compressor impellers, manual arc welding two-body / three-body fillet welding has the advantages of short cycle and low manufacturing cost compared with other forming methods such as brazing forming and integral milling. It is one of the most widely used centrifugal compressor impeller manufacturing methods when the structure allows. The impeller outlet width is an important dimension to measure the dimensional accuracy of the impeller, and its tolerance requirements are very strict during its manufacturing process. The degree of deviation in its manufacturing is an important indicator affecting the efficiency of the compressor.

[0004] At present, the manufacturing process of fillet welded impellers is long, involving multiple processes such as processing, preheating, welding, stress relief, performance heat treatment, stabilization treatment, etc. When manufacturing deviation occurs during the manufacturing process and the outlet width becomes narrower, if there is no appropriate adjustment solution, the impeller will not meet the design requirements and will be scrapped, which will increase the production cost and cycle of the impeller. Summary of the invention

[0005] The purpose of the present invention is to solve the technical problem that when manufacturing deviation occurs in the manufacturing process of the existing impeller, if the outlet width becomes narrower, the impeller will not meet the design requirements and will be scrapped, which will further increase the production cost of the impeller and increase the cycle time, and provide a process method for controlling the impeller size by utilizing the difference in thermal expansion coefficient.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A process method for controlling the size of an impeller by utilizing the difference in thermal expansion coefficients, which is special in that it comprises the following steps:

[0008] Step 1, measuring the width of each outlet of the impeller flow channel in the impeller to be adjusted, and recording the actual width value of each outlet;

[0009] Step 2, select the material of the adjustment tooling, the linear expansion coefficient of the material of the adjustment tooling must be greater than the linear expansion coefficient of the impeller material, and there is a preset difference between the two; the adjustment tooling refers to a tooling that can adjust the outlet width by heating and raising the temperature according to the difference in the linear expansion coefficient of the material;

[0010] Step 3, among all the outlets, determine the outlets whose actual width value is less than the lower limit of the design requirement value, calculate the deviation value between the actual width value and the lower limit of the design requirement value, and determine the outlets whose actual width value is less than the lower limit of the design requirement value as the outlets that need to be adjusted;

[0011] Step 4: among the outlets that need to be adjusted as determined in step 3, according to the deviation value and actual width corresponding to each outlet that needs to be adjusted, calculate the corresponding adjustment tooling with the appropriate installation size to be installed in each outlet that needs to be adjusted, and when the impeller and the adjustment tooling are heated to a preset temperature together, the difference in linear expansion and elongation between the two is calculated to determine whether the outlet width value that needs to be adjusted can be supported to be adjusted to the design requirement value;

[0012] If yes, install the corresponding adjustment tooling of the adapted installation size to the outlet of the impeller corresponding to the outlet that needs to be adjusted at room temperature, and then execute step 5;

[0013] If not, first heat the impeller to a first preset temperature and keep it warm for a first preset time, then measure the actual width value of each outlet that needs to be adjusted, and install the corresponding adjustment tooling with an installation size that matches the actual width value at room temperature to the outlet corresponding to the impeller that needs to be adjusted, and then execute step 5;

[0014] Step 5, heating the installed corresponding adjustment tooling and the impeller as a whole to a second preset temperature, and keeping the temperature for a second preset time;

[0015] Step 6: After the installed adjustment fixture and the impeller are cooled to room temperature, disassemble all adjustment fixtures and measure the actual width values ​​of all adjusted outlets to determine whether the actual width values ​​of all adjusted outlets are within the range of the design requirements; if so, complete the impeller size adjustment; if not, use the impeller as the impeller to be adjusted and return to step 1 until the actual width values ​​of all adjusted outlets are within the range of the design requirements.

[0016] Further, in step 4, the impeller is first heated to a first preset temperature at a first preset heating rate;

[0017] In step 5, the adjustment fixture and the installed impeller are heated together to a second preset temperature at a second preset heating rate.

[0018] Further, in step 4 and step 5, the range of the first preset heating rate and the second preset heating rate are both 80° C. / h to 100° C. / h;

[0019] The first preset temperature and the second preset temperature are both in the range of 300° C. to 500° C.;

[0020] The first preset time and the second preset time both range from 2 hours to 8 hours.

[0021] Furthermore, in step 4 and step 5, the first preset heating rate and the second preset heating rate are both 100° C. / h;

[0022] The first preset temperature and the second preset temperature are both 400° C.;

[0023] The first preset time is 3 hours, and the second preset time ranges from 5 hours.

[0024] Furthermore, the adjustment tool is an adjustment block, and the material of the adjustment tool is a high-temperature alloy.

[0025] The beneficial effects of the present invention are:

[0026] The impeller manufacturing outlet width adjustment tool and process method of the present invention utilize different linear expansion coefficients of materials, combined with the difference between the impeller outlet size and the design, calculate different adjustment tool heights, determine the installation method of the adjustment tool and the impeller, assemble the impeller and the adjustment tool, and then put them into a furnace for overall heating to adjust the size. During the impeller welding manufacturing process, repair and adjustment are performed through this adjustment tool and process method, and the impeller outlet width that does not meet the design requirements due to deformation or cracking of the impeller can be repaired, thereby improving the impeller qualification rate and avoiding unit efficiency problems caused by the key size outlet width not meeting the design requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of an existing impeller;

[0028] Figure 2 is a schematic diagram of the structure of the adjustment tooling in an embodiment of the present invention;

[0029] Figure 3 It is a schematic diagram of the installation structure of the adjustment tool and the impeller in an embodiment of the present invention.

[0030] In the figure: 1-wheel disc, 2-blades, 3-wheel cover, 4-inlet edge, 5-outlet edge, 6-adjustment tooling. DETAILED DESCRIPTION

[0031] In order to make the purpose, advantages and features of the present invention more clear, the following is a further detailed description of a process method for controlling the size of an impeller by using the difference in thermal expansion coefficients proposed by the present invention in combination with the accompanying drawings and specific embodiments. The advantages and features of the present invention will be more clear according to the following specific embodiments.

[0032] See also Figure 1 The existing manual arc welding fillet welded centrifugal impeller mainly includes a wheel disc 1, blades 2 and a wheel cover 3.

[0033] There are multiple blades 2. In this embodiment, 19 blades 2 are used as an example. The 19 blades 2 are arranged along the radial circumference of the wheel disc 1, and the wheel cover 3 covers the blades 2. The side of the blade 2 located at the center of the wheel disc 1 is the air inlet edge 4, and the side of the blade 2 located at the edge of the wheel disc 1 is the air outlet edge 5.

[0034] The impeller is a three-body manual arc welding impeller, and martensitic precipitation hardening stainless steel is used as the impeller material. The impeller diameter is 1200mm, and the outlet width design value is 160mm~161mm.

[0035] The impeller had welding cracks during use. After repair and welding, the width of the impeller outlet was too small and did not meet the design requirements. It needed to be repaired and adjusted to the design requirements.

[0036] The impeller is adjusted using a process method of the present invention for controlling the size of the impeller by utilizing the difference in thermal expansion coefficient, which specifically includes the following steps:

[0037] The first step is to measure the basic dimensions of the impeller to be repaired and adjusted, specifically measuring the width of each outlet of the impeller flow channel. The measurement position is specifically the intended installation position of the adjustment tool on the outlet. In this embodiment, the adjustment tool is an adjustment block. Its specific structure is shown in Figure 2 , and recorded the basic dimensions of a total of 19 flow channels, i.e., the actual width values. Among them, 6 flow channels showed different degrees of size reduction, which was about 0.6 to 0.8 mm smaller than the design requirement. See Table 1 for details:

[0038] Table 1

[0039] Serial number 1 2 3 4 5 6 Design requirement minimum value (mm) 160 160 160 160 160 160 Actual measurement value (mm) 159.4 159.2 159.2 159.4 159.2 159.3 Deviation value(mm) 0.6 0.8 0.8 0.6 0.8 0.7

[0040] The second step is to select the material of the adjustment tooling. The linear expansion coefficient is an inherent property of the material. The linear expansion coefficient of the material of the adjustment tooling must be greater than the linear expansion coefficient of the impeller material, and there is a preset difference between the two. The adjustment tooling refers to a tooling that can adjust the outlet width by heating according to the difference in the linear expansion coefficient of the material.

[0041] According to the impeller material is martensitic precipitation hardening stainless steel, high temperature alloy is used as the material of the adjustment tooling at room temperature, and its linear expansion coefficient at different temperatures is shown in Table 2:

[0042] Table 2 shows the linear expansion coefficients of the two materials at different temperatures

[0043]

[0044]

[0045] First, according to the value of outlet width L = 160mm, the following formula is used to calculate the thermal expansion elongation of different materials at different temperatures (the calculation results are shown in Table 3):

[0046] △L=α×(t2-t1)×L;

[0047] In the formula: △L: thermal expansion elongation (mm); α: linear expansion coefficient; t1: initial temperature; t2: final temperature; L: outlet width, adjustment tooling height (mm).

[0048] Table 3

[0049] Material 100℃ 200℃ 300℃ 400℃ 500℃ Martensitic stainless steel <![CDATA[11.4×10 -6 ]]> <![CDATA[11.8×10 -6 ]]> <![CDATA[12.1×10 -6 ]]> <![CDATA[12.4×10 -6 ]]> <![CDATA[12.8×10 -6 ]]> △L1(mm) 0.14592 0.3398 0.5421 0.7539 0.983 High temperature alloy <![CDATA[11.8×10 -6 ]]> <![CDATA[13.0×10 -6 ]]> <![CDATA[13.5×10 -6 ]]> <![CDATA[14.1×10 -6 ]]> <![CDATA[14.4×10 -6 ]]> △L2(mm) 0.15104 0.3744 0.6048 0.8573 1.1059 △L2-△L1(mm) 0.00512 0.03456 0.06272 0.10336 0.12288

[0050] According to the calculated values ​​in Table 3, taking advantage of the different linear expansion amounts of different materials, at 500°C, the maximum adjustable size is expected to be about 0.12 mm.

[0051] Step 3: Among all the outlets, determine the outlets whose actual width values ​​are less than the lower limit of the design requirement value, and calculate their deviation values ​​from the lower limit of the design requirement value. The calculation results are shown in Table 1. The six outlets whose actual width values ​​are less than the lower limit of the design requirement value are determined as the outlets that need to be adjusted.

[0052] Step 4. In the outlets that need to be adjusted as determined in the third step, calculate the adjusted outlet width according to "adjusted outlet width = actual outlet width + static elongation + thermal expansion elongation". According to the deviation value and actual width corresponding to each outlet that needs to be adjusted, calculate the static elongation and thermal expansion elongation of the corresponding adjustment tooling in each outlet that needs to be adjusted, so as to determine the height of the adjustment tooling. That is, according to the deviation value and actual width corresponding to each outlet that needs to be adjusted, calculate the corresponding adjustment tooling of the matching installation size to be installed in each outlet that needs to be adjusted. When the impeller and the adjustment tooling are heated to 400°C together, the difference in linear expansion elongation between the two can support the adjustment of the outlet width value that needs to be adjusted to the design requirement value.

[0053] If yes, install the corresponding adjustment tooling that matches the installation size at room temperature to the outlet of the impeller that needs to be adjusted, and then execute the fifth step.

[0054] If not, first heat the impeller to 400℃ and keep it warm for 3 hours, then measure the actual width value of each outlet that needs to be adjusted, and install the corresponding adjustment tooling with installation dimensions that match its actual width value at room temperature to the corresponding outlet in the impeller that needs to be adjusted, and then execute the fifth step.

[0055] The specific calculated values ​​of the adjustment tooling are shown in Table 4. The height of the adjustment tooling is designed according to the values ​​measured in the six flow channels.

[0056] Table 4

[0057] Serial number 1 2 3 4 5 6 Design requirements 160～161 160～161 160～161 160～161 160～161 160～161 Actual measurement 159.4 159.2 159.2 159.4 159.2 159.3 Deviation(mm) 0.6 0.8 0.8 0.6 0.8 0.7 Static elongation (mm) 0.75 0.75 0.75 0.75 0.75 0.75 Adjust tooling height 160.15 159.95 159.95 160.15 159.95 160.05 Adjusted outlet width 160.25 160.05 160.05 160.25 160.25 160.15

[0058] Note: Adjust the tooling height h = actual outlet width + static elongation;

[0059] Adjusted outlet width = actual outlet width + static elongation + thermal expansion elongation difference.

[0060] Step 5: Heat the installed corresponding adjustment tooling and the impeller as a whole to 400°C and keep it warm for 5 hours.

[0061] Step 6. After the installed adjustment fixture and impeller are cooled to room temperature, disassemble all adjustment fixtures and measure the actual width values ​​of all adjusted outlets (see Table 4 for the results) to determine whether the actual width values ​​of all adjusted outlets are within the range of the design requirements; if so, complete the impeller size adjustment; if not, use the impeller as the impeller to be adjusted and return to the first step until the actual width values ​​of all adjusted outlets are within the range of the design requirements.

Claims

1. A process for controlling the size of an impeller by utilizing the difference in thermal expansion coefficient, characterized in that: The following steps are involved: Step 1, measuring the width of each outlet of the impeller flow channel in the impeller to be adjusted, and recording the actual width value of each outlet; Step 2, select the material of the adjustment tooling, the linear expansion coefficient of the material of the adjustment tooling must be greater than the linear expansion coefficient of the impeller material, and there is a preset difference between the two; the adjustment tooling refers to a tooling that can adjust the outlet width by heating and raising the temperature according to the difference in the linear expansion coefficient of the material; Step 3, among all the outlets, determine the outlets whose actual width value is less than the lower limit of the design requirement value, calculate the deviation value between the actual width value and the lower limit of the design requirement value, and determine the outlets whose actual width value is less than the lower limit of the design requirement value as the outlets that need to be adjusted; Step 4: among the outlets to be adjusted as determined in step 3, according to the deviation value and actual width corresponding to each outlet to be adjusted, calculate the corresponding adjustment tooling with the appropriate installation size to be installed in each outlet to be adjusted, and when the impeller and the adjustment tooling are heated to a preset temperature together, use the difference in linear expansion elongation between the two to determine whether the outlet width value to be adjusted can be supported and adjusted to the design requirement value; If yes, install the adjustment tool at room temperature to the outlet of the impeller corresponding to the outlet that needs to be adjusted, and then execute step 5; If not, first heat the impeller to a first preset temperature and keep it warm for a first preset time, then measure the actual width value of each outlet that needs to be adjusted, and install the corresponding adjustment tooling at room temperature to the outlet corresponding to the impeller that needs to be adjusted, and then execute step 5; Step 5, heating the installed corresponding adjustment tooling and the impeller as a whole to a second preset temperature, and keeping the temperature for a second preset time; Step 6: After the installed adjustment fixture and the impeller are cooled to room temperature, disassemble all adjustment fixtures and measure the actual width values ​​of all adjusted outlets to determine whether the actual width values ​​of all adjusted outlets are within the range of the design requirements; if so, complete the impeller size adjustment; if not, use the impeller as the impeller to be adjusted and return to step 1 until the actual width values ​​of all adjusted outlets are within the range of the design requirements.

2. The process for controlling the size of an impeller by utilizing the difference in thermal expansion coefficient according to claim 1, characterized in that: In step 4, the impeller is first heated to a first preset temperature at a first preset heating rate; In step 5, the adjustment fixture and the installed impeller are heated together to a second preset temperature at a second preset heating rate.

3. The process for controlling the size of an impeller by utilizing the difference in thermal expansion coefficient according to claim 2, characterized in that: In step 4 and step 5, the first preset heating rate and the second preset heating rate are both in the range of 80°C / h to 100°C / h; The first preset temperature and the second preset temperature are both in the range of 300° C. to 500° C.; The first preset time and the second preset time both range from 2 hours to 8 hours.

4. The process for controlling the size of an impeller by utilizing the difference in thermal expansion coefficient according to claim 3, characterized in that: In step 4 and step 5, the first preset heating rate and the second preset heating rate are both 100° C. / h; The first preset temperature and the second preset temperature are both 400° C.; The first preset time is 3 hours, and the second preset time ranges from 5 hours.

5. The process for controlling the size of an impeller by utilizing the difference in thermal expansion coefficient according to claim 1, characterized in that: The adjusting tool is an adjusting block.

6. The process for controlling the size of an impeller by utilizing the difference in thermal expansion coefficient according to claim 5, characterized in that: The material of the adjustment tool is a high-temperature alloy.

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