Method for predicting axial brinell hardness of nickel-based alloy die forging

Abstract

The invention relates to an axial Brinell hardness prediction method of a nickel-based alloy die forging, and belongs to the technical field of Brinell hardness calculation, the method comprises the following steps: obtaining an axial distance h between a point location to be measured and the surface of the die forging; when h is smaller than or equal to 6.81 mm, the Brinell hardness HB (d) of the point position to be measured is calculated through a first formula; when h is greater than 6.81 mm, calculating the Brinell hardness HB (d) of the point location to be measured by using a second formula; the first formula is HB (d) = 3.29 to 0.011 h <-0.001 > h < 2 >; and the second formula is HB (d) = 3.36 to 20.6 e-h / 1.45. According to the method, the Brinell hardness value of the to-be-measured point position can be accurately calculated only by determining the axial distance between the to-be-measured point position of the core part of the die forging and the surface of the die forging, so that a designer can be helped to more accurately design the machining allowance of the die forging, and meanwhile, the working allowance of the die forging can be accurately calculated. And a designer can be helped to reversely calculate and check whether the surface Brinell hardness value of the machined forge piece meets the requirement or not according to the design allowance.

Description

Technical Field

[0001] The invention belongs to the technical field of Brinell hardness calculation, and in particular relates to a method for predicting the axial Brinell hardness of a nickel-based alloy die forging. Background Art

[0002] Nickel-based alloys with the grade of GH4698 are widely used in key parts such as turbine discs, guide discs, compressor discs, low-pressure turbine shafts and gas turbine wheels, turbine discs, compressor discs, flow sheets, bearing rings, etc. in aircraft engines. With the development of aircraft engines in recent years, the engines not only have higher and higher requirements for the high temperature performance and fatigue performance of turbine discs and guide discs, but also have a narrower range of Brinell hardness requirements for forgings than foreign Brinell hardness requirements. For example, the specific range of a domestic aircraft engine disc forging is HB (d) = 3.30 ~ 3.45mm. The faster cooling rate of the forging surface after die forging and solid solution makes the forging have a higher hardness on the surface after aging, while the core has a lower hardness. Therefore, in order to make the forging hardness meet the standard requirements, it is necessary to design a suitable machining allowance.

[0003] In the prior art, the design of forging machining allowance involves many factors, among which Brinell hardness is an important element. At present, although the surface Brinell hardness of die forgings can be measured by a measuring meter, the Brinell hardness of the core of the forging cannot be measured directly. The Brinell hardness of the core of the forging can only be predicted by experience and some methods that are not easy to implement. However, practice shows that the prediction results of the existing methods for predicting the Brinell hardness of the core of die forgings are low in accuracy, resulting in large errors in the design results of the machining allowance of die forgings. Summary of the invention

[0004] The invention provides a method for predicting the axial Brinell hardness of a nickel-based alloy die forging, which is used to solve the technical problem that the existing method has low accuracy in predicting the axial Brinell hardness of the core of the die forging.

[0005] The present invention is achieved through the following technical solution: A method for predicting the axial Brinell hardness of a nickel-based alloy die forging, comprising:

[0006] Obtaining the axial distance between the point to be measured and the surface of the die forging, wherein the axial distance is h;

[0007] When h≤6.81mm, the first formula is used to calculate the Brinell hardness HB(d) of the test point;

[0008] When h>6.81mm, the Brinell hardness HB(d) of the test point is calculated using the second formula;

[0009] The first formula is: HB(d)=3.29-0.011h-0.001h 2 ;

[0010] The second formula is: HB(d)=3.36-20.6e -h / 1.45 .

[0011] Furthermore, in order to better implement the present invention, the grade of the nickel-based alloy is GH4698.

[0012] Furthermore, in order to better implement the present invention, the die forging is a disc-type or short shaft-type die forging.

[0013] Furthermore, in order to better implement the present invention, the weight of the die forging is 90-220Kg.

[0014] Furthermore, in order to better implement the present invention, the axial thickness of the die forging is 30-220 mm.

[0015] Furthermore, in order to better implement the present invention, the heat treatment method of the die forging includes:

[0016] Step 1: Heat the die forging to 1100°C and keep it at that temperature for 8 hours, then air cool it;

[0017] Step 2: Heat the die forging after air cooling in the first step to 1000°C and keep it at that temperature for 4 hours, and then air cool it;

[0018] Step 3: Heat the die forging after air cooling in the second step to 775℃ and keep it at this temperature for 16h, and then air cool it.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The axial Brinell hardness prediction method of the nickel-based alloy die forging provided by the present invention comprises obtaining the axial distance between the point to be measured and the surface of the die forging, defining the axial distance as h, and when h≤6.81mm, using the first formula to calculate the Brinell hardness HB(d) of the point to be measured, and when h>6.81mm, using the second formula to calculate the Brinell hardness HB(d) of the point to be measured, and the above-mentioned first formula is HB(d)=3.29-0.011h-0.001h 2 , the second formula is HB(d)=3.36-20.6 -h / 1.45 .

[0021] Through the above method, it is only necessary to determine the axial distance between the test point at the core of the die forging and the surface of the die forging to accurately calculate the Brinell hardness value of the test point. This can not only help designers to design the machining allowance of the die forging more accurately, but also help designers to reversely calculate whether the surface Brinell hardness value of the forging after machining meets the requirements based on the design allowance. DETAILED DESCRIPTION

[0022] To make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0023] Embodiment 1:

[0024] The present embodiment provides a method for predicting the axial Brinell hardness of a nickel-based alloy die forging, comprising obtaining an axial distance between a point to be measured and a surface of the die forging, defining the axial distance as h, and calculating the Brinell hardness HB(d) of the point to be measured using a first formula when h≤6.81 mm, and calculating the Brinell hardness HB(d) of the point to be measured using a second formula when h>6.81 mm, wherein the first formula is HB(d)=3.29-0.011h-0.001h 2 , the second formula is HB(d)=3.36-20.6e -h / 1.45 It is worth noting that the Brinell hardness HB(d) described in this embodiment is actually the Brinell hardness indentation diameter.

[0025] The grade of the nickel-based alloy is GH4698, and the type of the die forging is a disc type or a short shaft type die forging. The weight is 90-220KG, for example, 90Kg, 100Kg, 110KgG, 120Kg, 130Kg, 140Kg, 150Kg, 160Kg, 170Kg, 180Kg, 190Kg, 200Kg, 210Kg, 220Kg, etc. The axial thickness of the die forging is 30-150mm, for example, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, 110mm, 120mm, 130mm, 140mm, 150mm, 160mm, 170mm, 180mm, 190mm, 200mm, 210mm, 220mm, etc. And the die forging needs to undergo heat treatment, the heat treatment method is as follows:

[0026] Step 1: Heat the die forging to 1100°C and keep it at that temperature for 8 hours, then air cool it;

[0027] Step 2: Heat the die forging after air cooling in the first step to 1000°C and keep it at that temperature for 4 hours, and then air cool it;

[0028] Step 3: Heat the die forging after air cooling in the second step to 775℃ and keep it at this temperature for 16h, and then air cool it.

[0029] Through the above method, it is only necessary to determine the axial distance between the test point at the core of the die forging and the surface of the die forging to accurately calculate the Brinell hardness value of the test point. This can not only help designers to design the machining allowance of the die forging more accurately, but also help designers to reversely calculate whether the surface Brinell hardness value of the forging after machining meets the requirements based on the design allowance.

[0030] Embodiment 2:

[0031] This embodiment is an example implementation of the prediction method provided in the embodiment, specifically using the above prediction method to predict the axial Brinell hardness of the core of a disc-type die forging. The raw material grade of the disc-type die forging is GH4698, the diameter of the die forging is 640 mm, the axial thickness is 110 mm, and the thickness of the thinnest part of the die forging is 61 mm, excluding the test ring, and the weight is 200 kg. The die forging is subjected to the following heat treatment:

[0032] Step 1: Heat the die forging to 1100°C and keep it at that temperature for 8 hours, then air cool it;

[0033] Step 2: Heat the die forging after air cooling in the first step to 1000°C and keep it at that temperature for 4 hours, and then air cool it;

[0034] Step 3: Heat the die forging after air cooling in the second step to 775℃ and keep it at this temperature for 16h, and then air cool it.

[0035] The axial Brinell hardness index requirement for die forgings is: HB(d)=3.30~3.45mm.

[0036] Generally, the hardness surface processing depth h of high-temperature alloy (such as GH4169, GH4648, GH706 and other alloys) die forgings is ≤3mm.

[0037] When h≤3mm, according to the first formula, HB(d)=3.29-0.011h-0.001h 2 It can be calculated that at this time HB(d)=3.25~3.29mm, and the axial Brinell hardness does not meet the index requirements.

[0038] In order to make the hardness of the die forging meet the index requirements, that is, HB(d)≥3.30mm, substitute the second formula HB(d)=3.36-20.6e -h / 1.45 The formula can be calculated that h needs to be no less than 8.5mm. That is, at this time, the rough machining allowance from the rough machining size after heat treatment to the delivery rough machining allowance needs to be at least 8.5mm. Therefore, the rough machining allowance before heat treatment is designed to be 9.0mm, and the HB hardness detection surface after heat treatment drops by 8.5+0.50mm. The axial Brinell hardness at the HB position is evenly tested at three locations, HB (d) = 3.30, 3.31, 3.31mm, which meets the index requirements.

[0039] Embodiment 3:

[0040] This embodiment is an example implementation of the prediction method provided in the embodiment, specifically:

[0041] In this embodiment, the raw material grade of the die forging is GH4698, the type is a short-shaft die forging, the diameter of the die forging is 265 mm, the axial thickness is 220 mm, and the weight is 100 kg. The die forging is subjected to the following heat treatment:

[0042] Step 1: Heat the die forging to 1100°C and keep it at that temperature for 8 hours, then air cool it;

[0043] Step 2: Heat the die forging after air cooling in the first step to 1000°C and keep it at that temperature for 4 hours, and then air cool it;

[0044] Step 3: Heat the die forging after air cooling in the second step to 775℃ and keep it at this temperature for 16h, and then air cool it.

[0045] The axial Brinell hardness index requirement of the short shaft die forging is: HB(d)=3.30~3.55mm.

[0046] The on-site operators processed a batch of short shaft forgings, but did not follow the processing requirements of the axial hardness of the GH4698 alloy die forgings, but processed the batch of forgings according to the processing requirements of the GH4169 alloy (h≤3mm). The on-site measurement showed that the processing depth of the batch of short shaft die forgings was about 2mm, and the measured axial Brinell hardness HB (d) = 3.25 ~ 3.26mm, which did not meet the index requirements.

[0047] Substituting HB(d)=3.30~3.55mm into the second formula above, it is found that h needs to be no less than 8.5mm. Therefore, the plane at the HB position of this batch of short-shaft die forgings is further lowered 6.5+0.50mm in the axial direction, and then the axial Brinell hardness is remeasured. The actual measured value HB(d)=3.30~3.32mm meets the index requirements.

[0048] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope of the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for predicting the axial Brinell hardness of a nickel-based alloy die forging, characterized in that: include: Obtaining the axial distance between the point to be measured and the surface of the die forging, wherein the axial distance is h; When h≤6.81mm, the first formula is used to calculate the Brinell hardness HB(d) of the test point; When h>6.81mm, the Brinell hardness HB(d) of the test point is calculated using the second formula; The first formula is: HB(d)=3.29-0.011h-0.001h 2 ; The second formula is: HB(d)=3.36-20.6e -h / 1.45 .

2. The method for predicting the axial Brinell hardness of a nickel-based alloy die forging according to claim 1, characterized in that: The grade of the nickel-based alloy is GH4698.

3. The method for predicting the axial Brinell hardness of a nickel-based alloy die forging according to claim 1, characterized in that: The die forging is a disc-type or short-shaft-type die forging.

4. The method for predicting the axial Brinell hardness of a nickel-based alloy die forging according to claim 1, characterized in that: The weight of the die forging is 90-220Kg.

5. The method for predicting the axial Brinell hardness of a nickel-based alloy die forging according to claim 1, characterized in that: The axial thickness of the die forging is 30-220 mm.

6. The method for predicting the axial Brinell hardness of a nickel-based alloy die forging according to claim 1, characterized in that: The heat treatment method of the die forging includes: Step 1: Heat the die forging to 1100°C and keep it at that temperature for 8 hours, then air cool it; Step 2: Heat the die forging after air cooling in the first step to 1000°C and keep it at that temperature for 4 hours, and then air cool it; Step 3: Heat the die forging after air cooling in the second step to 775℃ and keep it at this temperature for 16h, and then air cool it.