Preparation method of end hardenability test standard sample

Abstract

The invention relates to a preparation method of a standard sample for a terminal hardenability test. The preparation method comprises the following steps: 1) selecting 45 high-quality carbon hot-rolled structure round steel as a blank raw material; 2) preparing the 45 carbon hot-rolled structure round steel blank raw material into a cylindrical blank by using a lathe; (3) normalizing the cylindrical blank, namely heating the cylindrical blank to 850-870 DEG C, preserving heat for 30-35 minutes, discharging the cylindrical blank from a furnace, and air-cooling the cylindrical blank to room temperature; and (4) the cylindrical blank cooled to the room temperature is prepared into a tail end hardenability standard sample with a flange at the end through a lathe concentric lathe. The end hardenability standard sample prepared by the invention has good consistency of test results, can be used for performing end hardenability test benchmarking by different enterprises or scientific research institutes to accurately judge whether problems exist in the test process, and does not need to consider the influence of sample component segregation on the test results; and technical support is provided for solving the problem of dispute between the accuracy of the steel end hardenability test and the quality of steel products.

Description

Technical Field

[0001] The invention belongs to the technical field of inspection and testing, and particularly relates to a method for preparing a standard sample for an end hardenability test. Background Art

[0002] According to the national standard GB / T225 "End quenching test method for hardenability of steel", the accuracy of the test data is related to the chemical composition segregation of the end hardenability specimen and the standardization of the test process.

[0003] (1) Steels that require end hardenability testing generally have high alloy content and large chemical composition segregation. During the test, the test values ​​often fluctuate greatly, and the test data are prone to exceed the standard or agreement.

[0004] (2) The end hardenability test process is relatively complicated, including sampling, sample preparation, heat treatment, end quenching, hardness testing and data collation. Problems in any process will affect the test results.

[0005] When testing according to this standard, when there are issues with the accuracy of test results, it is impossible to determine whether the cause is the sample or non-standard testing procedures. The test results cannot effectively guide metallurgical process adjustments or resolve disputes over steel product quality.

[0006] Existing techniques involve sampling based on the test steel type, with the sample center located 20 mm from the round steel surface. Different steel types result in varying degrees of chemical composition segregation, and eccentric turning results in poor uniformity in chemical composition and metallographic structure across the sample surface.

[0007] When end-hardenability tests are conducted on samples prepared according to existing methods and compared between different companies, if any inspection deviation occurs, it cannot be accurately determined whether it is caused by the sample or the non-standard inspection process. Summary of the Invention

[0008] The object of the present invention is to provide a method for preparing a standard specimen for an end hardenability test, wherein 45 high-quality carbon hot-rolled structural round steel with a small diameter, low alloy content, and small chemical composition segregation is selected as the raw material for the end hardenability standard specimen, and after being prepared into a cylindrical blank, it is normalized and concentrically turned on a lathe, thereby ensuring the uniformity of the metallographic structure and chemical composition of the specimen and avoiding inspection deviation caused by sample reasons during inspection.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A method for preparing a standard specimen for an end hardenability test comprises the following steps:

[0011] 1) Raw material selection: 45 high-quality carbon hot-rolled structural round steel is selected as the blank raw material; the specifications of the selected 45 high-quality carbon hot-rolled structural round steel are: diameter 35mm~40mm, length 200mm~280mm.

[0012] 2) Blank processing: Use a lathe to prepare the 45 carbon hot-rolled structural round steel blank into a cylindrical blank with a diameter of φ30mm~φ32mm and a length of 150mm~φ160mm;

[0013] 3) Blank heat treatment: The cylindrical blank is normalized with the following process: heating to 850℃~870℃ and keeping it for 30min~35min, then air cooling to room temperature after being taken out of the furnace;

[0014] 4) Specimen Finishing: The cylindrical blank cooled to room temperature is concentrically turned on a lathe to produce a standard end hardenability specimen with a flange at the end. The cylinder diameter of the standard specimen is φ25mm to φ25.5mm, and the total length of the standard specimen is 100±0.5mm; the flange diameter is φ30mm to φ32mm, and the flange thickness is 3±0.5mm.

[0015] The surface roughness parameter Ra of the sample is not greater than 1.6μm.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The end hardenability standard specimen prepared by the method of the present invention has good consistency in test results. Different enterprises or research institutes use the specimen to conduct end hardenability test comparisons, and can accurately determine whether there are problems in the test process without considering the influence of sample composition segregation on the test results. This provides technical support for resolving the accuracy of steel end hardenability tests and product quality disputes. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the hot-rolled structural round steel sample used for sampling.

[0019] Figure 2 Schematic diagram of the cylindrical blank after sample processing of the present invention.

[0020] Figure 3 Schematic diagram of the hardenability standard specimen with flange end according to the present invention.

[0021] In the figure: 11-hot-rolled structural round steel, 21-cylindrical blank, 31-end hardenability standard specimen with flange, 32-flange. DETAILED DESCRIPTION

[0022] The specific embodiments of the present invention will be further described below in conjunction with examples. The following examples are used to specifically illustrate the content of the present invention. These examples are only general descriptions of the content of the present invention and do not limit the content of the present invention.

[0023] See Figure 1 A method for preparing a standard specimen for an end hardenability test comprises the following steps:

[0024] 1) Raw material selection: 45 high-quality carbon hot-rolled structural round steel 11 is selected as the blank raw material; the specifications of the selected 45 high-quality carbon hot-rolled structural round steel 11 are: diameter 35mm~40mm, length 200mm~280mm.

[0025] 2) Blank processing: 45 carbon hot-rolled structural round steel 11 blank raw material is prepared into cylindrical blanks 21 with a diameter of 30 mm to 32 mm and a diameter of 150 mm to 160 mm using a lathe;

[0026] 3) Blank heat treatment: The cylindrical blank 21 is subjected to normalizing treatment, and the treatment process is: heating to 850°C to 870°C and keeping the temperature for 30min to 35min, and then air cooling to room temperature after being taken out of the furnace;

[0027] 4) Specimen Finishing: The cylindrical blank cooled to room temperature is concentrically turned on a lathe to produce a standard end-hardenability specimen 31 with a flange at the end. The cylindrical diameter of the standard specimen is φ25 mm to φ25.5 mm, and the total length of the standard specimen is 100 ± 0.5 mm; the diameter of the flange 32 is φ30 mm to φ32 mm, and the thickness of the flange 32 is 3 ± 0.5 mm.

[0028] The surface roughness parameter Ra of the sample is not greater than 1.6μm.

[0029] The present invention selects 45 high-quality carbon hot-rolled structural round steel with a small diameter, low alloy content, and minimal chemical composition segregation as the raw material for the standard end-hardenability specimen. After being prepared into a cylindrical blank, it undergoes normalizing and concentric lathing, ensuring the uniformity of the specimen's metallographic structure and chemical composition, thereby avoiding inaccurate test results due to sample-related issues during the end-hardenability test. This invention allows for benchmarking end-hardenability tests of steel between different companies, using this standard specimen to accurately determine whether the end-hardenability test process is standardized.

[0030] Example 1:

[0031] The best embodiment of the present invention is selected: a method for preparing a standard sample for an end hardenability test, comprising the following steps:

[0032] Step 1: Sampling: Select 45 high-quality carbon hot-rolled structural round steel with a diameter of φ35mm and a length of 220mm.

[0033] Step 2: Processing: Use a lathe to concentrically turn the 45 round steel into a cylindrical blank with a diameter of φ30mm and a length of 150mm.

[0034] Step 3: Heat treatment: Normalize the cylindrical blank. Heat to 860°C and hold for 30 minutes. Air cool to room temperature after exiting the furnace.

[0035] Step 4. Finishing: The cylindrical blank cooled to room temperature is concentrically turned into an end hardenability standard specimen with a flange at the end, a cylindrical diameter of φ25 mm, and a total length of 100 mm. The thickness of the flange is 3 mm, the diameter is φ30 mm, and the surface roughness parameter Ra of the specimen is not greater than 1.6 μm.

[0036] The resulting standard end-hardenability specimen can be used for benchmarking end-hardenability tests between different companies or research institutes, avoiding inaccurate test results due to specimen issues. Using this standard specimen allows accurate assessment of the standardization of the end-hardenability test process.

Claims

1. A method for preparing a standard specimen for an end hardenability test, characterized in that: The method comprises the following steps: 1) Raw material selection: 45 carbon hot-rolled structural round steel is selected as the blank raw material; 2) Blank processing: 45 carbon hot-rolled structural round steel blanks are prepared into cylindrical blanks using a lathe; 3) Blank heat treatment: The cylindrical blank is normalized with the following process: heating to 850℃~870℃ and keeping it for 30min~35min, then air cooling to room temperature after being taken out of the furnace; 4) Specimen finishing: The cylindrical blank cooled to room temperature is concentrically turned on a lathe to prepare a cylindrical end hardenability standard specimen with a flange at the end.

2. The method for preparing a standard specimen for an end hardenability test according to claim 1, wherein: The specifications of the selected 45 carbon hot-rolled structural round steel are: diameter 35mm~40mm, length 200mm~280mm.

3. The method for preparing a standard specimen for an end hardenability test according to claim 1, wherein: The dimensions of the cylindrical blank are: diameter φ30mm to φ32mm, length 150mm to φ160mm.

4. The method for preparing a standard specimen for an end hardenability test according to claim 1, wherein: The cylindrical diameter of the standard sample is φ25 mm to φ25.5 mm, and the total length of the standard sample is 100±0.5 mm.

5. The method for preparing a standard specimen for an end hardenability test according to claim 1 or 4, wherein: The flange diameter is φ30mm to φ32mm, and the flange thickness is 3±0.5mm.

6. The method for preparing a standard specimen for an end hardenability test according to claim 1, wherein: The surface roughness parameter Ra of the sample is not greater than 1.6μm.

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