Method for determining a steel material upset cracking factor

Abstract

The application relates to the technical field of steel materials, and discloses a method for determining a steel material upset cracking factor. The method comprises the following steps: obtaining a steel material sample, pickling the steel material sample to obtain a pickling sample; checking defects on the surface of the pickling sample, marking the defect positions and recording defect data; performing an upset test on the pickling sample to obtain an upset sample; checking whether the surface of the upset sample is cracked; if the surface of the upset sample is cracked, obtaining the cracking position, the defect position and the defect data; obtaining the cracking position, the defect position and the defect data corresponding to a plurality of steel material samples; and analyzing the correlation degrees of the plurality of defect positions, the defect data and the cracking position. The cracking position, the marked defect position and the defect data corresponding to a plurality of steel material samples are obtained through a plurality of experiments, so that the correlation degrees of certain surface defects or near-surface defects and upset cracking are quantitatively analyzed, thereby targetedly guiding process control of a steel rolling production line, and finally improving product quality.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel materials, in particular, relates to a method for determining a top forging cracking factor of a steel material. BACKGROUND

[0002] At present, in recent years, high-quality special steel develops rapidly, and contributes to the economic development of China and the world. High-quality special steel generally needs to be further processed into parts by downstream users, and the quality of steel materials determines the service life and safety of machinery. Taking fastener steel as an example, the consumption of fastener steel in China broke through 100 million tons in 2019, accounting for about 45% of the global total output. In addition to the axial drawing process, the radial upsetting process is also added to the fastener steel, and the particularity and strictness of the quality requirement lies in that the user uses 100% inspection on the product in the process to ensure the service life and safety in mechanical connection.

[0003] The top forging cracking is generally affected by many factors, and the surface or near-surface defects of the steel material are the main causes of the top forging cracking of the steel material. The causes of the surface or near-surface defects of the steel material are complex, and the influence degree of various defects and their severity on the top forging cracking of the steel material is also different. It is of great significance to find out the main defect influencing factors by studying the correlation degree of different surface (near-surface) defect types and defect degrees on the top forging cracking, and performing qualitative and quantitative analysis, so as to guide the targeted improvement of the rolling production line and finally improve the product quality.

[0004] At present, some scholars at home and abroad have studied whether the multi-pass rolling of the casting crack defects can be welded, but there is no direct experimental evidence to support the influence of which type of surface defect on the top forging cracking of the steel material. SUMMARY

[0005] The purpose of the present application is to provide a method for determining a top forging cracking factor of a steel material, and to obtain the cracking position, marked defect position and defect data of a plurality of steel samples through a plurality of experiments, so as to quantitatively analyze the correlation degree of a certain surface defect (near-surface defect) and the top forging cracking, and to guide the optimization of the rolling production line in a targeted manner, and finally to improve the product quality.

[0006] Other characteristics and advantages of the present application will become apparent from the following detailed description, or will be learned by practice of the present application.

[0007] According to an aspect of the embodiments of the present application, a method for determining cracking factors of a steel material is provided. The method further comprises: obtaining a steel sample, pickling the steel sample as a pickled sample, checking defects on the surface of the pickled sample, marking defect positions and recording defect data, performing a top forging test on the pickled sample as a top forged sample, checking whether the surface of the top forged sample is cracked, and if the surface of the top forged sample is cracked, obtaining cracking positions, defect positions and defect data. The method further comprises: obtaining cracking positions, defect positions and defect data corresponding to a plurality of steel samples, and analyzing correlation degrees of a plurality of the defect positions, defect data and the cracking positions.

[0008] In some embodiments, in the obtaining a steel sample, the method further comprises: obtaining a steel sample with a preset height higher than an ideal height.

[0009] In some embodiments, the preset height is between 1 mm and 3 mm.

[0010] In some embodiments, after the checking defects on the surface of the pickled sample, marking defect positions and recording defect data, the method further comprises: sequentially performing coarse grinding, fine grinding and polishing on both ends of the steel sample, placing the steel sample on a metallographic microscope, and observing the steel sample, marking defect positions and recording defect data.

[0011] In some embodiments, in the sequentially performing coarse grinding, fine grinding and polishing on both ends of the steel sample, the method further comprises: sequentially performing coarse grinding, fine grinding and polishing on both ends of the steel sample according to a standard for preparing a metallographic sample.

[0012] In some embodiments, the defect data includes a defect type and a defect size.

[0013] In some embodiments, the defect type includes scratch defects, folding defects, crack defects, large inclusions and porosity defects.

[0014] In some embodiments, in the marking defect positions and recording defect data, the method further comprises: using different colored oil pens to mark different defect types.

[0015] In some embodiments, in the performing a top forging test on the pickled sample as a top forged sample, the method further comprises: using 1 / 3 cold top forging for the top forging test.

[0016] In some embodiments, in the obtaining cracking positions, defect positions and defect data corresponding to a plurality of steel samples, and analyzing correlation degrees of a plurality of the defect positions, defect data and the cracking positions, the method further comprises: analyzing correlation degrees of a plurality of the defect positions, defect data and the cracking positions by statistical analysis.

[0017] Compared with the prior art, the technical scheme of the present application has the following remarkable advantages:

[0018] (1) The present application uses multiple test methods on the same sample by acid pickling first, then making metallographic, and then performing 1 / 3 cold upset forging, which is superior to the traditional test method. The traditional test method has the disadvantage that different sample sampling positions may or may not discover intermittent defects by different test methods. However, the influence of a certain defect on the upset performance cannot be determined by the traditional acid pickling macroscopic test and metallographic test. The present application completes the three test methods of acid pickling sample preparation, metallographic sample preparation, and cold upset forging sample preparation on the same sample, and the causality is more deterministic. The sample height is determined according to the 1 / 3 cold upset height + (1-3mm), which is different from the traditional metallographic sample and acid pickling sample.

[0019] (2) The present application marks the surface defect (near-surface defect) position in the radial and axial directions, and determines the influence of the defect on the upset by whether the marked position cracks after upset, which is more direct, more accurate, and more deterministic in causality. The method of marking different defects with different colors can more effectively identify the influence of different defects on the upset cracking.

[0020] (3) The present application obtains the cracking position, marked defect position, and defect data of multiple steel samples through large-scale industrial production test, statistically analyzes the data, and finally obtains the correlation degree of surface defects (near-surface defects) on the upset cracking of steel, so as to guide the improvement of the rolling production line process control and finally improve the product quality.

[0021] (4) The test method of the present application can replace the macroscopic test and metallographic test, and reduce the test workload.

[0022] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0023] The above and other features and advantages of the present application will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings.

[0024] Figure 1 A flowchart according to one embodiment of the present application is shown. DETAILED DESCRIPTION

[0025] Example implementations will now be described more fully with reference to the accompanying drawings. Example implementations can be implemented in any

[0026] Moreover, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the application. One skilled in the relevant art will recognize, however, that the

[0027] The block diagrams in the drawings show only the functionality of the embodiments and do not imply any particular physical or architectural arrangement of the devices, systems, or methods. No inference should be drawn regarding the

[0028] The flow diagrams depicted herein are examples of sequences of operations that can be performed, for example, by a computing device. The depicted examples are not meant to be limiting, as one of skill in the art could readily devise other methods that are equivalent in function to those illustrated. Moreover, the steps recited in any of the examples are not necessarily to be performed in the order written. The order of the steps is permissible, for example, as some steps can be performed in an order other than the order described.

[0029] For a better understanding of the present application, reference will be made to the following Figure 1 A brief introduction is provided for the present application.

[0030] According to some embodiments, the present application provides a method for determining a cracking factor of a steel top forging, the method further comprising:

[0031] Step 101, obtaining a steel sample, and performing acid pickling on the steel sample to obtain an acid-pickled sample;

[0032] Step 102, checking defects on the surface of the acid-pickled sample, marking the defect positions and recording the defect data;

[0033] Step 103, performing a top forging test on the acid-pickled sample to obtain a top forging sample;

[0034] Step 104, checking whether the surface of the top forging sample is cracked, and if the surface of the top forging sample is cracked, obtaining the cracking position, the defect position, and the defect data;

[0035] In step 105, the cracking position, defect position and defect data corresponding to a plurality of steel samples are obtained, and the correlation degree of the plurality of defect positions, defect data and the cracking position is analyzed.

[0036] Based on the above embodiment, in step 101, a steel sample is obtained, and the steel sample is pickled, and after pickling, the sample is used as a pickling sample;

[0037] In step 102, the defects on the surface of the pickling sample after pickling are checked, the positions of the defects are marked for subsequent arrangement, and the defect data are recorded. The defect data include defect type and defect size, the defect type includes scratch defect, folding defect, crack defect, large inclusion and porosity defect, and the defect size includes length and depth. Different defect types are marked with different colored oil pens for easy identification.

[0038] In step 103, the pickling sample is subjected to a top forging test to obtain a top forging sample, and the top forging test adopts 1 / 3 cold top forging.

[0039] Further, the top forging test includes cold top forging and hot top forging, and 1 / 3 cold top forging requires that a steel material with a diameter of d and a height of h is cut, and then compressed along the height direction on a top forging testing machine until the height H is 1 / 3 h, and the steel material does not crack at this height. Top forging also includes 1 / 4 top forging and 1 / 2 top forging. Obviously, 1 / 4 top forging has higher requirements for the quality of the steel material, and vice versa, 1 / 2 top forging has relatively low requirements for the quality of the steel material. Generally, high-quality steel is subjected to 1 / 3 cold or hot top forging test. The difference between cold top forging and hot top forging is the top forging temperature of the material. Cold top forging is performed at room temperature, and hot top forging is performed at a temperature of 900 DEG C or higher.

[0040] In step 104, after 1 / 3 cold top forging, the surface of the top forging sample is carefully checked for cracking. If the surface of the top forging sample cracks, the cracking position, defect position and defect data are recorded, and a record table is filled in.

[0041] In step 105, steps 101 to 104 are repeated, the cracking position, defect position and defect data corresponding to a plurality of steel samples with cracking are obtained, and whether each different defect position and defect data is the cause of top forging cracking and the relationship between the defect position and the cracking position are analyzed. The correlation degree of the plurality of defect positions, defect data and the cracking position is analyzed by statistical analysis.

[0042] Finally, the correlation degree of surface defects (near-surface defects) to steel top forging cracking is obtained, which is used to guide the improvement of the rolling production line process control and finally improve the product quality.

[0043] According to some embodiments, in step 101, the method further comprises:

[0044] The steel sample with a preset height higher than the ideal height is obtained. The ideal height is the height h required by the standard, and the preset height can be set according to actual needs. In some embodiments, the preset height can be set to any value between 1 mm and 3 mm according to actual needs. That is, in step 101, when the steel sample is obtained, the steel sample with a height of h+the preset height is obtained. By increasing the preset height, there is a certain reserved height when the two ends need to be polished. Preventing the height of the product from being shortened due to grinding when there is no reserved height and the two ends of the product need to be ground.

[0045] According to some embodiments, after step 102, checking the defects on the surface of the pickling sample, marking the defect positions and recording the defect data, the method further comprises:

[0046] Step 1021, sequentially rough grinding, fine grinding and polishing are performed on the two ends of the steel sample;

[0047] Step 1022, the steel sample is placed on a metallographic microscope;

[0048] Step 1023, the steel sample is observed, the defect positions are marked and the defect data are recorded.

[0049] Based on the above embodiments, in step 1021, according to the standard for making metallographic samples, rough grinding is first performed on both ends of the steel sample; and then, according to the standard for making metallographic samples, fine grinding and polishing are performed on both ends of the steel sample, so as to facilitate subsequent observation by a microscope.

[0050] In step 1022, the steel sample is placed on a metallographic microscope, and the steel sample is rotated from a certain point along the circumferential direction of the cross section of the steel sample.

[0051] Step 1023, the steel sample is observed, and when a defect is encountered on the surface or near the surface, the defect position is marked and the defect data are recorded. The steel sample is turned over and the observation, marking and recording are continued, and the observation of the entire steel sample is completed, and all defect positions are marked and all defect data are recorded. Different colors of oil pens are used to mark different defect types for easy identification. For example, green marks scratches, blue marks folds, yellow marks cracks, black marks large inclusions, red marks pores, and so on.

[0052] (1) The present application is superior to the traditional test method by using multiple test methods on the same sample through acid pickling first, then making metallographic, and then 1 / 3 cold upset forging. The traditional test method has the disadvantage that different sample sampling positions may or may not be found by different experimental methods for intermittent defects, and it is not certain that a certain defect has what influence on the upset performance through the traditional acid pickling macroscopic test and metallographic test. The present application completes the three test methods of acid pickling sample preparation, metallographic sample preparation and cold upset forging sample preparation on the same sample, and the causality is more certain. The sample height is determined according to 1 / 3 cold upset height + (1-3mm), which is different from the traditional metallographic sample and acid pickling sample.

[0053] (2) The present application is more direct, more accurate and more certain in causality by marking the surface defect (near surface defect) position in the radial and axial directions, and judging whether the defect has an influence on the upset by whether it cracks after upsetting; and the method of marking different defects with different colors can more effectively identify the influence of different defects on the end cracking.

[0054] (3) The present application obtains the cracking position, marked defect position and defect data of multiple steel samples through large-scale industrial production test, and finally obtains the correlation degree of surface defects (near surface defects) to steel upset cracking through statistical analysis of the data, so as to guide the improvement of the rolling production line process control and finally improve the product quality.

[0055] (4) The present application can replace the macroscopic test and metallographic test to reduce the test workload.

[0056] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application.

[0057] Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the embodiments disclosed herein. It is intended that the present application cover any and all variations of the present application which come within the scope of the general inventive concepts and including all such variations as fall within the scope of the appended claims, the scope of which is not to be limited to the specific structures herein disclosed but in accordance with the prior art generally.

[0058] It should be understood that the present application is not limited to the precise construction that has been described above and shown in the accompanying drawings, and that various modifications and changes can be made by those skilled in the art without departing from the scope of the present application. The scope of the present application is limited only by the appended claims.

Claims

1. A method for determining a factor of a head forging cracking of a steel material, characterized by, The method further comprises: obtaining a steel sample, pickling the steel sample as a pickling sample; checking defects on the surface of the pickling sample, marking defect positions and recording defect data; after the checking defects on the surface of the pickling sample, marking defect positions and recording defect data, the method further comprises: rough grinding, fine grinding and polishing the two ends of the pickling sample in sequence; placing the pickling sample on a metallographic microscope; observing the pickling sample, marking defect positions and recording defect data; performing a upset test on the metallographic sample as a upset sample; checking whether the surface of the upset sample is cracked, if the surface of the upset sample is cracked, obtaining the cracking position, defect position and defect data; obtaining the cracking position, defect position and defect data corresponding to a plurality of steel samples, and analyzing the correlation degree of a plurality of the defect positions, defect data and the cracking position; in the obtaining a steel sample, the method further comprises: obtaining a steel sample with a preset height higher than the ideal height; the preset height is between 1mm and 3mm; in the performing a upset test on the metallographic sample as a upset sample, the method further comprises: the upset test adopts 1 / 3 cold upset; in the obtaining the cracking position, defect position and defect data corresponding to a plurality of steel samples, and analyzing the correlation degree of a plurality of the defect positions, defect data and the cracking position, the method further comprises: analyzing the correlation degree of a plurality of the defect positions, defect data and the cracking position by statistical analysis.

2. The method of claim 1, wherein, in the rough grinding, fine grinding and polishing the two ends of the pickling sample in sequence, the method further comprises: according to the standard for making metallographic samples, rough grinding, fine grinding and polishing the two ends of the pickling sample in sequence.

3. The method of claim 1, wherein, the defect data includes defect type and defect size.

4. The method of claim 3, wherein, the defect type includes scratch defect, folding defect, crack defect, large inclusion and porosity defect.

5. The method of claim 4, wherein, in the marking defect positions and recording defect data, the method further comprises: using different colored oil pens to mark different defect types.

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