Evaluation method for machinability of sulfur-containing free-cutting steel
By testing the hardness and sulfide distribution of sulfur-containing free-cutting steel and calculating its machinability, the problem of lack of evaluation methods in the existing technology is solved, and an effective assessment of processing efficiency and cost is achieved.
Patent Information
- Application Number
- CN202511135864.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-14
- Publication Date
- 2025-10-17
AI Technical Summary
The existing technology lacks an intuitive and effective method to grade the machinability of sulfur-containing free-cutting cold-drawn bars, which affects processing efficiency and cost accounting.
By testing the hardness, uniformity and sulfide distribution of the rods, using the Vickers hardness test method and scanning electron microscopy, the machinability of the rods is comprehensively evaluated by assignment calculation, including the absolute value of hardness, standard deviation and sulfide inclusion level, to determine its processing difficulty.
It provides an intuitive evaluation method to help enterprises estimate processing efficiency and costs and guide production and operations.
Smart Images
Figure CN120801085A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of steel processing, and particularly relates to a method for evaluating the machinability of sulfur-containing free-cutting steel. BACKGROUND
[0002] The sulfur-containing free-cutting cold-drawn bar has a wide application in the numerical control turning processing industry, and there is no intuitive and effective evaluation method for grading the machinability of the bar. The grading of the machinability of the bar can be used to estimate the processing efficiency, calculate the cost, and guide the production and operation of an enterprise. Therefore, it is necessary to research an intuitive and effective evaluation method for grading the machinability of the bar. SUMMARY
[0003] The application aims to provide a method for evaluating the machinability of sulfur-containing free-cutting steel, which can complete the grading of the machinability of the bar by testing the hardness of the bar, the uniformity of the bar, and the distribution mode of sulfides, and guide the production and operation of an enterprise.
[0004] To achieve the above-mentioned application purposes, the technical scheme of the application is as follows. A method for evaluating the machinability of sulfur-containing free-cutting steel, characterized in that the method steps are as follows: (1) Test the hardness value of the cross section: sample and test the longitudinal cross section of the sulfur-containing free-cutting cold-drawn bar, measure the hardness along the radial direction of the bar from a certain distance away from the surface, measure the hardness values of a plurality of points at equal intervals, and obtain a group of hardness values; according to the above method, a group of hardness values of the same number of points are obtained by measuring the same distance between each cross section of the same bar; (2) Assign values to the hardness test data: obtain the average value and the standard deviation of all the hardness values obtained in step (1); assign the absolute value grade of hardness to the obtained average value, and the absolute value grade of hardness assignment standard is that the range of hardness values less than 180HV or greater than 300HV is assigned a value of 3, representing difficult processing, the range of hardness values greater than or equal to 240HV and less than or equal to 300HV is assigned a value of 2, representing relatively easy processing, and the range of hardness values greater than or equal to 180HV and less than 240HV is assigned a value of 1, representing easy processing; assign the standard deviation grade of hardness to the obtained standard deviation, and the standard deviation grade of hardness assignment standard is that the standard deviation less than 5 is assigned a value of 1, representing good processing, the range of standard deviation greater than or equal to 5 and less than 10 is assigned a value of 2, representing relatively good processing, the range of standard deviation greater than or equal to 10 and less than 20 is assigned a value of 3, representing general processing difficulty, and the standard deviation greater than or equal to 20 is assigned a value of 4, representing difficult processing; (3) Sulfide inclusion rating: Test the sulfide inclusions of the bar, and divide them into 1st, 2nd, 3rd and 4th grades from easy to difficult according to the number of sulfide inclusion forms, and assign values 1, 2, 3 and 4 respectively to obtain the sulfide inclusion rating value; (4) Comprehensive value calculation: The product of the hardness absolute value rating, the hardness standard deviation rating and the sulfide inclusion rating is taken as the comprehensive value, and the turning performance of the material is sorted according to the comprehensive value, and the smaller the comprehensive value is, the easier the processing is.
[0005] Further, in the above step (1), the longitudinal section of the sulfur-containing free-cutting cold-drawn bar with a diameter of 4.0 mm or more is sampled and tested, and the Vickers hardness is measured under a force of 5KG. The hardness is measured along the radial direction of the bar starting from more than 0.1 mm from the surface, and the interval is more than 0.5 mm, and 7 or more hardness values are measured.
[0006] Further, in the above step (1), two longitudinal sections of the same bar are measured, and a group of hardness values of the same number of points are obtained by measuring at the same interval.
[0007] Further, in the above step (1), the radial direction of the bar is along the diameter direction when the bar is a round bar, and along the opposite edge distance direction when the bar is a hexagonal bar or an octagonal bar.
[0008] Further, in the above step (3), the sulfide inclusion form of the bar is tested by using a scanning electron microscope.
[0009] Further, the above method step (3) is completed before step (1).
[0010] The beneficial effects of the present application are: the evaluation method of the present application can intuitively evaluate the turning performance of the bar before the sulfur-containing free-cutting cold-drawn bar is cut, by detecting the hardness, the uniformity of the hardness and the distribution form of the non-metallic inclusions, and by assigning values and calculating, which can help the bar processing enterprises to estimate the processing efficiency and calculate the cost, and play a guiding role in the production and operation of enterprises. BRIEF DESCRIPTION OF DRAWINGS
[0011] Figure 1 The figure is a brief flow chart of the evaluation method of the present application; Figure 2 Figure 1 of the evaluation method of the present application: hardness test data of different test points of 1# sample and 2# sample; Figure 3 Figure 2 of the evaluation method of the present application: value assignment and calculation of 1# sample and 2# sample; Figure 4 Figure 3 of the evaluation method of the present application: hardness test data of different test points of 3# sample and 4# sample; Figure 5 Chart 4 for the evaluation method of the present application: 3# sample and 4# sample assignment calculation; Figure 6 Chart 5 for the evaluation method of the present application: 5# sample and 6# sample hardness test data at different test points; Figure 7 Chart 6 for the evaluation method of the present application: 5# sample and 6# sample assignment calculation.
[0012] Among them, S1, cross-section hardness value test, S2, hardness test data assignment, S3, sulfide inclusion grade evaluation, S4, comprehensive assignment calculation. DETAILED DESCRIPTION
[0013] The following gives an embodiment of the present application and explains the present application in combination with the given embodiment, but the given embodiment does not constitute any limitation on the present application: Example 1: as Figure 1 An evaluation method of cutting property of sulfur-containing free-cutting steel, the method steps are as follows: (1) Cross-section hardness value test: sample test is performed on the longitudinal section of a sulfur-containing free-cutting cold-drawn bar with a diameter of 6.0 mm, Vickers hardness is measured under a force of 5KG, hardness is measured along the diameter direction of the bar starting from more than 0.2mm away from the surface, the interval is 0.8mm, and the hardness values of 8 points are measured; another set of hardness values of 8 points are obtained by measuring the same interval on another longitudinal section of the same bar according to the above method.
[0014] (2) Hardness test data assignment: the average value and the standard deviation of the hardness values of the 16 test points obtained in step (1) are calculated respectively; the average value is assigned a hardness absolute value grade, and the hardness absolute value grade assignment standard is: the range of hardness value less than 180HV or greater than 300HV is assigned a value of 3, representing difficult to process, the range of hardness value greater than or equal to 240 and less than or equal to 300HV is assigned a value of 2, representing relatively easy to process, and the range of hardness value greater than or equal to 180 and less than 240HV is assigned a value of 1, representing easy to process; the standard deviation is assigned a hardness standard deviation grade, and the hardness standard deviation grade assignment standard is: the standard deviation less than 5 is assigned a value of 1, representing good processing; the range of standard deviation greater than or equal to 5 and less than 10 is assigned a value of 2, representing relatively good processing; the range of standard deviation greater than or equal to 10 and less than 20 is assigned a value of 3, representing general processing difficulty, and the standard deviation greater than or equal to 20 is assigned a value of 4, representing difficult to process.
[0015] (3) Sulfide inclusion grade evaluation: the sulfide inclusions of the bar are tested by using a scanning electron microscope, and are divided into 1st, 2nd, 3rd and 4th grades from easy to difficult according to the shape and quantity of the sulfide inclusions, and are assigned values of 1, 2, 3 and 4 respectively to obtain the sulfide inclusion grade assignment.
[0016] (4) Comprehensive evaluation calculation: the product of the hardness absolute value grade, the hardness standard deviation grade and the sulfide inclusion grade is taken as the comprehensive evaluation, and the turning performance of the material is ranked according to the comprehensive evaluation, and the smaller the comprehensive evaluation is, the easier the material is to process.
[0017] Figure 2 and Figure 3 Test and calculation are performed on the 1# sample and the 2# sample rods with a diameter of 6.0 mm: wherein chart 1 is the hardness test data of different test points of the 1# sample and the 2# sample, and chart 2 is the evaluation calculation of the 1# sample and the 2# sample; From the above comprehensive evaluation comparison, the 1# sample is better than the 2# sample in terms of machinability.
[0018] Example 2: as Figure 1 A method for evaluating the machinability of a sulfur-containing free-cutting steel material, the method steps are as follows: (1) Cross-sectional hardness value test: sample test is performed on the longitudinal cross section of the sulfur-containing free-cutting cold-drawn rod with a regular octagonal shape and a 5.0 mm opposite edge distance, Vickers hardness is measured under a 5KG force, the hardness is measured from more than 0.4 mm away from the surface along the opposite edge distance direction of the rod, the interval is 0.7 mm, and the hardness values of 7 points are measured; according to the above method, another group of hardness values of 7 points are obtained by measuring the same distance on another two longitudinal cross sections of the same rod.
[0019] (2) Hardness test data evaluation: the average value and the standard deviation of the hardness values of the 21 test points obtained in step (1) are calculated; the average value is evaluated according to the hardness absolute value grade, the hardness absolute value grade evaluation standard is: the range of hardness value less than 180HV or greater than 300HV is evaluated as 3, representing difficult to process, the range of hardness value greater than or equal to 240 and less than or equal to 300HV is evaluated as 2, representing relatively easy to process, and the range of hardness value greater than or equal to 180 and less than 240HV is evaluated as 1, representing easy to process; the standard deviation is evaluated according to the hardness standard deviation grade, the hardness standard deviation grade evaluation standard is: the standard deviation less than 5 is evaluated as 1, representing good processing; the range of standard deviation greater than or equal to 5 and less than 10 is evaluated as 2, representing relatively good processing; the range of standard deviation greater than or equal to 10 and less than 20 is evaluated as 3, representing general processing difficulty, and the standard deviation greater than or equal to 20 is evaluated as 4, representing difficult to process.
[0020] (3) Sulfide inclusion grade evaluation: the sulfide inclusions of the rod are tested by using a scanning electron microscope, and are divided into 1st, 2nd, 3rd and 4th grades from easy to difficult according to the sulfide inclusion form and quantity, and are evaluated as 1, 2, 3 and 4 respectively to obtain the sulfide inclusion grade evaluation.
[0021] (4) Comprehensive evaluation calculation: the product of the hardness absolute value grade evaluation, the hardness standard deviation grade evaluation and the sulfide inclusion grade evaluation is taken as the comprehensive evaluation, and the turning performance of the material is ranked according to the comprehensive evaluation, and the smaller the comprehensive evaluation is, the easier the material is to process.
[0022] Figure 4 and Figure 5 Test and calculate 3# and 4# samples with a regular octagonal opposite edge distance of 5.0mm: Wherein, chart 3 is the hardness test data of different test points of 3# and 4# samples, and chart 4 is the evaluation calculation of 3# and 4# samples. From the above comprehensive evaluation comparison, the machinability of 3# sample is better than that of 4# sample.
[0023] Example 3: An evaluation method for the machinability of a sulfur-containing free-cutting steel material, the method steps are as follows: (1) Sulfide inclusion grade evaluation: test the sulfide inclusions of the bar using a scanning electron microscope, and divide them into grades 1, 2, 3 and 4 according to the number of sulfide inclusion shapes, from easy to difficult, and assign values 1, 2, 3 and 4 respectively, to obtain the sulfide inclusion grade evaluation.
[0024] (2) Cross-sectional hardness value test: sample and test the longitudinal cross section of the sulfur-containing free-cutting cold-drawn bar with a regular hexagonal opposite edge distance of 4.0mm, measure the hardness under a force of 5KG using a Vickers hardness tester, measure the hardness from 0.2mm above the surface along the opposite edge distance direction of the bar, at an equal distance interval of 0.6mm, and measure the hardness values of 7 points; according to the above method, measure another set of 7 points at the same interval on the other longitudinal cross section of the same bar.
[0025] (3) Hardness test data evaluation: calculate the average value and the standard deviation of the hardness values of the 14 test points obtained in step (1); for the average value, perform hardness absolute value grade evaluation, the hardness absolute value grade evaluation standard is: assign a value of 3 to the range of hardness values less than 180HV or greater than 300HV, representing difficult to process, assign a value of 2 to the range of hardness values greater than or equal to 240HV and less than or equal to 300HV, representing relatively easy to process, and assign a value of 1 to the range of hardness values greater than or equal to 180HV and less than 240HV, representing easy to process; for the standard deviation, perform hardness standard deviation grade evaluation, the hardness standard deviation grade evaluation standard is: assign a value of 1 to the standard deviation less than 5, representing good processing; assign a value of 2 to the range of standard deviation greater than or equal to 5 and less than 10, representing relatively good processing; assign a value of 3 to the range of standard deviation greater than or equal to 10 and less than 20, representing general processing difficulty, and assign a value of 4 to the standard deviation greater than or equal to 20, representing difficult to process.
[0026] (4) Comprehensive assignment calculation: the product of the hardness absolute value grade assignment, the hardness standard deviation grade assignment and the sulfide inclusion grade assignment is taken as the comprehensive assignment, and the turning property of the material is sorted according to the comprehensive assignment, and the smaller the comprehensive assignment is, the easier the processing is.
[0027] Figure 6 and Figure 7 The 5# sample and the 6# sample with a side distance of 4.0 mm are tested and calculated: Wherein, the chart 5 is the hardness test data chart of different test points of the 5# sample and the 6# sample, and the chart 6 is the assignment calculation of the 5# sample and the 6# sample From the above comparison of the comprehensive assignment, the turning property of the 6# sample is better than that of the 5# sample.
[0028] The above is the preferred embodiment of the present application, it should be pointed out that, for the ordinary skilled in the art, without departing from the principles of the present application, can also make a number of improvements and modifications, these improvements and modifications are also considered to be the protection scope of the present application.
Claims
1. A method for evaluating the machinability of sulfur-containing free-cutting steel, characterized in that: The method steps are as follows: (1) Section hardness test: The longitudinal section of the sulfur-containing free-cutting cold-drawn bar is sampled and tested. The Vickers hardness test method is used to measure the hardness along the radial direction of the bar from a certain distance from the surface. The hardness values of several points are measured at equal intervals to obtain a set of hardness values; according to the above method, several other longitudinal sections of the same bar are measured at the same distance to obtain a set of hardness values with the same number of points; (2) Assignment of hardness test data: Calculate the average value and standard deviation of all hardness values obtained in step (1); assign the hardness absolute value grade to the average value obtained, and the standard for assigning the hardness absolute value grade is as follows: the hardness value is less than 180HV or greater than 300HV and is assigned a value of 3, which means difficult to process; the hardness value is greater than or equal to 240HV and less than or equal to 300HV and is assigned a value of 2, which means relatively easy to process; the hardness value is greater than or equal to 180HV and less than 240HV and is assigned a value of 1, which means easy to process; assign the hardness standard deviation grade to the standard deviation obtained, and the standard for assigning the hardness standard deviation grade is as follows: the standard deviation is less than 5 and is assigned a value of 1, which means good processing; the standard deviation is greater than or equal to 5 and less than 10 and is assigned a value of 2, which means relatively good processing; the standard deviation is greater than or equal to 10 and less than 20 and is assigned a value of 3, which means average processing difficulty; the standard deviation is greater than or equal to 20 and is assigned a value of 4, which means difficult processing; (3) Sulfide inclusion grade assessment: The sulfide inclusions of the bar are tested and divided into grades 1, 2, 3 and 4 according to the number of sulfide inclusion forms, with processing difficulty ranging from easy to difficult. The grades are assigned values of 1, 2, 3 and 4 respectively, and the sulfide inclusion grade is obtained. (4) Comprehensive assignment calculation: The product of the hardness absolute value grade assignment, the hardness standard deviation grade assignment and the sulfide inclusion grade assignment is taken as the comprehensive assignment. The turning properties of the materials are sorted according to the comprehensive assignment. The smaller the comprehensive assignment, the easier it is to process.
2. The method for evaluating the machinability of sulfur-containing free-cutting steel according to claim 1, wherein: In the step (1), a longitudinal section of a sulfur-containing free-cutting cold-drawn bar with a diameter of 4.0 mm or more is sampled and tested, and the Vickers hardness is measured under a force of 5 kg. The hardness is measured along the radial direction of the bar starting from 0.1 mm or more from the surface, and at equal intervals of 0.5 mm or more, and 7 or more hardness values are measured.
3. The method for evaluating the machinability of sulfur-containing free-cutting steel according to claim 1, wherein: In the above step (1), two longitudinal sections are measured on the same bar, and a group of hardness values with the same number of points are obtained by measuring each section at the same distance, so that two groups of hardness values are obtained in total.
4. The method for evaluating the machinability of sulfur-containing free-cutting steel according to claim 1, wherein: The radial direction of the rod in step (1) is along the diameter direction when the rod is a round rod, and along the opposite side distance direction when the rod is a hexagonal rod or an octagonal rod.
5. The method for evaluating the machinability of sulfur-containing free-cutting steel according to claim 1, wherein: In step (3), a scanning electron microscope is used to test the sulfide inclusion morphology of the rod.
6. The method for evaluating the machinability of sulfur-containing free-cutting steel according to claim 1, wherein: Step (3) of the method is completed before step (1).