1. A method for judging the crack generation stage of a forged workpiece is characterized in that: comprises the following steps of (a) carrying out,

acquiring a crack generation position of a forged workpiece, and cleaning and polishing the crack position of the workpiece to acquire a crack size parameter;

the crack appearance, metallographic structure, hardness change, element distribution and corrosion products of the forged workpiece are subjected to overall analysis by the aid of crack size parameters of the forged workpiece, and the cracks are analyzed in combination with the material, forging process and quenching process of the forged workpiece, so that the stage of crack generation is judged;

and qualitatively judging the crack properties by combining one or more of the crack morphology, the metallographic structure, the hardness change and the corrosion products, thereby further accurately judging the stage of crack occurrence.

2. The method of determining the stage of crack initiation in a forged workpiece according to claim 1, wherein: and the appearance analysis and judgment of the cracks realize the judgment of the initial stage of the cracks by observing and recording the change states of the cracks on the two sides of the cracks of the forged workpiece respectively.

3. The method of determining the stage of crack initiation in a forged workpiece according to claim 2, wherein: the crack morphology comprises a macrocrack morphology and a microcrack morphology; analyzing and judging the appearance of the macrocracks, and judging the initial stage of cracks by observing and recording the crack shapes and the crack shape change states presented on the two sides of the cracks of the forged workpiece;

and analyzing and judging the appearance of the micro cracks by observing and recording the crack shapes, the crack trend changes, the crack color change states and whether the cracks contain impurities or not, wherein the crack shapes, the crack trend changes and the crack color change states are presented on two sides of the cracks of the forged workpiece, and the appearance of the micro cracks is judged at the initial stage.

4. The method of determining the stage of crack initiation in a forged workpiece according to claim 1, wherein: in the step of analyzing and judging the macrocracks, if the macrocracks appear to be saw-toothed, the macrocracks are primarily judged to be quenching cracks; if the macrocracks are in a linear shape, the macrocracks are preliminarily judged to be non-quenched cracks.

5. A method of judging the stage of crack initiation in a forged workpiece according to claim 3, wherein: and in the step of analyzing and judging the appearance of the microcracks, carrying out appearance observation on the cracks of the forged workpiece by adopting a scanning electron microscope, and acquiring crack shapes, crack trend changes, crack color change states and whether the cracks contain impurities, wherein the crack shapes, the crack trend changes and the crack color change states are presented on two sides of the cracks.

6. A method of judging the stage of crack initiation in a forged workpiece according to claim 3, wherein: and the metallographic structure analysis adopts an optical microscope to carry out microscopic detection on the metallographic structure near the cracks of the forged workpiece, and the microscopic detection comprises the steps of detecting whether a bright white structure appears near the cracks, whether the pearlite content is reduced and whether decarburization characteristics appear.

7. The method of determining the stage of crack initiation in a forged workpiece according to claim 1, wherein: and the hardness change analysis comprises the steps of cutting in a direction perpendicular to the crack and a direction parallel to the crack, forming a cross detection point every 0.2mm to 0.8mm, enabling the cross detection point to be as close to the crack as possible, performing hardness test on the cross detection point by adopting a hardness tester, obtaining whether the hardness of the crack is reduced, judging whether decarburization occurs near the crack, and judging as a forged crack.

8. The method of determining the stage of crack initiation in a forged workpiece according to claim 7, wherein: and carrying out a hardness test on the cross detection point to obtain the change condition in the direction vertical to the crack, if the hardness in the direction from the matrix to the crack in the direction vertical to the crack is in a obviously descending trend, and comparing the hardness in the direction vertical to the crack with the hardness in the direction parallel to the crack to judge whether decarburization occurs in the vicinity of the crack.

9. The method of determining the stage of crack initiation in a forged workpiece according to claim 8, wherein: if the hardness in the direction parallel to the crack is smaller than the hardness in the direction perpendicular to the crack, decarburization occurs near the crack, and the crack is judged to be a forged crack; if the hardness in the direction parallel to the crack is not less than the hardness in the direction perpendicular to the crack, no decarburization occurs in the vicinity of the crack, and it is judged as a quench crack.

10. The method of determining the stage of crack initiation in a forged workpiece according to claim 1, wherein: the deterministic judgment of the crack property comprises the following steps:

step 10: scanning the vicinity of the crack by using a scanning electron microscope, detecting whether the pearlite content of a metallographic structure of the crack is obviously reduced or not, wherein the pearlite content is reduced to below 15 percent so as to determine that the crack is generated in a forging stage, observing the appearance of the crack and detecting corrosion products obviously attached to two sides of the crack, wherein if strip-shaped substances are obviously attached to two sides of the crack, the generated corrosion products are oxides, so that the decarburization phenomenon is generated, and further, the generation of the crack in the forging stage is explained;

step 11: performing semi-quantitative analysis on strip-shaped substances obviously attached to two sides of the crack by using an energy spectrum analyzer to determine whether the strip-shaped substances are oxides or not; if the oxygen content is more than 1% and the element contains iron, it is determined as an oxide and it is determined that cracks are generated at the forging stage.

Background

In the production and use of industrial products, the number of workpieces subjected to forging processing and normalizing treatment is large, cracks are generated in the manufacturing process frequently, cracking accidents are more, and the economic loss is large. Therefore, based on the above technical problems, it is urgently needed to provide a simple and clear determination method, which can quickly and accurately determine the stage of crack generation, so as to guide the production improvement process, avoid similar cracks, improve the qualification rate of products, and have important significance for clearing process responsibility and improving the process and technology.

Disclosure of Invention

The invention aims to provide a method for judging the crack generation stage of a forged workpiece, which can effectively analyze the crack generation stage of the forged workpiece so as to accurately judge the crack generation stage, thereby being beneficial to determining the failure reason and the responsibility definition of a workpiece matrix. In order to achieve the above object, the present invention adopts the following technical effects:

according to an aspect of the present invention, there is provided a method of determining a stage of crack generation in a forged workpiece, comprising the steps of:

acquiring a crack generation position of a forged workpiece, and cleaning and polishing the crack position of the workpiece to acquire a crack size parameter; the crack appearance, metallographic structure, hardness change, element distribution and corrosion products of the forged workpiece are subjected to overall analysis by the aid of crack size parameters of the forged workpiece, and the cracks are analyzed in combination with the material, forging process and quenching process of the forged workpiece, so that the stage of crack generation is judged; and qualitatively judging the crack properties by combining one or more of the crack morphology, the metallographic structure, the hardness change and the corrosion products, thereby further accurately judging the stage of crack occurrence.

Preferably, the crack appearance analysis and judgment respectively realize the judgment of the initial stage of crack occurrence by observing and recording the change state of the cracks on two sides of the forged workpiece.

Further preferably in the above aspect, the crack morphology includes a macrocrack morphology and a microcrack morphology; analyzing and judging the appearance of the macrocracks, and judging the initial stage of cracks by observing and recording the crack shapes and the crack shape change states presented on the two sides of the cracks of the forged workpiece; and analyzing and judging the appearance of the micro cracks by observing and recording the crack shapes, the crack trend changes, the crack color change states and whether the cracks contain impurities or not, wherein the crack shapes, the crack trend changes and the crack color change states are presented on two sides of the cracks of the forged workpiece, and the appearance of the micro cracks is judged at the initial stage.

Preferably, in the step of analyzing and judging the macrocracks, if the macrocracks are saw-toothed, the quenching cracks are primarily judged; if the macrocracks are in a linear shape, the macrocracks are preliminarily judged to be non-quenched cracks.

Preferably, in the step of analyzing and judging the appearance of the microcracks, a scanning electron microscope is used for observing the appearance of the microcracks at the crack generating positions of the forged workpiece, and the crack shapes, the crack trend changes, the crack color change states and whether the cracks contain impurities or not at both sides of the cracks are obtained, so that the crack properties can be judged deterministically according to the appearance observation results of the microcracks.

Preferably, the metallographic structure is analyzed by using an optical microscope to perform microscopic detection on the metallographic structure near the crack of the forged workpiece, and the microscopic detection includes detecting whether a bright white structure appears near the crack, whether the pearlite content is reduced and whether decarburization characteristics are presented.

Preferably, the hardness change analysis includes cutting in a direction perpendicular to the crack and a direction parallel to the crack, forming a cross detection point every 0.2mm to 0.8mm, and performing a hardness test on the cross detection point by using a hardness tester to obtain whether the hardness of the crack is reduced, so as to judge that decarburization occurs near the crack and judge as a forged crack.

Preferably, the hardness test is performed on the crisscross detection point to obtain the change condition perpendicular to the crack direction, if the hardness is in a significantly decreasing trend from the substrate to the crack direction perpendicular to the crack direction, the hardness perpendicular to the crack direction is compared with the hardness parallel to the crack direction, and thus whether decarburization occurs near the crack is determined.

More preferably, in the above aspect, if the hardness in the direction parallel to the crack is smaller than the hardness in the direction perpendicular to the crack, decarburization occurs in the vicinity of the crack, and it is determined that the crack is forged; if the hardness in the direction parallel to the crack is not less than the hardness in the direction perpendicular to the crack, no decarburization occurs in the vicinity of the crack, and it is judged as a quench crack.

Preferably, the method for deterministically judging the crack property comprises the following steps:

step 10: scanning the vicinity of the crack by using a scanning electron microscope, detecting whether the pearlite content of a metallographic structure of the crack is obviously reduced or not, wherein the pearlite content is reduced to below 15 percent so as to determine that the crack is generated in a forging stage, observing the appearance of the crack and detecting corrosion products obviously attached to two sides of the crack, wherein if strip-shaped substances are obviously attached to two sides of the crack, the generated corrosion products are oxides, so that the decarburization phenomenon is generated, and further, the generation of the crack in the forging stage is explained;

step 11: performing semi-quantitative analysis on strip-shaped substances obviously attached to two sides of the crack by using an energy spectrum analyzer to determine whether the strip-shaped substances are oxides or not; if the oxygen content is more than 1% and the element contains iron, it is determined as an oxide and it is determined that cracks are generated at the forging stage.

In summary, the invention adopts the above technical scheme, and the invention has the following technical effects:

(1) the method integrates the influence factors of various aspects such as materials, processes, tissues, hardness, components and the like, effectively analyzes the crack generation stage of the forged workpiece, and can quickly and accurately judge the stage of crack generation.

(2) The method is effective in judging the crack defects of the forged and normalized workpiece, and the forged workpieces similar to the forged workpieces in various industries such as petrifaction, machinery, metallurgy and the like can be analyzed and judged by the method, so that the method has a general reference value.

(3) The method can accurately judge the forming stage of the surface cracks of the forged workpiece substrate, and can accurately judge whether the forming time of the surface cracks of the workpiece substrate is generated before or after forging and quenching and in the live quenching process in the forging process, thereby being beneficial to determining the failure reason and the definition of responsibility of the workpiece substrate, and the responsibility cannot be determined because the cracking time of the surface cracks is not accurately judged in the past.

Drawings

FIG. 1 is a schematic view of the present invention showing the macrocracks locations for a tee;

FIG. 2 is a schematic diagram of a macro topography state of an accident tee joint pipe crack;

FIG. 3 is a schematic representation of the metallographic structure of a forged workpiece in the vicinity of a crack;

FIG. 4 is a schematic view showing the direction of hardness test of a forged workpiece

FIG. 5 is a parallel crack direction (A) hardness curve of a forged workpiece;

FIG. 6 is a vertical crack direction (B) hardness curve of a forged workpiece

FIG. 7 shows a crack-neighborhood structure of a forged workpiece

FIG. 8 is a schematic view of the distribution of corrosion product constituents in the middle of a crack;

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to the accompanying drawings by way of examples of preferred embodiments. It should be noted, however, that the numerous details set forth in the description are merely for the purpose of providing the reader with a thorough understanding of one or more aspects of the present invention, which may be practiced without these specific details.

According to the method for judging the crack generation stage of the forged workpiece, the crack generation stage of the hot-pressed tee joint is judged as an example, as shown in fig. 1, the position schematic diagram of the crack generation is shown, a tee joint pipe newly installed on a natural gas pipe of a petrochemical enterprise leaks during a trial operation hydrostatic test, the material is 20# steel, a long crack is found on the middle surface of the tee joint during surface penetration inspection, the crack length is about 22mm after grinding and polishing treatment, the crack is further inspected and is penetrated, effective suggestions are provided for finding out the crack generation stage of the tee joint, the analysis and judgment are carried out by using the method, the whole analysis strategy of the hot-pressed tee joint crack is provided, and the system considers the difference of the crack generation stages of the two stages; the method for judging the crack generation stage comprises the following steps of performing overall analysis by combining a workpiece material, a forging process and a quenching process, analyzing the appearance, the structure, the hardness, the element distribution and corrosion products of the crack, and judging the crack generation stage: acquiring a crack generation position of a forged workpiece, and cleaning and polishing the crack position of the workpiece to acquire a crack size parameter; the crack appearance, metallographic structure, hardness change, element distribution and corrosion products of the forged workpiece are subjected to overall analysis through the crack size parameters of the forged workpiece, and the cracks are judged to be generated by combining the material, forging process and quenching process of the forged workpiece; and analyzing and verifying the crack structure by combining one or more of the crack appearance, the metallographic structure, the hardness change and the corrosion product, so as to qualitatively judge the crack property, further accurately judge the stage of crack occurrence, and establish the period of rapid identification and rapid judgment of crack cracking.

In the invention, the appearance analysis and judgment of the cracks realize the judgment of the initial stage of the cracks by observing and recording the change states of the cracks on two sides of the cracks of the forged workpiece respectively; the crack morphology comprises a macrocrack morphology and a microcrack morphology; analyzing and judging the appearance of the macrocracks, and judging the initial stage of cracks by observing and recording the crack shapes and the crack shape change states presented on the two sides of the cracks of the forged workpiece; in the process of analyzing and judging the appearance of the macrocracks, if the appearance of the macrocracks of the forged workpiece is zigzag, the macrocracks are preliminarily judged to be quenching cracks; if the macrocrack appearance is linear, as shown in fig. 2, the macrocrack appearance is a macroscopic appearance schematic diagram of the crack, and the macrocrack is preliminarily judged to be a non-quenched crack; analyzing and judging the appearance of the micro cracks, and judging whether the cracks contain impurities or not by observing and recording the crack shapes, the crack trend changes, the crack color change states and the impurities on the two sides of the cracks of the forged workpiece; in the process of analyzing and judging the appearance of the microcracks, a scanning electron microscope is adopted to observe the appearance of the microcracks at the crack generating positions of the forged workpiece, and the crack shapes, the crack trend changes, the crack color change states and whether the cracks contain impurities or not, so that the crack properties can be judged deterministically according to the appearance observation results of the microcracks, and if the colors of the middle parts of the cracks are darker (relative to the colors of the self-matrix), inclusions in the middle parts of the cracks can be judged; if the number of inclusions in the cracks is large, it can be preliminarily judged that the cracks occur in the early forging stage, and if the cracks are linear and have no inclusions or few inclusions, it can be preliminarily judged that the cracks occur in the quenching stage.

In the invention, the metallographic structure analysis adopts an optical microscope to carry out microscopic detection on the metallographic structure near the crack of the forged workpiece, the microscopic detection comprises the steps of detecting whether a bright white structure appears near the crack and determining whether the pearlite content is reduced and whether decarburization characteristics are presented or not, as shown in figure 3, a decarburization area appears near the crack, and the figure shows that little or no black pearlite exists near the crack; if the decarburization characteristic is presented, the crack is preliminarily judged to be formed in the forging forming stage, and the subsequent quenching process is conducted with decarburization and is a forging crack; if no decarburization characteristic exists, the quenching crack is judged to be quenching crack in the initial step.

In the invention, the hardness change analysis comprises cutting in the directions vertical to the crack and parallel to the crack, and forming a cross detection point every 0.2mm to 0.8mm, as shown in figure 4, wherein the diagram shows the microhardness analysis schematic diagram of the crack in two directions A and B; the cross detection point is as close to the crack as possible, a hardness detector is adopted to carry out hardness test on the cross detection point, whether the hardness of the crack is reduced (the hardness is reduced by more than 10 HB units) or not is obtained, and the cross detection point is used for judging that decarburization occurs near the crack and judging as a forged crack; and (3) carrying out a hardness test on the cross detection point to obtain the change condition in the direction vertical to the crack, if the hardness is in a significantly reduced trend from the matrix (the matrix is a normal position without cracking) to the crack direction in the direction vertical to the crack, and comparing the hardness in the direction vertical to the crack with the hardness in the direction parallel to the crack to judge whether decarburization occurs in the vicinity of the crack. If the hardness in the direction parallel to the crack is smaller than the hardness in the direction perpendicular to the crack, decarburization occurs near the crack, and the crack is judged to be a forged crack; if the hardness parallel to the crack direction is not less than the hardness perpendicular to the crack direction (the hardness near the crack is not greatly different from that of the matrix), no decarburization occurs near the crack, and the crack is judged to be a quenched crack; the hardness tests are carried out in a cross way in the directions perpendicular to the cracks and parallel to the cracks (as close to the cracks as possible), the tested hardness curves are respectively shown in fig. 5 and fig. 6, and as can be seen from fig. 5, the hardness is obviously reduced from the matrix to the directions of the cracks in the direction perpendicular to the directions of the cracks, the hardness near the cracks is lower, about HB120-130, the normal hardness is about HB140, and the reduction is about 10; in addition, the hardness parallel to the crack direction was low, and it was judged that cracking occurred in the forging stage, and it was found from FIG. 6 that the hardness was low (about HB 120-125) at the crack position (0.5mm) and increased in the direction away from the crack.

In the invention, the deterministic judgment of the crack property comprises the following steps:

step 10: scanning the vicinity of the crack by using a scanning electron microscope, and detecting whether the pearlite content of the metallographic structure of the crack is obviously reduced relative to the structure far away from the crack or not, as shown in fig. 7, so as to determine that the crack is generated in the forging stage, observe the appearance of the crack (the appearance of the microcrack) and detect that corrosion products are obviously attached to two sides of the crack, obtain the shape of the crack, the change of the crack and whether impurities are contained, if strip-shaped substances are obviously attached to two sides of the crack, corrosion products are generated, and if the corrosion products are oxides, further explaining that the crack is generated in the forging stage; according to the invention, the scanning electron microscope is adopted to further confirm the structure near the cracks, and the decarburization phenomenon is explained when the pearlite content is obviously reduced (reduced to below 15%), and the cracks are further explained to be generated in the forging stage; in addition, as shown in fig. 7, it was found that stripe-like substances, i.e., oxides, were clearly attached to both sides of the crack, further explaining the generation of the crack at the forging stage.

Step 11: performing semi-quantitative analysis on strip-shaped substances obviously attached to two sides of the crack by using an energy spectrum analyzer to determine whether the strip-shaped substances are oxides or not; if the oxygen content is high (more than 1 percent) and the iron element is contained, determining the oxygen element as an oxide and determining that the crack is generated in the forging stage; and (3) performing semi-quantitative analysis on strip-shaped substances obviously adhered to two sides of the crack by adopting energy spectrum analysis, namely generating a corrosion product, determining whether the corrosion product is an oxide (if the corrosion product is the oxide), and if the oxygen element content is high, the corrosion product also contains metal elements such as iron and the like, determining the corrosion product as the oxide, determining that the crack is generated in a forging stage, and performing energy spectrum analysis on the corrosion product near the crack as shown in the trivia of figure 7 to explain that the decarburization phenomenon is generated. The specific analysis method is that according to the energy spectrum standard, an energy spectrum analyzer is used for analyzing the edges close to two sides inside the crack. As shown in fig. 8, the material adhering to the middle of the crack was an oxide, and it was judged that the crack was generated during forging, and the oxygen content in the corrosion product component in the crack was high (54.5%) and was an oxide, as a proof that the crack was generated at the forging stage.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make various improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be construed as the protection scope of the present invention.