CN111855733A - Blue brittleness process method for detecting inclusions and white spots at macroscopic fracture of medium alloy steel - Google Patents
Blue brittleness process method for detecting inclusions and white spots at macroscopic fracture of medium alloy steel Download PDFInfo
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- CN111855733A CN111855733A CN202010723340.2A CN202010723340A CN111855733A CN 111855733 A CN111855733 A CN 111855733A CN 202010723340 A CN202010723340 A CN 202010723340A CN 111855733 A CN111855733 A CN 111855733A
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- 238000000034 method Methods 0.000 title claims abstract description 47
- 230000008569 process Effects 0.000 title claims abstract description 25
- 229910000851 Alloy steel Inorganic materials 0.000 title claims abstract description 24
- 241000519995 Stachys sylvatica Species 0.000 title claims abstract description 20
- 230000007547 defect Effects 0.000 claims abstract description 23
- 238000007689 inspection Methods 0.000 claims abstract description 16
- 238000001514 detection method Methods 0.000 claims abstract description 9
- 238000010438 heat treatment Methods 0.000 claims description 53
- 238000005452 bending Methods 0.000 claims description 11
- 239000000463 material Substances 0.000 claims description 9
- 238000004321 preservation Methods 0.000 claims description 9
- 230000009466 transformation Effects 0.000 claims description 8
- 238000003825 pressing Methods 0.000 claims description 7
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 4
- 238000005242 forging Methods 0.000 claims description 4
- 238000003754 machining Methods 0.000 claims description 4
- 238000002360 preparation method Methods 0.000 claims description 4
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 3
- 239000010931 gold Substances 0.000 claims description 3
- 229910052737 gold Inorganic materials 0.000 claims description 3
- 238000005520 cutting process Methods 0.000 claims description 2
- 229910000831 Steel Inorganic materials 0.000 description 18
- 239000010959 steel Substances 0.000 description 18
- 230000000694 effects Effects 0.000 description 14
- 230000007704 transition Effects 0.000 description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 230000000877 morphologic effect Effects 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 229910001339 C alloy Inorganic materials 0.000 description 1
- 229910000975 Carbon steel Inorganic materials 0.000 description 1
- FBPFZTCFMRRESA-JGWLITMVSA-N D-glucitol Chemical group OC[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-JGWLITMVSA-N 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 230000000007 visual effect Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/02—Investigating or analyzing materials by the use of thermal means by investigating changes of state or changes of phase; by investigating sintering
- G01N25/12—Investigating or analyzing materials by the use of thermal means by investigating changes of state or changes of phase; by investigating sintering of critical point; of other phase change
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Abstract
The invention relates to a blue brittleness process method for detecting inclusions and white spots at a macroscopic fracture of medium alloy steel, which belongs to the technical field of low-power fracture defect detection. The method can accurately judge fracture inclusions and white point defects, solves the technical problem and ensures the inspection accuracy.
Description
Technical Field
The invention belongs to the technical field of low-power fracture defect detection, and particularly relates to a blue brittleness process method for detecting inclusions and white spots at a medium alloy steel macroscopic fracture.
Background
The low-power fracture defect detection method is widely adopted as a classical method, and the principle is that a forging material is processed into a circular sheet sample by a transverse cutting machine, and after the circular sheet sample is pressed and broken by a bending machine from the center, whether the fracture surface has defects is detected by naked eyes.
Steel-iron-test standard (SEP 1584): the blue embrittlement test is a test for the presence of non-metallic impurities in the cross-section of a deformed steel product, which impurities are visible to the naked eye without the use of magnifying tools after passing the blue embrittlement test.
The white spots are one of the internal defects of the steel, and are generated because hydrogen dissolved in austenite is precipitated in a large amount due to the remarkable reduction of solubility during cooling phase transformation, is gathered at cavities and microscopic defects, generates large pressure, and generates non-directional and regular cracks in combination with the stress of a phase transformation structure. Since such defects cause a decrease in the strength, plasticity and toughness of the steel and cause breakage of the steel under stress, white spots are absolutely impermissible defects.
Disclosure of Invention
In order to overcome the defects of the prior art, clearly and accurately judge whether inclusions or white point defects exist through the macro fracture of the medium alloy steel and avoid errors caused by manual visual detection judgment, the invention provides the blue brittleness process method for detecting the inclusions and the white points at the macro fracture of the medium alloy steel.
The invention is realized by the following technical scheme.
1. Determining process test routes
Whether fracture inclusions and white point defects can be accurately judged is judged, and the fact that the fracture surface is subjected to blue-to-crisp conversion is a key factor. White point defects are generally present in carbon steels and alloy steels, and particularly occur frequently in martensitic steels, bainitic steels, and high alloy steels containing nickel. Therefore, the medium alloy steel is selected to research the blue brittleness test method aiming at different heat treatment equipment.
According to the standard requirements, a low-power fracture inspection sample with the diameter multiplied by the thickness of 20mm of steel is processed, the test is carried out according to the process shown in the table 1, after the center fracture, the sample is limited by the inner diameter of a hearth of a heating furnace, and two fracture surfaces can only be stacked in the direction facing to a heating element. After the test, the degree of brittleness of the fracture is very uneven, and when the section of the sample at the position close to the furnace opening is blue, the fracture surface inside is not changed; when the inner fracture surface is blue, the fracture surface at the position of the furnace opening is changed into light blue or brown, so that the whole fracture surface is uniformly blue, and the heat preservation time is difficult to control.
According to the blue brittleness principle, the sample needs to have a good oxidizing atmosphere when being subjected to blue brittleness transformation, and the furnace mouth has sufficient oxygen content to preferentially perform blue brittleness. Experimental research shows that the heat preservation time of the whole blue-crisp conversion process is an important factor, and meanwhile, the placing method and the position of the sample have obvious influence on the blue-forming effect of the fracture.
According to the table 2, the low-power fracture sample is subjected to a large heating furnace bluing process heating test, and the placing positions of the fracture surfaces of the sample are respectively in different directions, namely a furnace opening direction, a furnace top direction and a heating element direction. The test result shows that the overall ring-forming of the fracture of the sample, of which the fracture surface faces the furnace opening direction, is relatively uniform, and the ring-forming effect of the fracture of the uneven part of the fracture surface is relatively poor.
2. Tissue analysis
The fracture of the test piece is prepared by adopting a vertical downward pressing static force of a 50-ton bending tester, and the appearance of the fractured fracture directly influences the section bluing effect. When the fracture surface presents tearing-shaped characteristics, the bluing effect is very uneven, and the bluing hardly occurs in the tearing-shaped area; when the fracture surface is broken uniformly and no tearing-shaped appearance exists, the blue effect is obvious. This phenomenon may be related to the structural state of the steel material by analysis.
The delivery state of the steel is generally either a normalized state or an annealed state. When the steel is in a normalized state, the metallographic structure is fine and uniform, the fibrous section is uniformly distributed, and the characteristic of no tearing is realized; when the steel is in the annealed state, it exhibits more tear-like features due to the coarse and uneven fibrous cross-section of the structure.
3. Heat treatment process test
Through a large number of heat treatment process tests, it is known that for medium alloy steel, when the heating temperature is lower than 410 ℃, the degree of blue of the fracture surface is shallow, which is not beneficial to defect observation and judgment; when the temperature is higher than 500 ℃, the bluing speed is too high, the bluing effect is also difficult to control, particularly, two samples are stacked together, so that the bluing conversion time of the two samples is different, the bluing effect of the two samples is different after the same bluing time, and the phenomenon that one sample is bluish and the other sample is possibly under-bluing occurs.
4. Optimum blue effect process
Through experimental comparison, the optimal bluing effect can be obtained when the heat treatment bluing process adopted by the alloy steel is 460 +/-10 ℃ and the heat preservation time is 50 min.
In conclusion, the test determines the intermediate alloy steel fracture bluing heat treatment process, if inclusions and white spot defects exist in steel, the blue effect of the defects is obviously different from that of other fracture surfaces after fracture bluing heat treatment, the morphological characteristics are highlighted, so that the invention can effectively observe and judge the inclusions and white spot defects existing in the steel, and the blue brittleness process for detecting the inclusions and white spots at the macroscopic fracture of the intermediate alloy steel comprises the following steps:
1) and sample preparation: taking a gold phase sample at the position specified by a forging material standard, and grading the grain size of the sample:
A. when the grain size grade of the sample is greater than or equal to grade 7, directly pressing and breaking the processed slotted circular sheet sample from the center through a bending machine to prepare a fracture blue-crisp inspection sample;
B. when the grain size grade of the sample is less than 7 grades, normalizing the sample at 850 ℃, keeping the temperature for 30 minutes, then cooling the sample to room temperature in air, and then pressing the processed slotted round sheet sample from the center through a bending machine to obtain a fracture blue brittleness inspection sample;
2) and carrying out blue heat treatment on the fracture blue brittleness test sample: the heating temperature of the blue chip is as follows: 460 +/-10 ℃, after the heating furnace is heated to the blue brittleness heating temperature, putting the fracture blue brittleness inspection sample prepared in the step 1) into the heating furnace, wherein the number of the blue brittleness inspection samples in each heat treatment is one furnace and two samples; in order to ensure uniform conversion of the blue brittleness, a fracture blue brittleness test sample is placed in parallel to the furnace mouth direction, and the heat preservation time is 50 min;
3) blue complete detection: and (3) taking the sample subjected to the bluing heat treatment in the step 2) out of the heating furnace, and directly judging whether inclusions or white spot defects exist at the macroscopic fracture of the medium alloy steel by naked eyes.
Further, in the step 1), the forged material is transversely cut and mechanically processed into a circular sheet sample, grooving is carried out on the central line through machining equipment, the depth of the grooving is not more than 30% of the thickness of the test sample, then the test sample is pressed from the center by using a bending tester of more than 50 tons to prepare a fracture blue-brittle test sample, the interval time between fracture blue-brittle test sample fracture and heat treatment is not more than 12 hours, and the fracture surface is not contacted and collided, so that the fracture blue-brittle test sample is kept clean and intact.
Further, in the step 1), the size of the macro fracture detection sample is as follows: the diameter is 200 to 400mm and the thickness is 20 mm.
Further, the heating temperature of the blue chips in the step 2) is 460 +/-10 ℃.
Further, the step 3) of the process of converting into the fracture bluing is completed by the early stage of heating → red color → violet hair → dark blue → light blue → gray color.
Compared with the prior art, the invention has the beneficial effects that:
the invention determines the intermediate alloy steel fracture bluing heat treatment process method through tests, if inclusions and white spot defects exist in steel, the defects are obviously different from bluing effects of other fracture surfaces after fracture bluing heat treatment, morphological characteristics are highlighted, and therefore, the invention can effectively observe and judge the inclusions and white spot defects existing in the intermediate alloy steel.
Detailed Description
The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention. Unless otherwise specified, the examples follow conventional experimental conditions. In addition, it will be apparent to those skilled in the art that various modifications or improvements can be made to the material components and amounts in these embodiments without departing from the spirit and scope of the invention as defined in the appended claims.
1. Temperature of heating
The brittleness temperature of the medium alloy steel is 460 +/-10 ℃, and the sample is required to enter the furnace at the temperature.
2. Time of heat preservation
The blue-blue transition of the fracture is an intermediate process, and the length of time plays a decisive role. If the time is too short, the blue transition is not completely formed; if the time is too long, the blue-to-crisp transition ends. And determining the alloy steel in the corresponding heat preservation time to be 50min, and the number of the blue brittle fracture samples in each heat treatment is one furnace and two blocks.
3. Placement method
The placing method of the fracture sample is an important factor of blue transformation, when the fracture surface of the sample is placed perpendicular to the furnace mouth, under the influence of oxidizing atmosphere time, the position of the fracture surface close to the furnace mouth is firstly subjected to blue phenomenon, but when the rear section of the hearth is subjected to blue phenomenon, the blue end of the furnace mouth section is converted into other colors; when the fracture surface is placed upwards in the heating furnace, the fracture surface can also cause the phenomenon of uneven blue degree. To ensure uniform blue transition, it was experimentally determined that the specimens needed to be placed parallel to the direction of the furnace mouth. Because the specification of the low-power fracture inspection sample is generally 200-400 mm multiplied by 20mm in thickness, heating equipment with a furnace mouth width larger than the diameter of steel needs to be selected when a heating furnace is selected.
4. Tissue analysis
When the steel material is in an annealed state, the structure thereof is a pearlite structure. From the test results, when the structure state is an annealing state, the fracture surface of the sample has more tearing-shaped structures, the fracture surface shows uneven and uneven characteristics, the blue transformation effect is poor, crystal grains are refined after the normalizing by the heat treatment to form a sorbite structure, the fracture surface has no tearing-shaped characteristics after the sample is subjected to the pressure fracture, and the blue effect is good, so the structure state is one of important factors of the blue effect.
5. Sample preparation
A fracture blue brittleness inspection sample is firstly grooved by machining equipment, the depth is not more than 30% of the thickness, then a bending tester of more than 50 tons is adopted to prepare the fracture sample, the interval time from the fracture of the sample to the heat treatment is not more than 12 hours, and the fracture surface is not contacted and collided, so that the fracture surface is kept clean and intact.
6. Transformation process
The entire process of the fracture bluing transformation is completed by the early stage of heating → redness → purple blue → dark blue → light blue → graying.
7. Influencing factor
In the test process, important factors influencing the low-power fracture bluing are found to be heating temperature, heat preservation time, placement method and tissue state, but the factors are not limited.
8. Determining a process route
The blue brittleness process method for detecting inclusions and white spots at the macroscopic fracture of medium alloy steel comprises the following steps of:
1) and sample preparation: taking a gold phase sample at the position specified by a forging material standard, and grading the grain size of the sample:
A. when the grain size grade of the sample is greater than or equal to grade 7, directly pressing and breaking the processed slotted circular sheet sample from the center through a bending machine to prepare a fracture blue-crisp inspection sample;
B. when the grain size grade of the sample is less than 7 grades, normalizing the sample at 850 ℃, keeping the temperature for 30 minutes, then cooling the sample to room temperature in air, and then pressing the processed slotted round sheet sample from the center through a bending machine to obtain a fracture blue brittleness inspection sample;
2) and carrying out blue heat treatment on the fracture blue brittleness test sample: the heating temperature of the blue chip is as follows: 460 +/-10 ℃, after the heating furnace is heated to the blue brittleness heating temperature, putting the fracture blue brittleness inspection sample prepared in the step 1) into the heating furnace, wherein the number of the blue brittleness inspection samples subjected to heat treatment each time is one furnace and two sheets; in order to ensure uniform conversion of the blue brittleness, a fracture blue brittleness test sample is placed in parallel to the furnace mouth direction, and the heat preservation time is 50 min;
3) blue complete detection: and (3) taking the sample subjected to the bluing heat treatment in the step 2) out of the heating furnace, and directly judging whether inclusions or white spot defects exist at the macroscopic fracture of the medium alloy steel by naked eyes.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (5)
1. The blue brittleness process method for detecting inclusions and white spots at the macroscopic fracture of medium alloy steel is characterized by comprising the following steps of:
1) and sample preparation: taking a gold phase sample at the position specified by a forging material standard, and grading the grain size of the sample:
A. when the grain size grade of the sample is greater than or equal to grade 7, directly pressing and breaking the processed slotted circular sheet sample from the center through a bending machine to prepare a fracture blue-crisp inspection sample;
B. when the grain size grade of the sample is less than 7 grades, normalizing the sample at 850 ℃, keeping the temperature for 30 minutes, then cooling the sample to room temperature in air, and then pressing the processed slotted round sheet sample from the center through a bending machine to obtain a fracture blue brittleness inspection sample;
2) and carrying out blue heat treatment on the fracture blue brittleness test sample: the heating temperature of the blue chip is as follows: 460 +/-10 ℃, after the heating furnace is heated to the blue brittleness heating temperature, putting the fracture blue brittleness inspection sample prepared in the step 1) into the heating furnace, wherein the number of the blue brittleness inspection samples in each heat treatment is one furnace and two samples; in order to ensure uniform conversion of the blue brittleness, a fracture blue brittleness test sample is placed in parallel to the furnace mouth direction, and the heat preservation time is 50 min;
3) blue complete detection: and (3) taking the sample subjected to the bluing heat treatment in the step 2) out of the heating furnace, and directly judging whether inclusions or white spot defects exist at the macroscopic fracture of the medium alloy steel by naked eyes.
2. The method for detecting inclusions and white spots at macroscopic fracture of medium alloy steel as claimed in claim 1, wherein the method comprises the following steps: in the step 1), a forged material is subjected to cross-cutting machining to form a circular sheet sample, grooving is carried out on a center line through machining equipment, the depth of the grooving is not more than 30% of the thickness of the test sample, then, a bending test machine of more than 50 tons is adopted to press and break the test sample from the center to prepare a fracture blue-brittle test sample, the interval time between fracture blue-brittle test sample fracture and heat treatment is not more than 12 hours, and the fracture surface is not required to be contacted and collided, so that the test sample is kept clean and intact.
3. The method for detecting inclusions and white spots at macroscopic fracture of medium alloy steel as claimed in claim 1, wherein the method comprises the following steps: in the step 1), the size of the macro fracture detection sample is as follows: the diameter is 200 to 400mm and the thickness is 20 mm.
4. The method for detecting inclusions and white spots at macroscopic fracture of medium alloy steel as claimed in claim 1, wherein the method comprises the following steps: the heating temperature of the blue crisp in the step 2) is 460 +/-10 ℃.
5. The method for detecting inclusions and white spots at macroscopic fracture of medium alloy steel as claimed in claim 1, wherein the method comprises the following steps: the step 3) of the fracture bluing transformation process is completed by heating early → redness → lacca → dark blue → light blue → graying.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0611461A (en) * | 1992-06-25 | 1994-01-21 | Kanai Hiroyuki | Flaw inspection method for flat steel wire |
| CN104404241A (en) * | 2014-11-14 | 2015-03-11 | 山西太钢不锈钢股份有限公司 | Low-alloy-steel macroscopic fracture blue brittleness processing technology |
| CN105203383A (en) * | 2015-09-08 | 2015-12-30 | 西宁特殊钢股份有限公司 | Simple and feasible bluing fracture inspection method |
| CN108802432A (en) * | 2018-07-19 | 2018-11-13 | 邢台钢铁有限责任公司 | The detection method of large-sized inclusions in high-carbon steel |
-
2020
- 2020-07-24 CN CN202010723340.2A patent/CN111855733A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0611461A (en) * | 1992-06-25 | 1994-01-21 | Kanai Hiroyuki | Flaw inspection method for flat steel wire |
| CN104404241A (en) * | 2014-11-14 | 2015-03-11 | 山西太钢不锈钢股份有限公司 | Low-alloy-steel macroscopic fracture blue brittleness processing technology |
| CN105203383A (en) * | 2015-09-08 | 2015-12-30 | 西宁特殊钢股份有限公司 | Simple and feasible bluing fracture inspection method |
| CN108802432A (en) * | 2018-07-19 | 2018-11-13 | 邢台钢铁有限责任公司 | The detection method of large-sized inclusions in high-carbon steel |
Non-Patent Citations (2)
| Title |
|---|
| 何健楠等: "轴承钢非金属夹杂物的发兰断口检验研究", 《中国金属通报》 * |
| 李吉东等: "铁素体钢中白点缺陷的检验分析", 《钢铁》 * |
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Application publication date: 20201030 |