阅读说明：本技术 18CrNiMo7-6齿轮锻件及克服其皮下缺陷的制造方法及检测方法 (18CrNiMo7-6 gear forging and manufacturing method and detection method for overcoming subcutaneous defects of forging ) 是由 陈昌华 张利 张洪 孔德贵 陈海山 宋雷钧 哈曜 陈洁 刘晓磊 张思瑞 龚洋道 于 2020-12-02 设计创作，主要内容包括：本发明涉及一种18CrNiMo7-6齿轮锻件及克服其皮下缺陷的制造方法及检测方法,制造方法包括以下步骤：(1)下料,(2)第一火次,(3)锻造1,(4)第二火次,(5)锻造2,(6)第三火次,(7)锻造3。本制造方法具有如下有益效果：将原料通过锻造过程压把、墩粗及拔长,使得钢锭压密压实,使钢锭内部密度更均匀。最后等加工平整后再修整好,去除锻件表面缺陷,得到18CrNiMo7-6齿轮锻件。检测方法包括：(1)超声波检验,(2)解剖取样,(3)低倍检验,(4)金相检验,(5)扫描电镜检验,(6)结果分析,以检测出18CrNiMo7-6齿轮锻件皮下缺陷原因,以便更好克服。(The invention relates to an 18CrNiMo7-6 gear forging, a manufacturing method for overcoming subcutaneous defects of the forging and a detection method, wherein the manufacturing method comprises the following steps: (1) blanking, (2) carrying out first firing, (3) forging 1, (4) carrying out second firing, (5) forging 2, (6) carrying out third firing, and (7) forging 3. The manufacturing method has the following beneficial effects: the raw materials are pressed, upset and drawn out in the forging process, so that the steel ingot is compacted and compacted, and the internal density of the steel ingot is more uniform. And finally, finishing after the machining is smooth, and removing the surface defects of the forged piece to obtain the 18CrNiMo7-6 gear forged piece. The detection method comprises the following steps: (1) ultrasonic inspection, (2) anatomical sampling, (3) macroscopic inspection, (4) metallographic inspection, (5) scanning electron microscope inspection, and (6) result analysis, so as to detect out the reason of the subcutaneous defect of the 18CrNiMo7-6 gear forging, and better overcome the defect.)

1. A manufacturing method for overcoming the subcutaneous defect of an 18CrNiMo7-6 gear forging is characterized by comprising the following steps: the method comprises the following steps:

step 1: blanking: preparing a smelted 18CrNiMo7-6 steel ingot, and taking the 18CrNiMo7-6 steel ingot as a blank;

step 2: the first fire time: adding the blank into a forging heating furnace with the temperature of more than 200 ℃, heating the blank to 1150-1250 ℃, and preserving heat for 5-15 hours;

and step 3: forging 1: pressing a blank into a handle, chamfering, upsetting to H650-H750 in a drain pan, drawing out 8 times by using upper and lower flat anvils with the thickness of 800mm according to a program, pressing into an octagonal shape with the thickness of 820mm, and rolling to obtain a blank 1;

and 4, step 4: the second fire time: adding the blank 1 into a forging heating furnace at the temperature of more than 800 ℃, heating the blank to 1200 ℃, and preserving heat for 4-15 hours to obtain the blank 1 after the second firing;

and 5: forging 2: upsetting the blank 1 after the second firing in a blank bushing until the thickness is H700-H800, drawing out the blank for 8-10 times by using upper and lower flat anvils with the thickness of 800mm according to a program, pressing the blank into an octagonal shape with the thickness of 800mm, rounding, then cutting off a riser and a water gap, cogging and blanking to obtain a blank 2;

step 6: the third fire time: adding the blank 2 into a forging heating furnace with the temperature of more than 800 ℃, heating the blank to 1200 ℃, and preserving heat for 4-15 hours to obtain a blank 2 after the third firing;

and 7: forging 3: upsetting the blank 2 after the third firing to H780, then rounding to be flat, punching, and finally finishing to obtain the 18CrNiMo7-6 gear forging.

2. The manufacturing method for overcoming the subcutaneous defect of the 18CrNiMo7-6 gear forging according to claim 1, wherein the manufacturing method comprises the following steps: the method for smelting the 18CrNiMo7-6 steel ingot in the first step comprises melting, oxidizing, reducing and tapping, and feeding the wire after tapping, wherein the calming time during wire feeding is 20-30 minutes.

3. The manufacturing method for overcoming the subcutaneous defect of the 18CrNiMo7-6 gear forging according to claim 2, wherein the manufacturing method comprises the following steps: the inner wall of the ingot mould is free of impurities in the smelting process, and the pouring system is dry.

4. The utility model provides an 18CrNiMo7-6 gear forging which characterized in that: the 18CrNiMo7-6 gear forging is manufactured by the manufacturing method in the claim 1.

5. The method for detecting the subcutaneous defects of the 18CrNiMo7-6 gear forging is characterized by comprising the following steps of: the method comprises the following steps:

step S1: ultrasonic inspection: carrying out ultrasonic straight probe detection on the radial circular surface and the end surface of the 18CrNiMo7-6 gear forging;

step S2: and (3) anatomical sampling: sampling, dissecting and analyzing subcutaneous defects of the 18CrNiMo7-6 gear forging, sawing along a direction parallel to the diameter of the 18CrNiMo7-6 gear forging to obtain an arc-shaped sample A, sawing along a direction perpendicular to the cutting direction of the sample A to obtain an arc-shaped sample B, sawing the sample A and the sample B twice along a direction parallel to the high temperature of the 18CrNiMo7-6 gear forging, wherein the sawing position of the sample A is deviated to the arc end part, the sample B is close to the middle line position, middle samples are taken respectively, the two middle samples are sawed twice along the direction perpendicular to the length temperature of the middle samples, middle samples 2 are taken respectively, and the two middle samples 2 are sawed twice again to obtain samples A1, A2, B1 and B2;

step S3: and (3) low power test: processing the four samples A1, A2, B1 and B2 obtained in the step S2 by a planer and a mill, corroding the samples in a 1:1 industrial hydrochloric acid aqueous solution at 70 ℃ for 25 minutes, and observing the corroded samples;

step S4: and (3) metallographic examination: placing the sample A1 into a reagent to be corroded and then observing;

step S5: and (3) scanning electron microscope inspection: the metallographic sample obtained in the step S5 of sample a1 was subjected to scanning electron microscope analysis.

Technical Field

The invention relates to an 18CrNiMo7-6 gear forging, a manufacturing method and a detection method for overcoming subcutaneous defects of the forging, and belongs to the technical field of metal forging processes.

Background

The wheel rim is provided with mechanical elements which are continuously meshed with gears and transmit motion and power. The use of gears in transmissions has long emerged. Along with the development of production, the stability of gear operation is emphasized. The traditional method for processing the gear forging can cause excessive subcutaneous defects of the gear forging, the mechanical property of the gear forging can be reduced due to the excessive subcutaneous defects of the gear forging, the damage of forging of the forging is increased, and the forging can be directly turned into waste products seriously.

Disclosure of Invention

In order to solve the technical problems, the invention provides a manufacturing method for overcoming the subcutaneous defect of an 18CrNiMo7-6 gear forging, which has the following specific technical scheme:

the manufacturing method for overcoming the subcutaneous defect of the 18CrNiMo7-6 gear forging comprises the following steps:

step 1: blanking: preparing a smelted 18CrNiMo7-6 steel ingot, and taking the 18CrNiMo7-6 steel ingot as a blank;

step 2: the first fire time: adding the blank into a forging heating furnace with the temperature of more than 200 ℃, heating the blank to 1150-1250 ℃, and preserving heat for 5-15 hours;

and step 3: forging 1: pressing a blank into a handle, chamfering, upsetting to H650-H750 in a drain pan, drawing out 8 times by using upper and lower flat anvils with the thickness of 800mm according to a program, pressing into an octagonal shape with the thickness of 820mm, and rolling to obtain a blank 1;

and 4, step 4: the second fire time: adding the blank 1 into a forging heating furnace at the temperature of more than 800 ℃, heating the blank to 1200 ℃, and preserving heat for 4-15 hours to obtain the blank 1 after the second firing;

and 5: forging 2: upsetting the blank 1 after the second firing in a blank bushing until the thickness is H700-H800, drawing out the blank for 8-10 times by using upper and lower flat anvils with the thickness of 800mm according to a program, pressing the blank into an octagonal shape with the thickness of 800mm, rounding, then cutting off a riser and a water gap, cogging and blanking to obtain a blank 2;

step 6: the third fire time: adding the blank 2 into a forging heating furnace with the temperature of more than 800 ℃, heating the blank to 1200 ℃, and preserving heat for 4-15 hours to obtain a blank 2 after the third firing;

and 7: forging 3: upsetting the blank 2 after the third firing to H780, then rounding to be flat, punching, and finally finishing to obtain the 18CrNiMo7-6 gear forging.

Further, the method for smelting the 18CrNiMo7-6 steel ingot in the first step comprises the steps of melting, oxidizing, reducing, tapping and feeding the wire after tapping, wherein the wire feeding time is 20-30 minutes.

Furthermore, the inner wall of the ingot mould is free of impurities in the smelting process, and a pouring system is dry.

Further, the 18CrNiMo7-6 gear forging is manufactured by the manufacturing method in the claim 1.

Further, the detection method comprises the following steps:

step S1: ultrasonic inspection: carrying out ultrasonic straight probe detection on the radial circular surface and the end surface of the 18CrNiMo7-6 gear forging;

step S2: and (3) anatomical sampling: sampling, dissecting and analyzing subcutaneous defects of the 18CrNiMo7-6 gear forging, sawing along a direction parallel to the diameter of the 18CrNiMo7-6 gear forging to obtain an arc-shaped sample A, sawing along a direction perpendicular to the cutting direction of the sample A to obtain an arc-shaped sample B, sawing the sample A and the sample B twice along a direction parallel to the high temperature of the 18CrNiMo7-6 gear forging, wherein the sawing position of the sample A is deviated to the arc end part, the sample B is close to the middle line position, middle samples are taken respectively, the two middle samples are sawed twice along the direction perpendicular to the length temperature of the middle samples, middle samples 2 are taken respectively, and the two middle samples 2 are sawed twice again to obtain samples A1, A2, B1 and B2;

step S3: and (3) low power test: processing the four samples A1, A2, B1 and B2 obtained in the step S2 by a planer and a mill, corroding the samples in a 1:1 industrial hydrochloric acid aqueous solution at 70 ℃ for 25 minutes, and observing the corroded samples;

step S4: and (3) metallographic examination: placing the sample A1 into a reagent to be corroded and then observing;

step S5: and (3) scanning electron microscope inspection: the metallographic sample obtained in the step S5 of sample a1 was subjected to scanning electron microscope analysis.

The invention has the beneficial effects that: the gear manufactured by the method can ensure the running stability, and the subcutaneous defect of the gear can be reduced by matching with the method for detecting the subcutaneous defect of the gear, so that the mechanical property of the gear is improved, the damage of forging of the forging is reduced, the cost of the forging is reduced, and the working efficiency is improved.

Drawings

Figure 1 is a gear forging tooling size of the present invention,

figure 2 is an end-face ultrasonic inspection waveform of the present invention,

figure 3 is an exploded schematic view of a gear forging coupon of the present invention,

FIG. 4 is an exploded view of a small semi-circle specimen of the gear forging of the present invention,

figure 5 is an exploded schematic view of a gear forging wire-cutting specimen,

figure 6 is a macroscopic view of a low power sample,

figure 7 is a macroscopic view of a low power specimen at a local magnification,

figure 8 is a 50x crack signature,

figure 9 is a 100x inclusion morphology near non-crack,

figures 10-11 are 100x crack features,

figure 12 is a 500x inclusion morphology near non-crack,

figures 13-15 are 500x crack features,

figure 16 is a 50x crack morphology,

figures 17-18 are 100x crack morphology,

figure 19 is a 500x crack morphology,

figure 20 is a 100x matrix organization,

figure 21 is a 500x matrix weave,

figure 22 is a 1500X defect profile,

figure 23 is a 1000X defect profile,

figure 24 is a scanning electron microscope spectrum of position a,

FIG. 25 is a B-position scanning electron microscopy spectrum.

Detailed Description

The present invention will now be described in further detail with reference to the accompanying drawings.

As shown in FIG. 1, an 18CrNiMo7-6 gear forging is produced by the above-described manufacturing method to the dimensions shown.

The manufacturing method for overcoming the subcutaneous defect of the 18CrNiMo7-6 gear forging comprises the following steps:

step 1: blanking: preparing a smelted 18CrNiMo7-6 steel ingot, and taking the 18CrNiMo7-6 steel ingot as a blank;

step 2: the first fire time: adding the blank into a forging heating furnace with the temperature of more than 200 ℃, heating the blank to 1150-1250 ℃, and preserving heat for 5-15 hours;

and step 3: forging 1: pressing a blank into a handle, chamfering, upsetting to H650-H750 in a drain pan, drawing out 8 times by using upper and lower flat anvils with the thickness of 800mm according to a program, pressing into an octagonal shape with the thickness of 820mm, and rolling to obtain a blank 1;

and 4, step 4: the second fire time: adding the blank 1 into a forging heating furnace at the temperature of more than 800 ℃, heating the blank to 1200 ℃, and preserving heat for 4-15 hours to obtain the blank 1 after the second firing;

and 5: forging 2: upsetting the blank 1 after the second firing in a blank bushing until the thickness is H700-H800, drawing out the blank for 8-10 times by using upper and lower flat anvils with the thickness of 800mm according to a program, pressing the blank into an octagonal shape with the thickness of 800mm, rounding, then cutting off a riser and a water gap, cogging and blanking to obtain a blank 2;

step 6: the third fire time: adding the blank 2 into a forging heating furnace with the temperature of more than 800 ℃, heating the blank to 1200 ℃, and preserving heat for 4-15 hours to obtain a blank 2 after the third firing;

and 7: forging 3: upsetting the blank 2 after the third firing to H780, then rounding to be flat, punching, and finally finishing to obtain the 18CrNiMo7-6 gear forging.

The method for smelting the 18CrNiMo7-6 steel ingot in the first step comprises melting, oxidizing, reducing and tapping, and feeding the wire after tapping, wherein the calming time during wire feeding is 20-30 minutes. The inner wall of the ingot mould is free of impurities in the smelting process, and the pouring system is dry.

The method for detecting the subcutaneous defects of the 18CrNiMo7-6 gear forging comprises the following steps:

step S1: ultrasonic inspection: carrying out ultrasonic straight probe detection on the radial circular surface and the end surface of the 18CrNiMo7-6 gear forging;

step S2: and (3) anatomical sampling: sampling, dissecting and analyzing subcutaneous defects of the 18CrNiMo7-6 gear forging, sawing along a direction parallel to the diameter of the 18CrNiMo7-6 gear forging to obtain an arc-shaped sample A, sawing along a direction perpendicular to the cutting direction of the sample A to obtain an arc-shaped sample B, sawing the sample A and the sample B twice along a direction parallel to the high temperature of the 18CrNiMo7-6 gear forging, wherein the sawing position of the sample A is deviated to the arc end part, the sample B is close to the middle line position, middle samples are taken respectively, the two middle samples are sawed twice along the direction perpendicular to the length temperature of the middle samples, middle samples 2 are taken respectively, and the two middle samples 2 are sawed twice again to obtain samples A1, A2, B1 and B2;

step S3: and (3) low power test: processing the four samples A1, A2, B1 and B2 obtained in the step S2 by a planer and a mill, corroding the samples in a 1:1 industrial hydrochloric acid aqueous solution at 70 ℃ for 25 minutes, and observing the corroded samples;

step S4: and (3) metallographic examination: observing a sample A1 after being corroded by 4% nitric acid alcohol;

step S5: and (3) scanning electron microscope inspection: the metallographic sample obtained in the step S5 of sample a1 was subjected to scanning electron microscope analysis.

2-25, an 18CrNiMo7-6 gear forging was tested to demonstrate whether the subcutaneous defects of the forging were overcome:

1. results of ultrasonic examination

Carrying out ultrasonic straight probe detection on the radial circular surface of the gear forging, and displaying no defect; ultrasonic straight probe inspection of the end face revealed a number of small defects near the outer circle, with a maximum of FBH1.7mm, as shown in FIG. 2.

2. Anatomical sampling

Sampling, dissecting and analyzing the subcutaneous defect of the gear forging, and sawing along the A position line and the B position line of the gear forging to manufacture a semicircular sample, which is shown in figure 3. And sawing the sample A and the sample B along the red line positions to obtain small samples, which are shown in figure 4. And (3) further carrying out ultrasonic flaw detection and defect positioning on the small samples A and the small samples B, respectively sawing the small samples A into two samples along the red line position of the samples as shown in FIG. 5, carrying out low power detection on the two samples, and numbering the four samples as A1, A2, B1 and B2.

3. Macroscopic examination results

After being planed and ground, 4 pieces of low-power samples are corroded in 1:1 industrial hydrochloric acid aqueous solution at 70 ℃ for 25 minutes. After corrosion, no defects are seen in A2, B1 and B2, and the A1 sample has a crack on the surface, is parallel to the end face and is 10mm away from the outer circular surface, has the length of about 1.5mm, and has a rigid shape as shown in FIGS. 6 and 7. The surface of the sample has no other obvious macroscopic defects such as looseness, holes and the like.

4. Results of metallographic examination

Metallographic examination of A1 specimens

The A1 sample has the defect length of about 1.6mm, the defect is fine, intermittent and not slightly circular, the interior is filled with impurities, and the impurities can be seen on the surface of the matrix, and the microscopic appearance is shown in figures 8-15.

And corrosion observation shows that the interior of two sides of the defect is not oxidized and decarburized. Large inclusions can be seen on the two sides of the middle part and the tail part of the defect, and the microscopic appearance is shown in figures 16-19. The matrix structure is good and is bainite, grain bainite and ferrite, and the microscopic morphology is shown in figures 20-21.

5. Scanning electron microscope test results

And (3) analyzing the A1 sample by a scanning electron microscope, wherein the surface defect appearance of the sample is shown in figures 22 and 23, and the scanning electron microscope can see more inclusions in the defect joint. The inclusions are subjected to energy spectrum non-standard sample semi-quantitative component analysis, and contain Ca, Mg and Al elements, as shown in figures 24 and 25.

6. Analysis of results

Detecting by an ultrasonic straight probe, and displaying if no defect is found; ultrasonic straight probe detection was performed on the end face, and it was found that a large number of small defects were present near the outer circle, and that the maximum was FBH1.7mm. And observing after macroscopic corrosion, the surface of the sample has a crack which is parallel to the end face and is 10mm away from the outer circular surface, the crack is about 1.5mm long, the shape is rigid, and the surface of the sample has no other obvious macroscopic defects such as looseness, holes and the like.

Metallographic analysis shows that the sample has the defect length of about 1.6mm, the defect is fine, intermittent and not slightly rounded, the interior is filled with impurities, and the surface of the matrix is also visible with the impurities. And corrosion observation shows that the interior of two sides of the defect is not oxidized and decarburized. The large inclusions can be seen on the two sides of the middle part and the tail part of the defect, and the matrix structure is normal and is bainite, grain bainite and ferrite. The scanning electron microscope analysis shows that more inclusions are in the defect joint, the inclusions are subjected to energy spectrum standard-sample-free semi-quantitative component analysis, and the inclusions mainly contain Ca, Mg and Al elements, belong to alumina inclusions and are derived from deoxidation products.

7. Conclusion

1) The defect interior was filled with inclusions, indicating that the formation of defects was related to inclusions;

2) the treatment of the aluminum killed steel is recommended to be enhanced, the calming time after the wire feeding is ensured, and the secondary oxidation of the molten steel is prevented;

3) the subcutaneous defect is worm-shaped and non-expandable, and the detection result is judged to be smaller than the specification of FBH2mm comprehensively, thereby meeting the technical requirements of processing.

In light of the foregoing description of the preferred embodiment of the present invention, many modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.