CN111716083B - Method for overcoming explosion defect of 4140 steel tubing hanger body - Google Patents
Method for overcoming explosion defect of 4140 steel tubing hanger body Download PDFInfo
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- CN111716083B CN111716083B CN202010624571.8A CN202010624571A CN111716083B CN 111716083 B CN111716083 B CN 111716083B CN 202010624571 A CN202010624571 A CN 202010624571A CN 111716083 B CN111716083 B CN 111716083B
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Abstract
The invention relates to a method for overcoming the burst defect of a 4140 steel tubing hanger body, which comprises the steps of heating blanks in a segmented manner, preparing basic procedures, forging a die, cooling by using sand lime, and finally performing quenching and tempering heat treatment on a formed workpiece. This application is through heating the blank slowly, makes its internal structure change slowly, plays the effect that the crystalline grain refines and even structure, and actual grain size can reach 7 ~ 10 grades, has avoided harmful organizations such as widmannstatten structure because of overburning and overheated production. By using a die forging mode, the excessive surface stress caused by the hammer forging of free forging is avoided, the forging is successively performed from multiple directions, the flowability of the blank is increased, and the generation of knife patterns and the formation of main cracks are avoided. And finally, during quenching, the quenching cooling speed is slowed down, and the cooling speed of the martensite transformation area is reduced, so that the transcrystalline expansion is avoided, the tissue stress of the martensite transformation is reduced, and the macrocracks are avoided.
Description
Technical Field
The invention relates to a method for overcoming the burst defect of a 4140 steel tubing hanger body, and belongs to the technical field of workpiece forging.
Background
The 350-square 4140 blank is forged into an oil pipe hanger body through a 3t forging hammer, the hanger body forging blank is subjected to rough machining and then is subjected to final quenching and tempering heat treatment, and ring cracks and longitudinal cracks are found on the surfaces of a large number of hanger bodies after the quenching and tempering heat treatment. To ascertain the cause of the defect, one of the pieces is examined by anatomical sampling.
According to investigation and research, the cracks of the pendant body are formed by the coexistence of ring cracks and longitudinal cracks, and the cracks are rigid and straight. The annular cracks are located at the transition circular arc of the step and distributed along the circumferential direction. The longitudinal cracks are connected with the annular cracks at the first large step and distributed along the radial direction. Whether the cracks are annular cracks or longitudinal cracks, the macro-morphology features of the cracks belong to stress cracks. And (3) decomposing the pendant body (the mark is 1-5), and performing macroscopic analysis on the appearance of No. 2 fracture and No. 5 fracture of a part of crack opened manually, wherein the macroscopic appearance of the two fractures is very similar, and the same oxidation areas, namely a dark black oxidation area and a light white oxidation area, exist at almost the same positions. And judging the fracture expansion path according to the depth of the oxidation color and the privacy, and performing multi-source expansion. The main fracture sources of the longitudinal fractures are located at the R angle of the first large step transition arc of the pendant body, and the main fracture sources of the circumferential fractures are located at the R angle of the second middle step transition arc of the pendant body.
And (3) sequentially preparing 5 metallographic samples from the fracture of the No. 2 test block between the second step and the third step, wherein the oxidation pollution degree of the fracture surfaces of the No. 1 metallographic sample, the No. 2 metallographic sample and the No. 3 metallographic sample is relatively light, and decarburization and cracks are not found on the side surface of the fracture by metallographic examination. The metallographic examination results of samples No. 4 and 5 with the higher oxidation pollution degree of the fracture surface are as follows: the sample No. 4 is located on the side surface of the fracture and starts to be decarburized, and the decarburized layer is transited to the sample No. 5 from shallow to deep, so that the main crack is judged to be initiated in the sample No. 5 and the sample No. 4 firstly. The main cracks of the samples 5 and 4, combined with the decarburized layer of the sample 5, were formed and terminated during or before the heat treatment heating, and then further propagated under the quenching stress to form macroscopic visible cracks.
Starting from metallographic specimens No. 4 and 5, the fracture side surfaces developed several fissured saw-tooth cracks, similar to the "secondary" cracks accompanying the fracture process. The fact that no inclusion is seen in the secondary cracks, iron oxide is contained in the secondary cracks, more oxide points exist nearby, the cracks are located in the ferrite structure of the fully decarburized area and distributed along the ferrite grain boundary indicates that the forming temperature of the secondary cracks is higher than the recrystallization temperature of the material and is far higher than the forming temperature of the main cracks, namely the secondary cracks are formed before the main cracks. The characteristic that the included angle between the secondary cracks and the main fracture surface is acute angle or approximately parallel is combined, and the secondary cracks are the longitudinal folding knife-edge cracks in nature. As the No. 5 and No. 4 samples are positioned at the transition circular arcs of the first step and the second step of the pendant body, the defect of folding knife patterns exists in the transition circular arcs of the pendant body.
By combining the above, aiming at the macroscopic characteristics of the pendant body cracks, the macroscopic and microscopic appearance of the opened crack fracture and the inspection result of the obtained metallographic sample, the transition arc part of the step of the pendant body has the defect of folding knife patterns. Under the effect of the thermal stresses formed during heating, the folding knurl and its vicinity develop stress concentrations which, when concentrated in a manner greater than the breaking strength which the material can withstand at the corresponding temperature, release the stress in the form of cracks. Therefore, the folding knife pattern is the main reason for the crack formation of the pendant body.
Accordingly, there is a need for a method of overcoming the burst defect of 4140 steel tubing hanger bodies.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for overcoming the burst defect of a 4140 steel tubing hanger body, which has the specific technical scheme that:
the method comprises the following steps: selecting 4140 blank, adding into a heating furnace, and half opening the furnace door; setting the temperature to be 500 +/-10 ℃, setting the heating speed to be 100 ℃/hour, closing the furnace door when the temperature in the furnace reaches 500 +/-10 ℃, and preserving the heat for two hours; setting the temperature to be 800 +/-10 ℃, setting the heating speed to be 50 ℃/hour, and keeping the temperature for two hours when the temperature in the furnace reaches 800 +/-10 ℃; setting the temperature at 1250 +/-10 ℃, setting the heating speed at 25 ℃/h, keeping the temperature for two hours and then discharging the furnace when the temperature in the furnace reaches 1250 +/-10 ℃;
step two: performing rough machining on the blank, including drawing, stamping, shoulder cutting, step forging and rounding;
step three: finishing the blank by using a die, wherein the die successively forges and presses the blank from four directions, the forging ratio is 6.6, and the finish forging temperature is kept above 800 ℃;
step four: cooling by using a sand-lime cooling mode;
step five: and (4) carrying out quenching and tempering heat treatment, taking out the formed workpiece from the cooling liquid when the surface temperature is reduced to 250 ℃ in the quenching process, putting the formed workpiece into the air for 20 minutes, and then continuously putting the formed workpiece into the cooling liquid for cooling.
Further, in the second step, the feeding amount for drawing is kept 0.3-0.5 times; the blank temperature is maintained at 1100 +/-100 ℃ while drawing, stamping, shoulder cutting, step forging and rounding are carried out.
Furthermore, the three dies in the step comprise four movable sub dies which are arranged up and down, left and right, and the blank is forged and molded in the following, left, up and right sequence.
Further, in the fourth step, the mixture is placed in the sand lime for two hours, and is taken out when the mixture is cooled to 150 ℃.
Further, in the fifth step, the workpiece is heated to 900 ℃ before quenching, kept warm for 2 hours and then cooled to normal temperature in air; heating to 650 ℃ again, keeping for 1 hour, continuing to heat to 860 ℃, carrying out F2000 quenching, taking out the workpiece from the cooling liquid when the temperature of the workpiece is reduced to 250 ℃, air-cooling for 20 minutes, and continuing to put into the cooling liquid for quenching to 50 ℃; then heated to 715 ℃ for 4 hours, and cooled to normal temperature by air.
Furthermore, a circulating stirring system of the cooling pool is started before quenching, so that the temperature of the cooling liquid is controlled to be 15-40 ℃.
The invention has the beneficial effects that:
points out the cause of secondary crack in defect analysis, this application has used the mode of segmentation slow heating when heating the blank for the blank is heated evenly, and internal structure changes slowly, plays the effect of grain refinement and even tissue, and actual grain size can reach 7 ~ 10 grades, has avoided harmful structures such as weishi tissue because of overburning and overheated production.
In addition, when the forging is carried out, the method of forging and pressing in four directions is adopted, the fluidity of the blank is increased, the folding of the blank is reduced, and therefore the knife patterns formed inside the blank are reduced.
Finally, in a conventional quenching link, the cooling speed is reduced by increasing the cooling speed of the sand ash, and the cooling speed of a martensite transformation area is reduced, so that the transgranular expansion is avoided, the structural stress of the martensite transformation is reduced, the heat treatment brittle fracture is avoided, and the stress crack is reduced.
Drawings
Figure 1 is a logic flow diagram of the present invention,
fig. 2 is a metallographic picture of a secondary crack in the prior art of the present invention.
Detailed Description
The present invention will now be described in further detail with reference to the accompanying drawings.
As shown in figure 1, the invention provides a method for overcoming the burst defect of a 4140 steel tubing hanger body, which comprises the following steps
The method comprises the following steps: selecting 350-square 4140 blank, and adding the blank into a heating furnace; the temperature is set to be 500 plus or minus 10 ℃, the furnace door is half opened, the heating speed is set to be 100 ℃/hour, when the temperature in the furnace reaches 500 plus or minus 10 ℃, the furnace door is closed, and the temperature is kept for two hours.
Setting the temperature at 800 +/-10 ℃, setting the heating speed at 50 ℃/h, and keeping the temperature for two hours when the temperature in the furnace reaches 800 +/-10 ℃.
Setting the temperature at 1250 +/-10 ℃, setting the heating speed at 25 ℃/h, keeping the temperature for two hours and then discharging the furnace when the temperature in the furnace reaches 1250 +/-10 ℃.
Step two: and (3) performing rough machining on the blank, including drawing, stamping, shoulder cutting, step forging and rounding. Wherein the feeding amount of the drawing is kept 0.3-0.5 times. The temperature of drawing, stamping, shoulder cutting, step forging and rounding is not lower than 1100 ℃.
Step three: and finishing the blank by using a die, wherein the die successively forges the blank from four directions, the forging ratio is 6.6, and the finish forging temperature is kept at 800 ℃. The die comprises four sub dies which can move up and down, left and right, and the blank is forged and molded by the following, left, upper and right steps.
Step four: cooling is carried out by using a sand-lime cooling mode. Placing in sand lime for two hours, cooling to 150 deg.C, and taking out
Step five: and (5) roughly processing the forging piece, and removing redundant blanks on the surface.
Step six: heating the workpiece to 900 ℃ before quenching, preserving heat for 2 hours, and then air-cooling to normal temperature; heating to 650 ℃ again, keeping for 1 hour, continuing to heat to 860 ℃, carrying out F2000 quenching, taking out the workpiece from the cooling liquid when the temperature of the workpiece is reduced to 250 ℃, air-cooling for 20 minutes, and continuing to put into the cooling liquid for quenching to 50 ℃; then heated to 715 ℃ for 4 hours, and cooled to normal temperature by air.
This application is through heating the blank slowly, makes its internal structure change slowly, plays the effect that the crystalline grain refines and even structure, and actual grain size can reach 7 ~ 10 grades, has avoided harmful organizations such as widmannstatten structure because of overburning and overheated production. By using the die forging mode, the excessive surface stress caused by the hammer forging of the free forging is avoided, and the forging is performed successively from four directions, so that the flowability of the blank in the die is increased, the blank is prevented from being folded, and the further fracture of the knife pattern is avoided. In the final quenching stage, the quenching cooling speed is slowed down, and the cooling speed of the martensite transformation area is reduced, so that the transgranular expansion is avoided, the structure stress of the martensite transformation is reduced, the heat treatment brittle fracture is avoided, and the stress crack is reduced.
It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the prior art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
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.
Claims (4)
1. A method for overcoming the burst defect of a 4140 steel tubing hanger body is characterized in that: the method comprises the following steps: selecting 4140 blank, adding into a heating furnace, and half opening the furnace door; setting the temperature to be 500 +/-10 ℃, setting the heating speed to be 100 ℃/hour, closing the furnace door when the temperature in the furnace reaches 500 +/-10 ℃, and preserving the heat for two hours; setting the temperature to be 800 +/-10 ℃, setting the heating speed to be 50 ℃/hour, and keeping the temperature for two hours when the temperature in the furnace reaches 800 +/-10 ℃; setting the temperature at 1250 +/-10 ℃, setting the heating speed at 25 ℃/h, keeping the temperature for two hours and then discharging the furnace when the temperature in the furnace reaches 1250 +/-10 ℃;
step two: performing rough machining on the blank, including drawing, stamping, shoulder cutting, step forging and rounding;
step three: finishing the blank by using a die, wherein the die successively forges and presses the blank from four directions, the forging ratio is 6.6, and the finish forging temperature is kept above 800 ℃;
step four: cooling by using a sand-lime cooling mode; placing the mixture in the sand lime for two hours, and taking out the mixture when the mixture is cooled to 150 ℃;
step five: carrying out quenching and tempering heat treatment, heating the workpiece to 900 ℃ before quenching, preserving heat for 2 hours, and then air-cooling to normal temperature; heating to 650 ℃ again, keeping for 1 hour, continuing to heat to 860 ℃, carrying out F2000 quenching, taking out the workpiece from the cooling liquid when the temperature of the workpiece is reduced to 250 ℃, air-cooling for 20 minutes, and continuing to put into the cooling liquid for quenching to 50 ℃; then heated to 715 ℃ for 4 hours, and cooled to normal temperature by air.
2. The method of overcoming the burst defect of 4140 steel tubing hanger body as set forth in claim 1 wherein: in the second step, the feeding amount for drawing is kept 0.3-0.5 times; the blank temperature is maintained at 1100 +/-100 ℃ while drawing, stamping, shoulder cutting, step forging and rounding are carried out.
3. The method of overcoming the burst defect of 4140 steel tubing hanger body as set forth in claim 1 wherein: the third step die comprises four movable sub-dies which are arranged up and down, left and right, and the blank is forged and molded in the following sequence, left, up and right.
4. The method of overcoming the burst defect of 4140 steel tubing hanger body as set forth in claim 1 wherein: and (3) starting a circulating stirring system of the cooling pool in advance before quenching, so that the temperature of the cooling liquid is controlled to be 15-40 ℃.
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| CN202010624571.8A CN111716083B (en) | 2020-07-02 | 2020-07-02 | Method for overcoming explosion defect of 4140 steel tubing hanger body |
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| CN202010624571.8A CN111716083B (en) | 2020-07-02 | 2020-07-02 | Method for overcoming explosion defect of 4140 steel tubing hanger body |
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| CN111716083B true CN111716083B (en) | 2022-03-01 |
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| CN114603073A (en) * | 2020-12-08 | 2022-06-10 | 南京迪威尔高端制造股份有限公司 | Forging method for overcoming 4130 forging crack |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN88102197A (en) * | 1987-03-27 | 1988-10-26 | Mre公司 | Differential strength materials formed by high speed deformation |
| US5109605A (en) * | 1988-05-17 | 1992-05-05 | Ford Motor Company | Making a fractured powder metal connecting rod |
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2020
- 2020-07-02 CN CN202010624571.8A patent/CN111716083B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN88102197A (en) * | 1987-03-27 | 1988-10-26 | Mre公司 | Differential strength materials formed by high speed deformation |
| US5109605A (en) * | 1988-05-17 | 1992-05-05 | Ford Motor Company | Making a fractured powder metal connecting rod |
Non-Patent Citations (3)
| Title |
|---|
| 4140圆管锻件热处理裂纹检验分析;哈曜;《物理测试》;20171231;第38-42页 * |
| 锻件加热规范的制订;李志广;《锻压装备与制造技术》;20061030;第38-40页 * |
| 锻造技术的发展现状及趋势;李建军;《热处理技术与装备》;20150625;第57-62页 * |
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