CN115786819A - Large-pipe-diameter pipe die with long service life and high metallurgical quality and preparation method thereof - Google Patents
Large-pipe-diameter pipe die with long service life and high metallurgical quality and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a large-diameter pipe die with long service life and high metallurgical quality and a preparation method thereof, and relates to the technical field of hot work die steel and processing engineering thereof. The large-diameter pipe die with long service life and high metallurgical quality comprises the following raw materials in percentage by mass: si 0.60-1.00%, mo 0.45-0.75%. According to the invention, by increasing the contents of Si and Mo in the pipe die, the reduction trend of the hardness and the strength of the pipe die in the service process is controlled, the high-temperature strength and the thermal fatigue property of the pipe die are improved, the service life of the pipe die is prolonged, the cracking time of the pipe die in service is prolonged, the production count of the nodular cast pipes before the cracking of the pipe die is caused is increased, the production efficiency is improved, and the production cost is reduced.
Description
Technical Field
The invention relates to hot work die steel and the technical field of processing engineering thereof, in particular to a large-diameter pipe die with long service life and high metallurgical quality and a preparation method thereof.
Background
In the production of centrifugally cast ductile iron pipe, the pipe die is a consumable item. The pipe die is generally subject to cracking and failure at its inner wall surface during use due to the effects of the alternating thermal stresses. Therefore, the more the number of the nodular cast iron pipes produced by the pipe die before cracking failure occurs, the smaller the material cost amortization is, and the higher the economic benefit is. Even if the pipe die can be continuously used after the parts with cracking cracks on the inner wall of the pipe die are turned and repaired by overlaying welding, the service life of the pipe die is prolonged, but the replacement of the pipe die before and after the turning welding inevitably takes longer time, the production progress of the nodular cast iron pipe is delayed, and the production cost is also increased. And the times of the car welding repair are limited, and once the surface of the inner wall of the pipe diameter has larger cracks and can not be repaired by car welding, the pipe diameter must be scrapped. Therefore, the influence of the service life of the pipe die, especially the water-cooling pipe die with large pipe diameter (DN 500 and above) on the production cost and the production efficiency is very large.
The nodular cast iron pipe is formed by pouring molten iron into an inner cavity of a pipe die which rotates continuously in a centrifugal casting mode and solidifying. Therefore, compared with the service condition of the conventional hot work die steel, the service condition of the pipe die is worse, the inner wall of the pipe die directly contacts molten iron with the temperature of 1300-1400 ℃ or higher, and the outer wall of the pipe die is circularly cooled by water with the temperature of 50-60 ℃, so that the temperature difference between the inner wall and the outer wall of the water-cooled pipe die is extremely large. And along with the continuous output of the nodular cast iron pipe, when the inner wall of the water-cooling pipe die is repeatedly injected with molten iron, solidified and pulled out, the outer wall of the cold die is always cooled by cooling water, so that the inner wall and the outer wall of the water-cooling pipe die, particularly the inner wall of the water-cooling pipe die, are subjected to the alternate change of great temperature difference to generate great alternating thermal stress on the surface layer of the inner wall of the cold die, and further generate thermal fatigue failure, namely cracking. Therefore, in order to prolong the service life of the water-cooled pipe die, the high-temperature and the large alternating thermal stress borne by the inner wall of the water-cooled pipe die are reduced from the perspective of service working conditions, and the high-temperature strength and the thermal fatigue performance of the cold die material can be improved from the perspective of materials.
According to the national standard GB/T25715-2010 centrifugal nodular cast iron pipe die, the pipe die is made of 21CrMo10 steel, 30CrMo steel and 15CrMoQ steel, and the pipe die material with the largest use amount at present is 21CrMo10 steel.
In order to further prolong the service life of the pipe die, chinese patent with publication number CN110257704A discloses a pipe die with long service life and anti-cracking deformation and a manufacturing method thereof, the patent is improved from the material perspective, and the chemical components of the pipe die are improved to 0.23-0.40 percent on the basis of the chemical components of 21CrMo10 steel required by national standard; the Cr content is increased to 2.4-2.9%; the Mn content is increased to 0.7-1.0%; and the other components: the Si content is controlled to be 0.20-0.30%, the Mo content is controlled to be 0.3-0.4%, the V content is controlled to be less than or equal to 0.25%, and the Al content is controlled to be less than or equal to 0.02%. Smelting the pipe die material according to the designed chemical components; after the molten steel smelting sedation time is more than or equal to 10 minutes, the casting of steel ingots is started; and when the steel ingot is ready to adopt hot delivery, the hot delivery is carried out after the steel ingot is air-cooled to the temperature of 500-550 ℃ in the middle of the steel ingot. And then, upsetting, drawing, forging and forming the obtained pipe die steel ingot under a 5000-ton oil press. And reasonable upsetting speed is calculated in the upsetting process, so that the phenomenon that the upsetting speed is too high to causeThe core of the steel ingot is heated to generate composition segregation, so that the structure is not uniform. The upsetting speed is reduced to 20-26mm/s, the whole upsetting process is stopped for 1-2 times, and the stopping time is 10-15 seconds each time. The deformation of the pipe die is increased by improving the forging ratio through upsetting, the difference between the longitudinal performance and the transverse performance of the raw material is improved, and the final performance is improved. And then carrying out quenching and tempering heat treatment on the obtained pipe die forging stock, wherein the heat treatment and the subsequent processes are as follows: normalizing, quenching, primary tempering, hardness detection, secondary tempering, mechanical property detection and metallographic phase detection. In order to improve the strength and hardness index and control the elongation rate within the design range, the performance index after quenching and tempering heat treatment reaches the hardness HB of more than or equal to 300 and the tensile strength R m Not less than 900MPa, yield strength R p0.2 The requirement of more than or equal to 750 MPa: in the quenching and tempering heat treatment process, the primary tempering temperature is 30-50 ℃ lower than the tempering temperature of a normal pipe die, and the secondary tempering temperature is correspondingly lower than the primary tempering temperature. Specifically, the primary tempering temperature is 590-620 ℃, and the secondary tempering temperature is 540-580 ℃. And finally, machining the pipe die by deep hole fine boring, fine turning and the like by adopting an optimized machining process flow.
That is, in this patent document, the object is to increase the contents of elements such as C and Cr in the material and to lower the tempering temperature of the thermal refining by a method of obtaining high hardness. However, how the actual effect of these methods is to be verified, it is possible that the effect is just the opposite, and the service life of the pipe die is reduced, because the occurrence of cracking failure indicates that the alternating thermal stress in the pipe die is a main contradiction of the pipe die failure, and the main measure of reducing the alternating thermal stress in the pipe die in service is to increase the thermal conductivity of steel from the perspective of material design to reduce the temperature difference in addition to changing the service condition of the pipe die. Chinese patent publication No. CN110257704A adopts a method of increasing the content of elements such as C and Cr in steel and reducing tempering temperature, which will reduce the thermal conductivity of steel, further aggravate the alternating thermal stress of pipe die, and thus more easily cause it to crack and fail prematurely.
Therefore, how to effectively prolong the service life of the pipe die, prolong the cracking time of the pipe die in service, increase the production count of the nodular cast iron pipe before the cracking of the pipe die, improve the production efficiency and reduce the production cost becomes a difficult problem to be solved urgently by technical staff of enterprises.
Disclosure of Invention
The invention provides a large-pipe-diameter pipe die with long service life and high metallurgical quality and a preparation method thereof, and aims to solve the problems in the background art.
In order to achieve the technical purpose, the invention mainly adopts the following technical scheme:
in a first aspect, the invention discloses a large-diameter pipe die with long service life and high metallurgical quality, which comprises the following raw materials in percentage by mass: si 0.60-1.00%, mo 0.45-0.75%.
In some embodiments, the invention relates to a large-diameter pipe die with long service life and high metallurgical quality, which comprises the following raw materials in percentage by mass: 0.19 to 0.22 percent of C, 0.60 to 1.00 percent of Si, 0.34 to 0.37 percent of Mn, 2.42 to 2.50 percent of Cr, 0.45 to 0.75 percent of Mo0.009 to 0.010 percent of P, 0.002 to 0.004 percent of S, 0.12 to 0.26 percent of Ni and the balance of Fe.
In a second aspect, the invention discloses a method for preparing a large-pipe-diameter pipe die as described in the first aspect, which comprises the following steps:
s1, sequentially carrying out electric arc furnace steelmaking, ladle refining and vacuum degassing on molten steel to enable the molten steel to reach required chemical components, then adopting a bottom casting method to cast into an octagonal steel ingot, and slowly cooling;
s2, after the steel ingot is slowly cooled to the middle temperature of the steel ingot to reach the proper temperature, demoulding, and conveying the steel ingot to a forging heating furnace for heating and heat preservation;
s3, removing a water gap and a riser of the steel ingot by hot cutting the steel ingot after heating and heat preservation on an oil press;
s4, upsetting the steel ingot with the nozzle and the feeder head removed in the step S3, and punching the axial center of the steel ingot in the axial direction when upsetting is carried out to 1/2 of the height;
s5, inserting a steel core rod into the steel ingot subjected to punching from the orifice, flaring, drawing and pressing a shoulder until the steel ingot reaches the required size, and then cooling the steel ingot by air;
s6: carrying out rough machining, water cooling and thermal refining on the hollow pipe die forging stock obtained in the step S5;
s7: and (3) performing semi-finishing and finish machining on the hollow pipe die blank subjected to quenching and tempering, and obtaining a finished product of the large-pipe-diameter pipe die after the blank is qualified through size, low-power, metallographic phase, mechanical property and ultrasonic flaw detection.
In some embodiments, in step S2, the ingot is slowly cooled until its middle temperature reaches 500-550 ℃, then demolded, and transferred to a forging furnace for heating at 1200 ℃, and the temperature is maintained for 20-60 hours.
In some embodiments, the weight of the nozzle removed in step S3 is 3-6% of the weight of the ingot and the weight of the riser removed is 15-21% of the weight of the ingot.
In some embodiments, in step S4, the size of the hole diameter of the punched hole is 1/6 to 1/4 of the size of the thickest middle part of the upset steel ingot.
Further, in the step S4, the pipe diameter of the punched pipe die is in the range of 350-900 mm.
In some embodiments, in step S5, the start forging temperature and the finish forging temperature of the steel ingot of the pipe die are 1200 ℃ and 800 ℃, respectively.
In some embodiments, in step S6, a quenching and tempering process with water cooling at 920 ℃ and tempering at 640 ℃ is adopted.
Compared with the prior art, the invention has the following beneficial effects:
1. by increasing the contents of Si and Mo in the pipe die, the reduction trend of the hardness and the strength of the pipe die in the service process is controlled, and the high-temperature strength and the thermal fatigue performance of the pipe die are improved.
2. The metallurgical quality of the water-cooled pipe die is greatly improved by increasing the removal amount of a water gap, a riser and the axle center part of a steel ingot containing more casting defects of the pipe die steel ingot and prolonging the homogenization annealing time for reducing the chemical components and the tissue unevenness of the steel ingot. Because the reduction of the amount of microscopic defects such as air holes, shrinkage cavities, inclusions and the like in the pipe die and the reduction of the size of the pipe die, and the reduction of the degree of nonuniformity of chemical components and tissues in a micro-area, the cracking cracks are not easy to nucleate and expand, and the service life of the pipe die is prolonged.
Drawings
FIG. 1 is a structural diagram of a tempered sorbite with high strength and toughness after the pipe die is subjected to thermal refining treatment.
Detailed Description
In order to make the objects and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
A large-diameter pipe die with long service life and high metallurgical quality is disclosed, wherein the mass fraction of Si and Mo is as follows: si 0.60-1.00%, mo 0.45-0.75%.
In the application, the Si content in the pipe die material is increased to 0.60-1.00%, and the Mo content is increased to 0.45-0.75%. The improvement of the content of the Si element fully utilizes the characteristic that the Si element has high tempering resistance in steel, and is used for achieving the purpose of slowing down and even avoiding the reduction of the surface hardness of the pipe die due to the tempering action under the service working condition that the inner wall of the pipe die continuously and repeatedly contacts high-temperature molten iron. However, when the Si content is lower, the increase of the Si content can reduce the thermal conductivity of the tube die and is not beneficial to improving the thermal fatigue performance of the tube die, so that the Si content is not suitable to be increased too much. And the Mo element content is increased to improve the heat strength of the pipe die under the service working condition. But the cost of the pipe die is greatly increased due to the addition of Mo element. Therefore, by comprehensive consideration and optimization of the relevant experiments, the Si content and Mo content in the pipe die were determined to be 0.60-1.00% Mo and 0.45-0.75%, respectively, which were both higher than those required in the national standard GB/T25715-2010 centrifugal nodular cast pipe die, with the Si content of 0.20-0.30% and the Mo content of 0.3-0.4% in the application No. 201910577989.5 patent.
The following is a description of an example of a method for preparing a pipe die with a specific large pipe diameter.
Example 1
For DN600 water-cooled tube die.
The chemical composition (mass%) of the steel was 0.22% C, 0.65% Si, 0.34% Mn, 2.42% Cr, 0.51% Mo, 0.010% P, 0.003% S, 0.14% Ni. The manufacturing steps are as follows:
step 1: after molten steel was made to have a desired chemical composition by 40 tons of electric arc furnace steel making (EAF), 50 tons of ladle refining (LF), and vacuum degassing (VOD), 16.5 tons of octagonal ingots were cast by bottom casting, and slow cooling was started.
Step 2: slowly cooling the steel ingot until the middle temperature reaches 500-550 ℃, demoulding, hoisting the steel ingot to a transport vehicle, adding a heat preservation cover, and heating and preserving heat for 25 hours in a forging heating furnace at 1200 ℃.
And step 3: and (3) removing a water gap and a riser of the steel ingot after heating and heat preservation on a 5000-ton hydraulic press in a hot cutting mode, wherein the removal amount of the water gap and the riser is 5% and 20% of the weight of the steel ingot respectively.
And 4, step 4: upsetting the steel ingot on the basis of the step 3, and when upsetting is carried out to the height of 1/2, punching a hole in the axial direction of the steel ingot at the axial center part, wherein the hole diameter is 1/6 of the size of the thickest part in the middle of the upset steel ingot and is 450mm.
And 5: and inserting a steel core rod into the steel ingot after punching, flaring, drawing and pressing a shoulder until the steel ingot reaches the required size, and then cooling in the air.
The initial forging temperature and the final forging temperature of the pipe die steel ingot during forging forming are 1200 ℃ and 800 ℃ respectively.
Step 6: and (4) carrying out rough machining, water cooling at 920 ℃ and tempering at 640 ℃ on the hollow pipe die forging stock obtained in the step (5).
And 7: and performing semi-finishing and finishing on the hollow pipe die blank subjected to thermal refining, and performing size and macroscopic, metallographic, mechanical property and ultrasonic flaw detection to obtain a finished pipe die product.
The physical and chemical inspection results of the manufactured pipe die (close to the steel ingot casting head end) are as follows: the general porosity, central porosity and dotted segregation in the macrostructure are respectively 0.5 grade, 0 grade and 1 grade; sulfide type, alumina type, silicate type, spherical oxide type and single-particle spherical type inclusions in the inclusions are respectively 0.5 grade, 0 grade, 1 grade and 1 grade; the metallographic structure is a tempered sorbite, and the grain size is 6.0 grade; the yield strength, tensile strength, elongation and shrinkage were 735MPa, 818MPa, 15.0% and 70.3%, respectively. In the production process of the manufactured pipe die, the number of the produced nodular cast iron steel when the manufactured pipe die begins to crack and fail is increased to 1451 from 879 in the original pipe die, and the increase amplitude reaches 65.1%.
Example 2
Aiming at DN800 water-cooling pipe die.
The chemical composition (mass%) of the steel was 0.19% C, 0.95% Si, 0.37% Mn, 2.48% Cr, 0.68% Mo, 0.010% P, 0.004% S, 0.12% Ni. The manufacturing steps are as follows:
step 1: after molten steel was made to have a desired chemical composition by 40 tons of electric arc furnace steel making (EAF), 50 tons of ladle refining (LF), and vacuum degassing (VOD), 27.1 tons of dodecagonal steel ingots were cast by bottom casting, and slow cooling was started.
Step 2: slowly cooling the steel ingot until the temperature of the middle part of the steel ingot reaches 500-550 ℃, demoulding, hoisting the steel ingot to a transport vehicle, additionally installing a heat preservation cover, and heating and preserving the heat in a 1200 ℃ forging heating furnace for 35 hours.
And 3, step 3: and (3) removing a water gap and a riser of the steel ingot from the heated and heat-insulated steel ingot on an oil press in a hot cutting mode, wherein the removal amount of the water gap and the riser is 4.0 percent and 18.0 percent of the weight of the steel ingot respectively.
And 4, step 4: upsetting the steel ingot on the basis of the step 3, and punching a hole in the axial direction at the axial center part of the upset steel ingot when the upsetting is 1/2 of the height, wherein the hole diameter is 600mm.
And 5: and inserting a steel core rod into the steel ingot subjected to punching from the orifice, flaring, drawing and pressing a shoulder until the steel ingot reaches the required size, and then cooling in the air.
The initial forging temperature and the final forging temperature of the pipe die steel ingot during forging forming are 1200 ℃ and 800 ℃ respectively.
And 6: and (4) carrying out rough machining, water cooling at 920 ℃ and tempering at 640 ℃ on the hollow pipe die forging stock obtained in the step (5).
And 7: and (3) performing semi-finishing and finish machining on the hollow pipe die blank subjected to quenching and tempering, and obtaining a pipe die finished product after the size, the macroscopic phase, the metallographic phase, the mechanical property and the ultrasonic flaw detection are qualified.
The physical and chemical inspection results of the manufactured pipe die (close to the steel ingot casting end) are as follows: the general porosity, central porosity and punctate segregation in the macrostructure are respectively 0.5 grade, 0 grade and 0.5 grade; the sulfide, alumina, silicate, spherical oxide and single-particle spherical inclusion in the inclusion are respectively 0.5 grade, 0 grade, 1 grade and 1 grade; the metallographic structure is a tempered sorbite (the metallographic structure is shown in the description of the attached drawing), and the grain size is 6.5 grade; the yield strength, tensile strength, elongation, shrinkage and impact work (20 ℃) were 698MPa, 805MPa, 18.5%, 71.0% and 209J, respectively. In the production process of the manufactured pipe die, the number of the produced nodular cast iron steel is increased from the average 718 of the original pipe die to 1126 when the manufactured pipe die begins to crack and fail, and the increase amplitude is 56.8 percent.
Example 3
For DN1200 water-cooled tube die.
The chemical composition (mass%) of the steel was 0.20% C, 0.73% Si, 0.37% Mn, 2.50% Cr, 0.71% Mo, 0.009% P, 0.002% S, 0.26% Ni. The manufacturing steps are as follows:
step 1: after molten steel was subjected to 40 tons of electric arc furnace steelmaking (EAF), 50 tons of ladle refining (LF), and vacuum degassing (VOD) in this order to have a desired chemical composition, a dodecagonal-shaped steel ingot of 37.4 tons was cast by the bottom casting method, and slow cooling was started.
And 2, step: slowly cooling the steel ingot until the middle temperature reaches 500-550 ℃, demoulding, hoisting to a transport vehicle, adding a heat preservation cover, and heating and preserving heat in a forging heating furnace at 1200 ℃ for 50 hours.
And step 3: and (3) removing a water gap and a riser of the steel ingot on the oil press in a hot cutting mode, wherein the removing amount of the water gap and the riser is 3.5 percent and 16.0 percent of the weight of the steel ingot respectively.
And 4, step 4: upsetting the steel ingot on the basis of the step 3, and punching a hole in the center of the upset steel ingot along the axial direction when upsetting is 1/2 of the height before upsetting, wherein the hole diameter is 1/4 of the size of the thickest part in the middle of the upset steel ingot and is 850mm.
And 5: and inserting a steel core rod into the steel ingot subjected to punching from the orifice, flaring, drawing and pressing a shoulder until the steel ingot reaches the required size, and then cooling in the air.
The initial forging temperature and the final forging temperature of the pipe die steel ingot during forging forming are 1200 ℃ and 800 ℃ respectively.
Step 6: and (4) carrying out rough machining on the hollow pipe die forging stock obtained in the step (5), and then carrying out quenching and tempering treatment by water cooling at 920 ℃ and tempering at 640 ℃.
And 7: and performing semi-finishing and finishing on the hollow pipe die blank subjected to thermal refining, and performing size and macroscopic, metallographic, mechanical property and ultrasonic flaw detection to obtain a finished pipe die product.
The manufactured pipe die has the following physical and chemical inspection results: the general point segregation and central porosity in the macrostructure are 1.0 grade, and sulfide, alumina, silicate, spherical oxide and single-particle spherical inclusion are 1 grade, 0.5 grade, 0 grade, 1 grade and 1.5 grade respectively; the metallographic structure is a tempered sorbite, and the grain size is 6.0 grade; the yield strength, tensile strength, elongation, shrinkage and impact energy (room temperature) were 666MPa, 786MPa, 19.0%, 72.5% and 201J, respectively. In the production process of the manufactured pipe die, the number of the produced nodular cast iron steel is increased from the average 625 of the original pipe die to 922 when the manufactured pipe die begins to crack and fail, and the increase amplitude reaches 47.5 percent.
According to the invention, the removal amount of a water gap and a riser of a steel ingot of the pipe die is respectively 3-6% and 15-21% of the weight of the steel ingot, and when the steel ingot is upset to 1/2 of the height, the central part of the upset steel ingot is axially punched, the aperture size is 1/6-1/4 of the size of the thickest part in the middle of the upset steel ingot, and the aperture size is in the range of 350-900mm according to the pipe diameter of the pipe die. This is mainly due to the fact that the ingot solidified in the ingot mould is composed of the following parts: (1) a fine equiaxed crystal region on the outermost layer; (2) a secondary layer dendritic crystal region growing from outside to inside; (3) the large equiaxed grain area with more serious deviation of the ingot core part and more looseness; (4) a conical deposition cone area (close to a water gap of the steel ingot) deposited by crystals and fragment dendrites which are formed at the beginning of molten steel at the bottom of the steel ingot in the solidification process; (5) and a riser region where low melting point materials and inclusions having high contents of elements including S and P are continuously floated upward along with molten steel and then solidified, and have a large number of various casting defects after final solidification shrinkage at the top of the steel ingot. Meanwhile, the solidification sequence of the molten steel in the steel ingot mould is from bottom to top and from the surface to the inside: when the lower layer molten steel is solidified, the upper layer molten steel can fill feeding to the lower layer; when the outer molten steel is solidified, the upper central molten steel still feeds downwards, and finally, more shrinkage cavities, looseness and more serious component segregation are formed at the top of the steel ingot and the central part of the steel ingot, particularly in a top riser area, and more inclusions with larger sizes exist in areas with more shrinkage cavities, looseness and more serious component segregation. The existence of casting defects such as shrinkage cavities, looseness, inclusions, component segregation and the like can become cores of thermal fatigue cracks in the service process of the pipe die, so that cracking failure occurs prematurely, and the service life of the pipe die is shortened. The presence of these defects is reduced during the manufacture of the tube mould, i.e. the elimination of the cap-off zone, the water-mouth zone and the defect zones in the central zone of the ingot, but these zones should not be eliminated too much, which would reduce the yield of the ingot and increase the raw material costs of the tube mould.
In the homogenizing annealing time before forging the steel ingot of the pipe die. The pipe die adopts the heat preservation time of 20-60 hours to reduce the degree of component segregation of the pipe die when the pipe die is subjected to homogenizing annealing at 1200 ℃. Although higher heating temperatures and longer homogenization times can reduce the degree of segregation of the pipe die material to a greater extent, they also increase the raw material cost of the pipe die, and therefore, the heating temperature and the holding time should be considered together.
Although the increase of the content of alloy elements, the reduction of the yield of the steel ingot (the increase of the removal amount of the defect part of the steel ingot) and the prolongation of the homogenization time of the large-caliber pipe die prepared by the method all increase the cost of the raw materials of the pipe die, through the control of the claim, compared with the increase of the cost of the raw materials of the pipe die, the service life of the pipe die is prolonged more obviously, so that the manufactured high-metallurgical-quality pipe die has very high cost performance.
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.
Claims (9)
1. The large-diameter pipe die with the advantages of long service life and high metallurgical quality is characterized by comprising the following raw materials in percentage by mass: si 0.60-1.00% and Mo 0.45-0.75%.
2. The large-diameter pipe die with long service life and high metallurgical quality is characterized by comprising the following raw materials in percentage by mass: 0.19 to 0.22 percent of C, 0.60 to 1.00 percent of Si, 0.34 to 0.37 percent of Mn, 2.42 to 2.50 percent of Cr, 0.45 to 0.75 percent of Mo, 0.009 to 0.010 percent of P, 0.002 to 0.004 percent of S, 0.12 to 0.26 percent of Ni and the balance of Fe.
3. A method for preparing a large-diameter pipe die according to any one of claims 1 to 2, comprising the steps of:
s1, sequentially carrying out electric arc furnace steelmaking, ladle refining and vacuum degassing on molten steel to enable the molten steel to reach required chemical components, then adopting a bottom casting method to cast into an octagonal steel ingot, and slowly cooling;
s2, after the steel ingot is slowly cooled to the middle temperature of the steel ingot to reach the proper temperature, demoulding, and conveying the steel ingot to a forging heating furnace for heating and heat preservation;
s3, removing a water gap and a riser of the steel ingot by hot cutting the steel ingot after heating and heat preservation on an oil press;
s4, upsetting the steel ingot with the nozzle and the feeder head removed in the step S3, and punching the axial center of the steel ingot in the axial direction when upsetting is carried out to 1/2 of the height;
s5, inserting a steel core rod into the steel ingot subjected to punching from the orifice, flaring, drawing and pressing a shoulder until the steel ingot reaches the required size, and then cooling the steel ingot by air;
s6: carrying out rough machining, water cooling and thermal refining on the hollow pipe die forging stock obtained in the step S5;
s7: and (3) performing semi-finishing and finish machining on the hollow pipe die blank subjected to quenching and tempering, and obtaining a finished product of the large-pipe-diameter pipe die after the blank is qualified through size, low-power, metallographic phase, mechanical property and ultrasonic flaw detection.
4. The method for preparing the large-caliber pipe die as claimed in claim 3, wherein: in step S2, the steel ingot is slowly cooled until the middle temperature reaches 500-550 ℃, then the steel ingot is demoulded, and is conveyed to a forging heating furnace to be heated at 1200 ℃, and the temperature is kept for 20-60 hours.
5. The method for preparing the large-caliber pipe die as claimed in claim 3, wherein: in step S3, the weight of the removed nozzle is 3-6% of the weight of the steel ingot, and the weight of the removed riser is 15-21% of the weight of the steel ingot.
6. A method of making a large diameter pipe die as claimed in claim 3, wherein: in the step S4, the aperture size of the punched hole is 1/6-1/4 of the size of the thickest part in the middle of the upset steel ingot.
7. The method for preparing the large-caliber pipe die according to claim 6, wherein: in the step S4, the pipe diameter of the punched pipe die is in the range of 350-900 mm.
8. The method for preparing the large-caliber pipe die as claimed in claim 3, wherein: in step S5, the initial forging temperature and the final forging temperature of the steel ingot of the pipe die are 1200 ℃ and 800 ℃ respectively.
9. The method for preparing the large-caliber pipe die as claimed in claim 3, wherein: and S6, adopting a quenching and tempering mode of water cooling at 920 ℃ and tempering at 640 ℃.
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| CN202211578063.6A CN115786819A (en) | 2022-12-09 | 2022-12-09 | Large-pipe-diameter pipe die with long service life and high metallurgical quality and preparation method thereof |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1646717A (en) * | 2002-04-03 | 2005-07-27 | 法国安达斯戴乐公司 | Bulk steel for the production of injection moulds for plastic material or for the production of pieces for working metals |
| CN1878881A (en) * | 2003-12-19 | 2006-12-13 | 大同特殊钢株式会社 | Hot work tool steel and mold member excellent in resistance to melting |
| CN102650020A (en) * | 2012-05-14 | 2012-08-29 | 上海大学 | High-silicon high-manganese type high-thermal stability hot work die steel and thermal treatment process thereof |
| CN113953430A (en) * | 2021-10-13 | 2022-01-21 | 洛阳中重铸锻有限责任公司 | Process method for prolonging service life of nodular cast iron pipe die |
-
2022
- 2022-12-09 CN CN202211578063.6A patent/CN115786819A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1646717A (en) * | 2002-04-03 | 2005-07-27 | 法国安达斯戴乐公司 | Bulk steel for the production of injection moulds for plastic material or for the production of pieces for working metals |
| CN1878881A (en) * | 2003-12-19 | 2006-12-13 | 大同特殊钢株式会社 | Hot work tool steel and mold member excellent in resistance to melting |
| CN102650020A (en) * | 2012-05-14 | 2012-08-29 | 上海大学 | High-silicon high-manganese type high-thermal stability hot work die steel and thermal treatment process thereof |
| CN113953430A (en) * | 2021-10-13 | 2022-01-21 | 洛阳中重铸锻有限责任公司 | Process method for prolonging service life of nodular cast iron pipe die |
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