CN112575246A - High-weldability and high-toughness core rod steel and manufacturing method thereof - Google Patents
High-weldability and high-toughness core rod steel and manufacturing method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
Abstract
A high-toughness core rod steel with good weldability and a manufacturing method thereof are disclosed, which comprises the following components in percentage by mass: 0.25-0.28% of C, 0.62-0.72% of Si, 0.60-0.70% of Mn, less than or equal to 0.005% of S, less than or equal to 0.015% of P, 3.30-3.50% of Cr, 0.60-0.80% of Mo, 0.25-0.35% of V, less than or equal to 0.040% of Al, less than or equal to 2.5ppm of H, less than or equal to 30ppm of O, less than or equal to 100ppm of N, and the balance of Fe and other inevitable impurities, and simultaneously: m is 474C +33Mn +17Cr +21Mo, and the value of M is less than or equal to 220. The quantity of hard and brittle liquated carbides in the steel structure of the core rod is greatly reduced or basically does not appear, the impact toughness is greatly improved under the condition that the strength is not reduced, and the improvement of the toughness is beneficial to resisting fatigue cracking and screw thread fracture accidents in the recycling process of the core rod; and the component design for reducing the content of C is also beneficial to the improvement of weldability, and is beneficial to the cyclic surfacing repair of the core rod.
Description
Technical Field
The present invention relates to a high-toughness core rod steel with good weldability and a manufacturing method thereof.
Background
The core rod is one of important tools and appliances with large consumption in the continuous rolling production process of the seamless steel tube, and mainly plays a role in rolling the hollow billet into a pierced billet with required outer diameter and wall thickness. The performance and quality of the mandrel affects the service life of the mandrel or the cost of the tool for rolling a ton of steel and the quality of the inner surface of the steel tube. When the mandrel is used, the mandrel is subjected to the interaction of cold and hot temperature circulation, rolling force and friction force, stress fatigue, cold and hot fatigue, high-temperature abrasion and the like can occur, and the defects of cracking, abrasion, ring crack and the like are generated on the surface, so that the mandrel fails and is off-line.
The core rod material mainly used at present in China is H13 steel (4Cr5MoSiV1), and the core rod is characterized in that the heat strength is good due to the fact that the addition amount of alloy elements such as Cr, Mo and V is large, the impact toughness is low, fatigue fracture failure is prone to occurring in the recycling process, tool cost loss is caused, and normal production is affected. The mandrel steel can be used only by being connected with other parts through the processed screw thread, and the screw thread is generally made of a material at a half radius position of a mandrel steel round billet, so that the strength and the fatigue resistance of the screw thread can be ensured by requiring enough strength.
The core rod steel obtains the required toughness and strength combination performance through quenching and tempering heat treatment, so that the strength requirement of the screw thread can be ensured by ensuring that the half radius position and the position closer to the center part can be fully quenched and hardened after quenching when alloy design is carried out.
In addition, after the core rod is recycled for a certain period, the core rod is turned off and heavy-duty vehicle is carried out after the surface defects are formed and exceed a certain standard, the surface defects are thoroughly removed, then the wear-resistant alloy with enough thickness is overlaid and clad, and then the core rod is machined to the original size for recycling. Therefore, the composition design of the core rod also needs to consider the actual use requirement of the cyclic surfacing repair, namely the requirement on weldability, so as to ensure that the core rod can obtain high cumulative service life.
Chinese patent CN1616700A discloses a steel for processing retained mandrel of continuous tube rolling mill and its production process, the chemical composition of the material is C0.30-0.43%, Mn is less than or equal to 0.60%, Si 0.70-1.00%, P is less than or equal to 0.010%, S is less than or equal to 0.007%, Cr 4.5-5.5%, Mo 1.00-1.50%, V0.70-1.00%, Nb 0-0.25%, Al is less than or equal to 0.015%, Ni 0.10-0.75%, Cu is less than or equal to 0.10%, O is less than or equal to 30ppm, and H is less than or equal to 2 ppm. Also contains 0.008 to 0.10 percent of RE, 0.30 to 1.70 percent of W, less than or equal to 0.005 percent of B, 0.002 to 0.01 percent of Ca, 0.002 to 0.012 percent of Mg, 0.01 to 0.15 percent of Zr and 0.005 to 0.05 percent of Ti.
Chinese patent CN103555912A discloses a method for producing a core rod by using 30Cr3MoV steel as a round material, which relates to specific process methods such as forging, heat treatment and the like, wherein the heat treatment mainly adopts a normalizing and tempering (quenching and tempering). The chemical components of the electrode blank are 0.28-0.33% of C, 0.55-0.70% of Si, 0.40-0.60% of Mn, 3.00-3.30% of Cr, 0.45-0.55% of Mo, 0.20-0.30% of V, less than or equal to 0.008% of S and less than or equal to 0.012% of P. The chemical components of the electroslag ingot are 0.28-0.33% of C, 0.45-0.65% of Si, 0.40-0.60% of Mn, 3.00-3.30% of Cr, 0.45-0.55% of Mo, 0.20-0.30% of V, less than or equal to 0.008% of S and less than or equal to 0.012% of P.
Chinese patent CN101486044A discloses a method for manufacturing a retained mandrel with a diameter of more than 330mm for a continuous tube mill, and relates to quenching and twice high-temperature tempering processes. The chemical components of the used material are 0.30-0.38% of C, 0.70-1.10% of Si, less than or equal to 0.60% of Mn, 4.5-5.5% of Cr, less than or equal to 0.005% of S, less than or equal to 0.015% of P, 1.00-1.50% of Mo and 0.80-1.20% of V.
Chinese patent CN102069345A discloses a method for manufacturing a large-specification steel pipe retained mandrel. The segregation problem of the core rod is solved by adopting a high-temperature diffusion process, and the process of intermittent spray water cooling and high-temperature tempering after rolling eliminates the net-shaped carbide in the core rod blank, thereby improving the production quality of the large-size core rod.
Chinese patent CN102162071A discloses a retained mandrel steel material for a high-performance rolled pipe and a manufacturing method thereof. The chemical components of the used material are 0.40-0.48% of C, 0.40-0.80% of Si, 0.30-0.60% of Mn, less than or equal to 0.010% of P, less than or equal to 0.008% of S, 2.30-3.00% of Cr, 2.0-2.5% of Mo, 1.0-1.5% of V, 0.50-0.80% of Ni, 0.04-0.10% of Nb and 0.015-0.035% of Al.
Chinese patent CN104998905A discloses an alloy steel, a retained mandrel and a production method thereof. All the chemical components of the material are as follows: 0.27-0.31% of C, 0.60-0.80% of Si, 0.70-0.90% of Mn, less than or equal to 0.015% of P, less than or equal to 0.005% of S, 3.50-3.70% of Cr, 0.20-0.30% of Ni, 0.40-0.50% of V, 0.50-0.58% of Mo and less than or equal to 0.025% of Al.
At present, the domestic core rod does not consider the use requirement of the subsequent cyclic surfacing repair of the core rod during the component design, so the service life of the surfacing repair core rod for reuse is greatly reduced, the accumulated service life of the core rod is greatly reduced, and the use cost is higher.
Disclosure of Invention
The invention aims to provide a mandrel steel with good weldability and high toughness and a manufacturing method thereof, which can improve the weldability and the impact toughness while ensuring that the strength of the mandrel round steel at the position of half radius is not reduced; the yield strength Rp0.2 of the mandrel steel at room temperature is more than or equal to 880MPa, the tensile strength Rm is 1050-1280 MPa, the elongation is more than or equal to 10%, and the impact toughness AKV average value is more than or equal to 25J.
In order to achieve the purpose, the technical scheme of the invention is as follows:
the invention improves the weldability and the toughness by reasonable component design of C, V, Mn, Mo and Cr, reduces the formation of brittle hard phase liquated carbide by reducing V, and ensures that the strength is not reduced after C, V is reduced by increasing Mn, Mo and Cr, thereby obtaining the core rod steel which meets the requirement on strength and has good weldability and high toughness. Under the condition of not reducing the strength, the cold and hot fatigue resistance of the mandrel at the working temperature can be effectively improved by improving the toughness, so that the service life of the rolled steel pipe of the mandrel is effectively prolonged; the formation of retained austenite is reduced by comprehensively controlling the contents of C, Mn, Cr and Mo, so that the strength is ensured, and the problems of low service life of a mandrel rolled steel pipe caused by strength change and mandrel deformation due to transformation of the retained austenite in the use process at the working temperature and incapability of using the mandrel are solved.
Specifically, the core rod steel with good weldability and high toughness comprises the following chemical elements in percentage by mass: 0.25-0.28% of C, 0.62-0.72% of Si, 0.60-0.70% of Mn, less than or equal to 0.005% of S, less than or equal to 0.015% of P, 3.30-3.50% of Cr, 0.60-0.80% of Mo, 0.25-0.35% of V, less than or equal to 0.040% of Al, less than or equal to 2.5ppm of H, less than or equal to 30ppm of O, less than or equal to 100ppm of N, and the balance of Fe and other inevitable impurities, and simultaneously: m is 474C +33Mn +17Cr +21Mo, and the value of M is less than or equal to 220.
The design principle of each chemical element in the plug is as follows:
carbon (C): the strength is improved by precipitation strengthening and solid solution strengthening. The content is too low, and the strength is not enough; too high content, poor welding performance and obviously reduced toughness. In addition, the C content is reduced, so that the martensite transformation point Ms of the steel is at a relatively high temperature level, excessive residual austenite formed in the quenching process is reduced, and the phenomenon that the residual austenite is transformed at the working temperature to influence the working performance or deformation of the core rod is avoided. Therefore, the content of C is required to be controlled to be 0.25-0.28%.
Silicon (Si): plays a role in deoxidation in the steelmaking process and is beneficial to improving the high-temperature oxidation resistance of the steel. Si can also play a role in tempering stability and improving hardenability. However, the Si content is too high, which is detrimental to the toughness of the material. Therefore, the invention needs to control the Si content between 0.62 and 0.72 percent.
Manganese (Mn): mn is a solid solution strengthening element, and is beneficial to improving the strength of the matrix. However, too high Mn content tends to cause component segregation, resulting in uneven structure properties at various parts of the material, and unfavorable cold and hot fatigue resistance. Therefore, the Mn content is controlled to be 0.60-0.70%.
Chromium (Cr): cr is a carbide Cr which can be combined with C to form at lath interface7C3And Cr23C6The precipitation strengthening effect is generated to improve the strength and the hardenability. However, the Cr content is too highResulting in too high a material strength to reduce toughness and too high a Cr content to lower the Ms point, causing too much retained austenite to be formed during quenching and thus transformed at the working temperature to affect the working properties or deformation of the core rod. Therefore, the Cr content is controlled to be between 3.30 and 3.50 percent.
Molybdenum (Mo): mo is added to improve the solid-solution strengthening effect and the effect of forming Mo2C carbide in the strip in combination with C to produce precipitation strengthening effect to improve strength and hardenability. However, too high Mo content may result in too high material strength and reduced toughness, and too high Mo content may lower the Ms point, causing too much retained austenite to be formed during quenching and thus transformed at the working temperature to affect the working performance or deformation of the core rod. Therefore, the content of Mo is controlled to be 0.60-0.80%.
Vanadium (V): v is added to form carbide V4C3 by combining with C to produce precipitation strengthening effect and improve the strength. However, too high a V content promotes the formation of brittle hard phase liquated carbides in the steel and reduces toughness. Therefore, the content of V is controlled to be 0.25-0.35%.
Aluminum (Al): al is added for deoxidation, but too high an Al content results in a decrease in toughness. Therefore, the Al content is controlled to be less than or equal to 0.040 percent.
Sulfur (S), phosphorus (P), hydrogen (H), oxygen (O), nitrogen (N): in order to reduce the adverse effect of sulfur, phosphorus, hydrogen, oxygen and nitrogen on the toughness, the invention controls S to be less than or equal to 0.005, P to be less than or equal to 0.015, H to be less than or equal to 2.5ppm, O to be less than or equal to 30ppm and N to be less than or equal to 100 ppm.
M: the M value reflects the comprehensive influence of the contents of various alloy elements (C, Mn, Cr and Mo) in the core rod steel on the temperature of the martensite start transformation point, and the larger the M value is, the lower the martensite start transformation point is, and the higher the content of the retained austenite is; the smaller the value of M, the higher the martensite transformation point and the smaller the residual austenite content. Therefore, the present invention controls the value of M to be 220 or less.
The invention also provides the core rod steel with good weldability and high toughness and the manufacturing method thereof, comprising the following steps: smelting and casting according to the chemical components, heating steel ingots, rolling round billets, annealing and quenching and tempering heat treatment; wherein the quenching heating temperature in the quenching and tempering heat treatment is 920-960 ℃, and the tempering temperature is 600-640 ℃. In the invention, the retained austenite is controlled by reasonable content design of C, Mn, Cr and Mo in the component design; meanwhile, the reasonable design of the quenching and tempering heat treatment process is further matched with the control of retained austenite, excessive C, Mn, Cr and Mo alloy elements are prevented from being dissolved into a matrix and austenite grains are coarse by controlling the upper limit of the quenching and heating temperature, so that the stability of the super-cooled austenite is improved, the retained austenite is increased in the quenching and cooling process, and in addition, through sufficient tempering, the strength is ensured, most of the retained austenite formed in the quenching process is converted into martensite in the heat treatment process, and the influence on the size stability caused by the conversion in the use process is avoided.
In the step of quenching and tempering heat treatment, the quenching and heating temperature is controlled to be 920-960 ℃.
If the quenching heating temperature is lower than 920 ℃, the alloy elements are not fully dissolved in the solution, the effect of improving the hardenability of the alloy elements cannot be effectively exerted, the requirement of completely quenching the center of a large-size core rod cannot be met, and the adjustment of the strength and toughness matching in the subsequent tempering process through precipitation control is not favorable; if the quenching heating temperature is higher than 960 ℃, austenite grains can grow and coarsen rapidly, so that the grains are too large to reduce the toughness, and the quenching heating temperature is too high, so that the content of carbon and alloy elements which are dissolved into a matrix in a solid manner is increased, the austenite grains are coarsened, the martensite starting phase transformation point is reduced, and the content of retained austenite is increased. Therefore, the quenching heating temperature needs to be controlled to be 920-960 ℃.
In the step of quenching and tempering heat treatment, the tempering temperature is controlled to be 600-640 ℃: in the invention, if the tempering temperature is lower than 600 ℃, the martensite structure obtained by quenching is not fully recovered, and the alloy elements are not fully combined with C and precipitated in the form of carbide, so that the material has over-high strength and lower toughness, and is unfavorable for the accident resistance of the mandrel in the recycling process; if the tempering temperature is higher than 640 ℃, the degradation softening degree of the martensite structure lath is high, the dislocation density is obviously reduced, the carbide grows and coarsens rapidly, and although the toughness of the material is higher, the strength is too low, so that the requirement on the strength of the mandrel round steel meeting the position of half radius is not favorable. Therefore, the tempering temperature needs to be controlled within 600-640 ℃.
The invention has the beneficial effects that:
the invention adopts low-C and low-V component design to improve the weldability and the impact toughness, and improves the contents of Mn, Mo and Cr to ensure that C, V reduces the through hardenability and the strength of half radius position, thereby meeting the use requirement of the screw fastener.
The weldability and toughness are improved by reducing C, the toughness is improved by reducing the formation of brittle hard phase liquated carbide by reducing V, and the strength is ensured not to be reduced after C, V is reduced by increasing Mn, Mo and Cr, so that the core rod steel which meets the requirement of strength, has good weldability and high toughness is obtained. Under the condition of not reducing the strength, the cold and hot fatigue resistance of the mandrel at the working temperature can be effectively improved by improving the toughness, so that the service life of the rolled steel pipe of the mandrel is effectively prolonged.
The formation of retained austenite is reduced by comprehensively controlling the contents of C, Mn, Cr and Mo, so that the strength is ensured, and the problem that the service life of a mandrel-rolled steel pipe is short due to deformation and incapability of use caused by the transformation of the retained austenite in the use process at the working temperature is solved.
According to the invention, the toughness of the mandrel is improved, and the residual austenite content is controlled by a component-process to reduce the deformation of the mandrel in the using process, so that the service life of the rolled steel pipe of the mandrel reaches 1500-2000 counts, the service life of the rolled steel pipe of H13 steel is 1000-1200 counts under the same condition, the content of Mn, Cr, Mo and V alloy is reduced, the service life is obviously prolonged, and the production cost of the rolled steel pipe is effectively reduced.
Drawings
FIG. 1 is a photograph of the microstructure of a steel according to an example of the present invention.
FIG. 2 is a photograph of the microstructure of comparative example steel.
Detailed Description
The good weldability and high toughness core rod steel according to the present invention will be further explained with reference to specific examples, but the specific examples and the related explanations do not constitute undue limitations on the technical solution of the present invention.
The compositions of the examples of the high-toughness core rod steel according to the invention are shown in table 1, with the balance of the compositions being Fe and other unavoidable impurities.
The manufacturing method of the embodiment of the invention comprises the following steps:
1) smelting: smelting in a converter or an electric furnace;
2) casting: casting into steel ingots;
3) heating a steel ingot, and controlling the heating and heat preservation temperature to be 1250-1300 ℃;
4) rolling a round steel billet, and controlling the total compression ratio to be more than or equal to 6;
5) annealing, wherein the annealing heat preservation temperature is 720-780 ℃;
6) and (4) quenching and tempering heat treatment.
Wherein the quenching and tempering heat treatment process is shown in table 2.
In order to compare with the existing core rod material and technology, the quenching and tempering heat treatment process of the H13 steel as the comparative example adopts the processes generally adopted by the core rod manufacturing industry, namely, the quenching temperature of 1030 ℃ and the tempering temperature of 650 ℃.
As can be seen from table 2, the transverse impact toughness of the mandrel round steel manufactured by the reasonable component design of C, V, Mn, Cr and Mo and the design of the quenching and tempering heat treatment process at the half radius position is improved by about 85.5% compared with that of H13 steel (i.e. comparative examples 1 to 3) (the impact toughness improvement rate is (the impact toughness mean value of the examples-the impact toughness mean value of the comparative examples)/the impact toughness mean value of the comparative examples x 100%), but the strength is not significantly reduced, which indicates that the mandrel round steel obtains better toughness matching, and the improvement of the toughness is beneficial to the fatigue fracture resistance and the screw thread fracture failure resistance in the recycling process of the mandrel.
The improvement of the impact toughness is benefited by the reduction of the C content on the one hand and the V content on the other hand, so that the formation amount of the hard and brittle phase of the liquated carbide is reduced or basically not appeared (fig. 1 and fig. 2 respectively show typical structures of an example and a comparative example, wherein white massive liquated carbide is not seen in the typical structure of the example, and white massive liquated carbide is seen in the typical structure of the comparative example).
Table 1 units: weight percent of
| C | Si | Mn | Cr | Mo | V | Al | M | |
| Example 1 | 0.25 | 0.71 | 0.65 | 3.32 | 0.62 | 0.26 | 0.030 | 208.7 |
| Example 2 | 0.27 | 0.66 | 0.61 | 3.49 | 0.63 | 0.33 | 0.029 | 219.9 |
| Example 3 | 0.26 | 0.63 | 0.63 | 3.4 | 0.66 | 0.31 | 0.035 | 214.9 |
| Example 4 | 0.26 | 0.65 | 0.62 | 3.42 | 0.64 | 0.29 | 0.028 | 214.5 |
| Example 5 | 0.27 | 0.64 | 0.64 | 3.46 | 0.61 | 0.32 | 0.036 | 219.9 |
| Example 6 | 0.26 | 0.69 | 0.70 | 3.35 | 0.61 | 0.27 | 0.033 | 215.3 |
| Example 7 | 0.25 | 0.70 | 0.67 | 3.46 | 0.69 | 0.25 | 0.027 | 213.2 |
| Example 8 | 0.26 | 0.62 | 0.64 | 3.34 | 0.66 | 0.28 | 0.033 | 214.2 |
| Example 9 | 0.27 | 0.67 | 0.63 | 3.44 | 0.6 | 0.34 | 0.028 | 219.0 |
| Example 10 | 0.26 | 0.68 | 0.66 | 3.38 | 0.64 | 0.3 | 0.034 | 215.1 |
| Comparative example 1 | 0.42 | 1.10 | 0.40 | 5.00 | 1.22 | 0.97 | 0.035 | 321.6 |
| Comparative example 2 | 0.39 | 0.90 | 0.25 | 5.20 | 1.43 | 1.15 | 0.032 | 310.4 |
| Comparative example 3 | 0.34 | 1.00 | 0.35 | 5.45 | 1.35 | 0.90 | 0.038 | 292.7 |
Remarking: M474C +33Mn +17Cr +21Mo
TABLE 2
Claims (6)
1. A core rod steel with good weldability and high toughness comprises the following chemical components in percentage by mass: 0.25-0.28% of C, 0.62-0.72% of Si, 0.60-0.70% of Mn, less than or equal to 0.005% of S, less than or equal to 0.015% of P, 3.30-3.50% of Cr, 0.60-0.80% of Mo, 0.25-0.35% of V, less than or equal to 0.040% of Al, less than or equal to 2.5ppm of H, less than or equal to 30ppm of O, less than or equal to 100ppm of N, and the balance of Fe and other inevitable impurities, and simultaneously: m is 474C +33Mn +17Cr +21Mo, and the value of M is less than or equal to 220.
2. The good weldable and high toughness core rod steel according to claim 1, wherein the microstructure of the core rod steel is tempered martensite.
3. The good weldable and high toughness core rod steel according to claim 1 or 2, wherein the yield strength Rp0.2 at room temperature of the core rod steel is not less than 880MPa, the tensile strength Rm is 1050-1280 MPa, the elongation is not less than 10%, and the AKV mean value of the impact toughness is not less than 25J.
4. The method for producing a high toughness core rod steel having good weldability according to claim 1, characterized by comprising the steps of: smelting, casting, steel ingot heating, round billet rolling, annealing and quenching and tempering heat treatment; in the quenching and tempering heat treatment, the quenching temperature is 920-960 ℃, and the tempering temperature is 600-640 ℃.
5. The process for producing a high toughness core rod steel having good weldability according to claim 4, wherein the microstructure of said core rod steel is tempered martensite.
6. The method for producing a high-toughness mandrel steel with good weldability according to claim 4 or 5, wherein the yield strength Rp0.2 at room temperature of the mandrel steel is not less than 880MPa, the tensile strength Rm is 1050-1280 MPa, the elongation is not less than 10%, and the AKV mean value of the impact toughness is not less than 25J.
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| CN104998905A (en) * | 2015-08-03 | 2015-10-28 | 山东墨龙石油机械股份有限公司 | Alloy steel, retained mandrel and production method of retained mandrel |
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| JPS57192247A (en) * | 1981-05-21 | 1982-11-26 | Sumitomo Metal Ind Ltd | Steel excellent in sulfide stress corrosion cracking resistance for high strength oil well pipe |
| JP2011179042A (en) * | 2010-02-26 | 2011-09-15 | Jfe Steel Corp | Method for manufacturing thick-wall high-tensile-strength hot-rolled steel plate superior in low-temperature toughness |
| CN101956137A (en) * | 2010-10-12 | 2011-01-26 | 衡阳华菱钢管有限公司 | Seamless steel tube for manufacturing hollow core rod and production method |
| CN102330024A (en) * | 2011-09-02 | 2012-01-25 | 上海大学 | Steel for tandem tube mill hollow mandrel and preparation technology thereof |
| CN102337464A (en) * | 2011-09-02 | 2012-02-01 | 上海大学 | Steel for high-strength continuous pipe-mill core rod and preparation process thereof |
| JP2013076160A (en) * | 2011-09-15 | 2013-04-25 | Nisshin Steel Co Ltd | Steel sheet for rotor core of ipm motor excellent in punching property, method for manufacturing the same, rotor core of ipm motor, and ipm motor |
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| CN113584390A (en) * | 2021-08-03 | 2021-11-02 | 宝武杰富意特殊钢有限公司 | Round steel for high-strength bolt and preparation method thereof |
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