CN111471920B - Non-quenched and tempered steel for U-shaped bolt and production method thereof - Google Patents
Non-quenched and tempered steel for U-shaped bolt and production method thereof Download PDFInfo
- Publication number
- CN111471920B CN111471920B CN202010360166.XA CN202010360166A CN111471920B CN 111471920 B CN111471920 B CN 111471920B CN 202010360166 A CN202010360166 A CN 202010360166A CN 111471920 B CN111471920 B CN 111471920B
- Authority
- CN
- China
- Prior art keywords
- equal
- less
- percent
- steel
- quenched
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Classifications
-
- 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
- C22C33/06—Making ferrous alloys by melting using master alloys
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/16—Control of thickness, width, diameter or other transverse dimensions
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
-
- 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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- 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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- 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
-
- 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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
-
- 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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
-
- 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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
-
- 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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
The invention discloses non-quenched and tempered steel for a U-shaped bolt and a production method thereof, wherein the non-quenched and tempered steel comprises the following elements in percentage by mass: c: 0.43% -0.45%, Si: 0.30% -0.40%, Mn: 1.55-1.65%, Cr: 0.20% -0.25%, V: 0.08% -0.10%, N: 0.012 to 0.016 percent, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.20 percent of Ni, less than or equal to 0.20 percent of Cu, less than or equal to 0.10 percent of Mo, less than or equal to 0.0015 percent of [ O ], and the balance of Fe. The invention has reasonable component design and advanced process, and has higher precision, finer grain size and higher strength compared with the U-shaped bolt steel supplied in the current market. The dimensional accuracy is controlled within +/-0.25 mm, Rm is more than or equal to 930MPa, Rel is more than or equal to 650MPa, and the grain size is more than or equal to 8 grade. Through reasonable proportioning of the components, the non-quenched and tempered steel for the U-shaped bolt developed by means of microalloying and controlled rolling technology has the advantages of economy, energy conservation, environmental protection and the like, can well overcome the defects of the traditional U-shaped bolt, realizes cost reduction and efficiency improvement, and improves market competitiveness.
Description
Technical Field
The invention belongs to the technical field of alloy steel, relates to non-quenched and tempered steel for fasteners in the steel industry, and particularly relates to high-precision and high-strength non-quenched and tempered steel for U-shaped bolts, which replaces 40Cr, and a production method thereof.
Background
U-bolts, also known as horseback bolts, are non-standard parts with threads at both ends for connecting to nuts, and are mainly used for fixing tubular objects such as water pipes or sheet objects such as automobile leaf springs, generally applied to trucks for stabilizing automobile chassis and frames, and the quality of the U-bolts determines the service life of the leaf springs. The automobile plate spring mainly plays a role in buffering in a suspension system, can also transmit force and moment, plays a role in guiding, can reduce vibration and can replace a vibration absorber. This requires that the U-bolt not only can bear all directions of load but also can bear the friction of the leaf spring, and the stress is complicated, and the surface quality and fatigue life are of great importance, which puts a very high demand on the quality of the steel for the U-bolt, and therefore, high precision, high strength and high fatigue life are required.
The 8.8-grade high-strength U-shaped bolt commonly used in China is mainly prepared and produced by using 40Cr steel. Quenching cracking and deformation are easy to occur in 40Cr quenching and tempering, quality risks exist, and the dimensional accuracy cannot be guaranteed. In addition, waste water and waste gas are generated in the production process of the quenching and tempering process, and the energy consumption is large, the production period is long, and the production cost is high. Due to the new concept of national environmental protection policy and green development, the modulation process adopted by the method does not accord with the basic national policy, and the U-shaped bolt manufactured by non-quenched and tempered steel and formed by cold bending is commonly adopted by the countries of Europe and America. High accuracy, the non quenched and tempered steel for high strength U type bolt that huai steel developed according to market demand are because through stirring vortex KR desulfurization, sublance converter smelting, RH vacuum refining, Ca modification treatment, square billet continuous casting, control rolling, KOCKS finish rolling, phased array ultrasonic inspection + magnetic leakage flaw detection disappearance, and size precision is high, the purity is high, and fatigue life is high, and surface quality is good, and the comprehensive cost is low.
40Cr in the national structural alloy steel (GB/T3077-2015) standard: c: 0.37% -0.44%, Si: 0.17% -0.37%, Mn: 0.50-0.80%, Cr: 0.80-1.10 percent of P, less than or equal to 0.030 percent of S, less than or equal to 0.030 percent of Cu, less than or equal to 0.20 percent of Ni, less than or equal to 0.30 percent of Mo and less than or equal to 0.10 percent of Mo. The mechanical properties of the steel after oil quenching at 850 ℃ and tempering at 600 ℃ can reach: rm is more than or equal to 900Mpa, Rel is more than or equal to 630Mpa, A is more than or equal to 13%, and Z is more than or equal to 40%; delivery hardness: not less than 250 HBW; the grain size is more than or equal to grade 5; the non-metallic inclusion A is less than or equal to 2.0 grade, A is less than or equal to 2.5 grade, B is less than or equal to 1.5 grade, B is less than or equal to 2.5 grade, C is less than or equal to 1.0 grade, C is less than or equal to 1.5 grade, D is less than or equal to 1.0 grade, D is less than or equal to 1.5 grade, and Ds is less than or equal to 2.0 grade. The quenched and tempered steel has the advantages of complex production process, low production efficiency, high production cost, energy waste and environmental pollution.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide non-quenched and tempered steel for U-shaped bolts to replace the conventional 40Cr prepared steel, and the invention also aims to provide a production process of the steel. The method produces the high-precision and high-strength non-quenched and tempered steel for the U-shaped bolt through the design of chemical components, the optimization of a smelting process, controlled rolling, KOCKS finish rolling and phased array ultrasonic flaw detection.
By adding V, N element into steel, the precipitation of vanadium carbonitride is promoted, austenite grains are refined, V microalloying can be carried out by recrystallization and controlled rolling and controlled cooling of a non-recrystallization area, and the toughness of non-quenched and tempered steel is obviously improved; by adding a small amount of Cr element, Cr carbide is formed, and the strength of the steel is improved; by adopting a non-quenched and tempered steel production process, quenching and tempering can be avoided, heat treatment deformation is prevented, and processing procedures are reduced; through the reasonable proportioning of the components, the structural performance of the parts is ensured by depending on the microalloying technology and controlled rolling and controlled cooling, so that the non-quenched and tempered steel U-shaped bolt has the advantages of economy, energy conservation, environmental protection and the like, can well overcome the defects of the traditional U-shaped bolt, realizes cost reduction and efficiency improvement, and improves the market competitiveness. The high-precision and high-strength non-quenched and tempered steel for the U-shaped bolt has the following properties: rm is more than or equal to 930Mpa, Rel is more than or equal to 650Mpa, A is more than or equal to 16 percent, and Z is more than or equal to 45 percent; delivery hardness: more than or equal to 260 HBW; the grain size is more than or equal to grade 8; the non-metallic inclusion A is less than or equal to 1.5 grade in thickness, the B is less than or equal to 1.0 grade in thickness, the B is less than or equal to 1.5 grade in thickness, the C is less than or equal to 0.5 grade in thickness, the D is less than or equal to 1.0 grade in thickness and.
The invention is realized by the following technical scheme:
the non-quenched and tempered steel for the U-shaped bolt comprises the following elements in percentage by mass: c: 0.43% -0.45%, Si: 0.30% -0.40%, Mn: 1.55-1.65%, Cr: 0.20% -0.25%, V: 0.08% -0.10%, N: 0.012 to 0.016 percent, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.20 percent of Ni, less than or equal to 0.20 percent of Cu, less than or equal to 0.10 percent of Mo, less than or equal to 0.0015 percent of [ O ], and the balance of Fe.
The invention further improves the scheme as follows:
a method for producing the non-quenched and tempered steel for the U-shaped bolt comprises the following steps: KR desulfurization → converter smelting → ladle refining → RH vacuum degassing → soft blowing → continuous casting → slow cooling → heating → controlled rolling → KOCKS finish rolling → slow cooling → straightening → shot blasting → chamfering → phased array ultrasonic flaw detection + leakage flux flaw detection → warehousing.
Further, the KR desulfurization adopts a stirring KR desulfurization method, molten iron is stirred in a ladle and continuously stirred for 8-10 minutes to form a vortex, a self-made desulfurizer is put into the center of the vortex to enable the desulfurizer to fully react with sulfur in the molten iron, and desulfurization products are removed through slag skimming to reduce the content of S in the molten iron and ensure that the S content of the desulfurized molten iron is less than or equal to 0.005%.
Further, when the converter is smelted, the converter adopts a sublance system, C and O are rapidly and accurately determined, Al cakes and carbon powder are accurately added, and the condition that the refining furnace C: 0.38 to 0.43 percent.
Further, when the RH vacuum degassing is carried out, the RH is broken to be empty, after the liquid level is stable, the manganese nitride core-spun yarn is fed immediately, and the N is adjusted to be in place once.
Further, during rolling control, a heating method of heating at a high temperature of 1120-1150 ℃ and cooling, heat preservation and soaking at a temperature of 1050-1080 ℃ is adopted in a heat accumulating type gas stepping heating furnace, the initial rolling temperature is controlled to be 950-980 ℃, the final rolling temperature is controlled to be 800-850 ℃, and the temperature difference of the steel surface in the rolling process is less than or equal to 20 ℃.
Furthermore, when the KOCKS finish rolling is carried out, a reducing sizing mill set is used for producing high-precision round steel with the diameter of 16 mm-30 mm, and the hot rolling size is controlled within +/-0.25 mm.
After rolling, the finishing processes of straightening, shot blasting, mechanical chamfering, phased array ultrasonic flaw detection, magnetic leakage flaw detection and coping are adopted to eliminate the internal and external defects of the steel.
The non-quenched and tempered steel for the U-shaped bolt, which is produced by the invention, has the characteristics of high precision, high strength and the like, and the material performance can reach the following level: rm is more than or equal to 930Mpa, Rel is more than or equal to 650Mpa, A is more than or equal to 16 percent, and Z is more than or equal to 45 percent; delivery hardness: more than or equal to 260 HBW; the grain size is more than or equal to grade 8; the non-metallic inclusion A is less than or equal to 1.5 grade in thickness, the B is less than or equal to 1.0 grade in thickness, the B is less than or equal to 1.5 grade in thickness, the C is less than or equal to 0.5 grade in thickness, the D is less than or equal to 1.0 grade in thickness and less than or equal to 1.5 grade in Ds.
The chemical component comparison condition of the hardened and tempered steel 40Cr for the U-shaped bolt currently used in China and the non-hardened and tempered steel for the U-shaped bolt of the invention is shown in the following table 1:
TABLE 1 chemical composition comparison (wt%)
The invention relates to a U-shaped bolt used non-quenched and tempered steel, which has the following chemical composition limitation reason:
the invention needs to reach the mechanical property of 40Cr conditioning material without heat treatment, the chemical components are completely new designed, the strength of the steel is ensured by designing high contents of C, Si and Mn, and a small amount of Cr, N and V are matched for grain refinement, wherein Cr element forms Cr carbide on the premise of not influencing toughness, so that the effect of fine grain strengthening is achieved, and the strength is improved; v, N element forms granular VN in steel, VN can effectively refine austenite grains, promote the precipitation of small-grain ferrite in steel, effectively partition coarse pearlite, improve the toughness of non-quenched and tempered steel, and further promote the precipitation of vanadium carbonitride in steel by appropriate nitrogen increase in steel, thereby remarkably playing the precipitation strengthening role of V; finally, the comprehensive performance of the steel grade reaches the level of quenching and tempering 40 Cr.
C: is the element that most affects the strength of steel, and is the cheapest element. C can be combined with elements such as Mn, Cr, V and the like to form carbide, which is beneficial to increasing the strength, but the toughness of the steel is reduced due to the excessively high content of C. In general terms, the C content of the invention is limited to 0.43-0.45%.
Si: can be dissolved in ferrite and austenite to play a role in solid solution strengthening, so that the strength and the hardness of the steel are obviously improved, and particularly the yield strength of the steel is improved; silicon also has a deoxidizing effect, but the fatigue strength and durability are reduced when the content exceeds 0.40%, so that the content of Si is controlled to 0.30-0.40%.
Mn: the steel has the solid solution strengthening effect, can enlarge an austenite region, reduce the transformation temperature from austenite to ferrite, further refine ferrite grains and improve the toughness of the steel, and when the content of Mn is lower than 1.80%, the strength of the steel is continuously increased along with the increase of the content of Mn, and the toughness is not obviously damaged. However, the excessive Mn content can generate segregation, the fatigue performance of the bolt is influenced, if the Mn content is higher than 1.65%, the alloy cost is relatively high, the segregation is obvious, the mechanical property can meet the design requirement, but the stability is poor, and the fluctuation is large; under the condition of less than 1.55 percent, the strength margin is small, the risk of unqualified performance exists, and the designed target Rm is not less than 930MPa, Rel is not less than 650 MPa. Therefore, the performance and the production cost of the steel are integrated, and the Mn content is controlled to be between 1.55 and 1.65 percent;
cr: the steel exists in a carbide form, the strength of the steel can be obviously improved, the steel has the characteristics of oxidation resistance, corrosion resistance, wear resistance, high hardness and the like, and meanwhile, the influence on the plasticity and toughness of the steel is small, and the steel can have a strengthening effect by adding more than 0.20 percent of Cr, so that the Cr element of the steel is controlled between 0.20 and 0.25 percent;
v: the grain can be refined, and the toughness and the wear resistance of the steel can be improved, so that the fatigue life of the product can be prolonged, but the V element is very expensive and is not suitable for being added in a large amount. The V content of the steel grade is controlled to be 0.08-0.10%.
P: the cold-brittleness of the steel is generated, the impact toughness of the steel is reduced, meanwhile, the welding performance of the steel is deteriorated, the plasticity is reduced, and the cold-bending performance is deteriorated. Therefore, the P content is controlled below 0.015 percent;
s: is an easily segregated element, reduces the ductility and toughness of steel, and also has adverse effects on welding performance and corrosion resistance. Therefore, the S content is strictly controlled and must be less than or equal to 0.005 percent.
O: the strength of the steel is not greatly influenced at room temperature, but the elongation and the surface shrinkage of the steel are obviously reduced, and the strength and the plasticity of the material are sharply reduced along with the increase of the O content at lower temperature and extremely low O content. With the increase of the O content, the oxide inclusion content of the material is obviously increased, and the fatigue life of the material is seriously influenced. The invention and the production process can stably control the O content within 0.0015 percent.
N: nitrogen can strengthen steel, but obviously reduce the plasticity and toughness of the steel, and increase the aging tendency and cold brittleness. Generally, the content is required to be less than 0.0080%. The invention uses N element and V element to carry out fine grain strengthening and precipitation strengthening together. The N element and the V element can precipitate granular VN which can effectively refine austenite grains, promote the precipitation of small-grain ferrite in steel, effectively partition coarse pearlite and improve the toughness of steel; nitrogen is added into steel, and the precipitation of vanadium carbonitride in the steel can be further promoted, the content of V is designed to be 0.08-0.10%, and the content of N is designed to be more than 0.010% so as to remarkably play the precipitation strengthening role of V; the invention comprehensively considers the toughness requirement and the production cost, and the N content is controlled to be 0.010 to 0.016 percent by the invention and the production process.
The invention has the beneficial effects that:
(1) the method produces the high-precision and high-strength non-quenched and tempered steel for the U-shaped bolt through the design of chemical components, the optimization of a smelting process, controlled rolling, KOCKS finish rolling and phased array ultrasonic flaw detection.
(2) By adding V, N element into steel, the precipitation of vanadium carbonitride is promoted, austenite grains are refined, V microalloying can be carried out by recrystallization and controlled rolling and controlled cooling of a non-recrystallization area, and the toughness of non-quenched and tempered steel is obviously improved;
(3) by adding a small amount of Cr element, Cr carbide is formed, and the strength of the steel is improved;
(4) controlling the oxygen content and reducing the content of oxide inclusions as much as possible;
(5) by adopting a non-quenched and tempered steel production process, quenching and tempering can be avoided, heat treatment deformation is prevented, and processing procedures are reduced;
(6) the steel grade adopts the BOF + LF + RH + CCM process, so that the lower content of gas and harmful residual elements is ensured, and the material has excellent comprehensive mechanical properties.
(7) The steel is heated by a heat accumulating type stepping heating furnace, and the eighteen continuous rolling units and the four KOCKS finish rolling units improve the size precision of products and the comprehensive mechanical property of steel.
(8) Through the reasonable proportioning of the components, the structural performance of the parts is ensured by depending on the microalloying technology and controlled rolling and controlled cooling, so that the non-quenched and tempered steel U-shaped bolt has the advantages of economy, energy conservation, environmental protection and the like, can well overcome the defects of the traditional U-shaped bolt, realizes cost reduction and efficiency improvement, and improves the market competitiveness.
Detailed Description
Examples 1 to 4
The preparation method comprises the following steps:
(1) pretreating molten iron: stirring molten iron in a ladle by adopting a stirring KR desulfurization method, continuously stirring for 8-10 minutes to form a vortex, adding a self-made desulfurizer to the center of the vortex to ensure that the desulfurizer fully reacts with sulfur in the molten iron, removing desulfurization products by slagging off, reducing the content of S in the molten iron, and ensuring that the S content of the desulfurized molten iron is less than or equal to 0.005%;
(2) smelting in a converter: smelting in a top-bottom combined blowing type converter of more than 100 tons, carrying out primary smelting by taking molten iron and high-quality scrap steel as raw materials to realize pre-removing P, adding lime, synthetic refining slag and various high-purity alloys into steel tapping to carry out pre-deoxidation and primary component adjustment, and adopting a sliding plate to block slag and prevent non-return P during slag-free steel tapping; the converter adopts a sublance system, quickly and accurately determines C and [ O ], accurately adds Al cakes and carbon powder, and ensures that the converter reaches a refining furnace C: 0.38% -0.43%;
(3) refining: deep deoxidation and alloying of molten steel are carried out in an LF furnace with the weight of more than 100 tons, and the alkalinity R: 5-8 of refining slag; the steel slag reaction is used for strengthening S removal and removing impurities, the whole refining process is stirred, the early stage of refining is stirred greatly, and the later stage of refining is stirred weakly to prevent secondary oxidation of molten steel;
(4) vacuum degassing: after LF refining, RH circulation degassing equipment is adopted for vacuum degassing and inclusion removal treatment, the mixture is kept under high vacuum for more than 30 minutes, the O is ensured to be less than or equal to 0.0008 percent, and all components enter the required range; RH is broken empty, after the liquid level is stable, manganese nitride core-spun yarn is fed immediately, and N is adjusted to be in place once;
(5) removing impurities by soft blowing: after vacuum treatment, soft blowing is carried out for more than 20 minutes to ensure that impurities are fully floated and removed;
(6) continuous casting: a square billet continuous casting machine is adopted, a low-silicon tundish covering agent and special crystallizer covering slag are used, automatic baking and automatic adding devices for covering slag are adopted to ensure uniform and timely addition, and full-protection casting in the whole process is carried out to produce continuous casting round billets;
(7) steel rolling and finishing: heating by adopting a heat accumulating type stepping heating furnace, controlling the temperature of a soaking section to be 1050-1080 ℃, controlling rolling, controlling the initial rolling temperature to be 950-980 ℃, controlling the final rolling temperature to be 800-850 ℃, and controlling the temperature difference of the steel surface in the rolling process to be less than or equal to 20 ℃; after continuous rolling, adopting KOCKS finish rolling, producing high-precision round steel with the diameter of 16 mm-30 mm by using a reducing sizing mill set, and controlling the hot rolling size within +/-0.25 mm;
(8) after rolling, the finishing processes of straightening, shot blasting, mechanical chamfering, phased array ultrasonic flaw detection, magnetic leakage flaw detection and coping are adopted to eliminate the internal and external defects of the steel.
The process conditions not limited in the above preparation method can be referred to the conventional techniques in the art.
The chemical compositions of the obtained non-quenched and tempered steel for U-shaped bolts are shown in Table 2,
TABLE 2 non-used quenched and tempered steel composition (wt%) for U-bolt
Mechanical properties of the U-shaped bolt non-purposed quenched and tempered steels prepared in examples 1 to 4 were respectively tested according to GB/T228.1, and the test results are shown in Table 3, and the grain sizes and nonmetallic inclusions of the U-shaped bolt non-purposed quenched and tempered steels prepared in examples 1 to 4 are shown in tables 4 and 5 compared with the prior art.
TABLE 3 comparison of the mechanical Properties of the invention with those of the prior art
| Steel grade | Rm/Mpa | Rel/Mpa | A/％ | Z/％ | Grain size |
| Example 1 | 936 | 669 | 18 | 49 | Stage 8.0 |
| Example 2 | 936 | 672 | 19 | 48 | Stage 8.5 |
| Example 3 | 936 | 666 | 18 | 50 | Stage 8.5 |
| Example 4 | 936 | 668 | 19 | 48 | Stage 8.5 |
| Hardened and tempered steel for existing U-shaped bolt | 912 | 630 | 16 | 50 | Grade 6.0 |
Table 4 comparison of grain size of the present invention with the prior art
TABLE 5 comparison of the level of control of non-metallic inclusions according to the invention with the prior art
As can be seen from tables 2, 4 and 5, the performance of the non-used quenched and tempered steel material for the U-shaped bolt can reach the following level: rm is more than or equal to 930Mpa, Rel is more than or equal to 650Mpa, A is more than or equal to 16 percent, and Z is more than or equal to 45 percent; delivery hardness: more than or equal to 260 HBW; the grain size is more than or equal to grade 8; the non-metallic inclusion A is not more than 1.5 grade thick, the A is not more than 1.5 grade thin, the B is not more than 1.0 grade thick, the B is not more than 1.5 grade thin, the C is not more than 0.5 grade thick, the C is not more than 0.5 grade thin, the D is not more than 1.0 grade thick, the D is not more than 1.0 grade thin, and the Ds is not more than 1.5 grade, thus having the characteristics of high precision and high strength.
Claims (4)
1. A production method of non-quenched and tempered steel for U-shaped bolts is characterized by comprising the following steps: KR desulfurization → converter smelting → ladle refining → RH vacuum degassing → soft blowing → continuous casting → slow cooling → heating → controlled rolling → KOCKS finish rolling → slow cooling → straightening → shot blasting → chamfering → phased array ultrasonic flaw detection + magnetic flux leakage flaw detection → warehousing;
during the RH vacuum degassing, RH is broken empty, after the liquid level is stable, manganese nitride core-spun yarn is fed immediately, and N is adjusted to be in place once;
during rolling control, a heating method of heating at a high temperature of 1120-1150 ℃ and cooling, insulating and soaking at 1050-1080 ℃ is adopted in a heat accumulating type gas stepping heating furnace, the initial rolling temperature is controlled to be 950-980 ℃, the final rolling temperature is controlled to be 800-850 ℃, and the temperature difference of the steel surface in the rolling process is less than or equal to 20 ℃;
the prepared non-quenched and tempered steel for the U-shaped bolt comprises the following elements in percentage by mass: c: 0.43% -0.45%, Si: 0.30% -0.40%, Mn: 1.55-1.65%, Cr: 0.20% -0.25%, V: 0.08% -0.09%, N: 0.012 to 0.016 percent, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.20 percent of Ni, less than or equal to 0.20 percent of Cu, less than or equal to 0.10 percent of Mo, less than or equal to 0.0015 percent of [ O ], and the balance of Fe.
2. The method for producing a non-quenched and tempered steel for U-bolts according to claim 1, wherein the method comprises the steps of: the KR desulfurization adopts a stirring KR desulfurization method, molten iron is stirred in a ladle and continuously stirred for 8-10 minutes to form a vortex, a self-made desulfurizer is put into the center of the vortex to enable the desulfurizer to fully react with sulfur in the molten iron, desulfurization products are removed through slagging-off, the content of S in the molten iron is reduced, and the desulfurized molten iron S is ensured to be less than or equal to 0.005%.
3. The method for producing a non-quenched and tempered steel for U-bolts according to claim 1, wherein the method comprises the steps of: when the converter is smelted, the converter adopts a sublance system, C and O are rapidly and accurately determined, Al cakes and carbon powder are accurately added, and the condition that the refining furnace C is reached is ensured: 0.38% -0.43%.
4. The method for producing a non-quenched and tempered steel for U-bolts according to claim 1, wherein the method comprises the steps of: when the KOCKS is used for finish rolling, a reducing sizing mill set is used for producing high-precision round steel with the diameter of 16 mm-30 mm, and the hot rolling size is controlled within +/-0.25 mm.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010360166.XA CN111471920B (en) | 2020-04-30 | 2020-04-30 | Non-quenched and tempered steel for U-shaped bolt and production method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010360166.XA CN111471920B (en) | 2020-04-30 | 2020-04-30 | Non-quenched and tempered steel for U-shaped bolt and production method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN111471920A CN111471920A (en) | 2020-07-31 |
| CN111471920B true CN111471920B (en) | 2021-09-17 |
Family
ID=71764246
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202010360166.XA Active CN111471920B (en) | 2020-04-30 | 2020-04-30 | Non-quenched and tempered steel for U-shaped bolt and production method thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN111471920B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111961975A (en) * | 2020-08-24 | 2020-11-20 | 青岛汽车零部件有限公司 | Micro-alloyed steel applied to U-shaped bolt and preparation method thereof |
| CN114774760A (en) * | 2022-02-23 | 2022-07-22 | 中国重汽集团济南动力有限公司 | High-strength riding bolt for heavy-duty automobile and manufacturing method thereof |
| CN114934239B (en) * | 2022-06-22 | 2023-02-07 | 江苏利淮钢铁有限公司 | Forged non-quenched and tempered steel for hydraulic cylinder rod head and production method thereof |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0882807A1 (en) * | 1997-06-07 | 1998-12-09 | Thyssen Stahl Aktiengesellschaft | Heat resistant, nickel free constructional steel and process for making plate from it |
| CN103266287A (en) * | 2013-05-14 | 2013-08-28 | 莱芜钢铁集团有限公司 | Medium-carbon ferrite-pearlite non-quenched and tempered steel and manufacturing method thereof |
| CN104831189A (en) * | 2015-04-16 | 2015-08-12 | 河北钢铁股份有限公司 | HB600 grade wear-resistant non-quenched and tempered steel plate and making method thereof |
| CN106216391A (en) * | 2016-08-09 | 2016-12-14 | 湖北新冶钢有限公司 | A kind of rolling production method reducing 42CrMo hardness |
| CN106929622A (en) * | 2017-03-27 | 2017-07-07 | 武钢集团昆明钢铁股份有限公司 | A kind of preparation method of high-quality 40Cr structural alloy steel hot rolling wire rods |
| CN108779534A (en) * | 2016-03-16 | 2018-11-09 | 新日铁住金株式会社 | Micro Alloying bar steel |
| CN109666856A (en) * | 2018-12-29 | 2019-04-23 | 江苏利淮钢铁有限公司 | A kind of high-strength tenacity semiaxis non-hardened and tempered steel and its production method instead of 42CrMo quenched and tempered steel |
-
2020
- 2020-04-30 CN CN202010360166.XA patent/CN111471920B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0882807A1 (en) * | 1997-06-07 | 1998-12-09 | Thyssen Stahl Aktiengesellschaft | Heat resistant, nickel free constructional steel and process for making plate from it |
| CN103266287A (en) * | 2013-05-14 | 2013-08-28 | 莱芜钢铁集团有限公司 | Medium-carbon ferrite-pearlite non-quenched and tempered steel and manufacturing method thereof |
| CN104831189A (en) * | 2015-04-16 | 2015-08-12 | 河北钢铁股份有限公司 | HB600 grade wear-resistant non-quenched and tempered steel plate and making method thereof |
| CN108779534A (en) * | 2016-03-16 | 2018-11-09 | 新日铁住金株式会社 | Micro Alloying bar steel |
| CN106216391A (en) * | 2016-08-09 | 2016-12-14 | 湖北新冶钢有限公司 | A kind of rolling production method reducing 42CrMo hardness |
| CN106929622A (en) * | 2017-03-27 | 2017-07-07 | 武钢集团昆明钢铁股份有限公司 | A kind of preparation method of high-quality 40Cr structural alloy steel hot rolling wire rods |
| CN109666856A (en) * | 2018-12-29 | 2019-04-23 | 江苏利淮钢铁有限公司 | A kind of high-strength tenacity semiaxis non-hardened and tempered steel and its production method instead of 42CrMo quenched and tempered steel |
Also Published As
| Publication number | Publication date |
|---|---|
| CN111471920A (en) | 2020-07-31 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN109252097B (en) | Non-quenched and tempered steel of high-strength expansion-fracture connecting rod and continuous casting production process thereof | |
| CN110791708B (en) | Non-quenched and tempered steel for automobile parts and production process thereof | |
| CN112853211B (en) | Cold forging steel for universal joint fork of passenger vehicle and manufacturing method thereof | |
| CN111471920B (en) | Non-quenched and tempered steel for U-shaped bolt and production method thereof | |
| CN110343954B (en) | Steel for automobile engine connecting rod and manufacturing method thereof | |
| CN111961988B (en) | Production process and forging method of medium-carbon non-quenched and tempered steel for automobile expansion fracture connecting rod | |
| CN112899560B (en) | High-strength gear steel 23CrMnMoS and manufacturing method thereof | |
| CN111363976B (en) | Microalloyed steel with long service life, high strength and toughness for high-speed rail plate spring and production process thereof | |
| CN112481546B (en) | Production method of steel plate P20 for extra-thick plastic mold | |
| CN111763883A (en) | Steel for hollow stabilizer bar and production method thereof | |
| CN113215472A (en) | Niobium-vanadium microalloyed high-strength fine-grain non-quenched and tempered cold forging steel square billet and manufacturing method thereof | |
| CN115584441A (en) | Hot-rolled coil for hydrogen transmission pipeline with 245 MPa-level yield strength and production method thereof | |
| CN112899572A (en) | High-performance QGLZ-X steel for non-quenched and tempered plastic machine tie bar and production method thereof | |
| CN115125448A (en) | Non-quenched and tempered steel for cold machining of hydraulic piston rod and preparation method | |
| CN103882301B (en) | J55 level Low-cost electric welding resistance oil casing pipe steel and manufacture method thereof | |
| CN109112393B (en) | Anti-riot steel plate for 900 MPa-grade ATM and manufacturing method thereof | |
| CN114480987A (en) | Rare earth-containing NM600 wear-resistant steel plate and preparation method thereof | |
| CN111471936A (en) | Improved steel for agricultural machinery cutting tool and production method thereof | |
| CN116043104B (en) | Low-cost Q550D steel produced by TMCP (thermal mechanical control process) technology and production method thereof | |
| CN114934239B (en) | Forged non-quenched and tempered steel for hydraulic cylinder rod head and production method thereof | |
| CN113604748B (en) | Thick-specification weather-resistant corrosion-resistant Cr alloy steel plate and production method thereof | |
| CN109930063A (en) | A kind of engineering machinery crawler body wheel body steel and its production method | |
| CN113122779B (en) | Fine-grain normalizing-free tool steel and production method thereof | |
| CN115572905A (en) | 690 MPa-grade tempering-resistant low-temperature quenched and tempered steel and manufacturing method thereof | |
| CN104862599A (en) | Steel for railway wagon axle and manufacturing method of steel |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |