CN109252097B

CN109252097B - Non-quenched and tempered steel of high-strength expansion-fracture connecting rod and continuous casting production process thereof

Info

Publication number: CN109252097B
Application number: CN201811175895.7A
Authority: CN
Inventors: 张磊; 许晓红; 白云; 黄镇; 王新社; 李冰; 王鹏; 朱国荣; 顾秋豪; 孙艺凡; 华刘开
Original assignee: Jiangyin Xingcheng Special Steel Works Co Ltd
Current assignee: Jiangyin Xingcheng Special Steel Works Co Ltd
Priority date: 2018-10-10
Filing date: 2018-10-10
Publication date: 2020-09-29
Anticipated expiration: 2038-10-10
Also published as: CN109252097A

Abstract

The invention relates to a high-strength fractured connecting rod non-quenched and tempered steel and a continuous casting production process thereof, wherein the steel comprises the following chemical components in percentage by mass: 0.32 to 0.40%, Si: 0.90-1.25%, Mn: 0.85-1.30%, P: 0.008-0.045%, S: 0.055-0.095%, Cr: less than or equal to 0.35 percent, Ni: less than or equal to 0.30 percent, Cu: less than or equal to 0.25 percent, Mo: less than or equal to 0.10 percent, Al: less than or equal to 0.035%, Ti: 0.030-0.070%, V: 0.25-0.35%, N: 0.009-0.022%, and the balance of Fe and impurity elements; the product is in the form of hot rolled round steel bar. The technological process includes electric furnace or converter, external refining, VD or RH vacuum degassing, continuous casting and continuous rolling. The steel can obtain uniform ferrite and pearlite, and is forged into an expansion fracture connecting rod, the mechanical property Rel of the connecting rod is more than or equal to 900MPa, Rm is more than or equal to 1100MPa, and the hardness is as follows: 305-360 HBW.

Description

Non-quenched and tempered steel of high-strength expansion-fracture connecting rod and continuous casting production process thereof

Technical Field

The invention relates to the technical field of metal materials, in particular to non-quenched and tempered steel for manufacturing a high-strength expansion-fracture connecting rod on an automobile engine and a manufacturing method thereof.

Background

The expansion-breaking connecting rod and its manufacturing technology are a new connecting rod and its processing technology which are developed by Germany in the 90 s of 20 th century. At present, the engines of many saloon cars and commercial vehicle manufacturing enterprises at home and abroad adopt the expansion broken connecting rods.

The steel for the expansion-fracture connecting rod is microalloyed non-quenched and tempered steel which is specially used for producing the engine connecting rod by the expansion-fracture process, steel is forged into a connecting rod blank and then is machined and expanded and fractured by an expansion-fracture connecting rod machining line, the manufacturing process of the connecting rod does not need to be subjected to heat treatment, and the manufacturing process of the connecting rod is simple and efficient. The steel is ferrite-pearlite type non-quenched and tempered steel and can be used for replacing quenched and tempered steel connecting rods of 40Cr, 45, 42CrMo and the like; more importantly, because the connecting rod cap is separated by adopting the expansion-fracture process, a series of machining processes such as milling, drawing, grinding and the like are not needed like the traditional connecting rod manufacturing process, so that the connecting rod manufacturing process becomes very simple, and the connecting rod manufacturing method has the advantages of high manufacturing precision, high efficiency, energy conservation, low cost and the like.

At present, the steel for the expansion fracture connecting rod is mainly C70 series non-quenched and tempered steel and also a small part of MnVS series steel. The strength performance indexes of the connecting rod made of C70 series steel are as follows: rel is more than or equal to 550MPa, Rm is more than or equal to 900 MPa; the strength performance indexes of the connecting rod made of MnVS series steel are as follows: rel is more than or equal to 750MPa, and Rm is more than or equal to 950 MPa.

The invention discloses high-strength non-quenched and tempered free-cutting steel for an automobile connecting rod and a process method thereof, which are disclosed by application number 200810048807.7, and the strength of the non-quenched and tempered free-cutting steel connecting rod reaches Rel more than or equal to 750MPa and Rm more than or equal to 1000MPa through quenching and tempering components from the principle of improving the strength of the non-quenched and tempered free-cutting steel

The patent application No. 2012280024294.0 discloses a non-heat treated steel and a non-heat treated steel part, which is designed by chemical composition, can be formed into a predetermined shape by hot forging and then broken and divided, and is suitable for use as an automobile engine connecting rod requiring high fatigue strength to Rel ≥ 450 MPa.

The invention discloses 'steel for automobile engine expansion broken connecting rod' with application number 201510332645.X, through scientific design of an alloy system, the steel for the automobile expansion broken connecting rod with high strength, proper brittleness and good cutting processability can be produced without major adjustment of the existing production process, the strength of the connecting rod reaches Rel more than or equal to 800MPa, and Rm more than or equal to 1100 MPa.

With the development of energy conservation and light weight of cars, higher requirements are put forward on the engine connecting rod of the power transmission part of the car, and the connecting rod is required to have higher strength.

Disclosure of Invention

The invention aims to solve the technical problem of providing the high-strength-grade non-quenched and tempered steel for manufacturing the engine connecting rod and the manufacturing method thereof aiming at the prior art, wherein a connecting rod forging Rel is more than or equal to 900MPa, Rm is more than or equal to 1100MPa, the hardness is 305 plus 360HBW, the metallographic structure of the forging is fine ferrite plus pearlite, the grain size is more than or equal to 8 grade, and the lightweight of an automobile engine is facilitated.

The technical scheme adopted by the invention for solving the problems is as follows: a non-quenched and tempered steel for manufacturing a high-strength fractured connecting rod comprises the following chemical components in percentage by mass: 0.32 to 0.40%, Si: 0.90-1.25%, Mn: 0.85-1.30%, P: 0.008-0.045%, S: 0.055-0.095%, Cr: less than or equal to 0.35 percent, Ni: less than or equal to 0.30 percent, Cu: less than or equal to 0.25 percent, Mo: less than or equal to 0.10 percent, Al: less than or equal to 0.035%, Ti: 0.030-0.070%, V: 0.25-0.35%, N: 0.009-0.022%, and the balance of Fe and impurity elements; the product is in the form of hot rolled round steel bar.

The chemical components of the invention are designed according to the following steps:

1) determination of C content

C is the most economic and basic strengthening element in steel, can obviously improve the strength of the steel, and increases the yield strength and the tensile strength with the increase of the carbon content in the steel, but reduces the plasticity and the impact resistance. The range of the C content is determined to be 0.32-0.40%, and the invention relates to a steel product belonging to the category of medium carbon steel;

2) determination of the Si content

Si is dissolved in ferrite in steel, so that the elastic limit, yield strength and tensile strength of the steel can be obviously improved, the plasticity and toughness of the steel are reduced, the effect of Si on increasing the cold deformation hardening rate of the ferrite is strong, the cold processing of the steel is difficult, and in order to achieve the purpose of improving the strength and simultaneously ensure the processing and expansion and fracture performance of an engine connecting rod, the Si content is determined to be 0.90-1.25%.

3) Determination of Mn content

Mn is an important alloy element for improving the strength and the toughness of the non-quenched and tempered steel, and is a weak carbide forming element, mainly exists in the steel in a solid solution form, and is solid-dissolved in ferrite at room temperature; the solid-dissolved Mn has a strong solid-solution strengthening effect. The solid solution strengthening effect of Mn is inferior to that of P and Si, and when the Mn content is less than 0.80%, the strengthening effect is not significant, and when the Mn content exceeds 1.5%, the bainitization of the steel is promoted, and the productivity of bainite in steel increases as the Mn content increases. Mn is combined with sulfur in the steel to form MnS which has less harm to the performance of the steel, the generation of FeS is reduced or inhibited, the cutting performance and the expansion-fracture performance can be improved, and the abrasion to a cutter is reduced; the Mn content range of the invention is determined to be 0.85-1.30%

4) Determination of the P content

P can strengthen ferrite phase, increase the strength and hardness of steel, show the function of inhibiting the deformability well in the course of processing materials, and can cause the plasticity, impact toughness to reduce apparently, in order to improve the broken effect of swelling, need add a small amount of P, but can not add too high, P content exceeds 0.045%, the continuous casting billet that the arc conticaster produces, the casting billet centre crack, the edge angle is cracked very easy to appear, the poor surface quality of continuous casting billet can only adopt the mode of casting steel ingot; therefore, the range of the P content is determined to be 0.008-0.045%.

5) Determination of the S content

S is an element for improving the machinability of steel. S is combined with Mn in steel to form MnS inclusion or composite inclusion, which is very beneficial to the cutting processing of materials; however, the addition of too much S not only deteriorates the mechanical properties of the steel, but also causes severe segregation in the steel to adversely affect the continuous casting and rolling of the steel. The S content range of the invention is determined to be 0.055-0.095%.

6) Determination of the Cr content

Cr is a carbide forming element, and Cr dissolved into austenite during heating can obviously shift the C curve to the right, and can obviously improve hardenability, so that the strength and hardness of the steel are improved, but the content is not too much, otherwise, a bainite structure is easily generated, and the toughness is reduced. The Cr content of the invention is determined to be less than or equal to 0.35 percent.

7) Determination of Ni content

Ni is a non-carbide forming element. Ni exists in solid solution in steel to exert a solid solution strengthening effect, but shows only a relatively weak strengthening effect; when Ni is used in combination with Cr, hardenability can be remarkably improved. More Ni more easily leads to the appearance of bainite structure in the steel. The range of the Ni content of the invention is determined to be less than or equal to 0.30 percent.

8) Determination of the Cu content

Cu can improve the stability of austenite in steel and has the function of strengthening ferrite, the steel has hot brittleness when the Cu content is higher, so that the hot forging and rolling processing is difficult, and the Cu content is determined to be less than or equal to 0.25 percent.

9) Determination of Mo content

Mo exists in solid solution and carbide of steel and has certain strengthening effect; but Mo can remarkably improve the hardenability of the steel, has remarkable delay effect on pearlite transformation and has small influence on bainite transformation, so that the steel containing Mo can easily obtain a bainite structure and has adverse effect on the toughness of the steel; the steel of the invention belongs to ferrite-pearlite non-quenched and tempered steel, so the steel of the invention strictly controls the Mo content, and the range of the Mo content of the invention is determined to be less than or equal to 0.10 percent.

10) Determination of Al content

Al is an effective element for deoxidation, the content of Al is too high, and Al is easily formed in the molten steel smelting process₂O₃And the purity of the molten steel is reduced by the aid of the brittle inclusions, and the range of the Al content is determined to be less than or equal to 0.035%.

11) Determination of V, Ti and N contents

V is a main alloy element for strengthening non-quenched and tempered steel. The steel exists in the state of V carbonitride, and the V carbonitride is dispersed in the proeutectoid ferrite in the form of very fine particles to produce precipitation strengthening, thereby achieving the effect of improving the strength of ferrite-pearlite type non-quenched and tempered steel, and particularly remarkably improving the yield strength of the steel. In addition, in the rolling or forging process of the steel, a part of V carbonitride can be precipitated by strain induction to play a role in pinning austenite grain boundaries, so that the recrystallization of austenite is inhibited, the grain growth is prevented, the effect of refining the grains is achieved, and the purpose of improving the strength and the toughness is achieved, wherein the effect is particularly obvious when the V content is higher.

Stable fine and dispersed particles of TiN and the like can be formed by adding Ti, the dispersed TiN precipitated at high temperature in a solid state is most effective for preventing austenite grains from growing, and the Ti-containing non-quenched and tempered steel is heated to 1250 ℃ and still has finer austenite grains, so that the forging temperature of the connecting rod is higher, and the strength of the connecting rod is further improved. However, Ti cannot be too high because Ti has a higher affinity for N than V, and too high Ti consumes much N, thereby reducing the precipitation strengthening effect of V.

N is one of main strengthening elements in non-quenched and tempered steel, and forms a compound with a strong nitride forming element (Ti, V and the like) to play a role in improving the strength and refining grains, but the excessively high content of N is not favorable for continuous casting production and is easy to form continuous casting surface cracks.

The range of the V content is determined to be 0.25-0.35%, the range of the Ti content is determined to be 0.030-0.070%, and the range of the N content is determined to be 0.009-0.022%; the three elements must be strictly controlled within the aforementioned range at the same time.

The manufacturing process of the microalloying non-quenched and tempered steel for the connecting rod comprises the steps of electric furnace or converter, external refining, VD or RH vacuum degassing, continuous casting and continuous rolling

The main production process is characterized in that:

1) selecting materials: high-quality scrap steel such as crop ends and the like is selected and added with primary pig iron or high-quality molten iron to reduce harmful elements in the steel.

2) Smelting molten steel:

the steel type belongs to steel containing P, the P removing process is special and is a production difficulty, and the thin slag operation is adopted for the difficulty: reducing the lime content of slag during smelting (the lime content is reduced by 10-35 percent compared with the lime content of slag used for smelting molten steel without P), reducing the alkalinity and the oxidability, wherein P is removed in place once in the operation process of thin slag during smelting, the P content is controlled according to the proportion that P is more than or equal to 0.020% and less than or equal to 0.045%, the tapping temperature is controlled to be not less than 1550 ℃, and the prerequisite condition is provided for the subsequent smelting: namely the content of P is more than or equal to 0.020% during tapping; simultaneously, the adding sequence of the alloy during tapping is optimized: al, Si and Mn are strictly required to control the component of the end point C, P during tapping, and peroxidation caused by blowing-in is avoided; controlling the carbon at the tapping end point to be more than or equal to 0.05 percent, adding a deoxidizer for deoxidation during tapping, and reducing the steel slag entering a large ladle by adopting an eccentric bottom tapping mode.

The recarburizing agent and the additive alloy are dried before being added, chemical components are accurately controlled, the reducing atmosphere in the furnace is kept, argon is blown for stirring, so that nonmetallic inclusions in steel can fully float upwards, and the purity of molten steel is guaranteed.

The steel belongs to high-Si, Ti and V steel, and has the problem that the recovery rate is difficult to control, scientific calculation and smelting simulation are carried out before smelting, the control aim of low oxygen content (the oxygen content is 6ppm) is ensured, and meanwhile, a narrow component control process is adopted (Si is controlled to be within +/-0.03% of a target value, Ti is controlled to be within +/-0.01% of the target value, and V is controlled to be within +/-0.01% of the target value)

Vacuum degassing: because the steel belongs to high-N steel, the time proportion of RH strict control low vacuum and high vacuum (less than 130Pa) is not less than 2:1, wherein the high vacuum is not less than 10 minutes, excessive N removal is avoided, and the N increasing level of molten steel is ensured;

3) continuous casting: strictly controlling the temperature of the refining ladle at the upper stage, ensuring that the superheat degree of molten steel is controlled between 15 and 25 ℃, and adopting anti-oxidation casting measures in the whole continuous casting process;

the steel belongs to high-Si, P-containing and high-S non-quenched and tempered steel, has very strong crack sensitivity, and adopts a brand-new process design for the continuous casting process: firstly, a continuous casting soft reduction process is used, secondly, the pulling speed is reduced (0.40-0.6M/min), the continuous casting process adopts the double connection of M-EMS (head end electromagnetic stirring) and F-EMS (inter-stream electromagnetic stirring), the uniformity of cross-section components is ensured by increasing the head end and the inter-stream electromagnetic stirring, and then the internal temperature gradient of a casting blank is reduced by a weak cooling process (the water quantity of water mist cooling in a secondary cooling area is 0.12L/kg), so that the generation of internal cracks is avoided; and during offline, a high-temperature offline slow cooling process is implemented, so that the temperature gradient is reduced, and the generation of internal cracks is avoided. The method effectively improves and reduces the component segregation of the continuous casting billet, particularly after the inter-stream electromagnetic stirring is increased, the density of a casting billet solidification structure is improved, the center porosity and the shrinkage cavity of the casting billet are effectively controlled, the distance between secondary dendrite arms is obviously improved, the central equiaxial crystal rate is obviously improved, and crystal grains are refined, so that the quality of the casting billet is obviously improved, and the component segregation is reduced.

4) Heating a casting blank: the heating temperature (1150-1300 ℃) of the steel billet is strictly controlled in the rolling process, the heating time is more than 0.71min/mm, the furnace is heated under the protection of inert gas such as argon, so that the surface of the steel billet is not subjected to full decarburization, the decarburization is not over-standard, the heating temperature is favorable for fully playing the roles of Ti and V, and fine grain size is obtained, thereby obtaining high strength performance.

5) Continuous rolling: after the temperature of the billet is preserved, discharging the billet out of the furnace and carrying out high-pressure water descaling treatment; then the mixture enters a continuous rolling unit to be rolled into a required specification, the rolling compression ratio is not less than 20, the finish rolling temperature is not limited, and the mixture is air-cooled after the rolling is finished;

6) sawing;

7) cooling in a heap;

8) and (6) finishing.

Compared with the prior art, the invention has the advantages that:

1. the steel has the advantages of non-quenched and tempered steel, a user can directly perform subsequent processing and use without quenching and tempering heat treatment after forging, the mechanical property Rel of a forging piece is more than or equal to 900MPa, Rm is more than or equal to 1100MPa, the hardness is 305 plus 360HBW, the metallographic structure is a fine ferrite plus pearlite structure, the grain size reaches more than 8 grade, the mechanical property is far higher than that of the conventional C70 series and MnVS series expansion broken connecting rods, and the lightweight of an automobile engine is facilitated.

2. According to the application, a certain content of Ti (0.030-0.070%) is added into the non-quenched and tempered steel, stable fine and dispersed particles such as TiN are formed, grain refinement is further promoted, the forging temperature of the connecting rod is higher, and the strength of the connecting rod is more favorably improved.

3. The steel contains S, P elements for improving cutting performance and expansion breaking performance, and can raise the continuous casting performance of connecting rod.

4. The high-strength expansion-fracture steel is designed according to the high-strength expansion-fracture steel, B does not need to be added, and the effect of improving the expansion-fracture performance and machining is achieved through the content of P, S. In addition, the content of Si is improved to strengthen the tensile strength, and meanwhile, the highest addition amount of Si is limited to reduce the continuous casting difficulty, so that the continuous casting production of the steel product is realized, and a casting steel ingot production mode with longer production period is not needed.

Drawings

FIG. 1 shows the structure of a finished hot-rolled round steel bar in the embodiment of the invention.

FIG. 2 is a graph showing mechanical property curves of an engine connecting rod forged by a finished hot-rolled round steel bar in the embodiment of the invention.

Detailed Description

The present invention will be described in further detail with reference to examples.

The steel for the high strength spalling connecting rod of the embodiment 1-4 is manufactured by the processes of electric furnace or converter, external refining, vacuum degassing (VD or RH), continuous casting, continuous rolling, sawing, cold piling, finishing, surface and internal flaw detection and packaging.

Selecting high-quality scrap steel such as crop ends and the like according to the chemical component proportion, and adding primary pig iron or high-quality molten iron to reduce harmful elements in the steel; slag flowing operation in the smelting process is carried out, the control end point C is more than or equal to 0.15%, molten steel peroxidation is prevented, and thin slag operation is adopted: the lime content of the slag is reduced, the oxidizability is reduced, the lime content of the slag is reduced by 10-35% compared with the lime content of slag adopted in the smelting of molten steel without P, P is removed in place once in the operation process of thin slag, the P content is controlled according to the proportion that P is more than or equal to 0.020% and less than or equal to 0.045%, the tapping temperature is controlled to be not less than 1550 ℃, and the prerequisite condition is provided for the subsequent smelting: namely the P content of the steel is more than or equal to 0.020%; controlling the adding sequence of the alloy: the LF furnace enhances diffusion deoxidation, maintains the reducing atmosphere in the furnace, blows argon and stirs to ensure that the non-metallic inclusion in the steel fully floats and ensures the purity of the molten steel; the vacuum furnace ensures that the high vacuum time (less than or equal to 130Pa) is 15 minutes, strictly controls the time ratio of low vacuum to high vacuum to be not less than 2:1, avoids excessive N removal, and changes the appearance of the sulfide through sulfide deformation treatment.

The continuous casting process adopts low superheat degree pouring, the pouring superheat degree is not more than 25 ℃, a proper drawing speed is set to be 0.4M/min, the secondary cooling section cooling strength is set, the water quantity of water mist cooling is 0.12L/kg, and meanwhile, the continuous casting adopts advanced M-EMS and F-EMS dual measures, so that the component segregation of the continuous casting blank is effectively improved and reduced. The rolled steel is rolled at high temperature, the heating temperature is 1160-1210 ℃, the heating time is more than or equal to 4h, and precipitates of steel are improved.

Continuous rolling: the heating temperature of the steel billet is set to 1200-1300 ℃), the heating time is longer than 4 hours, the furnace is heated under the protection of inert gas such as argon, so that the surface of the steel is not decarburized completely, the decarburization is not overproof, the heating temperature is favorable for fully playing the roles of Ti and V, and fine grain size is obtained, thereby obtaining high strength performance.

5) Continuous rolling: after the temperature of the billet is preserved, discharging the billet out of the furnace and carrying out high-pressure water descaling treatment; then the steel is rolled into the required specification in a continuous rolling unit, the rolling compression ratio is not less than 20, the finish rolling temperature is not limited, and the steel is air-cooled after the rolling is finished.

The chemical components and the mechanical properties of the steel for the expansion-fracture connecting rod of the C70 series and the MnVS series are compared in the examples 1 to 4 of the invention, and are shown in tables 1 and 2

TABLE 1 chemical composition (wt%)

TABLE 2 mechanical Properties of the connecting rod

The metallographic structures of the products of examples 1-4 are ferrite and pearlite, the grain size is not less than 8 grades and is higher than three comparative example grades, and the products still have better machinability in terms of hardness.

The mechanical properties of the engine connecting rod forged from the non-quenched and tempered steel of the present application are shown in fig. 2.

In addition to the above embodiments, the present invention also includes other embodiments, and any technical solutions formed by equivalent transformation or equivalent replacement should fall within the scope of the claims of the present invention.

Claims

1. A continuous casting production process of non-quenched and tempered steel of a high-strength fractured connecting rod is characterized by comprising the following steps of: the non-quenched and tempered steel comprises the following chemical components in percentage by mass: 0.32 to 0.40%, Si: 0.90-1.25%, Mn: 0.85-1.30%, P: 0.008-0.045%, S: 0.055-0.095%, Cr: less than or equal to 0.35 percent, Ni: less than or equal to 0.30 percent, Cu: less than or equal to 0.25 percent, Mo: less than or equal to 0.10 percent, Al: less than or equal to 0.035%, Ti: 0.030-0.070%, V: 0.25-0.35%, N: 0.009-0.022%, and the balance of Fe and impurity elements;

the method comprises the following steps:

1) selecting high-quality scrap steel, and adding primary pig iron or high-quality molten iron;

2) smelting: the molten steel is sequentially subjected to converter or electric furnace primary smelting, external refining and vacuum degassing treatment, the carbon at the primary smelting tapping end point is controlled to be more than or equal to 0.05 percent, the molten steel is prevented from being oxidized by oxygen, a deoxidizing agent is added for deoxidation during tapping, and the steel slag entering a large ladle is reduced due to eccentric bottom tapping; accurately controlling chemical components during refining, maintaining the reducing atmosphere in the furnace, blowing argon and stirring to enable nonmetallic inclusions in steel to fully float upwards and ensure the purity of molten steel;

the thin slag operation is adopted in the primary smelting process: the lime content of the slag is reduced by 10-35 percent compared with the lime content of the slag adopted in the smelting of molten steel without P steel, the P is removed in place once in the operation process of slag thinning, the P content is controlled according to the proportion that P is more than or equal to 0.020% and less than or equal to 0.045%, the tapping temperature is controlled to be not less than 1550 ℃, and a prerequisite condition is provided for the subsequent smelting: namely the P content of the steel is more than or equal to 0.020%; simultaneously, the adding sequence of the alloy during tapping is optimized: al, Si and Mn are strictly required to control the component of the end point C, P during tapping, and peroxidation caused by blowing-in is avoided; controlling the carbon at the tapping end point to be more than or equal to 0.05 percent, adding a deoxidizer for deoxidation during tapping, and reducing the entering of steel slag into a large ladle by adopting an eccentric bottom tapping mode;

the refining adopts a narrow component control process: si is controlled to be within a target value of +/-0.03 percent, Ti content is controlled to be within a target value of +/-0.01 percent, and V content is controlled to be within a target value of +/-0.01 percent;

3) continuous casting: the continuous casting process adopts a process of combining head-end electromagnetic stirring and inter-stream electromagnetic stirring, and combines water mist cooling of a secondary cooling area, and anti-oxidation casting is adopted in the whole continuous casting process;

controlling the superheat degree of the molten steel to be 15-25 ℃, and adopting anti-oxidation casting measures in the whole continuous casting process; the drawing speed is reduced to 0.40-0.6m/min by adopting a continuous casting soft reduction process, head-end electromagnetic stirring and inter-stream electromagnetic stirring are adopted in the continuous casting process, and then the water quantity of water mist cooling in a secondary cooling area is set to be 0.12L/kg by adopting a weak cooling process, so that the temperature gradient in the casting blank is reduced, and the generation of internal cracks is avoided; implementing a high-temperature off-line slow cooling process during off-line;

4) heating a casting blank: controlling the heating temperature of the steel billet to 1150-1300 ℃, wherein the heating time is more than 7.9min/mm, and inert gas is adopted for protection in the furnace;

5) continuous rolling: after the temperature of the billet is preserved, discharging the billet out of the furnace and carrying out high-pressure water descaling treatment; then the rolled steel bar enters a continuous rolling unit to be rolled into a required specification, the rolling compression ratio is not less than 20, the finish rolling temperature is not limited, air cooling is carried out after rolling is finished, and the product is in the form of a hot-rolled round steel bar;

6) sawing;

7) cooling in a heap;

8) and (6) finishing.

2. The continuous casting production process of the non-quenched and tempered steel of the high-strength fractured connecting rod according to claim 1, wherein the continuous casting production process comprises the following steps: and 2, in the molten steel smelting process, the carburant and the added alloy are dried before being added.

3. The continuous casting production process of the non-quenched and tempered steel of the high-strength fractured connecting rod according to claim 1, wherein the continuous casting production process comprises the following steps: step 2, in the vacuum degassing process of molten steel smelting: controlling the time ratio of low vacuum to high vacuum to be not less than 2:1, wherein the high vacuum is not less than 10 minutes, and the vacuum degree of the high vacuum is not more than 130 Pa.

4. The continuous casting production process of the non-quenched and tempered steel of the high-strength fractured connecting rod according to claim 1, wherein the continuous casting production process comprises the following steps: cr, Ni, Cu, Mo, and Al are non-specific additive elements among the chemical components.

5. The continuous casting production process of the non-quenched and tempered steel of the high-strength fractured connecting rod according to claim 1, wherein the continuous casting production process comprises the following steps: the mechanical property Rel of the forged piece processed by the non-quenched and tempered steel is more than or equal to 900MPa, Rm is more than or equal to 1100MPa, the hardness is 305-plus 360HBW, the metallographic structure is a fine ferrite and pearlite structure, and the grain size reaches more than 8 grade.