A seamless steel pipe for a semi-trailer axle and a method of manufacturing the same

Abstract

The application discloses a kind of semi-trailer axle seamless steel tube and its preparation method, and the chemical composition and mass percentage of semi-trailer axle seamless steel tube are as follows: C: 0.15%~0.22%, Si: 0.15%~0.35%, Mn: 1.20%~1.60%, P: ≤0.015%, S≤0.010%, Cr: 0.05%~0.20%, Ni: ≤0.20%, Mo: ≤0.10%, Cu: ≤0.20%, Al: 0.01%~0.05%, Nb: 0.015%~0.06%, V: 0.11%~0.20%, the rest is Fe and other inevitable impurities, total 100%; wherein, carbon equivalent CEV (%) = C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15 ≤0.47. It has high tensile property, high low-temperature impact toughness, good welding performance and excellent fatigue resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of semi-trailer axle seamless steel pipe and its preparation method, belong to steel pipe technical field. BACKGROUND

[0002] At present, the transport industry needs to use container semi-trailer, and the axle of the semi-trailer is prepared from steel pipe, which has high requirements on welding performance, strength, etc. A trailer axle pipe and its production method are disclosed in Chinese patent CN109338221A, wherein the method needs to be quenched + water quenched + tempering heating to improve its performance. The trailer axle pipe obtained by production needs to be welded to form a trailer axle, but the trailer axle pipe prepared by the patent does not improve its welding performance. SUMMARY

[0003] The technical problem to be solved by the present application is to overcome the defects of the prior art and provide a semi-trailer axle seamless steel pipe with high tensile properties, high low-temperature impact toughness, good welding performance and excellent fatigue resistance.

[0004] To solve the above technical problems, the technical solution of the present application is as follows: a semi-trailer axle seamless steel pipe, the chemical composition and mass percentage of which are as follows:

[0005] C: 0.15% to 0.22%, Si: 0.15% to 0.35%, Mn: 1.20% to 1.60%, P: ≤0.015%, S ≤0.010%, Cr: 0.05% to 0.20%, Ni: ≤0.20%, Mo: ≤0.10%, Cu: ≤0.20%, Al: 0.01% to 0.05%, Nb: 0.015% to 0.06%, V: 0.11% to 0.20%, the rest is Fe and other unavoidable impurities, totaling 100%; wherein the carbon equivalent CEV (%) = C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15 ≤0.47.

[0006] Further, CEV (%): 0.43-0.47.

[0007] Further, the performance parameters of the semi-trailer axle seamless steel pipe are as follows: yield strength ≥440 MPa, tensile strength ≥560 MPa, impact at -20℃ ≥100 J, fatigue life ≥10 5 times.

[0008] The present application also provides a preparation method for a semi-trailer axle seamless steel pipe, which comprises the following steps:

[0009] S01: smelting according to the chemical composition and mass percentage of the semi-trailer axle seamless steel pipe and obtaining a pipe blank by continuous casting;

[0010] S02: heating treatment is performed on the pipe blank; wherein the pipe blank heating temperature is 1240-1290 DEG C, and the heating time is 1-4 hours;

[0011] S03: the pipe blank after the heating treatment is perforated to obtain a rough pipe; wherein the perforation temperature is 1220-1260 DEG C;

[0012] S04: the rough pipe is cooled to below 550 DEG C;

[0013] S05: the rough pipe after the cooling is re-heated; wherein the re-heating temperature is 900 DEG C-980 DEG C, and the holding time is 0.2-0.5 h;

[0014] S06: the rough pipe after the re-heating treatment is subjected to a stretch reducing process; wherein the stretch reducing start rolling temperature is ensured to be not lower than 880 DEG C, and the stretch reducing finish rolling temperature is 860-950 DEG C;

[0015] S07: the steel pipe after the stretch reducing process is subjected to a cold bed rapid cooling; wherein the cooling mode is water mist cooling and end wind cooling, the cooling speed of the steel pipe is controlled, and the average cooling speed is between 0.5 DEG C / s and 1.5 DEG C / s.

[0016] Further, in step S02, the pipe blank heating temperature is 1230 DEG C-1270 DEG C.

[0017] Further, in step S05, the re-heating temperature is 950 DEG C-980 DEG C.

[0018] Further, in step S06, the stretch reducing start rolling temperature is 930 DEG C-960 DEG C.

[0019] After the above technical scheme is adopted, the present application has the following beneficial effects:

[0020] 1) According to the requirements of the axle pipe on the welding performance, the product composition is designed as low carbon equivalent CEV (%) ≤0.47, reasonable proportion of trace alloy elements V, Nb is added, and the contents of P and S in the raw material are controlled. Through the V, Nb micro-alloying technology, combined with the controlled rolling and controlled cooling process, the precipitated carbon and nitride in the steel simultaneously play the roles of grain refinement and precipitation strengthening, so that the hot-rolled mother pipe for axle with high tensile property, high low-temperature impact toughness, good welding performance and excellent fatigue resistance is obtained.

[0021] 2) The semi-trailer axle seamless steel pipe prepared by the present application has the following performances: yield strength ≥440 MPa, tensile strength ≥560 MPa, -20 DEG C impact ≥100 J, and fatigue life ≥10 5 times;

[0022] 3) The method of the present application adopts continuous casting pipe blank, and through controlling reheating furnace temperature, reheating time and cooling speed of the pipe blank on the cooling bed after the pipe is stretched and reduced, a seamless steel pipe with high strength and toughness for semi-trailer axle is obtained. DETAILED DESCRIPTION

[0023] The present application provides a seamless steel pipe for semi-trailer axle and a preparation method thereof. Those skilled in the art can refer to the content herein and appropriately improve the process parameters to achieve. It is particularly pointed out that all similar replacements and changes are obvious to those skilled in the art and belong to the protection scope of the present application. The method and application of the present application have been described by preferred embodiments, and relevant personnel can obviously make changes or appropriate changes and combinations to the method and application herein without departing from the content, spirit and scope of the present application to achieve and apply the present application technology.

[0024] A seamless steel pipe for semi-trailer axle, the chemical composition and mass percentage thereof are as follows:

[0025] C: 0.15% to 0.22%, Si: 0.15% to 0.35%, Mn: 1.20% to 1.60%, P: ≤0.015%, S ≤0.010%, Cr: 0.05% to 0.20%, Ni: ≤0.20%, Mo: ≤0.10%, Cu: ≤0.20%, Al: 0.01% to 0.05%, Nb: 0.015% to 0.06%, V: 0.11% to 0.20%, the rest is Fe and other inevitable impurities, totaling 100%; wherein, carbon equivalent CEV(%) = C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15 ≤0.47.

[0026] Further, CEV(%) is 0.43-0.47.

[0027] Further, the performance parameters of the seamless steel pipe for semi-trailer axle are as follows: yield strength ≥440 MPa, tensile strength ≥560 MPa, impact at -20 ℃ ≥100 J, fatigue life ≥10 5 times.

[0028] The present application also provides a preparation method of the seamless steel pipe for semi-trailer axle, and the steps of the method comprise:

[0029] S01: smelting according to the chemical composition and mass percentage of the seamless steel pipe for semi-trailer axle and obtaining pipe blank by continuous casting;

[0030] S02: heating treatment of the pipe blank; wherein, the pipe blank heating temperature is 1240-1290 ℃, and the heating time is 1-4 hours; the pipe blank heating must meet the heating system to ensure the pipe blank out-of-furnace temperature and the pipe blank heating time, and in order to prevent overheating or overburning, the heating furnace temperature should not exceed the specified range.

[0031] S03: piercing the pipe blank after the heating treatment to obtain a hollow pipe; wherein the piercing temperature is 1220-1260°C; in this process, austenite dynamic recrystallization is prone to occur due to high temperature and large deformation, and the dynamic recrystallization grain size is controlled to realize austenite original grain refinement.

[0032] S04: cooling the hollow pipe to below 550°C;

[0033] S05: re-heating the cooled hollow pipe; wherein the re-heating temperature is 900-980°C, the holding time is 0.2-0.5h according to the furnace temperature and the specification;

[0034] S06: performing a stretch-reducing treatment on the hollow pipe after the re-heating treatment; wherein the austenite is not recrystallized by controlled rolling, and the stretch-reducing rolling temperature is not lower than 880°C, and the final stretch-reducing rolling temperature is 860-950°C; the austenite is deformed below the austenite recrystallization temperature, the austenite grains are elongated, part of the deformation energy is converted into phase transformation driving force, the ferrite nucleation work is reduced, the ferrite can nucleate from the grain boundary and inside the grain at the same time, and the stored deformation energy will provide driving force for the refinement of the rolled cooling phase transformation structure.

[0035] S07: rapidly cooling the steel pipe on a cooling bed after the stretch-reducing treatment; wherein the cooling method is water mist cooling and end air cooling, the cooling speed of the steel pipe is controlled, and the average cooling speed is 0.5-1.5°C / s. In the stretch-reducing sizing process, the hot deformed austenite increases the number of phase nucleation sites such as intragranular deformation bands, combined with post-rolling controlled cooling and rapid cooling speed, the ferrite grain is refined, the product structure is mainly fine ferrite+pearlite, and the strength and toughness of the steel pipe are improved.

[0036] In the present application, the carbon content is increased, the strength and hardness of the steel pipe are improved, but the toughness is decreased, and the welding performance is also reduced, so the content of C is limited between 0.15% and 0.22%; the addition of Si element can improve the hardness of the steel pipe, but the plasticity and toughness of the steel pipe will be decreased accordingly, the content of Si in the steel pipe is generally not more than 0.5%, which has little effect on the performance of the steel pipe, at the same time, Si is added as a reducing agent and deoxidizer in the steelmaking process, can form silicate slag with FeO in the molten steel with smaller density and be removed; Si as an alloying element in the steel pipe exists in ferrite or austenite in the form of solid solution, can reduce the austenite phase region, improve the hardenability of hypoeutectoid steel, so the content of Si is limited between 0.15% and 0.35%; appropriate addition of Mn can play a good strengthening effect on the steel pipe, improve the strength, hardness and wear resistance of the steel pipe material, and is also one of the alloy elements for strongly stabilizing austenite, which can effectively reduce the decomposition rate of austenite and improve the hardenability of the steel pipe, but the carbon equivalent will increase with the increase of the addition amount of Mn, which will affect the welding stability of the material, therefore, the content of Mn is limited between 1.2% and 1.6%; P is easy to segregate at the grain boundary, which is extremely easy to become a stress concentration inducing place, can increase the temper brittleness, significantly reduce the plasticity and toughness of the steel, P also has adverse effects on the welding performance, therefore, the content of P is limited to ≤0.015%; S is easy to form inclusions with manganese and other elements, the increase of the content of S will lead to the increase of the number of inclusions, destroy the continuity of the material matrix in the processing process, increase the risk of stress concentration, sulfur will make the steel produce thermal embrittlement, reduce the ductility and toughness of the steel, cause cracks during forging and rolling, and sulfur is also not conducive to the welding performance, therefore, the content of S is limited to ≤0.010%; in low alloy steel, chromium (Cr) can significantly enhance the performance of the material, including improving the strength, hardness and wear resistance, chromium can reduce the critical cooling rate of the steel, thereby enhancing the hardenability of the steel, and the effect is more significant when other alloying elements are added, therefore, the content of Cr is limited between 0.05% and 0.2%; V element is a strong carbide forming element, which has a strong segregation tendency, with the increase of the content of V, V(C, N) particles are caused to segregate, appropriate addition of V can strengthen the grain boundary and intergranular, and at the same time, with appropriate cooling speed after rolling, the proportion of fine second phase precipitation is increased, so as to improve the strength and have good plasticity and toughness, therefore, the addition of V is between 0.11% and 0.20%; niobium is a commonly used second phase strengthening element, which can effectively improve the performance of the steel by precipitating second phase, the addition of Nb can increase the austenite unrecrystallization temperature (Tnr) and expand the unrecrystallization region, the steel is rolled in the range of Ar3-Tnr, after heating to the austenitizing temperature, plastic deformation occurs below the austenite recrystallization temperature, and the austenite does not recrystallize after deformation (i.e. dynamic or static recrystallization does not occur).Therefore, the deformed austenite grains are elongated, there are a large number of deformation bands in the grains, nucleation points are many during the phase transformation, the ferrite grains are refined after the phase transformation, and the steel pipe is improved in strength and toughness, and the addition of Nb is 0.015% to 0.06%.

[0037] Preferably, in step S02, the pipe blank heating temperature is 1230-1270°C.

[0038] Preferably, in step S05, the reheating temperature is 950-980°C.

[0039] Preferably, in step S06, the stretch-reducing rolling temperature is 930-960°C.

[0040] In order to make the content of the present application more easily understood, the present application is further described in detail below according to specific embodiments.

[0041] Embodiment One

[0042] A seamless steel pipe for a semitrailer axle, which has the following chemical composition and mass percentage:

[0043] C: 0.16%, Si: 0.29%, Mn: 1.47%, Cr: 0.06%, Ni: 0.02%, Mo: 0.002%, Cu: 0.03%, Al: 0.023%, Nb: 0.04%, V: 0.12%, P: 0.010%, S: 0.003%, the rest being Fe and inevitable impurities, totaling 100%; CEV (%) is 0.44.

[0044] The preparation method of the seamless steel pipe for a semitrailer axle of the present embodiment contains the following steps in the method:

[0045] S01: smelting and continuous casting to obtain a pipe blank according to the chemical composition and mass percentage of the seamless steel pipe for a semitrailer axle;

[0046] S02: heating treatment of the pipe blank; wherein the pipe blank heating temperature is 1270±5°C, and the heating time is 3 hours;

[0047] S03: piercing the pipe blank after the heating treatment to obtain a rough pipe; wherein the piercing temperature is 1240±5°C;

[0048] S04: cooling the rough pipe to 550°C;

[0049] S05: reheating treatment of the cooled rough pipe; wherein the reheating temperature is 970±5°C, and the holding time is 0.25h;

[0050] S06: stretch-reducing treatment of the rough pipe after the reheating treatment; wherein the stretch-reducing rolling temperature is ensured to be 960°C, and the stretch-reducing final rolling temperature is 910°C.

[0051] S07: After the tension reduction treatment, the steel pipe is rapidly cooled on a cooling bed; wherein the cooling method is water mist cooling and end air cooling, the cooling speed of the steel pipe is controlled, and the average cooling speed is 0.5°C / s.

[0052] Example Two

[0053] A seamless steel pipe for a semi-trailer axle, which has the following chemical composition and mass percentage:

[0054] C: 0.15%, Si: 0.28%, Mn: 1.56%, Cr: 0.07%, Ni: 0.01%, Mo: 0.002%, Cu: 0.03%, Al: 0.021%, Nb: 0.02%, V: 0.16%, P: 0.013%, S: 0.002%, the rest being Fe and inevitable impurities, totaling 100%; CEV(%) is 0.46.

[0055] The preparation method of the seamless steel pipe for a semi-trailer axle in this example includes the following steps:

[0056] S01: smelting and continuous casting to obtain a pipe blank according to the chemical composition and mass percentage of the seamless steel pipe for a semi-trailer axle;

[0057] S02: heating treatment of the pipe blank; wherein the heating temperature of the pipe blank is 1260±5°C, and the heating time is 3 hours;

[0058] S03: perforating the pipe blank after the heating treatment to obtain a rough pipe; wherein the perforating temperature is 1230±5°C;

[0059] S04: cooling the rough pipe to 530°C;

[0060] S05: re-heating treatment of the cooled rough pipe; wherein the re-heating temperature is 960±5°C, and the holding time is 0.45h;

[0061] S06: tension reduction treatment of the rough pipe after the re-heating treatment; wherein the tension reduction start rolling temperature is 940°C, and the tension reduction finish rolling temperature is 900°C;

[0062] S07: after the tension reduction treatment, the steel pipe is rapidly cooled on a cooling bed; wherein the cooling method is water mist cooling and end air cooling, the cooling speed of the steel pipe is controlled, and the average cooling speed is 1°C / s.

[0063] Example Three

[0064] A seamless steel pipe for a semi-trailer axle, which has the following chemical composition and mass percentage:

[0065] C: 0.19%, Si: 0.27%, Mn: 1.38%, Cr: 0.07%, Ni: 0.02%, Mo: 0.002%, Cu: 0.04%, Al: 0.018%, Nb: 0.05%, V: 0.18%, P: 0.012%, S: 0.002%, the rest being Fe and inevitable impurities, totaling 100%; CEV (%): 0.47.

[0066] The method for manufacturing the seamless steel pipe for a semitrailer axle of the embodiment comprises the following steps:

[0067] S01: smelting and continuous casting a pipe blank according to the chemical composition and mass percentage of the seamless steel pipe for a semitrailer axle;

[0068] S02: heating treatment of the pipe blank; wherein the heating temperature of the pipe blank is 1250±5℃, and the heating time is 3 hours;

[0069] S03: piercing the pipe blank after the heating treatment to obtain a rough pipe; wherein the piercing temperature is 1230±5℃;

[0070] S04: cooling the rough pipe to 520℃;

[0071] S05: re-heating treatment of the cooled rough pipe; wherein the re-heating temperature is 955±5℃, and the holding time is 0.3h;

[0072] S06: tension-reduction treatment of the rough pipe after the re-heating treatment; wherein the tension-reduction open rolling temperature is ensured to be 930℃, and the tension-reduction final rolling temperature is 890℃;

[0073] S07: cold bed quick cooling of the steel pipe after the tension-reduction treatment; wherein the cooling mode adopts water mist cooling and end air cooling, the cooling speed of the steel pipe is controlled, and the average cooling speed is 1.5℃ / s.

[0074] Comparative Example One

[0075] The method for manufacturing the seamless steel pipe for a semitrailer axle in the comparative example is basically the same as that in the embodiment one, except that the chemical composition and mass percentage of the seamless steel pipe for a semitrailer axle are as follows:

[0076] C: 0.19%, Si: 0.23%, Mn: 1.65%, Cr: 0.03%, Ni: 0.01%, Mo: 0.002%, Cu: 0.02%, Al: 0.020%, P: 0.015%, S: 0.003%; the rest being Fe and inevitable impurities, totaling 100%; CEV: 0.47.

[0077] Comparative Example Two

[0078] The method for preparing the seamless steel pipe for semi-trailer axle in this comparative example is basically the same as that in Example Two, except that:

[0079] The seamless steel pipe for semi-trailer axle contains the following chemical components and mass percentages: C: 0.21%, Si: 0.25%, Mn: 1.58%, Cr: 0.02%, Ni: 0.02%, Mo: 0.004%, Cu: 0.04%, Al: 0.027%, V: 0.13%, P: 0.009%; S: 0.002%; the rest is Fe and inevitable impurities, totaling 100%; CEV: 0.51.

[0080] Comparative Example Three

[0081] The method for preparing the seamless steel pipe for semi-trailer axle in this comparative example is basically the same as that in Example Three, except that:

[0082] The seamless steel pipe for semi-trailer axle contains the following chemical components and mass percentages: C: 0.20%, Si: 0.28%, Mn: 1.52%, Cr: 0.07%, Ni: 0.02%, Mo: 0.002%, Cu: 0.02%, Al: 0.025%, Nb: 0.03%, V: 0.11%, P: 0.013%; S: 0.002%; the rest is Fe and inevitable impurities, totaling 100%; CEV: 0.49;

[0083] Comparative Example Four

[0084] This comparative example is basically the same as Example One, except that: in step S07, the cooling method is air cooling, without using a fan for air cooling and without water mist cooling.

[0085] Comparative Example Five

[0086] This comparative example is basically the same as Example One, except that: in step S07, the cooling method is air cooling, without water mist cooling.

[0087] Comparative Example Six

[0088] This comparative example is basically the same as Example One, except that: in step S04, the mandrel is cooled to 650°C for reheating; in step S05, the reheating temperature is 920°C; in step S06, the open-die temperature is 900°C, and the final rolling temperature is 850°C.

[0089] The seamless steel pipes for semi-trailer axle prepared in the above examples and comparative examples are detected for performance as shown in the following table:

[0090]

[0091] From the above table, it can be seen that the semi-trailer axle seamless steel pipes prepared in the first to third embodiments have yield strength ≥440 MPa, tensile strength ≥560 MPa, full-size impact energy KV8 at-20 ℃ ≥100 J, and CEV ≤0.47, which meet the use requirements.

[0092] In the comparative example one, the content of Mn is relatively high, and V and Nb are not intentionally added. In the comparative example two, Nb is not intentionally added. V can improve the strength of the material by second phase precipitation, and Nb can refine the grain by cooperating with the rolling process to improve the strength and toughness. Therefore, the comparative example one does not obtain sufficient strength and toughness, and the grain is relatively coarse. In the comparative example two, the strength meets the requirements, but the impact toughness is relatively low.

[0093] In the comparative example three, the chemical element ratio meets the requirements, and the strength and toughness also meet the use requirements. However, the CEV is 0.49, and the CEV in the comparative example two is 0.51. The comparative examples two and three do not meet the requirement that the carbon equivalent is not higher than 0.47. Although the welding performance of the comparative examples two and three is good, the welding performance of the comparative examples two and three is worse than that of the embodiments.

[0094] In the comparative examples four to five, the chemical element ratio of the present application is used, but in the pipe manufacturing process, the water mist cooling + end air cooling is not used in the cooling step after rolling, and the cooling rate does not reach the requirement. The material is softened due to partial recrystallization, and the strength of the material is reduced.

[0095] In the comparative example six, the chemical element ratio of the present application is used, but the temperature of the steel pipe is too high before entering the reheating furnace, and the austenite is not completely converted into ferrite + pearlite. After reheating, the austenite that does not change continues to grow, the original grain size is large, and the final grain size is affected. Therefore, after the cold deformation, fine ferrite + pearlite cannot be obtained, and the strength and toughness of the material are affected.

[0096] The above-described specific embodiments further illustrate the technical problems solved by the present application, technical solutions and beneficial effects. It should be understood that the above-described specific embodiments are only specific embodiments of the present application, and are not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing seamless steel pipes for semi-trailer axles, characterized in that, The chemical composition and mass percentage of the seamless steel pipe used for semi-trailer axles are as follows: C: 0.19%~0.22%, Si: 0.27%~0.35%, Mn: 1.20%~1.60%, P: ≤0.015%, S≤0.010%, Cr: 0.05%~0.07%, Ni: ≤0.20%, Mo: ≤0.10%, Cu: ≤0.20%, Al: 0.01%~0.05%, Nb: 0.015%~0.05%, V: 0.11%~0.12% or 0.16%~0.18%, with the remainder being Fe and other unavoidable impurities, totaling 100%; where, the carbon equivalent CEV (%) = C + Mn / 6 + (Cr + Mo + V) / 5 + (Ni + Cu) / 15 ≤ 0.47; The performance parameters are as follows: yield strength ≥ 440 MPa, tensile strength ≥ 560 MPa, impact strength at -20℃ ≥ 100 J, fatigue life ≥ 10 5 Second-rate; The method consists of the following steps: S01: The tube blank is obtained by smelting and continuous casting according to the chemical composition and mass percentage of the seamless steel pipe for semi-trailer axles; S02: Heat treatment of the tube blank; wherein the tube blank heating temperature is 1240~1290℃, and the heating time is 1-4 hours; S03: The tube blank after heat treatment is pierced to obtain a rough tube; wherein, the piercing temperature is 1220~1260℃; S04: Cool the capillary tube to below 550°C; S05: Reheat the cooled capillary tube; wherein the reheating temperature is 960℃~980℃ and the holding time is 0.2~0.5h; S06: Tension reduction treatment is performed on the reheated tube; wherein the initial rolling temperature of tension reduction is 930℃~960℃, and the final rolling temperature of tension reduction is 860~950℃. S07: After tension reduction treatment, the steel pipe is subjected to rapid cooling on a cooling bed; the cooling methods include water mist cooling and end air cooling, and the cooling rate of the steel pipe is controlled, with an average cooling rate between 0.5℃ / s and 1.5℃ / s. The microstructure of the steel pipe product is fine ferrite + pearlite.

2. The preparation method according to claim 1, characterized in that, CEV (%): 0.43-0.47.

Images