阅读说明：本技术 一种生产高强度SiCrV弹簧钢的热处理方法 (Heat treatment method for producing high-strength SiCrV spring steel ) 是由 李秋志 王德炯 沈朴恒 王杨 于 2019-09-18 设计创作，主要内容包括：本发明公开了一种生产高强度SiCrV弹簧钢的热处理方法,含有的化学成分及其重量百分比为,C:0.56-0.64％,Si：1.40％-1.80％,Mn：0.40-0.70％,Cr：0.90-1.20％,V:0.10-0.20％,其余部分为铁和不可去除的残余,所述热处理方法包括以下步骤：将加热炉内温度升至890-920℃,将弹簧钢置于电阻炉内加热,透烧后保温30-40Min；启动淬火油槽搅拌装置和控温装置,迅速将步骤中的弹簧钢放进淬火油槽的料框,油冷淬火10Min；样品出油后放进回火炉进行回火,回火炉炉内温度405-420℃,回火时间70-90Min；回火完成后进行水冷。通过适当的淬火加热控制实现合金元素成分回溶而晶粒不显著长大,配合适当的冷却方法达到高的淬火硬度,然后通过回火达到需要的高强度,同时保证良好的塑性。(The invention discloses a heat treatment method for producing high-strength SiCrV spring steel, which comprises the following chemical components in percentage by weight, 0.56-0.64% of C, Si: 1.40% -1.80%, Mn: 0.40-0.70%, Cr: 0.90-1.20%, V: 0.10-0.20%, the remainder being iron and non-removable residues, said heat treatment method comprising the steps of: the temperature in the heating furnace is raised to 890-920 ℃, the spring steel is placed in a resistance furnace for heating, and the temperature is kept for 30-40Min after thorough burning; starting a quenching oil tank stirring device and a temperature control device, rapidly putting the spring steel in the step into a material frame of a quenching oil tank, and carrying out oil cooling quenching for 10 Min; tempering the sample in a tempering furnace after the sample is subjected to oil extraction, wherein the temperature in the tempering furnace is 405-420 ℃, and the tempering time is 70-90 Min; and (5) performing water cooling after tempering is finished. The remelting of alloy element components is realized through proper quenching heating control, crystal grains do not grow up remarkably, high quenching hardness is achieved by matching with a proper cooling method, then the required high strength is achieved through tempering, and meanwhile, good plasticity is guaranteed.)

1. The heat treatment method for producing the high-strength SiCrV spring steel has the advantages that the high-strength SiCrV spring steel meets the requirements that the tensile strength is more than or equal to 1900MPa, the yield strength is more than or equal to 1700MPa, the elongation is more than or equal to 9 percent, and the reduction of area is more than or equal to 30 percent, and the high-strength SiCrV spring steel contains the following chemical components in percentage by weight: 0.56-0.64%, Si: 1.40% -1.80%, Mn: 0.40-0.70%, Cr: 0.90-1.20%, V: 0.10-0.20%, the remainder being iron and non-removable residues, characterized in that said heat treatment process comprises the following steps:

(1) the temperature in the resistance furnace is raised to 890-920 ℃, the high-strength SiCrV spring steel is placed in the resistance furnace to be heated, and the temperature is kept for 30-40min after thorough burning;

(2) starting a quenching oil tank stirring device and a temperature control device, rapidly putting the high-strength SiCrV spring steel in the step (1) into a material frame of a quenching oil tank, and carrying out oil cooling quenching for 10 min;

(3) after the high-strength SiCrV spring steel is discharged with oil, putting the high-strength SiCrV spring steel into a tempering furnace for tempering, wherein the temperature in the tempering furnace is 405-420 ℃, and the tempering time is 70-90 Min;

(4) and (5) performing water cooling after tempering is finished.

2. The heat treatment method for producing the high-strength SiCrV spring steel according to claim 1, wherein the quenching oil in the step (2) has a closed cup flash point of not less than 135 ℃ and a kinematic viscosity of 4.0-9.6 x 10-6m at 50 ℃²/s。

3. The heat treatment method for producing the high-strength SiCrV spring steel according to claim 1, wherein the quenching oil temperature in the step (2) is 40-50 ℃.

4. The heat treatment method for producing the high-strength SiCrV spring steel according to claim 1, wherein the high-strength SiCrV spring steel in the step (3) is subjected to oil discharge, oil filtration for 5min and tempering in a tempering furnace.

5. The heat treatment method for producing the high-strength SiCrV spring steel as claimed in claim 1, wherein the step (2) is carried out by quenching oil type 25# transformer oil.

Technical Field

The invention relates to a heat treatment method of spring steel, in particular to a heat treatment method for producing high-strength SiCrV spring steel.

Background

The high-strength SiCrV spring steel has the remarkable characteristics of high strength and good combination of strength and toughness, is widely applied to the industries of railways and engineering machinery, and has good development prospect in the automobile industry.

The typical representative steel No. 60Si2CrVAT is high comprehensive performance spring steel, which adjusts the technical requirements on the basis of GB/T122260 Si2CrVA, and the tensile strength is increased from 1860Mpa to 1900Mpa, the yield is increased from 1665Mpa to 1700Mpa, the elongation is increased from 6% to 9%, and the reduction of area is increased from 20% to 30% (GB/T1222, Total transport of iron [ 2013 ] 153, and transport and Loading truck [2004] 342). The heat treatment process plays a key role in playing the role of the good performance potential of the steel grade.

The main steel grade of the 60Si2CrVAT railway speed-up spring is widely applied to the railway freight car bogie spring at present, and with the establishment of the national intellectual property reviving number standard, the share of the 60Si2CrVAT in the fields with higher requirements is further expanded. According to the related policy of the state Ministry of transportation for steam-to-iron, 21 ten thousand new trucks are expected to be added within three years; the Xingxing high-speed rail is the main trend of railway passenger transportation; about 4 million tons of 60Si2CrVAT steel material are required annually for three years. In addition, the material of the automobile stabilizer bar has high strength, which is part of the light weight of the automobile, and the high-strength SiCrV spring steel has already started to be applied at present, so that the high-strength SiCrV spring steel has a good prospect.

The high-strength SiCrV spring steel (C: 0.56-0.64%, Si: 1.40-1.80%, Mn: 0.40-0.70%, Cr: 0.90-1.20%, V: 0.10-0.20%) has good comprehensive performance, and a typical mark 60Si2CrVAT has high-strength and high-plasticity matching potential with the tensile strength of more than or equal to 1900MPa, the yield strength of more than or equal to 1700MPa, the elongation of more than or equal to 9% and the reduction of area of more than or equal to 30%.

In the practical application process, the influence of a heat treatment effect is poor, the 60Si2CrVAT spring steel after heat treatment has the problems of insufficient plasticity when the tensile strength reaches 1900MPa or low strength when the plasticity is high (the elongation is more than or equal to 9 percent and the reduction of area is more than or equal to 30 percent), and the matching potential of high strength and high plasticity cannot be exerted.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a heat treatment method capable of ensuring that the SiCrV spring steel has high strength and high plasticity through experimental analysis and research on heat treatment phase change characteristics such as re-dissolution of alloy elements, grain growth tendency, influence of a cooling mode on martensite transformation and the like in high-strength SiCrV spring steel (comprising 0.56-0.64% of C, 1.40-1.80% of Si, 0.40-0.70% of Mn, 0.90-1.20% of Cr and 0.10-0.20% of V).

The technical scheme is as follows: the heat treatment method for producing the high-strength SiCrV spring steel provided by the invention has the advantages that the high-strength SiCrV spring steel can meet the requirements of the tensile strength of more than or equal to 1900MPa, the yield strength of more than or equal to 1700MPa, the elongation of more than or equal to 9 percent and the reduction of area of more than or equal to 30 percent, and comprises the following chemical components in percentage by weight: 0.56-0.64%, Si: 1.40% -1.80%, Mn: 0.40-0.70%, Cr: 0.90-1.20%, V: 0.10-0.20%, the remainder being iron and non-removable residues, characterized in that said heat treatment process comprises the following steps:

(1) the temperature in the resistance furnace is raised to 890-920 ℃, the high-strength SiCrV spring steel is placed in the resistance furnace to be heated, and the temperature is kept for 30-40min after thorough burning; the through-burning time is determined according to the size of the workpiece and the heat treatment quantity.

(2) Starting a quenching oil tank stirring device and a temperature control device, rapidly putting the high-strength SiCrV spring steel in the step (1) into a material frame of a quenching oil tank, and performing oil cooling quenching for 10 Min; controlling the quenching effect through a quenching device, quenching oil and an operation system; the scale and the form of the quenching device are controlled according to the size of the heat treatment workpiece and the heat treatment production requirement.

Typical quench oil groove key features: the quenching oil is stirred by the motor, and the oil temperature variation range is controllable: plus or minus 5 deg.c (electrically assisted heating, circular cooling).

(3) And (3) tempering the high-strength SiCrV spring steel in a tempering furnace after the high-strength SiCrV spring steel is subjected to oil discharge, wherein the temperature in the tempering furnace is 405-420 ℃, and the tempering time is 70-90 Min.

(4) And (5) performing water cooling after tempering is finished.

Preferably, the closed cup flash point of the quenching oil in the step (2) is more than or equal to 135 ℃, and the kinematic viscosity is 4.0-9.6 x 10-6m at the temperature of 50 DEG C²/s。

Preferably, the temperature of the quenching oil in the step (2) is 40-50 ℃.

Preferably, in the step (3), after the sample produces oil, the oil is filtered for 5Min, and then the sample is placed into a tempering furnace for tempering.

Preferably, the quenching oil in the step (2) is 25# transformer oil or quenching oil with the same cooling capacity.

The invention ensures the dissolution of alloy carbide and fully exerts the effect of alloy elements on hardenability by heating the high-strength SiCrV spring steel at 890-920 ℃. The heating temperature and the heating time have influence on the growth of steel grains. The test shows that the crystal grains of the sample steel are kept at 920 ℃ for 40min to keep fine crystal characteristics and play a role of strengthening and toughening the material by the fine crystal grains, as shown in figure 2. 890-920 ℃, stirring, cooling and quenching in the quenching oil to obtain fine and uniform martensite tissues, and obtaining high hardness of the test steel; tempering at a proper temperature to obtain the required strength level; and (3) tempering at the temperature of 420 ℃ with 405 ℃ to obtain high-strength and high-plasticity matching with the tensile strength of more than or equal to 1900MPa, the yield strength of more than or equal to 1700MPa, the elongation of more than or equal to 9 percent and the reduction of area of more than or equal to 30 percent. The strength of the steel material after heat treatment depends on the final tempering hardness and is hardly influenced by the quenching hardness; the yield strength, elongation and reduction of area are not only dependent on the tempering hardness, but also have a great relationship with the quenching hardness, and under the same tempering hardness condition, the indexes are improved along with the increase of the quenching hardness.

Has the advantages that: aiming at the problem that the coordination potential of high strength and high plasticity of the spring steel cannot be well exerted, the invention realizes the redissolution of alloy element components without significant growth of crystal grains through proper quenching and heating control, achieves high quenching hardness by matching with a proper cooling method, then achieves the required high strength through tempering, and simultaneously ensures good plasticity. The spring steel is suitable for various damping systems and balance systems (such as automobile stabilizer bars) with high stress and high fatigue life requirements.

Drawings

FIG. 1a is a SEM structural morphology comparison diagram of SiCrV spring steel after heat preservation at 870 ℃ for 30min and heat preservation at 890 ℃ for 30min and quenching;

FIG. 2920 ℃ heat preservation 40min austenite grain 500X;

FIG. 3 b is a SEM structural morphology comparison diagram of SiCrV spring steel after 890 ℃ heat preservation for 30min and c heat preservation for 920 ℃ for 30min heating temperature quenching.

Detailed Description

For a further understanding of the present invention, reference will now be made in detail to the embodiments illustrated in the drawings.