CN106893832A - A kind of BQ ＆ P Technologies for Heating Processing of carbides-free shellfish/horse Multiphase Steel - Google Patents

Abstract

The invention discloses a BQ&P heat treatment process for carbide-free shellfish/horse composite steel, which uses C-Mn-Si as the main alloy element and adds Al, Mo, Cr, Ni, Cu, Co, W, Ti, Nb and V and other elements, and the rest is Fe. After smelting, casting, forging or rolling, the carbide-free shellfish/horse composite steel is subjected to BQ treatment and P treatment, and the obtained carbide-free shellfish/horse composite steel has a tensile strength of 800-2500MPa and a yield strength of 600- 2000MPa, elongation 10-40%, impact value A _KV 20-300J/cm ² , performance is superior to conventional low-alloy high-strength steel. At the same time, it can avoid problems such as quenching and cracking of steel parts caused by excessive cooling rate and low quenching temperature in the traditional Q&P process.

Description

BQ&P heat treatment process of a carbide-free shellfish/horse composite steel

technical field

The invention relates to the field of heat treatment of low-alloy high-strength steel. More specifically, it relates to a BQ&P heat treatment process for carbide-free shellfish/horse composite steel.

Background technique

A large amount of low-alloy high-strength steel is required in fields such as rail transit, construction, machinery, and energy, and it is required that low-alloy high-strength steel can obtain sufficient elongation and impact toughness while maintaining high strength. But after conventional heat treatment, the toughness and plasticity of steel decrease with the increase of strength. Professor J. Speer in the United States proposed the Q&P process. After the steel is austenitized, it is quenched to between the martensitic transformation start temperature (Ms) and the martensite transformation end temperature (M _f ), to obtain untransformed Austenite and martensite, and then heated to a certain temperature for partitioning, promotes the diffusion of carbon from supersaturated martensite into austenite, stabilizing the austenite structure (J.Speer et al.Acta Materialia 51 (2003) 2611-2622). The QPT process proposed by academician Xu Zuyao introduces nano-precipitates into the martensite and austenite structures to further improve the strength of the steel (Xu Zuyao, Metal Heat Treatment, 34(2009) 1-8). On this basis, related invention patents include: low-alloy ultra-high-strength multi-phase steel and its heat treatment method (public number: 101225499), a high-strength toughness multi-phase steel and its heat treatment method (public number: 103045941A) and a Preparation method of bainite/martensite/austenite composite high-strength steel (publication number: 103243275A). However, the above documents and patents are all to obtain sufficient strength. After the steel is austenitized, it is directly quenched or cooled to a temperature between the start temperature of martensite transformation (M _s ) and the end temperature of martensite transformation (M _f ). None of them involved controlling the cooling of the steel to the temperature between the start temperature of bainite transformation (B _s ) and the end temperature of martensite transformation (M _f ) after austenitization. Since the martensite transformation starts at a lower temperature, and the transformation from austenite to martensite will cause volume expansion. Therefore, directly quenching the steel piece to below the martensitic transformation start temperature (M _s ) will easily cause excessive residual stress of the steel piece, resulting in problems such as quenching cracks.

Contents of the invention

The technical problem to be solved by the present invention is to provide a heat treatment process for carbide-free B/M complex phase steel, which combines BQ treatment and P treatment, first adopts two-stage controlled cooling, and cools the steel after austenitization To the bainite transformation start temperature (B _s ) and between the bainite transformation start temperature (B _s ) and the martensite transformation end temperature (M _f ), then use controlled heating to a certain temperature for P treatment, Promotes carbon partitioning from carbide-free bainitic ferrite and martensite to austenite. It avoids the problems of quenching and cracking of the steel parts caused by directly quenching the austenitized steel parts to the temperature between the martensite transformation start temperature (M _s ) and the martensite transformation end temperature (M _f ); and adopts Control the heating to make the temperature of the P stage of the steel part uniform, which can avoid the cracking of the steel part during the heating process. Finally, the plasticity and toughness of steel parts are improved.

To achieve the above object, the present invention adopts the following technical solutions:

A kind of BQ&P heat treatment process of carbide-free shellfish/horse composite phase steel, comprises the steps:

1) Smelting, casting, forging or rolling into carbide-free shellfish/horse composite steel by conventional steelmaking process, the components and mass percentages contained in the carbide-free shellfish/horse composite steel are:

C: 0.06～0.75wt%; Si: 0.3～2.0wt%; Al: 0.01～1.5wt%; Mn: 1.6～3.6wt%;

Mo: 0.1~0.6wt%; Cr: 0.1~1.5wt%; Ni: 0~1.0wt%; Co: 0~1.0wt%;

Cu: 0~0.8wt%; W: 0~1.2wt.%; Ti: 0~0.05wt%; Nb: 0~0.12wt.%;

V: 0~0.22wt%; P: 0.001~0.01wt%; S: 0.001~0.015wt%; the rest is Fe;

2) heating or cooling the carbide-free shellfish/horse composite steel obtained in step 1) to 800-1200°C;

3) BQ treatment: Controlled cooling of the carbide-free bainite/martensite composite phase steel to the temperature between the start temperature of bainite transformation and the end temperature of martensite transformation;

4) P treatment: Heat the carbide-free shellfish/horse composite steel to 200-500°C under control, keep it warm for 0.1-72h, and then cool to room temperature.

Preferably, in step 2), heating or cooling to 800-1200° C., the obtained microstructure is austenite or ferrite and austenite.

Preferably, in step 3), the controlled cooling is divided into two stages: the first stage cools to the bainite transformation start temperature at a cooling rate of 0.5-50°C/sec; the second stage cools at a cooling rate of 0.1-5°C/sec The cooling rate is cooled to between the start temperature of bainite transformation and the end temperature of martensite transformation.

Preferably, the bainite transformation start temperature is 210-615°C; the martensite transformation end temperature is -175-225°C.

Preferably, in step 3), the microstructure obtained after cooling is untransformed austenite, carbide-free bainite and martensite or untransformed austenite, ferrite, carbide-free bainite and martensite structures.

Preferably, in step 4), the controlled heating is heating at 10-100°C/minute to 200-500°C.

The beneficial effects of the present invention are as follows:

1. The carbide-free shellfish/horse composite phase steel of the present invention takes C-Mn-Si as the main alloy component, and the alloy cost is low, while adding 0.10-0.6wt% Mo and controlling the content of P to be 0.001-0.01wt%, Intergranular fracture of steel parts can be avoided, thereby improving the toughness of steel parts; Al and Co are used to promote bainite transformation, saving processing time and energy.

2. BQ treatment is different from the traditional Q&P process, which quenches the steel to between the martensitic transformation start temperature (M _s ) and the martensite transformation end temperature (M _f ), but controls the cooling of the steel to bainite Between the transformation start temperature (B _s ) and the martensitic transformation end temperature (M _f ). BQ treatment adopts two-stage controlled cooling, the first stage is cooled to the bainite transformation start temperature (B _s ) at a cooling rate of 0.5-50°C/s, and the second stage is cooled at a cooling rate of 0.1-5°C/s Between the start temperature of bainite transformation (B _s ) and the end temperature of martensite transformation (M _f ). There is no phase change in the cooling process of the first stage, and the production efficiency can be improved by adopting a faster cooling rate than that of the second stage, but if the cooling rate is too large, it will cause the problem of excessive thermal stress and deformation of the steel parts, so the first stage Adopting a cooling rate of 0.5-50°C/s in the first stage not only improves production efficiency, but also avoids deformation of steel parts. In the second stage, bainite transformation and martensitic transformation occur, and the cooling rate slower than that in the first stage can avoid cracking of steel parts caused by excessive phase transformation stress, and is conducive to the uniform temperature of steel parts, but if the cooling rate is too high Slow cooling will result in low production efficiency, so the second stage adopts a cooling rate of 0.1-5°C/s to avoid cracking of steel parts and ensure production efficiency.

3. P treatment adopts controlled heating, and the heating rate is 10-100°C/min, which can make the temperature of the carbide-free shellfish/horse composite phase steel P stage uniform, and can avoid cracking of steel parts during the heating process.

4. The carbide-free shellfish/horse composite steel obtained by applying the present invention can reach a tensile strength of 800-2500MPa, a yield strength of 600-2000MPa, an elongation of 10-40%, and an impact value A _KV of 20-300J/cm ² . The performance is higher than that of conventional low-alloy high-strength steel, and it has broad application prospects.

Description of drawings

The specific implementation manners of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Fig. 1 shows a schematic diagram of the heat treatment process of carbide-free shellfish/horse composite steel.

FIG. 2 shows the carbide-free shellfish/horse composite structure of Example 1.

FIG. 3 shows the carbide-free shellfish/horse composite structure of Example 4.

FIG. 4 shows the carbide-free shellfish/horse complex structure of Example 8.

FIG. 5 shows the carbide-free shellfish/horse composite structure of Example 11.

detailed description

In order to illustrate the present invention more clearly, the present invention will be further described below in conjunction with preferred embodiments and accompanying drawings. Similar parts in the figures are denoted by the same reference numerals. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not limit the protection scope of the present invention.

Table 1 Alloy components and mass percentages of various carbide-free shellfish/horse composite steels

The content of the carbide-free shellfish/horse composite steel alloy components in each embodiment is shown in Table 1, and the rest is iron.

Table 2 The bainite transformation start temperature (B _s ) and the martensite transformation end temperature (M _f ) of the carbide-free bainite/martensite composite steel in each example

Example 1

A kind of BQ&P heat treatment process of carbide-free shellfish/horse composite phase steel, comprises the steps:

1) Smelting, casting and rolling into 10-20mm thick carbide-free shellfish/horse composite steel plate by conventional steelmaking process;

2) The above-mentioned carbide-free shellfish/horse composite steel plate is smelted, cast, and rolled, then cooled to 900°C for austenitization;

3) BQ treatment: Cool the above-mentioned carbide-free shellfish/horse composite steel plate to 615°C at a cooling rate of 50°C/s, and then cool to 450°C at a cooling rate of 5°C/s;

4) P treatment: heat the above-mentioned carbide-free shellfish/horse composite steel plate at 50°C/min to 500°C, keep it warm for 0.1 hour, and then cool it down to room temperature.

Example 2

A kind of BQ&P heat treatment process of carbide-free shellfish/horse composite phase steel, comprises the steps:

1) Smelting, casting and rolling into 20-60mm thick carbide-free shellfish/horse composite steel plate by conventional steelmaking process;

2) The above-mentioned carbide-free shellfish/horse composite steel plate is smelted, cast, and rolled, then cooled to 800°C for austenitization;

3) BQ treatment: Cool the above-mentioned carbide-free shellfish/horse composite steel plate to 420°C at a cooling rate of 20°C/s, and then cool to 400°C at a cooling rate of 1°C/s;

4) P treatment: heat the above-mentioned carbide-free shellfish/horse composite steel plate to 450°C at 10°C/min, keep it warm for 0.5 hours, and then cool to room temperature.

Example 3

A kind of BQ&P heat treatment process of carbide-free shellfish/horse composite phase steel, comprises the steps:

1) Carbide-free shellfish/horse composite wheels with a diameter of 600-900m are smelted, cast, and rolled by conventional steelmaking processes;

2) Heating the carbide-free shellfish/horse composite wheel to 950°C for austenitization;

3) BQ treatment: Cool the above-mentioned carbide-free shellfish/horse composite wheel to 516°C at a cooling rate of 10°C/s, and then cool to 280°C at a cooling rate of 2°C/s;

4) P treatment: heat the above-mentioned carbide-free shellfish/horse composite wheel at 100°C/min to 300°C, keep it warm for 12 hours, and then cool it down to room temperature.

Example 4

A kind of BQ&P heat treatment process of carbide-free shellfish/horse composite phase steel, comprises the steps:

1) Carbide-free shellfish/horse composite wheels with a diameter of 800-1200m are smelted, cast, and rolled by conventional steelmaking processes;

2) Heating the carbide-free shellfish/horse composite wheel to 930°C for austenitization;

3) BQ treatment: Cool the above-mentioned carbide-free shellfish/horse composite wheel to 505°C at a cooling rate of 10°C/s, and then cool to 250°C at a cooling rate of 1°C/s;

4) P treatment: heat the above-mentioned carbide-free shellfish/horse composite wheel at 50°C/min to 300°C, keep it warm for 24 hours, and then cool it down to room temperature.

Example 5

A kind of BQ&P heat treatment process of carbide-free shellfish/horse composite phase steel, comprises the steps:

1) Smelting, casting and rolling into carbide-free shellfish/horse composite rails by conventional steelmaking process;

2) After smelting, casting and rolling, the above-mentioned carbide-free shellfish/horse composite rail is cooled to 950°C for austenitization;

3) BQ treatment: Cool the above-mentioned carbide-free shellfish/horse composite rail to 420°C at a cooling rate of 1°C/s, and then cool to 325°C at a cooling rate of 0.5°C/s;

4) P treatment: the above-mentioned carbide-free shellfish/horse composite rail is heated to 350°C at 10°C/min, kept for 0.3 hours, and then cooled to room temperature.

Example 6

A kind of BQ&P heat treatment process of carbide-free shellfish/horse composite phase steel, comprises the steps:

1) Smelting, casting and rolling into carbide-free shellfish/horse composite steel bars by conventional steelmaking process;

2) Cool the above-mentioned carbide-free shellfish/horse composite steel bars to 1000°C for austenitization after smelting, casting, and rolling;

3) BQ treatment: Cool the above-mentioned carbide-free shellfish/horse composite steel bars to 420°C at a cooling rate of 0.5°C/s, and then cool to 100°C at a cooling rate of 0.2°C/s;

4) P treatment: the above-mentioned carbide-free shellfish/horse composite steel bar was heated to 250°C at 10°C/min, kept for 72 hours, and then cooled to room temperature.

Example 7

A kind of BQ&P heat treatment process of carbide-free shellfish/horse composite phase steel, comprises the steps:

1) It is smelted and cast into a carbide-free shellfish/horse composite phase wear-resistant steel pipe by conventional steelmaking process;

2) Heating the above-mentioned carbide-free shellfish/horse composite wear-resistant steel pipe to 1000°C for austenitization;

3) BQ treatment: Cool the above-mentioned carbide-free shellfish/horse composite wear-resistant steel pipe to 322°C at a cooling rate of 1°C/s, and then cool to 200°C at a cooling rate of 0.1°C/s;

4) P treatment: heat the above-mentioned carbide-free shellfish/horse composite wear-resistant steel pipe at 10°C/min to 280°C, keep it warm for 72 hours, and then cool it to room temperature.

Example 8

A kind of BQ&P heat treatment process of carbide-free shellfish/horse composite phase steel, comprises the steps:

1) Using conventional steelmaking process to smelt, cast, forge and roll carbide-free shellfish/horse composite steel plate spring;

2) heating the above-mentioned carbide-free shellfish/horse composite steel plate spring to 950°C for austenitization;

3) BQ treatment: Cool the above-mentioned carbide-free shellfish/horse composite steel plate spring to 360°C at a cooling rate of 2°C/s, and then cool to 200°C at a cooling rate of 0.1°C/s;

4) P treatment: heat the above-mentioned carbide-free shellfish/horse composite steel plate spring to 360°C at 10°C/min, keep it warm for 2 hours, and then cool it down to room temperature.

Example 9

A kind of BQ&P heat treatment process of carbide-free shellfish/horse composite phase steel, comprises the steps:

1) Smelting, casting, forging and rolling into carbide-free shellfish/horse composite phase wear-resistant steel plate by conventional steelmaking process;

2) Heating the above-mentioned carbide-free shellfish/horse composite wear-resistant steel plate to 1050°C for austenitization;

3) BQ treatment: Cool the above-mentioned carbide-free shellfish/horse composite wear-resistant steel plate to 360°C at a cooling rate of 1°C/s, and then cool to 20°C at a cooling rate of 0.1°C/s;

4) P treatment: heat the above-mentioned carbide-free shellfish/horse composite wear-resistant steel plate at 20°C/min to 280°C, keep it warm for 48 hours, and then cool to room temperature.

Example 10

A kind of BQ&P heat treatment process of carbide-free shellfish/horse composite phase steel, comprises the steps:

1) Using conventional steelmaking process to smelt, cast, forge, and roll carbide-free shellfish/horse composite steel fasteners;

2) Heating the above-mentioned carbide-free shellfish/horse composite steel fastener to 1100°C for austenitization;

3) BQ treatment: Cool the above-mentioned carbide-free shellfish/horse composite steel fastener to 320°C at a cooling rate of 5°C/s, and then cool to 150°C at a cooling rate of 0.1°C/s;

4) P treatment: heat the above-mentioned carbide-free shellfish/mafu steel fastener at 20°C/min to 280°C, keep it warm for 36 hours, and then cool it down to room temperature.

Example 11

A kind of BQ&P heat treatment process of carbide-free shellfish/horse composite phase steel, comprises the steps:

1) Smelting, casting, forging and rolling into carbide-free shellfish/horse composite steel bearings by conventional steelmaking process;

2) heating the above-mentioned carbide-free shellfish/horse composite steel bearing to 900°C for austenitization;

3) BQ treatment: Cool the above-mentioned carbide-free shellfish/horse composite steel bearing to 254°C at a cooling rate of 1°C/s, and then cool to -100°C at a cooling rate of 0.1°C/s;

4) P treatment: heat the above-mentioned carbide-free Bei/Ma Fugang bearing to 280°C at 10°C/min, keep it warm for 4 hours, and then cool to room temperature.

Example 12

A kind of BQ&P heat treatment process of carbide-free shellfish/horse composite phase steel, comprises the steps:

1) Smelting, casting, forging and rolling into carbide-free shellfish/horse composite steel bearings by conventional steelmaking process;

2) heating the above-mentioned carbide-free shellfish/horse composite steel bearing to 900°C for austenitization;

3) BQ treatment: Cool the above-mentioned carbide-free shellfish/horse composite steel bearing to 210°C at a cooling rate of 0.5°C/s, and then cool to -150°C at a cooling rate of 0.1°C/s;

4) P treatment: heat the above-mentioned carbide-free shellfish/horse composite steel bearing to 250°C at 10°C/min, keep it warm for 24 hours, and then cool it down to room temperature.

Through universal tensile testing machine and impact testing machine, using standard tensile samples and impact samples, according to the sample conditions and sampling positions specified in GB/T 228.1-2010 and GB/T 229-2007 national standards, respectively, the The mechanical properties and performance ranges of the samples in each embodiment are shown in Table 3.

Table 3 The mechanical properties of carbide-free shellfish/horse composite steel in each embodiment after BQ&P treatment

Obviously, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, rather than limiting the implementation of the present invention. For those of ordinary skill in the art, on the basis of the above description, they can also make It is not possible to exhaustively list all the implementation methods here, and all obvious changes or changes derived from the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims (4)

1. a kind of BQ＆P Technologies for Heating Processing of carbides-free shellfish/horse Multiphase Steel, it is characterised in that including Following steps：

1) carbides-free shellfish/horse Multiphase Steel is smelted, casts, forges or is rolled into using conventional process for making, The component and mass percent that the carbides-free shellfish/horse Multiphase Steel is included be：

C：0.06~0.75wt%；Si：0.3~2.0wt%；Al：0.01~1.5wt%；Mn：1.6~3.6wt%；

Mo：0.1~0.6wt%；Cr：0.1~1.5wt%；Ni：0~1.0wt%；Co：0~1.0wt%；

Cu：0~0.8wt%；W：0~1.2wt.%；Ti：0~0.05wt%；Nb：0~0.12wt.%；

V：0~0.22wt%；P：0.001~0.01wt%；S：0.001~0.015wt%；Remaining is Fe；

2) by step 1) carbides-free shellfish/horse Multiphase Steel for obtaining is heated or cooled to 800~1200 DEG C；

3) BQ treatment：By the control of carbides-free shellfish/horse Multiphase Steel be cooled to bainite start temperature with Between martensite transfor mation end temp；

4) P treatment：Carbides-free shellfish/horse Multiphase Steel control is heated to 200~500 DEG C, 0.1~72h is incubated, It is cooled to room temperature.

2. BQ＆P Technologies for Heating Processing of carbides-free shellfish/horse Multiphase Steel according to claim 1, Characterized in that, step 3) in, the control cooling is divided into two stages：1st stage is with 0.5~50 DEG C The cooling velocity of/second is cooled to bainite start temperature；2nd stage is with 0.1~5 DEG C/sec of cooling speed Degree is cooled between bainite start temperature and martensite transfor mation end temp.

3. the BQ＆P of carbides-free shellfish/horse Multiphase Steel according to claim 1 and 2 is heat-treated work Skill, it is characterised in that the bainite start temperature is 210~615 DEG C；The martensite transfor mation knot Shu Wendu is -175~225 DEG C.

4. BQ＆P Technologies for Heating Processing of carbides-free shellfish/horse Multiphase Steel according to claim 1, Characterized in that, step 4) in, the control heating is to be heated to 200~500 DEG C with 10-100 DEG C/min.