X12cr13 martensitic stainless wire rod homogenization annealing process

Abstract

This invention discloses a homogenization annealing process for X12Cr13 stainless steel wire rod, belonging to the field of metal material heat treatment technology. Using 5.5mm diameter X12Cr13 stainless steel wire rod as raw material, this invention employs an isothermal annealing process at 860℃ with a holding time of 1-6 hours. This process causes the carbides to gradually spheroidize from point-like formations and become uniformly dispersed, while the chain-like morphology of carbides in the longitudinal structure gradually breaks down and disappears. After holding for more than 2 hours, the tensile strength and elongation after fracture of the material tend to stabilize, with minimal fluctuations in mechanical properties and high microstructure uniformity. This invention solves the problems of uneven carbide distribution, obvious chain-like structure, and poor processing performance under traditional annealing processes. The process is stable and controllable, suitable for industrial mass production, and can significantly improve the microstructure uniformity and subsequent processing adaptability of X12Cr13 stainless steel wire rod.

Description

Technical Field

[0001] This invention belongs to the field of heat treatment technology for metallic materials, specifically relating to a homogenization annealing process for X12Cr13 semi-martensitic stainless steel wire rod. Background Technology

[0002] X12Cr13 is a semi-martensitic stainless steel containing a small amount of ferrite. It possesses good toughness, corrosion resistance, low-temperature strength, and comprehensive mechanical properties, and is widely used in precision wire rods, shafts, cutting tools, and structural components. After rolling and drawing, the internal carbides of this steel tend to aggregate in a point-like or chain-like manner, resulting in poor microstructure uniformity, which directly affects subsequent cold working performance and finished product quality. Traditional annealing processes struggle to achieve sufficient spheroidization and uniform dispersion of carbides, easily leading to defects such as poor microstructure consistency and large fluctuations in mechanical properties. Currently, there is a lack of stable, efficient, and industrially feasible homogenization annealing regimes for 5.5mm X12Cr13 stainless steel wire rods. Therefore, developing an annealing process that can precisely control carbide morphology, eliminate chain-like structures, and stabilize mechanical properties has significant engineering application value. Summary of the Invention

[0003] This invention discloses a homogenization annealing process for X12Cr13 semi-martensitic stainless steel wire rod, with the aim of providing a homogenization annealing process that is uniform in structure, stable in performance, and suitable for mass production. Specific technical solutions X12Cr13 stainless steel wire rod with a diameter of 5.5mm was selected. Its chemical composition by mass percentage is as follows: carbon: 0.12, silicon: 0.14, manganese not more than 1.00, phosphorus not more than 0.035, sulfur not more than 0.030, chromium: 12.00~14.00, nickel not more than 0.60. The homogenization annealing process steps for X12Cr13 stainless steel wire rod are as follows (see...). Figure 1 ): 1) Place the wire rod in a heat treatment furnace and heat it to 860°C at a normal heating rate; 2) Perform isothermal annealing at 860℃, with holding time set to 1h, 2h, 3h, 4h, 5h or 6h; 3) After the heat preservation is completed, the furnace is cooled or controlled to room temperature. Mechanism of annealing process for controlling microstructure and properties 1) Tissue evolution: After holding for 1 to 3 hours, the carbides gradually transition from point-like to spherical and begin to diffusely distribute, while the longitudinal chain-like carbides gradually break apart; after holding for 4 to 6 hours, the carbides are completely spherical, the dispersion uniformity is further improved, and the tissue changes tend to be gradual. 2) Mechanical properties: After 1 hour of heat preservation, the tensile strength is 487.5 MPa and the elongation is 37.6%; after 2 hours of heat preservation, the tensile strength is 483.5 MPa and the elongation after fracture is 41.0%; after more than 3 hours of heat preservation, the tensile strength stabilizes at 479.5 MPa and the elongation stabilizes at 41.0%, and the properties no longer change significantly with the extension of time (see...). Figure 14 ). 3) The longitudinal structure can be used to visually determine the elimination effect of chain carbides, and the determination method is simple and accurate. Beneficial effects of the present invention 1) The carbides are fully spheroidized and uniformly dispersed, and the longitudinal chain structure is effectively eliminated, which significantly improves the subsequent drawing and cold working performance; 2) The mechanical properties are stable and controllable, with minimal fluctuations in tensile strength and elongation, resulting in high product consistency; 3) The process parameters are simple, the operation is convenient, and the stability is strong, making it suitable for continuous mass production in industrial settings; 4) Improve the structure of wire rod, increase product qualification rate and reliability, and expand high-end application scenarios. Attached Figure Description

[0004] Figure 1 This is a flowchart of the annealing process of the present invention; Figure 2 Transverse metallographic structure (500×) after heat treatment at 860℃ for 1 hour. Figure 3 Transverse metallographic structure (500×) after heat treatment at 860℃ for 2 hours. Figure 4 Transverse metallographic structure (500×) after heat treatment at 860℃ for 3 hours. Figure 5 Transverse metallographic structure (500×) after heat treatment at 860℃ for 4 hours. Figure 6 Transverse metallographic structure (500×) after heat treatment at 860℃ for 5 hours; Figure 7 Transverse metallographic structure (500×) after heat treatment at 860℃ for 6 hours. Figure 8 Longitudinal metallographic structure (500×) after holding at 860℃ for 1 hour. Figure 9 Longitudinal metallographic structure (500×) after holding at 860℃ for 2 hours; Figure 10 Longitudinal metallographic structure (500×) after holding at 860℃ for 3 hours. Figure 11 Longitudinal metallographic structure (500×) after heat treatment at 860℃ for 4 hours. Figure 12Longitudinal metallographic structure (500×) after heat treatment at 860℃ for 5 hours; Figure 13 Longitudinal metallographic structure (500×) after heat treatment at 860℃ for 6 hours. Figure 14 This is a graph showing the relationship between tensile strength, elongation after fracture, and annealing time. Detailed Implementation

[0005] Example 1 Raw material: X12Cr13 stainless steel wire rod with a diameter of 5.5mm. Annealing process: 860℃, hold for 1 hour. Metallographic structure: Carbides are mainly punctate, beginning to transform into spherical shapes, with a distinct chain-like distribution visible longitudinally. Figure 2 , Figure 8 ; Mechanical properties: tensile strength 487.5 MPa, elongation after fracture 37.6%. Example 2 Raw material: X12Cr13 stainless steel wire rod with a diameter of 5.5mm. Annealing process: 860℃, hold for 2 hours. Metallographic structure: Improved carbide spheroidization and dispersion, and significantly reduced chain-like structures. (See attached image) Figure 3 , Figure 9 ; Mechanical properties: tensile strength 483.5 MPa, elongation after fracture 41.0%. Example 3 Raw material: X12Cr13 stainless steel wire rod with a diameter of 5.5mm. Annealing process: 860℃, hold for 3 hours. Metallographic structure: Carbides are spherical with good dispersion and uniformity; longitudinal chain-like structures have largely disappeared. Figure 4 , Figure 10 ; Mechanical properties: tensile strength 479.5 MPa, elongation after fracture 41.0%. Example 4 Raw material: X12Cr13 stainless steel wire rod with a diameter of 5.5mm. Annealing process: 860℃, hold for 4 to 6 hours. Metallographic structure: Carbides are evenly distributed in spherical dispersions, the structure is stable, and there are no chain-like features. Figure 5 , Figure 6 , Figure 7 , Figure 11 , Figure 12 , Figure 13 ; Mechanical properties: tensile strength is stable at 479.5 MPa, and elongation after fracture is stable at 41.0%.

Claims

1. A homogenization annealing process for X12Cr13 martensitic stainless steel wire rod, characterized in that, X12Cr13 stainless steel wire rod with a diameter of 5.5mm was selected. Its chemical composition by mass percentage is as follows: carbon: 0.12, silicon: 0.14, manganese not more than 1.00, phosphorus not more than 0.035, sulfur not more than 0.030, chromium: 12.00~14.00, nickel not more than 0.

60. The homogenization annealing process for X12Cr13 stainless steel wire rod is as follows: 1) Place the wire rod in a heat treatment furnace and heat it to 860°C at a normal heating rate; 2) Perform isothermal annealing at 860℃, with holding time set to 1h, 2h, 3h, 4h, 5h or 6h; 3) After the heat preservation is completed, the furnace is cooled to room temperature either by hand or by controlled cooling. Tissue evolution: After holding for 1 to 3 hours, the carbides gradually transition from point-like to spherical and begin to diffusely distribute, while the longitudinal chain-like carbides gradually break apart; after holding for 4 to 6 hours, the carbides are completely spherical, the dispersion uniformity is further improved, and the tissue changes tend to be gradual. Mechanical properties: After 1 hour of heat treatment, the tensile strength is 487.5 MPa and the elongation is 37.6%; after 2 hours of heat treatment, the tensile strength is 483.5 MPa and the elongation after fracture is 41.0%; after 3 hours or longer of heat treatment, the tensile strength stabilizes at 479.5 MPa and the elongation stabilizes at 41.0%, and the properties no longer change significantly with the extension of time. The wire rod is placed in a heat treatment furnace and heated to 860℃ at a conventional heating rate.

2. The homogenization annealing process for X12Cr13 martensitic stainless steel wire rod according to claim 1, characterized in that, Annealing process: 860℃, hold for 1 hour; Metallographic structure: Carbides are mainly in the form of dots, beginning to transform into spherical shapes, with obvious chain-like distribution visible longitudinally; Mechanical properties: tensile strength 487.5 MPa, elongation after fracture 37.6%.

3. The homogenization annealing process for X12Cr13 martensitic stainless steel wire rod according to claim 1, characterized in that, Annealing process: 860℃, hold for 2 hours; Metallographic structure: Improved carbide spheroidization, better dispersion, and significantly reduced chain-like structure; Mechanical properties: tensile strength 483.5 MPa, elongation after fracture 41.0%.

4. The homogenization annealing process for X12Cr13 martensitic stainless steel wire rod according to claim 1, characterized in that, Annealing process: 860℃, hold for 3 hours; Metallographic structure: Carbides are spherical with good dispersion and uniformity, and longitudinal chain structure has basically disappeared; Mechanical properties: tensile strength 479.5 MPa, elongation after fracture 41.0%.

5. The homogenization annealing process for X12Cr13 martensitic stainless steel wire rod according to claim 1, characterized in that, Annealing process: 860℃, hold for 4-6 hours; Metallographic structure: Carbides are evenly distributed in spherical dispersions, the structure is stable, and there are no chain-like features; Mechanical properties: tensile strength is stable at 479.5 MPa, and elongation after fracture is stable at 41.0%.

Images