A low-alloy anchor cable resistant to stress corrosion and its preparation method

Abstract

The present invention discloses a low-alloy anchor cable resistant to stress corrosion and a preparation method thereof, and relates to the technical field of anchor cable processing. The low-alloy anchor cable of the present invention contains the following chemical components in mass percentage: C: 0.4~0.6%, Si: 0.2~0.25%, Mn: 0.7~0.9%, Cr: 0.1~0.5%, Ni: 1.2~1.8%, Sb: 0.04~0.06%, Nb: 0.03~0.05%, Cu: 0.4%~0.6%; the rest are Fe and inevitable impurities. The raw material cost of the anchor cable of the present invention is low, and it has good industrial and commercial prospects; at the same time, it also has excellent stress corrosion resistance, and when used in a mine water environment, it still has excellent stress corrosion resistance; the anchor cable of the present invention is simple to process and has low processing difficulty, and is easy to industrially produce and promote.

Description

Technical Field

[0001] The invention belongs to the technical field of anchor cable processing, and particularly relates to a stress corrosion resistant low alloy anchor cable and a preparation method thereof. Background Art

[0002] Anchor cables are the primary material for anchor support. Combined with anchor rods, they can expand the application scope of anchor support and significantly improve the stability of the support structure. As the use of anchor cables increases year by year, the service environment of anchor cables also deteriorates. Surveys and statistics have found that fracture accidents caused by stress corrosion and hydrogen embrittlement of some steel strands are very common in both domestic and foreign anchor cables. In many cases, anchor cables have even been in service for less than two years. After 6 to 8 years of service, corrosion fracture failures can be detected in almost all anchor cable reinforcement projects. This shows that stress corrosion is a major form of failure in anchor cables, seriously threatening their service life and service safety.

[0003] Traditional anchor steel materials contain very low alloy content, and the main alloying elements are only used to increase strength, with minimal effect on improving corrosion resistance. However, anchors in high-intensity service environments often interact with media such as chloride ions, sulfides, carbonates, sulfates, and microorganisms, which can easily cause stress corrosion cracking. Currently, commercial mining anchor steels have a high stress corrosion sensitivity in mines, generally exceeding 90% (high stress corrosion risk level). Therefore, improving the corrosion resistance of the material through microalloying to obtain a new type of stress corrosion-resistant anchor cable is of great significance in reducing anchor cable corrosion failure and increasing the service life of the anchor cable steel. However, due to the extremely high strength of the anchor cable material, generally requiring a grade of 1860MPa or above, this places stringent requirements on the design of the alloy composition and its processability, making the development of corrosion-resistant and fracture-resistant high-strength anchor cables difficult. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention provides a low-alloy anchor cable with stress corrosion resistance and a preparation method thereof. The low-alloy anchor cable developed by the present invention has the characteristics of stable mechanical properties and excellent stress corrosion resistance.

[0005] The present invention is achieved by adopting the following technical solution: a low-alloy anchor cable resistant to stress corrosion, comprising the following chemical components in mass percentage: C: 0.4-0.6%, Si: 0.2-0.25%, Mn: 0.7-0.9%, Cr: 0.1-0.5%, Ni: 1.2-1.8%, Sb: 0.04-0.06%, Nb: 0.03-0.05%, Cu: 0.4%-0.6%; the rest is Fe and inevitable impurities.

[0006] The content of main alloying elements in the present invention is based on the following principles:

[0007] Effect of Carbon: Carbon is the most essential element in steel and one of the most potent alloying elements for strengthening. Increased strength is achieved by increasing the content of carbon and carbon equivalent elements. Therefore, this invention utilizes a high-carbon design to improve the tensile and yield strength of the anchor cable, with the carbon content set at 0.4% to 0.6%.

[0008] Effect of Si: Si has a solid solution strengthening effect in steel. A moderate amount of Si also helps refine α-FeOOH, thereby reducing the overall corrosion rate of the steel. Combining Si with other elements such as Cr and Cu effectively improves the corrosion resistance of the steel. However, excessive Si content in steel can reduce cold drawing performance. Therefore, the Si content in this invention is set at 0.2% to 0.25%.

[0009] Effect of Mn: Mn is an alloying element that has a positive effect on both steel strength and toughness. However, the Mn content should not be too high, as excessive Mn can coarsen grains and increase temper brittleness. Therefore, the Mn content in this invention is set at 0.7% to 0.9%.

[0010] Effect of Cr: Cr can effectively improve the corrosion resistance of steel. Cr can promote the conversion of unstable γ-FeOOH into stable α-FeOOH, refine the rust layer grains, and improve the density and stability of the rust layer. While Cr significantly improves the strength, hardness, and wear resistance of steel, it can also increase the acidification within the rust layer, increase the material's corrosion brittleness, and reduce the steel's plasticity. Taking all these factors into consideration, the Cr content in this invention is set at 0.1% to 0.5%.

[0011] Effect of Ni: Ni is the primary element used in the present invention to control stress corrosion resistance. Its rational addition has multiple functions, including optimizing the processing properties and microstructure of the anchor steel, shifting the anchor steel's self-corrosion potential toward a positive shift, increasing its resistance to stress corrosion caused by hydrogen evolution, and enhancing the rust layer's ability to block the intrusion of corrosive ions. Furthermore, Ni exhibits synergistic stress corrosion resistance with Cu and Sb. However, Ni is expensive, so for these reasons, the Ni content in the present invention is set at 1.2% to 1.8%.

[0012] Influence of Cu-Sb: The combined addition of Cu-Sb is beneficial to improving the grain size of the anchor steel during the hot forming process, and can increase the pH at the crack tip and increase the electrochemical resistance to crack tip corrosion. However, a high Cu or Sb content will significantly reduce the plasticity of the anchor steel and increase the sensitivity to stress corrosion. The optimal addition ratio of Cu-Sb in the present invention is about 10:1, and the Ni-Cu mass ratio is greater than 2.5, otherwise the mechanical properties and stress corrosion resistance of the material will be reduced. Therefore, the Cu element content in the present invention is set at 0.4%~0.6%, and the Sb element content is set at 0.04%~0.06%.

[0013] Effect of Nb: Nb improves the material's strength and toughness by refining the grain size, comprehensively improving the material's mechanical properties. Adding less than 0.1% Nb refines the grain size by forming a nanophase, improving mechanical properties, effectively reducing dislocation density, reducing the number of grain boundaries, and reducing local stress concentration, thereby delaying the initiation and propagation of hydrogen-induced cracking. Furthermore, the addition of Nb reduces hydrogen diffusion within the material, thereby inhibiting the hydrogen-induced cracking mechanism and slowing the stress corrosion process. However, a Nb content exceeding 0.05% can reduce the plasticity and cold-drawing properties of the anchor steel. Therefore, the Sb content in the present invention is set at 0.03-0.05%.

[0014] The present invention also provides a method for preparing the stress corrosion resistant low alloy anchor cable, which comprises the following steps:

[0015] (1) preparing raw materials according to the chemical composition of the anchor cable, and smelting to obtain molten steel; then casting the molten steel into ingots;

[0016] (2) rolling the ingot at a temperature of 950-1030° C. for 10-12 passes to form a steel wire;

[0017] (3) spray cooling the steel wire to 400-450° C. to generate a sorbite structure;

[0018] (4) Air cooling to room temperature and then cold drawing;

[0019] (5) Keep the cold-drawn steel wire at 200-300°C for 2-5 hours to obtain an anchor cable.

[0020] Preferably, the final rolling temperature in step (2) is 850-900° C., and the diameter of the steel wire is 12 mm.

[0021] Preferably, the cooling rate in step (3) is 10-20°C / s.

[0022] Preferably, the number of cold drawing passes in step (4) is 4, and the diameter of the steel wire after cold drawing is 6 mm.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The raw material cost of the anchor cable of the present invention is low, and it has good industrial and commercial prospects; the anchor cable of the present invention has excellent stress corrosion resistance, and the anchor cable of the present invention still has excellent stress corrosion resistance when used in a mine water environment; the anchor cable of the present invention is simple to process and has low processing difficulty, and is easy to industrially produce and promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a metallographic structure diagram of the anchor cable described in Example 1 of the present invention;

[0026] Figure 2 This is a metallographic structure diagram of the anchor cable described in Example 2 of the present invention;

[0027] Figure 3 This is a metallographic structure diagram of the anchor cable described in Example 3 of the present invention;

[0028] Figure 4 This is the metallographic structure diagram of the common anchor cable of Comparative Example 1 of the present invention;

[0029] Figure 5 It is the stress corrosion sensitivity index of Examples 1-3 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, and the disclosure and materials cited therein are hereby incorporated by reference.

[0032] Technical equivalents to the specific embodiments described that are apparent to those skilled in the art using no more than routine experimentation are intended to be encompassed by this application.

[0033] The experimental methods in the following examples are all conventional methods unless otherwise specified. The instruments and equipment used in the following examples are all conventional laboratory instruments and equipment unless otherwise specified.

[0034] Example 1: A stress corrosion resistant low alloy anchor cable, comprising the following chemical components in mass percentage: C: 0.6%, Mn: 0.8%, Si: 0.21%, Cr: 0.2%, Ni: 1.48%, Cu: 0.51%, Sb: 0.06%, Nb: 0.049%, and the remainder being Fe and unavoidable impurities.

[0035] The preparation method of the low alloy anchor cable described in the present invention is as follows: high-purity molten steel is obtained by smelting in a vacuum induction furnace according to the above chemical composition, and then made into a cast billet; the cast billet is temperature-controlled to 1030°C for rolling, and then rolled through 12 passes, with the final rolling temperature between 850°C, to form a steel wire with a diameter of 12 mm; the rolled steel wire is spray-cooled to 420°C at a cooling rate of about 15°C / s; and then cooled to room temperature in air. After that, it is cold-drawn four times to a steel wire with a diameter of 6 mm. After cold drawing, it is kept at 250°C for 2 hours to finally make the finished anchor cable. The metallographic structure of the stress corrosion resistant anchor cable in this embodiment is shown in FIG. Figure 1 , it can be seen that its organization is Sorb body organization.

[0036] Example 2: A stress corrosion resistant low alloy anchor cable, comprising the following chemical components by mass percentage: C: 0.53%, Mn: 0.8%, Si: 0.21%, Cr: 0.2%, Ni: 1.65%, Cu: 0.45%, Sb: 0.04%, Nb: 0.046%, with the remainder being Fe and unavoidable impurities. The preparation process is the same as that of Example 1. The metallographic structure of the stress corrosion resistant anchor cable of this example is shown in FIG. Figure 2 , as can be seen from the figure, its organization is Sorbite organization.

[0037] Example 3: A low alloy anchor cable resistant to stress corrosion, comprising the following chemical compositions by mass percentage: C: 0.44%, Mn: 0.8%, Si: 0.21%, Cr: 0.5%, Ni: 1.80%, Cu: 0.45%, Sb: 0.05%, Nb: 0.05%, with the remainder being Fe and unavoidable impurities. The preparation process is the same as that of Example 1. The metallographic structure of the stress corrosion resistant anchor cable of this example is shown in FIG. Figure 3 , as can be seen from the figure, its organization is Sorbite organization.

[0038] Comparative Example 1: A low alloy anchor cable containing the following chemical components by mass percentage: C: 0.71%, Mn: 0.8%, Si: 0.21%, Cr: 0.2%, and the remainder being Fe and unavoidable impurities. The preparation process is the same as that of Example 1. The metallographic structure of the anchor cable prepared in this comparative example is shown in FIG. Figure 4 ,Depend on Figure 4 It can be seen that its organization is Sorb body organization.

[0039] The anchor cables prepared in the examples and comparative examples were tested, and their mechanical properties are shown in Table 1.

[0040] Table 1 Mechanical properties of anchor cables

[0041]

[0042] The stress corrosion sensitivity of different samples was analyzed by stress-strain curves, and the section shrinkage loss and elongation loss were measured. The results are as follows: Figure 5 It can be seen that the anchor cables prepared in Examples 1-3 have lower stress corrosion sensitivity than the comparative example, that is, the present invention can effectively improve the stress corrosion cracking resistance of the anchor cables.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A low alloy anchor cable resistant to stress corrosion, characterized in that: The invention relates to a low-alloy anchor cable steel having the following chemical components in percentage by mass: C: 0.4-0.6%, Si: 0.2-0.25%, Mn: 0.7-0.9%, Cr: 0.1-0.5%, Ni: 1.2-1.8%, Sb: 0.04-0.06%, Nb: 0.03-0.05%, Cu: 0.4%-0.6%; the remainder is Fe and unavoidable impurities; the mass ratio of Ni to Cu in the low-alloy anchor cable steel is greater than 2.5; the addition ratio of Cu to Sb is 10:1; and the method for preparing the stress corrosion resistant low-alloy anchor cable comprises the following steps: (1) preparing raw materials according to the chemical composition, and smelting to obtain molten steel; then casting the molten steel into ingots; (2) rolling the ingot at a temperature of 950-1030° C. for 10-12 passes to form a steel wire; (3) spray cooling the steel wire to 400-450° C. to generate a sorbite structure; (4) Air cooling to room temperature and then cold drawing; (5) Keep the cold-drawn steel wire at 200-300°C for 2-5 hours to obtain an anchor cable.

2. The stress corrosion resistant low alloy anchor cable according to claim 1, characterized in that: The final rolling temperature of step (2) is 850-900°C, and the diameter of the steel wire is 12 mm.

3. The stress corrosion resistant low alloy anchor cable according to claim 1, characterized in that: The cooling rate in step (3) is 10-20°C / s.

4. The stress corrosion resistant low alloy anchor cable according to claim 1, characterized in that: The number of cold drawing passes in step (4) is 4, and the diameter of the steel wire after cold drawing is 6 mm.

Images