Corrosion-resistant bolt steel and smelting method thereof

Abstract

The invention discloses corrosion-resistant bolt steel which comprises the following components in percentage by weight: 0.15%-0.45% of C, 0.10%-0.60% of Si, 0.30%-1.30% of Mn, less than or equal to 1.00% of Ni, less than or equal to 1.00% of Cu, less than or equal to 0.10% of Sn, less than or equal to 0.10% of Al, less than or equal to 0.10% of Ti, less than or equal to 0.030% of P, less than or equal to 0.010% of S and the balance of Fe and a small amount of inevitable impurities. Meanwhile, the invention discloses a smelting method of the corrosion-resistant bolt steel. The novel corrosion-resistant bolt steel is developed by adopting Ni + Cu + Sn micro-alloy component design and a route of EAF electric furnace + LF refining + VD vacuum refining + continuous casting smelting, the corrosion resistance of the bolt steel is ensured, and the engineering application requirements are met.

Description

Technical Field

[0001] The invention relates to the field of bolt steel, and in particular to a corrosion-resistant bolt steel and a smelting method thereof. Background Art

[0002] At present, the construction of transportation tunnels is developing in a blowout manner, and the amount of tunnel projects is increasing year by year. The corrosion environment of these submarine, river-crossing, mountain, subway and other transportation tunnels is complex, including sand and gravel bottom conditions, riverside water-rich environment, ground fissure environment, complex urban environment, high temperature and high humidity environment, etc.

[0003] Existing tunnel segment bolts are generally made of ordinary steel such as 45 and 40Cr, and are generally treated with zinc infiltration + salt-alkali resistance layer + electrophoretic long-term anti-corrosion coating. However, due to the influence of leakage water, ion corrosion, stray current, etc., the corrosion problem is still serious and does not meet the design requirement of durability of not less than 100 years.

[0004] In view of the complex environment and durability requirements of tunnels, the only way to solve the problem is to develop a bolt steel that is inherently corrosion-resistant to meet the urgent needs of the project. Summary of the invention

[0005] Purpose of the invention: In view of the shortcomings and defects of the prior art, the present invention provides a corrosion-resistant bolt steel and a smelting method thereof, adopts Ni+Cu+Sn micro-alloy composition design, EAF electric furnace + LF refining + VD vacuum refining + continuous casting smelting route, and develops a new type of corrosion-resistant bolt steel to ensure the corrosion resistance of the bolt steel and meet the needs of engineering applications.

[0006] Technical solution: A corrosion-resistant bolt steel of the present invention is characterized in that it includes the following components in weight percentage: C: 0.15% to 0.45%, Si: 0.10% to 0.60%, Mn: 0.30% to 1.30%, Ni: ≤1.00%, Cu: ≤1.00%, Sn: ≤0.10%, Al: ≤0.10%, Ti: ≤0.10%, P: ≤0.030%, S: ≤0.010%, and the balance is Fe and a small amount of inevitable impurities.

[0007] The smelting method of the corrosion-resistant bolt steel of the present invention is characterized by adopting a Ni+Cu+Sn micro-alloy composition design and adopting a smelting route of EAF electric furnace+LF refining+VD vacuum refining+continuous casting to make the steel.

[0008] Among them, the EAF electric furnace process adds molten iron + high-quality scrap steel + part of the alloy, adopts low phosphorus and low sulfur control, and the steel tapping end point P≤0.020%;.

[0009] Wherein, in the LF refining process, the composition is adjusted to the control range, the LF furnace adopts white slag operation, the white slag retention time is ≥30min, and the refining time is ≥35min.

[0010] The VD vacuum refining process reduces the O, N and H gas contents in the molten steel, with the vacuum holding time being ≥15 min, the static stirring time being ≥20 min, and H ≤3.0 ppm.

[0011] Among them, in the continuous casting process, the continuous casting is performed with full protection pouring, electromagnetic stirring of the crystallizer, and the crystallizer liquid level fluctuation is controlled to ≤±10mm.

[0012] Beneficial effect: Compared with the prior art, the present invention has the following significant advantages: In view of the problem of insufficient corrosion resistance of existing tunnel segment bolt steel, the present invention adopts Ni+Cu+Sn micro-alloy composition design, EAF electric furnace + LF refining + VD vacuum refining + continuous casting smelting route to develop a new type of corrosion-resistant bolt steel to meet the corrosion resistance performance. The samples of the bolt steel quenched and tempered long-term anti-corrosion coating are subjected to a neutral salt spray test in accordance with GB / T10125-20123.2.2, and no red rust appears for at least 1000 hours; and no red rust appears for at least 800 hours in a wet heat test in accordance with GB / T 2423.3-2016. DETAILED DESCRIPTION

[0013] The technical solution of the present invention is further described below in conjunction with specific implementation methods.

[0014] Example:

[0015] The corrosion-resistant bolt steel in this embodiment is a Φ25mm bar, which is designed with Ni+Cu+Sn micro-alloy composition, EAF electric furnace + LF refining + VD vacuum refining + continuous casting smelting route, and the bar is rolled to obtain the finished product that meets the technical requirements. The specific requirements are as follows:

[0016] 1) The chemical components of the corrosion-resistant bolt steel are as follows by weight percentage: C: 0.32%, Si: 0.28%, Mn: 0.8%, Ni: ≤1%, Cu: ≤1%, Sn: ≤0.1%, Al: 0.03%, Ti: 0.018%, P: 0.02%, S: 0.01%, and the balance is Fe and a small amount of unavoidable impurities.

[0017] 2) EAF process, adding molten iron + high-quality scrap steel + part of alloy, adopting low phosphorus and low sulfur control, the steel tapping end point P ≤ 0.02%.

[0018] 3) LF refining process, the composition is adjusted to the control range, the LF furnace adopts white slag operation, the white slag holding time is 32 minutes, and the refining time is 36 minutes.

[0019] 4) VD vacuum refining process, to reduce the content of gases such as O, N, H in molten steel, vacuum holding time 15min, static stirring time 20min, H≤2ppm.

[0020] 5) Continuous casting process: full protection pouring is performed, the crystallizer is electromagnetically stirred, and the crystallizer liquid level fluctuation is controlled to ≤±10mm.

[0021] The anti-corrosion bolt steel produced by the above process and the samples of long-term anti-corrosion coating on bolt steel in quenched and tempered state were subjected to neutral salt spray test in accordance with GB / T10125-20123.2.2, and no red rust appeared after 1000 hours; the wet heat test was carried out in accordance with GB / T 2423.3-2016, and no red rust appeared after 800 hours. All the tests were qualified.

Claims

1. A corrosion-resistant bolt steel, characterized in that: The invention comprises the following components in weight percentage: C: 0.15% to 0.45%, Si: 0.10% to 0.60%, Mn: 0.30% to 1.30%, Ni: ≤1.00%, Cu: ≤1.00%, Sn: ≤0.10%, Al: ≤0.10%, Ti: ≤0.10%, P: ≤0.030%, S: ≤0.010%, and the balance is Fe and a small amount of inevitable impurities.

2. The smelting method of corrosion-resistant bolt steel according to claim 1, characterized in that: It is designed with Ni+Cu+Sn micro-alloy composition and is made by the smelting route of EAF electric furnace + LF refining + VD vacuum refining + continuous casting.

3. The smelting method of corrosion-resistant bolt steel according to claim 1, characterized in that: The EAF electric furnace process adds molten iron + high-quality scrap steel + part of alloy, adopts low phosphorus and low sulfur control, and the steel tapping end point P≤0.020%;.

4. The smelting method of corrosion-resistant bolt steel according to claim 1, characterized in that: In the LF refining process, the composition is adjusted to the control range, the LF furnace adopts white slag operation, the white slag retention time is ≥30min, and the refining time is ≥35min.

5. The smelting method of corrosion-resistant bolt steel according to claim 1, characterized in that: The VD vacuum refining process reduces the O, N, and H gas contents in molten steel, with a vacuum holding time of ≥15 min, a static stirring time of ≥20 min, and H ≤3.0 ppm.

6. The method for smelting corrosion-resistant bolt steel according to claim 1, characterized in that: In the continuous casting process, the continuous casting is performed with full protection pouring, electromagnetic stirring of the crystallizer, and the crystallizer liquid level fluctuation is controlled to ≤±10mm.