CN115478222A

CN115478222A - Non-magnetic stainless steel with high purity and corrosion resistance and smelting method thereof

Info

Publication number: CN115478222A
Application number: CN202211174863.1A
Authority: CN
Inventors: 王怡群; 雷冲; 李占华; 高全德; 李玉标; 王文洋; 郑安雄; 周鹏; 马姣
Original assignee: Henan Zhongyuan Special Steel Equipment Manufacturing Co Ltd
Current assignee: Henan Zhongyuan Special Steel Equipment Manufacturing Co Ltd
Priority date: 2022-09-26
Filing date: 2022-09-26
Publication date: 2022-12-16
Anticipated expiration: 2042-09-26
Also published as: CN115478222B

Abstract

The invention relates to a non-magnetic stainless steel with high purity and corrosion resistance and a smelting method thereof, wherein an electric arc furnace or a converter is adopted to smelt primary molten steel; melting the alloy through an alloy melting furnace; blowing oxygen for decarburization in an argon-oxygen furnace until the carbon content is less than or equal to 0.015 percent, and then alloying manganese by using electrolytic manganese metal; stirring by argon to remove hydrogen in the molten steel; carrying out deoxidation and desulfurization on the reduction slag after slagging off; alloying nitrogen by nitrogen increasing; the purity of the molten steel is further improved through ladle furnace refining and calcium treatment; the invention can solve the problem that the corrosion resistance of the non-magnetic stainless steel is influenced by poor purity and coarse crystal grains, and can produce the non-magnetic stainless steel with high purity and corrosion resistance in batches.

Description

Non-magnetic stainless steel with high purity and corrosion resistance and smelting method thereof

Technical Field

The invention belongs to the technical field of metal smelting, and particularly relates to non-magnetic stainless steel with high purity and corrosion resistance and a smelting method thereof.

Background

The non-magnetic stainless steel is widely applied to the exploration and exploitation of petroleum and natural gas due to the excellent corrosion resistance, good impact toughness and low magnetism, and the non-magnetic property of the material is utilized to avoid the interference of a geological magnetic field on an exploration instrument and the remote sensing orientation of a drill bit underground; the drilling operation is carried out on high-sulfur and high-chlorine geology seriously eroded by underground corrosive medium by utilizing the high comprehensive performance and the high corrosion resistance of the material.

In order to reduce the cost and ensure the austenitic structure and high strength of the material, nickel-saving high-manganese high-nitrogen steel is generally selected, but the high manganese content easily causes coarse material grains, meanwhile, the alloying of a large amount of manganese causes the high MnO inclusion in the steel, the purity of the material is poor, and the coarse grains and the poor purity influence the corrosion resistance of the material to cause the failure of the material.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a non-magnetic stainless steel with high purity and corrosion resistance and a smelting method thereof, wherein the method adopts an electric arc furnace or a converter to smelt primary molten steel; melting the alloy through an alloy melting furnace; blowing oxygen for decarburization in an argon-oxygen furnace until the carbon content is less than or equal to 0.015 percent, and then alloying manganese by using electrolytic manganese metal; stirring by argon to remove hydrogen in the molten steel; carrying out deoxidation and desulfurization on the reduction slag generated after slagging-off; alloying nitrogen by nitrogen increasing; the purity of the molten steel is further improved through ladle furnace refining and calcium treatment; the purity of the molten steel is further improved and the non-magnetic stainless steel crystal grains are refined through rare earth cerium microalloying. The invention can solve the problem that the corrosion resistance of the non-magnetic stainless steel is influenced by poor purity and coarse crystal grains, and can produce the non-magnetic stainless steel with good purity and corrosion resistance in batches.

The purpose of the invention is realized by the following technical scheme:

the non-magnetic stainless steel with high purity and corrosion resistance is characterized by comprising the following chemical elements in percentage by mass: c = 0.01-0.06%, si = 0.10-0.60%, mn = 18.00-20.00%, P is less than or equal to 0.025%, S is less than or equal to 0.005%, ni = 3.00-4.50%, cr = 18.00-21.00%, mo = 1.50-2.50%, cu = 0.15-0.50%, nb = 0.02-0.10%, N = 0.50-0.70%, ce = 0.002-0.010%, al = 0.005-0.020%, and the balance of Fe and other unavoidable impurity elements;

a smelting method of non-magnetic stainless steel with high purity and corrosion resistance is characterized by comprising the following steps:

step 1), primarily smelting through an electric arc furnace or a converter, and reducing the phosphorus content of primarily smelted molten steel to be below 0.005 percent;

step 2), melting 200-300kg/t of high-carbon ferrochrome, 25-35kg/t of nickel plate and 20-30kg/t of ferromolybdenum through an alloy melting furnace to improve the yield of the alloy and accelerate the production efficiency, and adding the molten alloy and the primary molten steel obtained in the step 1) into an argon-oxygen furnace for smelting;

step 3), decarburization is carried out by dividing an argon-oxygen furnace into three stages, the oxygen lance and the air lance are opened for oxygen blowing decarburization in the first stage of decarburization according to the oxygen-nitrogen ratio of 5; when the carbon content in the steel is less than or equal to 0.45 percent, entering a decarburization second stage, stopping oxygen lance smelting, only starting an air lance for smelting, and controlling the oxygen-nitrogen ratio to be 1-1; entering a decarburization period III when the carbon content in the steel is less than or equal to 0.10%, controlling the oxygen-nitrogen ratio to be 1;

step 4), carrying out chromium reduction and manganese alloying in an argon-oxygen furnace, adding 20-25kg/t of ferrosilicon into the furnace for reduction when the carbon content in steel is less than or equal to 0.015%, and then adding 2-3 batches of electrolytic manganese metal for manganese alloying, wherein the addition amount of the electrolytic manganese metal is calculated according to 200-240kg/t, and the yield is considered according to 92% by weight;

step 5), carrying out temperature compensation on the argon oxygen furnace, wherein the alloying of manganese can cause the temperature of molten steel in the argon oxygen furnace to be greatly reduced, adding ferrosilicon or aluminum blocks for oxygen blowing and temperature rise, calculating according to the temperature reduced by the alloying of manganese, considering the increase of the oxygen blowing and temperature rise by 450-550 ℃, and calculating the specific dosage according to 3.88 kilograms of ferrosilicon or 2.87 kilograms of aluminum blocks required for the temperature rise of 100 ℃ per ton of molten steel;

step 6), after manganese alloying, switching the stirring gas into argon, and carrying out strong stirring for more than 1 minute according to the flow rate of 60m & lt 3 & gt/min to remove hydrogen brought by electrolytic manganese metal;

step 7), after alloying of manganese, oxygen blowing and temperature raising and argon stirring for dehydrogenation, the slag is slightly oxidizing and low in alkalinity, which is not beneficial to the purity of the molten steel, the slag needs to be removed, and 10-20kg/t of lime, 2-5kg/t of fluorite and 2-3kg/t of aluminum blocks are added again for deoxidation and desulfurization, so that the purity of the molten steel is improved;

step 8), nitrogen is blown by nitrogen to carry out nitrogen alloying, the flow of nitrogen is not lower than 40m < 3 >/h, nitrogen is blown to reach the nitrogen content of more than 0.50 percent, temperature measurement and sampling are carried out, AOD steel tapping is transferred into a ladle refining furnace for refining after the temperature and the components are qualified;

step 9), after the refining ladle is in place, adding 3-5kg/t of lime and 2-3kg/t of fluorite powder to adjust the slag, adding 1-3kg/t of calcium silicate powder to diffuse and deoxidize the slag by more than 3 batches, controlling the [ S ] to be less than or equal to 0.003%, feeding 3-5m/t of calcium silicate wire, weakly stirring the molten steel for 8 minutes at a nitrogen flow of 30-50NL/min, then adjusting the nitrogen flow to 100NL/min to expose the molten steel, adding rare earth cerium wrapped by iron sheet at the exposed part, calculating the addition rate according to 30%, then continuing weakly stirring the molten steel for more than 10 minutes at a nitrogen flow of 30-50L/min, and pouring by hanging a ladle at a temperature of 1470-1490 ℃.

Preferably, in order to ensure the intergranular corrosion capability of the non-magnetic stainless steel, the carbon content needs to be controlled to be less than or equal to 0.03 percent, and in order to achieve the control target, the ferrosilicon for reduction in the argon-oxygen furnace in the step 4) requires that C is less than or equal to 0.05 percent, and electrolytic manganese metal requires that C is less than or equal to 0.03 percent.

Preferably, the rare earth cerium used in the step 9) requires that the cerium content is more than or equal to 65 percent.

The method of the invention has the following advantages:

the invention provides a non-magnetic stainless steel with high purity and corrosion resistance and a smelting method thereof, and the alloy is melted by an alloy melting furnace, so that the smelting period of an argon-oxygen furnace and the corrosion of refractory materials are shortened; the decarburization is reasonably distributed in three stages of the argon-oxygen furnace, so that the phenomena of furnace lining erosion and oxidation of oxide powder caused by large temperature gradient of the argon-oxygen furnace can be avoided; by reasonably adding electrolytic manganese metal in batches and compensating the temperature, on one hand, the furnace lining erosion caused by the large temperature gradient of the argon-oxygen furnace is avoided, on the other hand, the yield of manganese is improved, and the molten steel is prevented from being polluted by a large amount of manganese oxidized into MnO; the partial pressure of hydrogen is reduced by strong stirring of argon, and dehydrogenation treatment is carried out in an argon-oxygen furnace, so that the influence of hydrogen brought into molten steel by electrolytic manganese on the purity is reduced; further deoxidizing and desulfurizing through argon-oxygen furnace secondary slagging to improve the purity of the molten steel; through ladle furnace refining and calcium treatment, the purity of the molten steel is further improved, and the inclusion is subjected to denaturation treatment; by microalloying rare earth cerium and designing the adding time and the adding method of the rare earth microalloying, the yield of the rare earth cerium is improved, the influence of inclusions on the quality of molten steel is avoided, the purity of the molten steel is further improved, and nonmagnetic stainless steel grains are refined. The invention can solve the problem that the corrosion resistance of the non-magnetic stainless steel is influenced by poor purity and coarse crystal grains, and can produce the non-magnetic stainless steel with high purity and corrosion resistance in batches.

Drawings

FIG. 1 is a flow chart of the present invention.

Detailed Description

The following examples are provided to further illustrate the embodiments of the present invention, and the specific examples described herein are only for the purpose of explaining the present invention and are not intended to limit the scope of the present invention. The following description of the embodiments of the present invention is made with reference to the accompanying drawings 1: example 1: a non-magnetic stainless steel with high purity and corrosion resistance and a smelting method thereof are disclosed: primary smelting of molten steel: smelting by adopting a 60-ton electric arc furnace, and finishing the end point [ C ]:0.06%, [ P ]:0.004 percent, the tapping temperature is 1660 ℃, and after tapping, the ladle is hung to an alloy melting furnace to receive the alloy molten iron.

Melting alloy in an alloy melting furnace: the furnace burden comprises 16 tons of high-carbon ferrochrome, 2 tons of nickel plates and 1.5 tons of ferromolybdenum, after the electric furnace taps, the steel ladle is arranged in an alloy melting furnace to receive molten alloy iron, and then the steel ladle is hung in an argon-oxygen furnace to be added with steel.

Blowing oxygen for decarburization in an argon-oxygen furnace: 1000 kg of lime is added into the furnace in advance, and the components of the added molten steel are shown in table 1.

TABLE 1 molten steel ingredients (mass%) added in an argon-oxygen furnace

Element(s)	C	Si	Mn	P	S	Cr	Ni	Mo	Cu	Al
											Composition (I)	1.1	0.45	0.70	0.015	0.009	19.80	5.60	3.0	0.20	0.015

And in the first stage of decarburization, an oxygen lance and an air lance are started to blow oxygen for decarburization, and 3000 kg of lime and 5000 kg of high-carbon ferrochrome are added in four batches at the temperature of 1700 ℃. Closing the oxygen lance when the carbon content is 0.50 percent; sampling at 1720 ℃ with the carbon content of 0.10%, adding 200kg of ferrosilicon into the sample, and reducing for 4 minutes.

When the carbon content is 0.40 percent, the second stage of decarburization is carried out, the oxygen lance is closed, and only the air lance is opened for smelting; the decarburization period is started when the carbon content is 0.08 percent, sampling is carried out at the temperature of 1720 ℃, and the reduction of chromium and the alloying of manganese are carried out when the carbon content is 0.015 percent.

Reduction in an argon-oxygen furnace, alloying of manganese and dehydrogenation: 1400kg of ferrosilicon is added and reduced for 8 minutes. 13000 kg of electrolytic manganese metal and 1100 kg of aluminum are added in three batches for manganese alloying and oxygen blowing and temperature rising, and then argon gas is stirred for 1 minute to remove hydrogen brought by the electrolytic manganese. Then sampling and measuring the temperature, wherein the temperature is 1680 ℃.

And (3) deoxidation and desulfurization in an argon-oxygen furnace and alloying of nitrogen: after more than 60% of slag is removed, 600 kg of lime, 200kg of fluorite and 150 kg of aluminum blocks are added again for slagging, the nitrogen flow is 50m & lt 3 & gt/h, stirring is carried out for 40 minutes, sampling components are qualified, tapping is carried out at the temperature of 1570 ℃, and the steel is transferred to a ladle refining furnace for refining after tapping.

6) Refining in a ladle refining furnace and microalloying rare earth cerium: 200kg of lime and 120kg of fluorite powder are added into a steel ladle after the steel ladle is in place, electric slagging is carried out, 120kg of calcium silicate powder is added into the steel ladle in four batches to carry out diffusion deoxidation on the slag, sampling [ S ] =0.002%, feeding a calcium silicate wire 200m, carrying out weak stirring on molten steel for 8 minutes at a nitrogen flow rate of 40NL/min, then adjusting the nitrogen flow rate to 100NL/min to expose the molten steel, adding 10 kg of rare earth cerium wrapped by an iron sheet into the exposed part, then continuing to carry out weak stirring on the molten steel for 12 minutes at the nitrogen flow rate of 40NL/min, and carrying out ladle hanging pouring at the temperature of 1490 ℃. The composition before tapping is shown in Table 2.

TABLE 2 molten steel composition before tapping (mass%,%)

Element(s)	C	Si	Mn	P	S	Cr	Ni	Mo	N	Cu	Nb	Ce
													Composition (I)	0.02	0.35	19.00	0.018	0.002	18.60	3.60	1.80	0.54	0.25	0.03	0.0035

Claims

1. The non-magnetic stainless steel with high purity and corrosion resistance is characterized by comprising the following chemical elements in percentage by mass: 0.01 to 0.06 percent of C, 0.10 to 0.60 percent of Si, 18.00 to 20.00 percent of Mn, less than or equal to 0.025 percent of P, less than or equal to 0.005 percent of S, 3.00 to 4.50 percent of Ni, 18.00 to 21.00 percent of Cr, 1.50 to 2.50 percent of Mo, 0.15 to 0.50 percent of Cu, 0.02 to 0.10 percent of Nb, 0.50 to 0.70 percent of N, 0.002 to 0.010 percent of Ce, 0.005 to 0.020 percent of Al, and the balance of Fe and other inevitable impurity elements.

2. A smelting method of non-magnetic stainless steel with high purity and corrosion resistance is characterized by comprising the following steps:

step 3), decarburization is carried out in three stages through an argon-oxygen furnace, the oxygen lance and the air lance are started for oxygen blowing decarburization in the first decarburization stage according to the oxygen-nitrogen ratio of 5, in order to avoid the condition that the temperature is too high to erode a furnace lining during decarburization, 30-50kg/t of lime and 80-100kg/t of high-carbon ferrochrome are added during oxygen blowing decarburization, and the temperature is controlled to be not more than 1700 ℃; when the carbon content in the steel is less than or equal to 0.45 percent, entering a decarburization second stage, stopping oxygen lance smelting, only starting an air lance for smelting, and controlling the oxygen-nitrogen ratio to be 1-1; entering a decarburization period III when the carbon content in the steel is less than or equal to 0.10%, controlling the oxygen-nitrogen ratio to be 1;

step 4), carrying out chromium reduction and manganese alloying in an argon-oxygen furnace, adding 20-25kg/t of ferrosilicon into the furnace for reduction when the carbon content in steel is less than or equal to 0.015 percent, and then adding 2-3 batches of electrolytic manganese metal for manganese alloying, wherein the adding amount of the electrolytic manganese metal is calculated according to 200-240kg/t, and the yield is considered according to 92 percent by weight;

step 6), after manganese alloying, switching the stirring gas into argon, and carrying out strong stirring for more than 1 minute according to the flow of 60m & lt 3 & gt/min to remove hydrogen brought by electrolytic manganese metal;

3. The method of claim 2, wherein the C content of the non-magnetic stainless steel is controlled to be less than or equal to 0.03% to ensure the intergranular corrosion resistance of the non-magnetic stainless steel, and for this purpose, the Si-Fe for reduction in the argon-oxygen furnace requires C to be less than or equal to 0.05% and the electrolytic manganese metal requires C to be less than or equal to 0.03%.

4. The method for smelting a non-magnetic stainless steel with high purity and corrosion resistance according to claim 2, wherein the cerium content of the rare earth cerium is required to be not less than 65%.