TWI751454B - High-strength corrosion-resistant austenitic iron stainless steel alloy and manufacturing method thereof - Google Patents

Abstract

A method for manufacturing a stainless steel alloy of Wostian iron, comprising the following steps: a temperature-maintaining smelting step: placing a plurality of smelting raw materials in an induction smelting equipment, extracting the air in the induction smelting equipment, and then introducing a pressure of 10-30 atmospheres After the nitrogen is removed, the smelting raw materials are smelted into a stainless steel molten soup with high nitrogen and low nickel content at a smelting temperature, wherein the smelting temperature is lower than the casting temperature of the stainless steel molten soup, and the smelting raw materials include iron-containing materials, The vanadium-containing material, the chromium-containing material, the molybdenum-containing material, the silicon-containing material, the nickel-containing material and the manganese-containing material; and a stainless steel molten soup solidification step: casting the stainless steel molten soup to solidify into a Vostian iron stainless steel alloy.

Description

High-strength and corrosion-resistant Vostian iron stainless steel alloy and its manufacturing method

The present invention relates to a stainless steel alloy and a manufacturing method thereof, and in particular to a high-strength corrosion-resistant Vostian iron stainless steel alloy and a manufacturing method thereof.

According to the definition of EN 10088-1, the steel is called stainless steel when it contains at least 10.5wt% chromium and no more than 1.2wt% carbon. Stainless steel has better corrosion resistance and heat resistance than ordinary steel, and can always maintain metallic luster in the atmosphere. The principle of stainless steel corrosion resistance is: chromium forms a continuous and dense oxide film (commonly known as passive film) on the metal surface. This passivation film can isolate the metal from contact with the external environment, so it has the function of corrosion resistance. The passivation film on the stainless steel surface can isolate the contact between the metal and the external environment. Different from the general carbon steel coating material, even if the surface passivation film is scratched by external force, it can still repair itself and generate a new surface passivation film. The corrosion resistance is related to the stability of the passive film, which is not only related to the chemical composition of stainless steel, but also related to the type, temperature, pressure, flow rate, etc. of the corrosive medium.

Wostian iron stainless steel alloys are mainly added elements of chromium, nickel and manganese, which are divided into 200 and 300 series. 200 series stainless steel and 300 series stainless steel belong to the Austenitic series. The method of 300 series stainless steel to maintain the iron structure of the Wostian is to add nickel, while the 200 series reduces the content of nickel and chromium, and increases the content of manganese and nitrogen to maintain the stability of the iron structure of the Wostian. Some 200 series stainless steels will add copper, which can not only stabilize the iron structure of the Wostian, but also improve the formability of the material.

The characteristics and application of Wostian iron series stainless steel alloy: its mechanical properties cannot be changed by heat treatment (no quench hardenability), but it has excellent ductility and toughness. It is often processed at low temperature to make it work hardening to increase strength and hardness. Wostian iron series stainless steel is resistant to general corrosion (General Corrosion), but has inter-granular corrosion (Inter-granular corrosion). Corrosion), the reason is that the temperature of 600 ~ 800 ℃ heating, the precipitation of chromium carbide recrystallized grain boundaries.

Since the composition of nickel is used to reduce the corrosion rate of the stainless steel, but the price of nickel is relatively expensive, so for the new generation of stainless steel materials, the resource-saving high nitrogen and low nickel stainless steel alloy with nitrogen instead of nickel came into being. Stainless steel alloys with high nitrogen and low nickel content still have high strength and low corrosion rates.

High-nitrogen and low-nickel Vostian iron stainless steel alloy means that the nitrogen content in the stainless steel is higher than that in the stainless steel produced by smelting in the atmosphere. The maximum nitrogen content is about 0.05% by weight. In today's industrial production, stainless steel melting processes generally use electric arc furnaces, induction furnaces, converters, oxygen-argon decarburization furnaces, or vacuum oxygen decarburization furnaces (VOD furnaces) to smelt stainless steel in atmospheric or low vacuum environments. Taking the melting of stainless steel in a large VOD furnace as an example, nitrogen is blown into the bottom of the furnace to increase the nitrogen content of the stainless steel.

Furthermore, if the nitrogen content of the stainless steel needs to be increased, for example, a nitride-containing alloy is often added in the smelting process. This method can produce a stainless steel material with a nitrogen content of about 0.7% by weight at most. Melting under high nitrogen pressure is also an effective method to increase the solubility of nitrogen in stainless steel. Fe-Cr-Mn iron stainless steel is smelted under high nitrogen pressure (nitrogen pressure up to 50 atmospheres) to produce a nitrogen content of 0.8% by weight. -1.5% or 0.8-1.8% stainless steel material, but this kind of high-pressure smelting equipment is expensive and consumes a lot of nitrogen during production, resulting in increased manufacturing costs, and smelting under high pressure also increases the risk of the process.

Therefore, there is a need to provide a high-strength corrosion-resistant Vostian iron stainless steel alloy with high nitrogen and low nickel content to solve the aforementioned problems.

One object of the present invention is to provide a method for producing a high-strength corrosion-resistant Vostian iron stainless steel alloy, which is smelted at a temperature lower than the casting temperature of the stainless steel molten bath.

According to the above-mentioned purpose, the present invention provides a method for manufacturing a stainless steel alloy of Wostian iron, comprising the following steps: a temperature-maintaining smelting step: placing a plurality of smelting raw materials in an induction smelting equipment, and extracting the air in the induction smelting equipment After the nitrogen gas of 10 to 30 atmospheres is introduced, the smelting raw materials are melted into a stainless steel molten soup with high nitrogen and low nickel content with a smelting temperature maintained at a temperature, wherein the smelting temperature is lower than the casting temperature of the stainless steel molten soup, The smelting raw materials include iron-containing materials, vanadium-containing materials, chromium-containing materials, molybdenum-containing materials, silicon-containing materials, nickel-containing materials and manganese-containing materials; and a stainless steel molten soup solidification step: casting the stainless steel molten soup to solidify Into a Vostian iron stainless steel alloy.

The present invention further provides a Vostian iron stainless steel alloy, calculated based on its total weight of 100w%, the Vostian iron stainless steel alloy includes the following elements: 16-18% of chromium, 1-5% of nickel, 0.7-1.0% of Nitrogen, 1~3% molybdenum, ≤ 0.075% carbon, ≤ 1% silicon, ≤ 2% manganese and 0.1~1% vanadium, phosphorus ≤ 0.045% and sulfur ≤ 0.03%, the rest is iron and unavoidable impurities.

The high-strength corrosion-resistant Vostian iron stainless steel alloy of the present invention has high nitrogen and low nickel content. Compared with the Fe-Cr-Mn iron stainless steel of the prior art, which must be smelted under high nitrogen pressure (nitrogen pressure as high as 50 atmospheres), the induction melting equipment of the present invention only needs to be smelted in a nitrogen environment of 10-30 atmospheres at a low temperature. It is not necessary to increase nitrogen solubility with nitrogen pressure as high as 50 atmospheres by holding temperature melting at the casting temperature of the stainless steel molten bath, which can avoid the consumption of a large amount of nitrogen, reduce the increase in manufacturing cost, and avoid the need for smelting under high pressure of 50 atmospheres. Increased process hazard.

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FIG. 1 is a flow chart of a manufacturing method of a high-strength corrosion-resistant Vostian iron stainless steel alloy according to an embodiment of the present invention.

Figure 2, which shows the effect of various alloying elements on the nitrogen solubility of liquid iron at 1600°C.

In order to make the above objects, features and characteristics of the present invention more obvious and easy to understand, the relevant embodiments of the present invention are described in detail as follows in conjunction with the drawings.

FIG. 1 is a high-strength corrosion-resistant Wasser field according to an embodiment of the present invention. The flow chart of the manufacturing method of iron stainless steel alloy. The manufacturing method of high-strength and corrosion-resistant Vostian iron stainless steel alloy includes the following steps: (1) temperature-smelting step S1: placing a plurality of smelting raw materials of stainless steel alloy in an induction smelting equipment, and extracting the air in the induction smelting equipment , after introducing 10~30 atmospheres (atm) of nitrogen, and smelting at a smelting temperature, the smelting raw materials are melted into a stainless steel molten soup with high nitrogen and low nickel content, wherein the melting temperature is lower than the casting temperature of the stainless steel molten soup , these smelting raw materials include iron-containing materials, vanadium-containing materials, chromium-containing materials, molybdenum-containing materials, silicon-containing materials, nickel-containing materials and manganese-containing materials; Casting to solidify into a stainless steel alloy of Worcestershire.

For example, the temperature-smelting step S1 of the present invention refers to, after vacuuming, under a nitrogen atmosphere of 10-30 atmospheres, smelting iron-based alloys, ferrovanadium, ferrochromium, ferromolybdenum, nickel-containing materials and manganese-containing materials, etc. The smelting temperature range is about 1385-1455 degrees Celsius (this temperature range is lower than the casting temperature range of the stainless steel molten bath is about 1580-1620 degrees Celsius) for at least 15 minutes of sustained temperature smelting to melt and mix the smelting raw materials. The smelting temperature is between the highest melting point and the lowest melting point of one of the smelting raw materials. Ferrosilicon may be added to the smelting raw materials, so that the smelting raw materials further contain silicon components after being smelted.

Since the higher the molten temperature of the stainless steel alloy in the smelting process, the smaller the effect of nitrogen solubility, the smelting temperature range of 1385-1455 degrees Celsius is the temperature range that can be smelted and is the best nitrogen solubility. In this way, the induction melting equipment only needs to Temperature smelting is carried out in a nitrogen atmosphere of 10~30 atmospheres, without the need to increase nitrogen solubility with nitrogen pressures up to 50 atmospheres.

Please refer to Figure 2, which shows the effect of various alloying elements on the nitrogen solubility of liquid iron at 1600°C. The effects of the various alloying elements were normalized relative to the effect of chromium (Cr) (the interaction coefficient of each alloying element divided by the chromium (Cr) coefficient). Due to the addition of vanadium (V) element in the present invention, it has a better nitrogen absorption function, so the solubility of nitrogen can also be increased. Nitrogen added to stainless steel as an alloying element has the effect of stabilizing the Wasserian iron structure and improving the mechanical properties and corrosion resistance of the Wasserian stainless steel. In addition, the alloy composition of nitrogen (N) element can expand the temperature range in which the Worcester iron phase exists stably, promoting the The Wostian iron phase can be reformed during the cooling process, so that the corrosion resistance and mechanical properties of the alloy are not greatly damaged by welding, and the tensile strength, pitting corrosion resistance and crevice corrosion resistance of low-nickel stainless steel alloys can be improved.

In another embodiment, in the temperature-sustaining smelting step S1 of the present invention, nitrogen-containing materials (such as iron nitride) can also be added to the smelting raw materials for melting into the induction smelting equipment, so that nitrogen can be increased. Proportion and uniformity in stainless steel molten soup.

Please refer to FIG. 1 again, the stainless steel molten steel solidification step S2 of the present invention casts the stainless steel molten soup, and after rapid cooling, it can be solidified into a stainless steel alloy with high nitrogen and low nickel content, thereby making the solidified stainless steel alloy Including by weight percentage: 16~18% chromium (Cr), 1~5% nickel (Ni), 0.5~1.0% nitrogen (N), 1~3% molybdenum (Mo), ≦0.075% Carbon (C), ≤ 1% silicon (Si), ≤ 2% manganese (Mn), 0.1~1% vanadium (V), and the rest are iron and inevitable impurities. Preferably, the stainless steel alloy includes 0.7-1.0% nitrogen (N). In detail, when the aforementioned materials are added to the induction melting equipment to form a molten alloy, the weight composition ratio of the molten alloy in the melting equipment is then sampled and measured, so as to determine that the composition weight percentage of the molten stainless steel molten soup is maintained at: 16~ 18% chromium, 1~5% nickel, 0.5~1.0% nitrogen, 1~3% molybdenum, ≤ 0.075% carbon, ≤ 1% silicon, ≤ 2% manganese, 0.1~1% vanadium , the rest is iron and inevitable impurities. Preferably, the stainless steel molten soup includes 0.7-1.0% nitrogen (N).

The alloy material also contains some impurities, such as sulfur (S), phosphorus (P) and other components. In terms of weight percentage, phosphorus is preferably less than 0.045%, and sulfur is preferably less than 0.03%. In this way, the above-mentioned composition ratio of the melt-mixed alloy is maintained, and after cooling and solidification, the stainless steel alloy with high nitrogen and low nickel content of the present invention can be obtained.

Please refer to Table 1, which is a table of differences between Embodiments 1 to 4 in different proportions of the present invention and Comparative Examples 11 and 12 of the previous case, as follows:

To sum up, the high-strength corrosion-resistant Vostian iron stainless steel alloy of the present invention has high nitrogen and low nickel content. Compared with the Fe-Cr-Mn iron stainless steel of the prior art, which must be smelted under high nitrogen pressure (nitrogen pressure as high as 50 atmospheres), the induction melting equipment of the present invention only needs to be smelted in a nitrogen environment of 10-30 atmospheres at a low temperature. It is not necessary to increase nitrogen solubility with nitrogen pressure as high as 50 atmospheres by holding temperature melting at the casting temperature of the stainless steel molten bath, which can avoid the consumption of a large amount of nitrogen, reduce the increase in manufacturing cost, and avoid the need for smelting under high pressure of 50 atmospheres. Increased process hazard.

To sum up, the present invention merely describes the preferred embodiments or examples of the technical means adopted by the present invention to solve the problem, and is not intended to limit the scope of the patent implementation of the present invention. That is, all the equivalent changes and modifications that are consistent with the context of the scope of the patent application of the present invention, or made in accordance with the scope of the patent of the present invention, are all covered by the scope of the patent of the present invention.

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Claims (7)

A method for manufacturing a stainless steel alloy of Wostian iron, comprising the following steps: a temperature-maintaining smelting step: placing a plurality of smelting raw materials in an induction smelting equipment, extracting the air in the induction smelting equipment, and then pouring it into the induction smelting equipment for 10-30 After nitrogen at atmospheric pressure, the smelting raw materials are smelted into a stainless steel molten soup with high nitrogen and low nickel content at a smelting temperature, wherein the smelting temperature is lower than the casting temperature of the stainless steel molten soup, and the smelting raw materials include iron material, vanadium-containing material, chromium-containing material, molybdenum-containing material, silicon-containing material, nickel-containing material, and manganese-containing material; and a stainless steel molten soup solidification step: casting the stainless steel molten soup to solidify into a Wostian iron stainless steel Alloys; wherein iron-based alloys, ferrovanadium, ferrochromium, ferromolybdenum, ferrosilicon, nickel-containing materials and manganese-containing materials are smelted under a nitrogen atmosphere of 10 to 30 atmospheres at a constant temperature; and the smelting temperature is between these smelting Between the highest melting point and the lowest melting point of one of the raw materials. The manufacturing method of the Vostian iron stainless steel alloy described in claim 1, wherein in the temperature-maintaining melting step: the temperature-maintaining melting is performed for at least 15 minutes in the melting temperature range of 1385-1455 degrees Celsius. The manufacturing method of the Vostian iron stainless steel alloy as described in item 2 of the patent application scope, wherein the casting temperature ranges from about 1580°C to 1620°C. A method for manufacturing a stainless steel alloy of Wostian iron, comprising the following steps: a temperature-maintaining smelting step: placing a plurality of smelting raw materials in an induction smelting equipment, extracting the air in the induction smelting equipment, and then pouring it into the induction smelting equipment for 10-30 After nitrogen at atmospheric pressure, the smelting raw materials are smelted into a stainless steel molten soup with high nitrogen and low nickel content at a smelting temperature, wherein the smelting temperature is lower than the casting temperature of the stainless steel molten soup, and the smelting raw materials include iron material, vanadium-containing material, chromium-containing material, molybdenum-containing material, silicon-containing material, nickel-containing material, and manganese-containing material; and a stainless steel molten soup solidification step: casting the stainless steel molten soup to solidify into a Wostian iron stainless steel Alloys; wherein the smelting raw materials further include nitrogen-containing materials. According to the manufacturing method of the Vostian iron stainless steel alloy described in item 4 of the patent application scope, the Vostian iron stainless steel alloy includes the following elements: 16-18% chromium, 1- 5% nickel, 0.7~1.0% nitrogen, 1~3% molybdenum, ≤ 0.075% carbon, ≤ 1% silicon, ≤ 2% manganese and 0.1~1% vanadium, the rest is iron and unavoidable impurities. The manufacturing method of the Vostian iron stainless steel alloy described in item 5 of the patent application scope, wherein the Vostian iron stainless steel alloy further comprises the following elements: phosphorus≦0.045% and sulfur≦0.03%. A Vostian iron stainless steel alloy, calculated based on its total weight of 100wt%, the Vostian iron stainless steel alloy includes the following elements: 16~18% chromium, 1~5% nickel, 0.701~1.0% nitrogen, 1 ~3% molybdenum, ≦0.075% carbon, ≦1% silicon, ≦2% manganese and 0.1~1% vanadium, phosphorus ≦0.045% and sulfur ≦0.03%, the rest is iron and inevitable impurities.

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