KR810001803B1 - Austenite stainless steel - Google Patents

Abstract

Hot workable austenitic stainless steel of improved pitting and crevice corrosion resistance to chloride ion, consists of (by wt.) 19-23% Cr, 1-16% Ni, 3-5% Mo, 2.5-15% Mn, <= 0.01% S, 0.01% of >= 1 of Cl, Ca and Mg, from 0.2% up to its solubility limit of N, <= 0.1% C, 1% Si, <= 3% Cu, <= 1% Nb, <= 0.3% V, <= 0.3% Ti, and balance Fe. The steel has a wt. loss of <= 1 pt. in 10,000 in a 72 hour, room temp., 10% FeCl3, 90% distilled water, rubber band test. Pref. steel contains 19.5-22% Cr, <= 0.38 (0.23-0.33)% N, 9-13% Ni, and 8-13.5% Mn.

Description

Austenitic stainless steel

The present invention relates to austenitic stainless steel.

On contact between the metal surface and the salt ions, a corrosion known to occur occurs, particularly in seawater, in chemical processes and in pumps and paper processing media. Most forms of corrosion progress at a uniform rate that can weaken, but the viscosity is unpredictable. The ignition concentrates on certain unpredictable parts of the metal surface, and once ignition begins, it concentrates on the ignition where chlorine ions have started, causing self-acceleration. Throughout this specification we include both meanings of pitting and crevise crevice corrosion. The attack form is described as crevice corrosion when it is present in form or through deposition in crevice corrosion.

The present invention relates to an austenitic alloy having high corrosion resistance, which exhibited a weight loss of less than 1 part in 10,000 in 72 hours of 10% ferric chloride and 90% distilled water lab band tests at room temperature. The special addition of chromium, especially molybdenum, increases the corrosion resistance or chromium and molybdenum are the elements that promote the phosphide, so the alloy should contain sufficient austenite promoting water to form austenite steel. These elements also include nickel and manganese (up to a certain level) copper and nitrogen, which simplify corrosion resistance. Austenitic steels have greater availability than ferritic and marsite steels because of their general blendability, including ease of welding, excellent strength and general corrosion resistance.

The alloy of the present invention is characterized by improved heating workability. This improvement can be obtained by the alloy being fully austenite and having a very low sulfur content. Low sulfur content can be obtained through the addition of calcium and manganese and the alloy is present only when the alloy has only traces of ferrite (usually 1-2%), depending on conventional steel preparations and any possible sigma or chi yarns. It is regarded as austenite within the limits of.

Some implementations of alloys have additional features that are particularly suitable for applications including welding. The chemical composition of this embodiment is carefully balanced to include a sufficient amount of element and especially a sufficient amount of manganese to increase the solubility of the alloy in nitrogen.

Many conventional alloys have significant differences despite having some similarities to this specification. Conventional inventions include US Pat. Nos. 2,553,330, 2,894,833, 3,171,738, 3,311,511; 3,561,953: 3,598,574: 3,726,668: 3,854,935, 26,903 and 28,972, and US specification serial number 571,460 (filed April 25, 1975), which do not describe the alloys herein. None of the prior patents describe the combination of elements with synergistic effects that give particular alloying properties to the alloy of the invention.

It is therefore an object of the present invention to provide austenitic steels in the combination of elements with synergistic effects giving the desired compoundability.

The alloy of the present invention is a heatable austenite steel with the corrosion resistance described below for chlorine ions, which is 19-23% chromium by weight; 5-16% Nickel; 3-5% molybdenum; 2.5-15% manganese, at least 0.01% sulfur; At least 0.1% of one element selected from cerium, calcium and magnesium; 0.2% -solubility limit of 0.1% carbon of nitrogen; At least 0.1% silicon; At least 0.3% copper; It is composed of 1% or more corrubium, 0.3% or more vanadium, 0.3 or more titanium and equilibrated with iron.

Chromium, molybdenum and silicon are ferrite elements and chromium is added not only for corrosion resistance but also for oxidation and general corrosion resistance. The suitable level of chromium is 19.5-22%. Molybdenum should be present at a level of at least 3% to provide sufficient resistance to chlorine ions, with the alloy being part of 10,000 in 10% ferric chloride and 90% distilled rubber band experiments at room temperature for 72 hours. It has the characteristics which show the following weight loss. The proper level of molybdenum is 4.5%. The silicon helps to melt the alloy, and the silicon level is appropriate to keep the silicon less than 0.75% with ferrite jade, and if it is more than that, the fluidity of the alloy becomes too large to prevent welding.

Since the alloy of the present invention is austenite, the ferrite effect of arbitrary elements such as chromium, molybdenum, silicon and chromium should be offset by the austenite elements. The austenitic elements of the alloy of the present invention are Niddon, manganese (up to some level) copper, nitrogen and carbon. In addition to acting as an austenitic agent, nickel, nitrogen and manganese contribute to the properties of the alloy. Nickel increases the impact strength of the alloy and generally should be present in an amount of at least 8% and the more appropriate level of nickel is 9-13%. Nitrogen provides strength to the alloy and enhances corrosion resistance. This is generally present in an amount of 0.2-0.38%, with a level of 0.23-0.33% being particularly suitable. Manganese increases the solubility of the alloy in nitrogen and makes it suitable for welding purposes. If the alloy is to be welded the ratio of manganese to nitrogen is at least 25 in particular. Manganese levels generally exceed 7.5% and 8-13.5% are appropriate. Carbon provides corrosion resistance in zones affected by weld salts and should be maintained at 0.08% or less. In another embodiment, carbon cooperates with the addition of stabilizing elements from the group consisting of corium, vanadium and titanium. This embodiment includes at least 0.1% one or more of the above elements. In order to increase the resistance to sulfuric acid the alloy comprises at least 3% copper and the copper included in the examples generally has at least 1% copper.

In order to increase the heating workability of the alloy of the invention, sulfur maintains a level below 0.01%, in particular a maximum of 0.007%. Low sulfur is obtained through the addition of cerium, calcium and magnesium, wherein the alloys in the present invention generally comprise 0.01-0.1% of these elements, in particular 0.014-0.1%. Cerium addition is achieved through the addition of mischmetal, and in addition to reducing the sulfur level, cerium, calcium and magnesium are thought to reduce the cooling shortening which increases fecal check.

Side checks, including cracks and heat in edges and corners, are a combination of heating operations resulting from poor ductility at the end of cooling of the combustible working range.

The following examples illustrate various forms of the invention.

Example 1

Two alloys (alloys A and B) were annealed at 1121 ° C and subjected to a 10% ferric chloride and 90% distilled water Rover band test at room temperature for 72 hours. The chemical composition of the alloy is shown in Table 1.

TABLE 1

Table 2 shows the results of a Lave band test on three samples of each alloy (A ₁ , A ₂ and B B ₂ and B ₃ ).

TABLE 2

From Table 2, alloy A samples had a weight loss of less than 1 part in 10.000 in a three-day ferric chloride labband test, while samples of alloy A produced a significant reduction of more than 1 part in 10.000. Alloy A samples meet the chemical requirements of the present invention while alloy B samples do not. Alloy A samples have a molybdenum content of more than 3% while containing less than 3% for samples of Alloy B.

Example 2

The two alloys (alloys C and D) were heated at 1238 ° C within 10 seconds, left for 1 minute, then cooled to -95 ° C per second at the test temperature, and then left for 1 second to determine the malleability observed at the lower end. Perform the Griball test as shown. The chemical components of the alloys are shown in Table 3.

TABLE 3

The results of the Griball test are listed in Table 4.

TABLE 4

From Table 4, the heating workability of alloy C is superior to that of alloy. High alloy C satisfies the chemical requirements of the present invention, while alloys do not. Alloy D has a sulfur content of less than 0.01%, while alloys have a sulfur content of greater than 0.01%.

The novel principles of the invention described in connection with the specific embodiments are susceptible to many other variations and meltings, which are not intended to be limited to the specific embodiments of the invention described but are within the scope of the appended claims.

Claims (1)

The steel produced is characterized by a weight loss of less than 1 part in 10.000 in a 10% ferric chloride and 90% distilled water rubber band test at room temperature for 19-23% chromium, 1-16% Nickel 3-5% molybdenum, 2.5-15% manganese up to 0.01% sulfur; One element up to 0.01% selected from cerium, calcium and magnesium, 0.2% to limit solubility. Excellent corrosion resistance and corrosion resistance to chlorine ions consisting of nitrogen, up to 1% silicon, up to 3% copper, up to 1% corbicum, up to 0.3 vanadium, up to 0.3% titanium and up to 0.3% iron Workability austenitic stainless steel.