TWI651419B - Dual-phase stainless steel - Google Patents

Abstract

A dual-phase ferritic-martensitic stainless steel comprising about 11.5% to about 12% Cr, about 0.8% to about 1.5% Mn, about 0.75% to about 1.5% Ni, 0% to about 0.5% by weight Si, 0% to about 0.2% Mo, 0% to about 0.0025% B, Fe, and impurities. In various embodiments, the steel has Brinell hardness (HB) and a sand ratio V-notch impact energy (CVN) at -40 ° C such that CVN (ft-lb) + (0.4 × HB) is about 160 or 160 or more. Articles including these stainless steels are also disclosed.

Description

Duplex stainless steel

The invention relates to a duplex stainless steel, which has the microstructure of ferrite and tempered martensite. In particular, the present invention relates to cost-effective stainless steels with improved hardness for abrasion and / or wear resistance applications.

Duplex stainless steels can exhibit a combination of desired properties that make them suitable for a variety of industrial applications, such as in the oil sands extraction and sugar manufacturing industries. These steels are generally characterized by the microstructure of tempered martensite dispersed in a ferritic matrix.

An example of duplex stainless steel is ATI 412 ^TM stainless steel (UNS 41003), which typically contains 11.75% chromium (Cr), 0.90% manganese (Mn), 0.70% silicon (Si), 0.40% nickel (Ni), 0.030% sulfur (S), 0.020% carbon (C), 0% to 0.040% phosphorus (P), 0% to 0.030% nitrogen (N), and the rest is iron (Fe) and other incidental impurities. ATI 412 ^™ stainless steel typically has a Brinell hardness (HB) of about 177 when annealed at about 766 ° C and a Brinell hardness of about 258 when annealed at about 843 ° C.

Another Duracorr ^® as duplex stainless steel, which comprises by weight 11.0% to 12.5% Cr, 0.20% to 0.35% molybdenum (Mo), 0% to 1.50% Mn, 0% to 1.00% Ni, 0% to 0.70 % Si, 0% to 0.040% P, 0% to 0.030% N, 0% to 0.025% C, 0% to 0.015% S, and the rest is Fe. Notably, Duracorr ^® stainless steel contains Mo as an alloying element, i.e., intentionally added alloy elements, rather than as incidental impurities. However, due to the increased cost of Mo, so Duracorr ^® stainless steel costs may be too high for some applications. Although stainless steel is typically Duracorr ^® have a hardness of about 223HB, but it can be processed to exhibit a nominal hardness of 300HB, as the level Duracorr ^® 300 commercially available stainless steel. Duracorr ^® and Duracorr ^® 300 stainless steel having the same composition to a large extent, but the hardness Duracorr ^® 300 stainless steel varied between 260HB to 360HB. However, increasing the hardness of the stainless steel-based Duracorr ^® 300 reduction is achieved by the tenacity. For example, at -40 ℃ Duracorr ^® 300 stainless steel, sand V-notch impact energy (Charpy V-notch impact energy) averaged only about 15ft-lb.

The need to have wear resistance and corrosion resistance / or wear-resistant applications of stainless steel, for example up to about 350HB hardness high and is higher than the required level may be obtained from a combination of toughness Toughness Duracorr ^® 300 stainless steel. In addition, in some applications, work hardening properties such as service up to about 450-500 HB may be required. In addition, any such alloy needs to be cost-effective.

According to a non-limiting aspect of the present invention, one embodiment of a high-hardness dual-phase ferritic-martensitic stainless steel is described. The stainless steel contains about 11.5% to about 12% Cr, about 0.8% to about 1.5% Mn, about 0.75% to about 1.5% Ni, 0% to about 0.5% Si, 0% to about 0.2% Mo, 0 % To about 0.0025% B, Fe and impurities. In certain non-limiting embodiments, the stainless steel of the present invention exhibits Brinell hardness (HB) and sand ratio V-notch impact energy (CVN) at -40 ° C such that CVN (ft-lb) + (0.4 × (HB) is about 160 or more.

According to another non-limiting aspect of the present invention, one embodiment of an article including a high hardness duplex ferrite-martensite stainless steel is described. The stainless steel contains about 11.5% to about 12% Cr, about 0.8% to about 1.5% Mn, about 0.75% to about 1.5% Ni, 0% to about 0.5% Si, 0% to about 0.2% Mo, 0 % To about 0.0025% B, Fe and impurities. According to certain non-limiting embodiments of the article, stainless steel exhibits Brinell hardness (HB) and sand ratio V-notch impact energy (CVN) at -40 ° C such that CVN (ft-lb) + (0.4 × HB ) It is about 160 or more.

The features and advantages of stainless steel and products described herein can be better understood by referring to the accompanying drawings, in which: Figure 1 is a Brinell hardness and sand drawing of a non-limiting embodiment of the stainless steel of the present invention Figure of specific V-notch impact energy compared to some conventional steels.

The reader will understand the above details and others after considering the following detailed description of certain non-limiting embodiments of the stainless steel and articles of the present invention. The reader may also understand some of these other details after manufacturing or using the stainless steel and articles described herein.

In the description of the invention of the non-limiting embodiment and in the scope of the patent application, all numbers representing the quantities or characteristics of components, alloys and articles, processing conditions and the like, except in the operating examples or otherwise indicated It is understood to be modified in all cases by the term "about". Therefore, unless indicated to the contrary, any numerical parameter set forth in the description below and in the scope of the attached patent application is an approximation that may vary depending on the desired characteristics sought to be obtained in the stainless steel and articles of the present invention. Minimally and without attempting to limit the scope of application of the principle of equivalence to patent applications, each numerical parameter should be interpreted at least based on the reported number of significant digits and by applying conventional rounding techniques.

Any patents, publications or other disclosures allegedly incorporated herein by reference are in whole or in part only to the extent that the incorporated material does not conflict with existing definitions, statements or other disclosures set forth in the present invention Is incorporated in this article. Thus and to the extent necessary, the invention as set forth herein supersedes any contradictory material incorporated herein by reference. Any material or portion thereof allegedly incorporated herein by reference, but inconsistent with existing definitions, statements, or other disclosed materials set forth herein, will only occur between the incorporated material and the existing disclosed material Conflicting degrees are incorporated.

Part of the invention is directed to cost-effective dual-phase ferrite-martensite Rust steel, which has favorable hardness and is suitable for use in various applications where abrasion resistance and / or abrasion resistance is required. In particular, certain embodiments of the dual-phase ferritic-martensitic stainless steel of the present invention include from about 11.5% to about 12% Cr, from about 0.8% to about 1.5% Mn, from about 0.75% to about 1.5 by weight. % Ni, 0% to about 0.5% Si, 0% to about 0.2% Mo, 0% to about 0.0025% B, Fe, and impurities. In certain embodiments, stainless steel exhibits Brinell hardness (HB) and a sand ratio V-notch impact energy (CVN) at -40 ° C so that the following is satisfied: CVN (ft-lb) + (0.4 × HB) is About 160 or more.

Cr may be provided in the alloy of the present invention to impart corrosion resistance. A Cr content of about 11.5% by weight or more may be required to provide sufficient corrosion resistance. On the other hand, excess Cr may undesirably (1) stabilize the ferrite phase and / or (2) the embrittlement phase, such as the sigma phase. Therefore, certain embodiments of the stainless steel of the present invention include a Cr content of about 11.5% to about 12% by weight.

Mn may be provided in the alloy of the present invention to improve work hardenability. A Mn content of about 0.8% (by weight) or more may be required to achieve the desired work hardening effect. On the other hand, excess Mn may undesirably segregate during processing of stainless steel. Accordingly, certain embodiments of the stainless steel of the present invention include a Mn content of about 0.8% to about 1.5% by weight. In certain other embodiments, the Mn content of the stainless steel may be from about 1.0% to about 1.5% by weight. In certain embodiments of the stainless steel of the present invention, the addition of Mn in combination with the addition of other alloying elements can advantageously affect the work hardenability such that the steel reaches a hardness of about 450 HB or more.

Ni may be provided in the alloys of the present invention to help stabilize the martensite phase of a dual-phase (martensite-ferrite) alloy. May need to about 0.75% (by weight) 0.75% or more of Ni content providing a level higher than the martensitic stainless steel of Duracorr ^® 300 material. Without wishing to be bound by any theory, the nickel content of the alloy can be stabilized by austenite formation during heat treatment, allowing more time for carbon diffusion to promote the hardness of the martensitic phase of the alloy. On the other hand, due to the high cost of Ni, it may be necessary to limit the Ni content. Therefore, some embodiments of the steel of the present invention include a Ni content of about 0.75% to about 1.5% (by weight) to provide a cost-effective duplex stainless steel having a high hardness level of up to about 350HB, and higher than Duracor The toughness combination of typical toughness of ^® 300 stainless steel. In other embodiments, the Ni content of the stainless steel of the present invention may be from about 1.0% to about 1.5% by weight.

In certain embodiments of the stainless steel of the present invention, the level of Si may be limited to (1) destabilize the ferrite phase of the duplex stainless steel and / or (2) avoid embrittlement phases, such as the sigma phase. Therefore, certain embodiments of the steel of the present invention include from 0% to no more than about 0.5% Si by weight.

In certain embodiments of the stainless steel of the present invention, the level of Mo may be limited to (1) destabilize the ferrite phase of the duplex stainless steel and / or (2) avoid embrittlement phases, such as the sigma phase. Therefore, certain embodiments of the steel of the present invention include 0% to not more than about 0.2% Mo by weight. In certain other embodiments of the steel of the present invention, the Mo concentration is from 0% to not more than about 0.1% by weight.

B can be provided in the duplex stainless steel of the present invention to improve the martensite hardness. Certain embodiments of the steel of the present invention include 0% to about 0.0025% B by weight. In certain embodiments of the steel, the B content may be from about 0.002% to about 0.0025% by weight.

The incidental elements and impurities in the disclosed alloy may include, for example, one or more of C, N, P, and S. In one embodiment of the stainless steel of the present invention, the total content of these elements does not exceed 0.1% by weight. In certain embodiments, C may be present in the steel disclosed herein in an amount not exceeding 0.025% by weight. In certain embodiments, S may be present in the steel disclosed herein in an amount not exceeding 0.01% by weight. In certain embodiments, N may be present in the steel disclosed herein in an amount not exceeding 0.03% by weight. Various levels of metal elements may also be present in embodiments of the alloys of the present invention. For example, certain non-limiting embodiments of the alloys of the present invention may include up to 0.25% copper (Cu) by weight.

According to certain non-limiting embodiments, the duplex ferrite-horse of the present invention The austenitic stainless steel comprises, by weight: about 11.5% to about 12% Cr; about 1.0% to about 1.5% Mn; about 1.0% to about 1.5% Ni; 0% to about 0.5% Si; 0% to about 0.1% Mo 0% to about 0.0025% B; 0% to about 0.025% C; 0% to about 0.01% S; 0% to about 0.03% N, Fe and impurities. In certain embodiments, the stainless steel further comprises P. In certain embodiments, the total concentration of C, N, P, and S is no greater than about 0.1% by weight. In certain embodiments, the concentration of B in the steel is from about 0.002% to about 0.0025% by weight. In certain embodiments, the steel comprises no more than 0.25% Cu by weight.

According to certain non-limiting embodiments, the duplex ferritic-martensitic stainless steel of the present invention consists essentially of the following: about 11.5% to about 12% chromium; about 0.8% to about 1.5% manganese; about 0.75% to about 1.5% nickel; 0% to about 0.5% silicon; 0% to about 0.2% molybdenum; 0% to about 0.0025% boron; 0% to about 0.025% carbon; 0% to about 0.01% sulfur; 0% To about 0.03% nitrogen; optionally at least one of copper and phosphorus; iron; and impurities.

According to certain non-limiting embodiments, the dual-phase ferritic-martensitic stainless steel of the present invention consists essentially of the following: about 11.5% to about 12% chromium; about 1.0% to about 1.5% manganese; about 1.0% to about 1.5% nickel; 0% to about 0.5% silicon; 0% to about 0.1% molybdenum; 0% to about 0.0025% boron; 0% to about 0.025% carbon; 0% to about 0.01% sulfur; 0% To about 0.03% nitrogen; optionally at least one of copper and phosphorus; iron; and impurities.

According to certain non-limiting embodiments, the dual-phase ferritic-martensitic stainless steel of the present invention consists of the following by weight: about 11.5% to about 12% chromium; about 0.8% to about 1.5% manganese; about 0.75% To about 1.5% nickel; 0% to about 0.5% silicon; 0% to about 0.2% molybdenum; 0% to about 0.0025% boron; 0% to about 0.025% carbon; 0% to about 0.01% sulfur; 0% to about 0.03% nitrogen; as appropriate, at least one of copper and phosphorus; iron; and impurities.

According to certain non-limiting embodiments, the dual phase ferritic-martensitic stainless steel of the present invention consists of the following by weight: about 11.5% to about 12% chromium; about 1.0% to about 1.5% manganese; about 1.0% To about 1.5% nickel; 0% to about 0.5% silicon; 0% to about 0.1% molybdenum; 0% to about 0.0025% boron; 0% to about 0.025% carbon; 0% to about 0.01% sulfur; 0% to about 0.03% Nitrogen; optionally at least one of copper and phosphorus; iron; and impurities.

For a given steel, hardness is generally inversely related to toughness. In the present invention, the Brinell hardness (HB) is the main measure of hardness, and the sand ratio V-notch impact energy (CVN) at -40 ° C is the main measure of toughness. Referring to FIG. 1, for certain embodiments of the steel of the present invention, the steel has a CVN (ft-lb) + (0.4 × HB) of about 160 or more. In certain embodiments of the steel of the present invention, the hardness is about 300 HB or more and the CVN is about 50 ft-lb or more. In certain embodiments, the steels of the present invention have in-service work hardenability of hardnesses up to about 450 HB or more.

Examples

Table 1 includes a duplex ferrite of the present invention - 412 ^TM conventional composition Duracorr ^® 300 stainless steel, martensitic stainless steel and certain features of one embodiment and conventional stainless steel and ATI. The hot blocks of the three alloys listed in Table 1 were melted into slabs weighing about 15,000 lb and rolled at a temperature of about 1950 ° F to produce a material about 6 mm thick. After the rolling process, the steel was annealed at 766 ° C or 843 ° C for 15 minutes and air cooled.

The mechanical properties of the experimental steels listed in Table 1 were measured and compared with the mechanical properties of the two listed conventional steels. Table 1 shows the Brinell hardness of the three alloys and the CVN (ft-lb) at -40 ° C. According to American Society for Testing and Materials (ASTM) standard A370, a tungsten carbide ball indenter was used at room temperature to perform a tensile test on a sample with a gauge length of about 5 cm and a thickness of about 0.5 cm. . According to ASTM standards A370 and E23, a Charpy test was performed on a transverse sample of about 10 mm × 2.5 mm measured at about -40 ° C. Since these samples are considered small size according to ASTM-A370, the measured impact energy is converted into the standard size test piece values in Table 1.

As shown in the experimental results in Table 1, the experimental steel samples of the present invention exhibit extremely favorable hardness and toughness (CVN impact energy) relative to conventional alloys. This is particularly unexpected and surprising. Commercially available alloys that provide comparable hardness and toughness are usually carbon steel, which will Will not withstand corrosive environments.

In some possible non-limiting embodiments, the duplex stainless steels of the present invention are prepared using conventional stainless steel production practices, including, for example, melting of starting materials in an electric furnace, decarburization via AOD, and casting into ingots. The ingot can be cast, for example, by continuous casting or ingot casting. In certain embodiments, the cast material may be heat treated (austenitized) or sold in a rolled state.

The potential uses of the alloys of the present invention are numerous. As described and demonstrated above, the duplex stainless steels described herein can be used in many applications where abrasion resistance and / or abrasion resistance are important. Articles in which the steel of the invention will be particularly advantageous include, for example, components and equipment used in oil sands extraction and components and equipment used in sugar processing. Other applications of the stainless steel of the present invention will be readily apparent to those of ordinary skill. Those of ordinary skill can readily manufacture these and other products from the stainless steel of the present invention using conventional manufacturing techniques.

Although the above description has necessarily shown only a limited number of implementations, those of ordinary skill in the relevant art will understand that those skilled in the art may make other details of the alloys and articles and examples that have been described and illustrated herein. Various changes, and all such modifications will remain within the principles and scope of the invention as expressed herein and in the scope of the appended patent applications. For example, although the present invention has necessarily presented only a limited number of embodiments of the stainless steel of the present invention, and it has been necessary to discuss only a limited number of articles including stainless steel, it should be understood that the scope of the present invention and related patent applications is not This limitation. Those of ordinary skill will readily identify other steel compositions and may produce other articles along these routes and within the spirit of the necessary limited number of embodiments discussed herein. Therefore, it should be understood that the present invention is not limited to the specific embodiments discussed or incorporated herein, but is intended to cover modifications within the principles and scope of the invention as defined by the scope of the patent application. Those skilled in the art should also understand that the above embodiments can be changed without departing from the broad inventive concept of the above embodiments.

Claims (17)

A duplex ferritic-martensitic stainless steel comprising, by weight: about 11.5% to about 12% chromium; about 0.8% to about 1.5% manganese; about 0.75% to about 1.5% nickel; 0% to about 0.5 % Silicon; 0% to about 0.2% molybdenum; 0% to about 0.0025% boron; iron; and impurities; wherein the steel has Brinell hardness (HB) and a sand ratio V-notch impact energy (CVN) at -40 ° C ) So that CVN (ft-lb) + (0.4 × HB) is about 160 or more. For example, the dual-phase ferrite-martensitic stainless steel in the scope of application for patent No. 1 has a molybdenum content of 0% to about 0.1%. For example, the dual-phase ferritic-martensitic stainless steel in the scope of application for patent No. 1 has a nickel content of about 1.0% to about 1.5%. For example, the dual-phase ferritic-martensite stainless steel of the first patent application range, wherein the manganese content is about 1.0% to about 1.5%. For example, the dual-phase ferrite-martensitic stainless steel in the scope of application for patent No. 1 has a boron content of about 0.002% to about 0.0025%. For example, the dual-phase ferritic-martensitic stainless steel of the first patent application scope, wherein the hardness of the steel is about 300HB or above 300HB, and the CVN of the steel is about 50ft-lb or above 50ft-lb. For example, the dual-phase ferritic-martensitic stainless steel of item 1 of the patent application scope, wherein the steel has a work hardenability up to about 450HB or more. For example, the dual-phase ferritic-martensitic stainless steel in the scope of application for the patent includes the following by weight: about 11.5% to about 12% chromium; about 1.0% to about 1.5% manganese; about 1.0% to about 1.5% Nickel; 0% to about 0.5% silicon; 0% to about 0.1% molybdenum; 0% to about 0.0025% boron; 0% to about 0.025% carbon; 0% to about 0.01% sulfur; 0% to about 0.03% nitrogen; Iron; and impurities. For example, the dual-phase ferritic-martensitic stainless steel according to item 8 of the patent application scope, which further includes at least one of copper and phosphorus. For example, the dual-phase ferrite-martensitic stainless steel in the scope of application for the patent No. 8, the total concentration of carbon, nitrogen, phosphorus and sulfur present therein is not more than about 0.1% by weight. For example, the dual-phase ferritic-martensite stainless steel in the scope of application for patent No. 8 has a boron content of about 0.002% to about 0.0025%. For example, the dual-phase ferritic-martensitic stainless steel in the scope of application for the patent, which basically consists of the following by weight: about 11.5% to about 12% chromium; about 0.8% to about 1.5% manganese; about 0.75% To about 1.5% nickel; 0% to about 0.5% silicon; 0% to about 0.2% molybdenum; 0% to about 0.0025% boron; 0% to about 0.025% carbon; 0% to about 0.01% sulfur; 0% to about 0.03% nitrogen; as appropriate, at least one of copper and phosphorus; iron; and impurities. For example, the dual-phase ferritic-martensitic stainless steel in the scope of application for the patent, which basically consists of the following by weight: about 11.5% to about 12% chromium; about 1.0% to about 1.5% manganese; about 1.0% To about 1.5% nickel; 0% to about 0.5% silicon; 0% to about 0.1% molybdenum; 0% to about 0.0025% boron; 0% to about 0.025% carbon; 0% to about 0.01% sulfur; 0% to about 0.03% nitrogen; as appropriate, at least one of copper and phosphorus; iron; and impurities. For example, the dual-phase ferritic-martensitic stainless steel in the scope of application for patent, which consists of the following by weight: about 11.5% to about 12% chromium; about 0.8% to about 1.5% manganese; about 0.75% to about 1.5% nickel; 0% to about 0.5% silicon; 0% to about 0.2% molybdenum; 0% to about 0.0025% boron; 0% to about 0.025% carbon; 0% to about 0.01% sulfur; 0% to about 0.03% Nitrogen; optionally at least one of copper and phosphorus; iron; and impurities. For example, the dual-phase ferritic-martensitic stainless steel in the scope of the patent application, which consists of the following by weight: about 11.5% to about 12% chromium; about 1.0% to about 1.5% manganese; about 1.0% to about 1.5% nickel; 0% to about 0.5% silicon; 0% to about 0.1% molybdenum; 0% to about 0.0025% boron; 0% to about 0.025% carbon; 0% to about 0.01% sulfur; 0% to about 0.03% Nitrogen; optionally at least one of copper and phosphorus; iron; and impurities. A product comprising a dual-phase ferritic-martensite stainless steel as claimed in any one of claims 1, 12, 13, 14 and 15. For example, the product under the scope of application for patent No. 16 wherein the product is selected from components and equipment used in oil sands extraction and components and equipment used in sugar processing.