ES2808627T3 - Dual phase stainless steel - Google Patents

Abstract

A double phase ferritic-martensitic stainless steel consisting, by weight, of: 11.5% to 12% chromium; 0.8% to 1.5% manganese; 0.75% to 1.5% nickel; <= 0.5% silicon; <= 0.2% molybdenum; <= 0.0025% boron; <= 0.25% copper; <= 0.025% carbon; <= 0.01% sulfur; <= 0.03% nitrogen; where the total concentration of carbon + nitrogen + sulfur + phosphorus <= 0.1%; the rest of iron and incidental impurities; wherein the steel has a Brinell hardness (HB) of 300 HB or more and a Charpy V-notch impact energy at -40 ° C (CVN) such that CVN (ft-lb) + (0.4 x HB ) is approximately 160 or greater.

Description

DESCRIPTION

Dual phase stainless steel

Technology field

The present disclosure relates to a dual phase stainless steel having a tempered ferrite and martensite microstructure. In particular, the present disclosure relates to cost-effective stainless steels having improved toughness for abrasion and / or wear resistant applications.

Description of the technology background

Dual-phase stainless steels can exhibit a combination of desirable properties that make them useful for a wide variety of industrial applications, such as oil sands extraction and in the sugar industry. These steels are generally characterized by a tempered martensite microstructure dispersed in a ferrite matrix.

An example of a double phase stainless steel is ATI 412 ™ stainless steel (UNS 41003), which normally contains, by weight, 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 iron (Fe) and other incidental impurities. ATI 412 ™ stainless steel typically has a Brinell hardness (HB) of approximately 177 when annealed at approximately 766 ° C, and a Brinell hardness of approximately 258 when annealed at approximately 843 ° C.

Another double-phase stainless steel is Duracorr® steel, which contains, by weight, 11.0% a. 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 Fe. Specifically, The Duracorr® stainless steel contains Mo as an alloying element, that is, an intentional alloying addition, and not as an incidental impurity. However, due to increased Mo costs, Duracorr® stainless steel can be too expensive for certain applications. Although Duracorr® stainless steel generally has a hardness of approximately 223 HB, it can be processed to exhibit a nominal hardness of 300 HB, a grade that is commercially available as Duracorr® 300 stainless steel. Duracorr® and Duracorr® 300 stainless steels They have largely the same composition, but the hardness of Duracorr® 300 stainless steel ranges from 260 HB to 360 HB. However, the higher the hardness of Duracorr® 300 stainless steel is accompanied by a reduction in toughness. For example, the Charpy V-notch impact energy of Duracorr® 300 stainless steel at -40 ° C is only about 20.3 Nm (15 ft-lb) on average.

KR20030037751A discloses a 12Cr martensitic and ferritic hot rolled stainless steel manufacturing method. The method includes the steps of hot rolling a steel slab comprising 0.03% by weight or less of C, 11 to 13.5% by weight of Cr, 1.0% by weight or less of Ni, 1.0% by weight or less of Si, 0.2% by weight or less of Mo, 1.0% by weight or less of Cu, 1.0% by weight or less of Mn, the rest of Fe and incidental impurities; heat treatment of the hot rolled steel sheet in a specific temperature range for at least 10 min, followed by cooling.

Document CN102899587A refers to a double-phase stainless steel, which comprises the following chemical components, by weight: less than or equal to 0.02% of C, less than or equal to 0.02% of N, less than or equal to 0 .03% P, less than or equal to 0.015% S, less than or equal to 0.35% Si, 1.0-3.0% Mn, 10.5-13.5% Cr, 0.5-1.5% Ni, 8 (C + N) -0.35% Ti, 0.10-0.30% Nb Mo, and the rest of Fe and unavoidable impurities, in the that the ferrite factor KFF is 6.0-11.5.

JP2008138270A relates to a high strength Cr-containing stainless steel sheet having excellent workability. The high strength stainless steel sheet having excellent workability has a composition comprising, by mass, 0.001 to 0.03% C, 0.001 to 0.03% N, 0.05 to 0.5 % Si, 0.05 to 5% Mn, <0.05% P, 0.3 to 5% Ni, 0.01 to 3% Cu, 10 to 18% Cr and from 0.005 to 0.50% of Al, and the rest of Fe with unavoidable impurities.

In applications requiring a stainless steel with resistance to abrasion and / or wear, high levels of hardness, for example up to about 350 HB, may be desirable in combination with higher toughness than is available in stainless steel. Duracorr® 300. On the other hand, an in-service work hardenability of up to approximately 450-500 HB, for example, may be required in certain applications. Furthermore, it is desirable that such alloys are profitable

Summary

The invention provides a double phase ferritic-martensitic stainless steel according to claim 1 of the appended claims.

According to a non-limiting aspect of the present disclosure, an embodiment of a stainless steel is described. high hardness double phase ferritic-martensitic. Stainless steel comprises, by weight, 11.5 % a. 12% Cr, 0.8% to 1.5% Mn, 0.75% to 1.5% Ni, 0% to 0.5% Si, 0% to 0.2% Mo, up to 0.0025% B, Fe and impurities. Stainless steel according to the present disclosure exhibits a Brinell hardness (HB) of 300 HB or more and a Charpy V-notch impact energy at -40 ° C (CVN) such that CVN (ft-lb) (0 , 4xHB) is 160 or greater.

In accordance with another non-limiting aspect of the present disclosure, an embodiment of an article of manufacture including a high hardness double phase ferritic-martensitic stainless steel is disclosed. Stainless steel comprises, by weight, 11.5% a. 12% Cr, 0.8% to 1.5% Mn, 0.75% to 1.5% Ni, 0% to 0.5% Si, 0% to 0.2% Mo, up to 0.0025% B, Fe and impurities. Stainless steel has a Brinell hardness (HB) of 300 HB or more and a Charpy V-notch impact energy at -40 ° C (CVN) such that CVN (ft-lb) (0.4xHB) is 160 o higher.

Brief description of the drawings

The characteristics and advantages of stainless steels and articles of manufacture described herein can be better understood with reference to the accompanying drawing in which:

Figure 1 is a graph depicting Brinell hardness and Charpy V-notch impact energy of non-limiting embodiments of stainless steels in accordance with the present disclosure as compared to certain conventional steels.

The reader will appreciate the above details, as well as others, when considering the following detailed description of certain non-limiting embodiments of stainless steels and articles of manufacture in accordance with the present disclosure. The reader may also understand certain additional details in making or using the stainless steels and articles of manufacture described herein.

Detailed description of certain non-limiting embodiments

The invention is defined in the claims.

The present disclosure, in part, relates to cost-effective double phase ferritic-martensitic stainless steels which have advantageous toughness and which are suitable for use in various applications requiring abrasion resistance and / or wear resistance. In particular, embodiments of double phase ferritic-martensitic stainless steels according to the present disclosure comprise, by weight, 11.5% a. 12% Cr, 0.8% to 1.5% Mn, 0.75% to 1.5% Ni, 0% to 0.5% Si, 0% to 0.2% Mo, up to 0.0025% B, Fe and impurities. Stainless steels exhibit Brinell hardness (HB) of 300 HB or more and Charpy V-notch impact energy at -40 ° C (CVN) such that the following is true: CVN (ft-lb) (0.4xHB) is 160 or greater.

Cr can be provided in the alloys of the present disclosure to impart corrosion resistance. A Cr content of about 11.5% (by weight) or more may be required to provide adequate corrosion resistance. On the other hand, an excess of Cr can undesirably (1) stabilize the ferrite phase and / or (2) embrittle the phases like the sigma phase. Accordingly, embodiments of stainless steels according to the present disclosure include a Cr content of 11.5% to 12%, by weight.

Mn can be provided in the alloys of the present disclosure to improve work hardenability. A Mn content of about 0.8% (by weight) or more may be necessary to achieve the desired work tempering effects. On the other hand, excessive excess Mn can be undesirably segregated during the processing of stainless steels. Accordingly, embodiments of stainless steels according to the present disclosure include a Mn content of 0.8% to 1.5%, by weight. In certain other embodiments, the Mn content of the stainless steels can be 1.0% to 1.5%, by weight. In certain embodiments of stainless steels according to the present disclosure, the addition of Mn in combination with the addition of other alloying elements can advantageously affect work hardenability such that the steels reach a hardness of 450 HB or more.

Ni can be provided in the alloys of the present disclosure to help stabilize the martensitic phase of dual phase (martensitic-ferritic) alloys. A Ni content of about 0.75% by weight or more may be necessary to provide a material that includes higher levels of martensite than Duracorr® 300 stainless steel. Without wishing to be bound by theory, the nickel content of alloys can promote the hardness of the martensite phase of alloys by stabilizing austenite formation during heat treatment, allowing more time for carbon diffusion. On the other hand, due to the high cost of Ni, it may be desirable to limit the content of Ni. Accordingly, embodiments of the steels according to the present disclosure include a Ni content of 0.75% to 1.5% (by weight) to provide cost-effective dual phase stainless steel with high hardness levels up to about 350 HB, in combination with a higher than normal toughness of Duracorr® 300 stainless steel. In further embodiments, the Ni content of stainless steels according to the present disclosure can be 1.0% to 1.5%, in weigh.

In certain embodiments of stainless steels in accordance with the present disclosure, the level of Si can be limited to (1) destabilize the ferritic phase of double phase stainless steels and / or (2) avoid brittle phases such as the sigma phase. Accordingly, certain embodiments of the steels in accordance with the present disclosure include 0% to no more than about 0.5% Si, by weight.

In certain embodiments of stainless steels in accordance with the present disclosure, the level of Mo can be limited to (1) destabilize the ferritic phase of double phase stainless steels and / or (2) avoid brittle phases such as the sigma phase. Accordingly, embodiments of the steels according to the present disclosure include 0% to no more than 0.2% Mo, by weight. In certain other embodiments of the steels according to the present disclosure, the Mo concentration is from 0% to no more than 0.1%, by weight.

B can be provided in the dual phase stainless steels of the present disclosure to improve martensite hardness. The steels of the present disclosure can include up to 0.0025% B, by weight. In certain embodiments of the steels, the B content is 0.002% to 0.0025%, by weight.

Incidental elements and impurities in the disclosed alloys may include, for example, one or more of C, N, P, and S. In a certain embodiment of the stainless steels according to the present disclosure, the total content of these elements is no more 0.1%, by weight. In certain embodiments, C may be present in the steels disclosed herein in an amount of no more than 0.025%, by weight. In certain embodiments, S may be present in the steels disclosed herein in an amount of no more than 0.01%, by weight. In certain embodiments, N may be present in the steels disclosed herein in an amount of no more than 0.03%, by weight. Incidental levels of various metallic elements may also be present in alloy embodiments in accordance with the present disclosure. For example, certain non-limiting embodiments of alloys in accordance with the present disclosure may include up to 0.25% copper (Cu), by weight.

According to certain non-limiting embodiments, the double phase ferritic-martensitic stainless steels according to the present disclosure comprise by weight: 11.5% to 12% Cr; 1.0% to 1.5% Mn; 1.0% to 1.5% Ni; 0% to 0.5% Si; 0% to 0.1% Mo; up to 0.0025% B; 0% to 0.025% C; 0% to 0.01% S; 0% to 0.03% of N, Fe and impurities. In certain embodiments, the stainless steels further comprise P. In certain embodiments, the total concentration of C, N, P, and S is not more than 0.1%, by weight. In certain embodiments, the concentration of B in the steels is 0.002% to 0.0025%, by weight. The steels include no more than 0.25% Cu, by weight.

According to certain non-limiting embodiments, the double phase ferritic-martensitic stainless steels according to the present disclosure consist essentially of, by weight: 11.5% to 12% chromium; 0.8% to 1.5% manganese; 0.75% to 1.5% nickel; 0% to 0.5% silicon; 0% to 0.2% molybdenum; up to 0.0025% boron; 0% to 0.025% carbon; 0% to 0.01% sulfur; 0% to 0.03% nitrogen; optionally at least one of copper and phosphorus; iron; and impurities.

According to certain non-limiting embodiments, the double phase ferritic-martensitic stainless steels according to the present disclosure consist essentially of, by weight: 11.5% to 12% chromium; 1.0% to 1.5% manganese; 1.0% to 1.5% nickel; 0% to 0.5% silicon; 0% to 0.1% molybdenum; up to 0.0025% boron; 0% to 0.025% carbon; 0% to 0.01% sulfur; 0% to 0.03% nitrogen; optionally at least one of copper and phosphorus; iron; and impurities.

According to certain non-limiting embodiments, the double phase ferritic-martensitic stainless steels according to the present disclosure consist of, by weight: 11.5% to 12% chromium; 0.8% to 1.5% manganese; 0.75% to 1.5% nickel; 0% to 0.5% silicon; 0% to 0.2% molybdenum; up to 0.0025% boron; 0% to 0.025% carbon; 0% to 0.01% sulfur; 0% to 0.03% nitrogen; optionally at least one of copper and phosphorus; iron; and impurities.

According to certain non-limiting embodiments, the double phase ferritic-martensitic stainless steels according to the present disclosure consist of, by weight: 11.5% to 12% chromium; 1.0% to 1.5% manganese; 1.0% to 1.5% nickel; 0% to 0.5% silicon; 0% to 0.1% molybdenum; up to 0.0025% boron; 0% to 0.025% carbon; 0% to 0.01% sulfur; 0% to 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 disclosure, Brinell hardness (HB) is the primary measure of hardness, and Charpy V-notch impact energy at -40 ° C (CVN) is the primary measure of hardness. Referring to Figure 1, for certain embodiments of the steels in accordance with the present disclosure, CVN (ft-lb) (0.4xHB) of the steels is approximately 160 or greater. In certain embodiments of the steels according to the present disclosure, the hardness is about 300 HB or more, and CVN is about 67.8 Nm (50 ft-lb) or more. In certain embodiments, the steels in accordance with the present disclosure have an in-service work hardenability of up to a hardness of about 450 HB or greater.

Examples

Table 1 includes the compositions and certain properties of one embodiment of the double phase ferriticomartensitic stainless steels according to the present disclosure and of the conventional ATI 412 ™ stainless steel and the conventional Duracorr® 300 stainless steel. Upon heating the three alloys listed in Table 1 were cast into slabs weighing approximately 6818 kg (15,000 lb) and rolled at a temperature of approximately 1066 ° C (1950 ° F) to produce material approximately 6 mm thick. Following the rolling process, the steels were annealed at 766 ° C or 843 ° C for 15 minutes and air cooled.

The mechanical properties of the experimental steel embodiment listed in Table 1 were measured and compared with those of the two listed conventional steels. Brinell hardness and CVN at -40 ° C (ft-lb) are shown in Table 1 for the three alloys. Tensile tests were performed in accordance with the American Society for Testing and Materials (ASTM) A370 standard at room temperature, using a tungsten carbide ball indenter, on samples measuring approximately 5 cm in gauge length and approximately 0.5 cm thick. Charpy tests were performed in accordance with ASTM A370 and E23 at approximately -40 ° C on cross-sectional specimens measuring approximately 10mm x 2.5mm. Because these samples are considered undersized according to ASTM-A370, the measured impact energy was brought to standard size sample values in Table 1.

As shown by the experimental results in Table 1, the experimental steel sample of the present disclosure showed very favorable hardness and toughness (CVN impact energy) relative to conventional alloys. This was particularly unexpected and surprising. Commercially available alloys that provide comparable toughness and toughness are typically carbon steels, which would not withstand corrosive environments.

In certain possible non-limiting embodiments, the dual phase stainless steels in accordance with the present disclosure are prepared using conventional stainless steel production practices including, for example, melting raw materials in an electric furnace, decarburization through AOD and casting to an ingot. Ingots can be cast, for example, by continuous casting or ingot pouring. In certain embodiments, the cast material can be heat treated (austenitized) or sold raw.

Table 1

The potential uses for alloys in accordance with the present disclosure are numerous. As described and evidenced above, the dual phase stainless steels described herein can be used in many applications where abrasion and / or wear resistance is important. Articles of manufacture for which steels according to the present disclosure would be particularly advantageous include, for example, parts and equipment used in the extraction of oil sands and parts and equipment used in the processing of sugar. Other applications for stainless steels in accordance with the present disclosure will be readily apparent to those skilled in the art. Those of ordinary skill can easily manufacture these and other articles of manufacture from the stainless steels in accordance with the present disclosure using conventional fabrication techniques.

Although the foregoing description has necessarily presented only a limited number of embodiments, those with Those of ordinary skill in the relevant art will appreciate that various changes can be made to the alloys and the article and other details of the examples that have been described and illustrated herein, and all such modifications will remain within the principle and scope of the present disclosure. as expressed herein and in the appended claims.

Claims (9)

1. A double phase ferritic-martensitic stainless steel consisting, by weight, of: 11.5% to 12% chromium; 0.8% to 1.5% manganese; 0.75% to 1.5% nickel; <0.5% silicon; <0.2% molybdenum; <0.0025% boron; <0.25% copper; <0.025% carbon; <0.01% sulfur; <0.03% nitrogen; where the total concentration of carbon nitrogen sulfur phosphorus <0.1%; the rest of iron and incidental impurities; where the steel has a Brinell hardness (HB) of 300 HB or more and a Charpy V-notch impact energy at -40 ° C (CVN) such that CVN (ft-lb) (0.4 x HB) it is approximately 160 or greater. 2. The double phase ferritic-martensitic stainless steel of claim 1, wherein the boron content is 0.002% to 0.0025%. 3. The double phase ferritic-martensitic stainless steel of claim 1 or claim 2, wherein the molybdenum content is <0.1%. 4. The double phase ferritic-martensitic stainless steel of any one of the preceding claims, wherein the nickel content is 1.0% to 1.5%. The double phase ferritic-martensitic stainless steel of any one of the preceding claims, wherein the manganese content is 1.0% to 1.5%. 6. The double phase ferritic-martensitic stainless steel of any one of the preceding claims, wherein the CVN of the steel is 67.8 Nm (50 ft-lb) or greater. 7. The double phase ferritic-martensitic stainless steel of any one of the preceding claims, wherein the steel has a work hardenability to a hardness of 450 HB or greater. 8. An article of manufacture including a dual phase stainless steel according to any one of the preceding claims. The article of manufacture of claim 8, wherein the article of manufacture is selected from parts and equipment used in the extraction of oil sands and parts and equipment used in the processing of sugar.