EP1420077A1 - Inert material with high hardness for elements used at high temperature - Google Patents

Abstract

Material comprises an alloy containing (in wt.%) 0.01-0.25 C, 0.35-2.5 Si, 0.4-4.3 Mn, 16.0-28.0 Cr, 15.0-36.0 Ni, 0.01-0.29 N and a balance of Fe, with the proviso that the Ni content of the alloy fulfills the following equation: Ni at least Cr + 1.5 x Si -0.12 x Mn - 18 x N - 30 x C - 6. The material has a hardness formed by cold forming of at least 230 HB. An Independent claim is also included for a process for the production of the material

Description

The invention relates to a material with high inertia, in particular high oxidation resistance and increased hardness for thermally resilient components and tools.

According to DIN 50900 is a reaction of a metallic material with its Environment that causes a measurable change in the material as corrosion Are defined. Corrosion can occur with and without mechanical stress on the Component, as well as after various types of chemical attack and different temperatures.

A surface attack of objects is most common electrochemical corrosion in the presence of an ion conducting phase or through chemical corrosion and hot corrosion at elevated temperatures. Also in molten media at elevated temperature, for example in liquid Glasses can be a corrosive attack with a change in the surface of a metal part in contact therewith.

In modern technology, components and tool parts are mostly a number of exposed to different stresses at the same time, in particular the thermal and mechanical loads also alternating or swelling can be effective. Accordingly, there are many intensified Corrosion conditions, which may be caused by a deformation of the near the surface of the part.

Corrosion- and heat-resistant steels and alloys are supposed to, also one thermal resilience with temperatures above 600 ° C because of a cubic face-centered atomic lattice structure or an austenitic structure exhibit. In terms of alloy technology, this means that such materials are higher Have nickel and / or cobalt contents or with a view to an increased Strength and hardness at high temperatures as nickel-based or Cobalt-based alloys are formed, but from corrosion-chemical Cobalt-based alloys are formed, but from corrosion-chemical Chromium content of at least greater than 13 wt .-% must be present.

Although a material with a high nickel concentration consistently increased has mechanical strength or high material hardness, whereby the Usage properties of components and tool parts at high temperature are improved, there is a desire for economic reasons, the nickel content lower than 36 wt .-% and to increase the corrosion resistance To increase the chromium content of the alloy to over 16% by weight.

An austenitic iron base material with a nickel content of less than 36 % By weight may be due to a high chromium concentration, possibly in Connection with other corrosion-inhibiting elements, definitely one Corrosion attack at high temperatures, for example at 600 ° C and above, Resist over a required minimum amount of time, however, the material shows a low hardness as well as a similar strength and a limited Creep behavior. Despite these disadvantages, alloys, for example according to DIN material no. 1.2780 and 1.2782 and 1.2786 for reasons of Profitability and for production reasons as tools for one Glass processing used.

Here, the invention seeks to remedy this and has set itself the goal of being a material Specify initially mentioned type with a hardness of greater than 230 HB, which a high creep resistance even at temperatures above 600 ° C improved durability and similar corrosion resistance having.

Furthermore, it is an object of the invention to provide a process for economical production to create a material for components and tools that improved Performance characteristics with high hardness and increased corrosion resistance have.

Finally, the invention aims to use an iron-based alloy as Material for hot work tools that work at temperatures above 550 ° C be used from.

The aforementioned goal is achieved in the case of a material of the type mentioned at the outset, consisting of an alloy with a composition essentially in% by weight of Carbon (C) 0.01 to 0.25 Silicon (Si) 0.35 to 2.5 Manganese (Mn) 0.4 to 4.3 Chrome (Cr) 16.0 to 28.0 Nickel (Ni) 15.0 to 36.0 Nitrogen (N) 0.01 to 0.29 with the proviso that the nickel content of the alloy is equal to or possibly greater by a maximum of 4.8% by weight than the value formed from the content of chromium plus 1.5 silicon minus 0.12 manganese minus 18 nitrogen minus 30 carbon minus the numerical value 6 Ni ≥ Cr + 1.5 x Si - 0.12 Mn - 18 x N- 30 x C - 6 Rest iron (Fe), as well as accompanying elements and impurities, which material has a hardness of at least 230 HB formed by cold forming.

The advantages achieved with the invention are in particular the synergy of corrosion-chemical resistance of the selected alloy and that of this chemical composition achievable by means of cold forming Properties of the material. In the case of cold forming or deformation below the recrystallization temperature of the face-centered cubic austenite the material solidifies by blocking dislocations in the Crystal lattice. A related increase in hardness and an increase in The strength of the material according to the invention remains for the person skilled in the art surprisingly, even at temperatures above 600 ° C expected recovery processes in the strained lattice, such as a thermal activated cross sliding and a recombining of dislocations can be done in usual Periods are not observed. In other words, one by one Cold forming increased the heat resistance of the composite according to the invention Contrary to the specialist opinion, material remains high Preserve usage temperatures of the component because of a high creep resistance of the steel improves its creep behavior. Especially with swelling thermal stress, as is the case with a mold for the production of Glasses are the case, strong on the work surface Temperature fluctuations and thus local volume changes in the material on. It was found that material hardness increased according to the invention and heat resistance the local or near-surface deformation of the material, for example, a glass mold, in the elastic range and that this leads to fatigue crack formation, even with low plastic Form changes occur and can lead to failure of the form, counteracted becomes.

To ensure an improved property profile of the material, it is It is important that this also applies to cold forming in the stable austenitic range remains and has no zones with deformation martensite. this will according to the invention by the nickel and Chromium concentration and given by the restrictive Concentration range of nickel depending on chromium, silicon, manganese, Nitrogen and carbon reached. Higher nickel levels deteriorate as has shown the creep behavior. In contrast, at low Nickel concentrations, the austenite stability and the heat resistance of the material abruptly reduced. Essentially the same applies to the elements carbon and nitrogen, nitrogen in particular being the fatigue strength of the Material increased.

The performance properties of components and tools according to the invention can be improved if the material for one or more alloy elements has a content in% by weight of C = 0.02 to 0.20, preferably 0.04 to 0.15 Si = 0.50 to 2.48, preferably 1.22 to 2.36 Mn = 0.62 to 4.05, preferably 1.00 to 3.95 Cr = 20.1 to 27.6, preferably 23.9 to 26.5 Ni = 16.1 to 27.3, preferably 17.9 to 25.45 N = 0.014 to 0.23, preferably 0.018 to 0.20 having. It should be noted that cobalt, as is known per se, can also improve the heat resistance of the material in the alloy according to the invention from a content of 0.52% by weight.

Although the elements molybdenum, vanadium, tungsten, titanium and niobium increase the creep resistance of the material at high temperatures and copper, as well as aluminum, are classic hardening elements, these steel companions have a highly reliable concentration in the material according to the invention because, as was found, higher contents of the same reduce the corrosion resistance, in particular if they come into contact with pasty glass at times, and, due to the surface roughness of the mold, impair the transparency of the glass. The reason for this has not yet been sufficiently clarified, but the acceptor atoms Na ⁺ , K ⁺ , Ca ²⁺ , B ³⁺ , Al ³⁺ and Si ⁴⁺ are hard Lewis acids, with the mold exposed to hot corrosion after each glass molding is.

Impurities can of course degrade the material properties, so that the alloy according to the invention for the accompanying elements and / or impurity elements has concentration values in% by weight of Molybdenum (Mo) less than 1.0 Vanadium (V) to 0.5 Tungsten (W) to 0.5 Copper (Cu) to 0.5 Cobalt (Co) to 6.5 Titanium (Ti) to 0.5 Aluminum (AI) to 1.5 Niobium (Nb) to 0.5 Oxygen (O) max 0.05 Phosphorus (P) max 0.03 Sulfur (S) max 0.03 having.

The object of the invention is achieved by a method for producing a material for components and tools with high inertia, in particular high oxidation resistance and increased hardness under thermal loads with a temperature of up to 750 ° C, according to which an alloy with a composition in wt. -% of essentially Carbon (C) 0.01 to 0.25 Silicon (Si) 0.35 to 2.5 Manganese (Mn) 0.4 to 4.3 Chrome (Cr) 16.0 to 28.0 Nickel (Ni) 15.0 to 36.0 Nitrogen (N) 0.01 to 0.29 with the proviso that the nickel content of the alloy is equal to or possibly greater by a maximum of 4.8% by weight than the value formed from the content of chromium plus 1.5 silicon minus 0.12 manganese minus 18 nitrogen minus 30 carbon minus the numerical value 6 Ni ≥ Cr + 1.5 x Si - 0.12 x Mn - 18 x N - 30 x C - 6 Remainder iron (Fe), as well as accompanying elements and impurities, a preliminary product is formed and this is subsequently processed by cold forming into a material with a hardness of greater than 230 HB.

By means of cold working the alloy according to the invention, the Elasticity limit of the material can be raised to a stress level, which is also close to the work surface of the component or tool at a Volume change due to changing thermal load is not achieved. Accordingly, no zones occur in the area of the grain boundaries, which at Temperature changes are plastically deformed, causing cracking Material fatigue can be avoided. This is also a grain boundary attack largely avoidable by chemical or hot corrosion, so how, for Example with a glass mold, also a high work surface or surface quality with high loads and large quantities of production over a long time preserved. Conventional glass shapes, on the other hand, often show up after a short time Period of use at the grain boundaries of the structure Have a distance in the range of a few microns. The shaped glass thereby conveying unevenness in the lightwave range, causing reflection interference and frosted glass effects can arise.

The corrosion and heat resistance can be further increased and a Fatigue cracking can be effectively suppressed if, according to the process the invention by cold working, a material with a hardness greater than 250 HB, especially 300 HB and higher is formed.

If a preliminary product with a composition according to the invention by means of Hot forming formed, this is subjected to a solution treatment or from the deformation temperature, if necessary amplified, cooled and is cold formed, a particularly homogeneous material with improved Corrosion resistance can be created.

Especially for largely axially symmetrical tools, such as Bottle molds and the like, it can be beneficial if the Cold deformation of the material completely radially perpendicular to the longitudinal axis of the Intermediate product is carried out.

For an increased quality of the product, it is provided that the alloy with contents of one or more alloy elements in% by weight C = 0.02 to 0.20, preferably 0.04 to 0.15 Si = 0.05 to 2.48, preferably 1.22 to 2.36 Mn = 0.62 to 4.05, preferably 1.00 to 3.95 Cr = 20.1 to 27.6, preferably 23.9 to 26.5 Ni = 16.1 to 27.3, preferably 17.9 to 25.45 N = 0.014 to 0.23, preferably 0.018 to 0.2

Finally, the further object of the invention is achieved when using an iron-based alloy with alloying elements in% by weight Carbon (C) up to 0.25 Silicon (Si to 2.5 Manganese (Mn) to 4.3 Chrome (Cr) 16.0 to 28.0 Nickel (Ni) 15.0 to 36.0 Nitrogen (N) 0.01 to 0.29 with the proviso that the nickel content of the alloy is equal to or possibly greater by a maximum of 4.8% by weight than the value formed from the content of chromium plus 1.5 silicon minus 0.12 manganese minus 18 nitrogen minus 30 carbon minus the numerical value 6 Ni ≥ Cr + 1.5 x Si - 0.12 x Mn - 18 x N - 30 x C - 6 Remainder iron (Fe), as well as accompanying elements and impurities, which alloy is solidified by cold working of the preliminary product formed from it to a material hardness of at least 230 HB, preferably greater than 250 HB, as a material for hot work tools with a working temperature of higher than 555 ° C , preferably higher than 602 ° C, in particular up to 750 ° C.

Particularly advantageous in terms of product quality and economical Manufacturing, is a use of the aforementioned iron base alloy as Tool material in the glass industry, especially as a mold material for Maschinenpreßgläser.

Based on comparative test results, the invention Material are shown in more detail.

Fig. 1 Festigkeit in Anhängigkeit vom Kaltverformungsgrad eines erfindungsgemäßen Werkstoffes bei 604°C

Fig. 2 Härteverlauf bei Raumtemperatur nach einer Langzeit-Temperaturbeanspruchung bei 600°C

Show it

Fig. 1 strength depending on the degree of cold deformation of a material according to the invention at 604 ° C.

Fig. 2 hardness curve at room temperature after a long-term temperature stress at 600 ° C.

In Fig. 1, the strength of the material according to the invention is at Test temperature of 604 ° C depending on the extent of the cold deformation shown. The sample material was forged at a temperature of 1010 ° C and increasingly cooled from the forming heat and a solution heat treatment Subject to 1060 ° C. Parts of the material were cold worked with a degree of deformation of 21%, 35%, 47% and 55%, thereafter from it Tensile tests were created. The strength determinations, namely the 0.2% Yield strength and tensile strength took place at a temperature of 604 ° C, where the samples were kept at this temperature for 20 minutes. For comparison standard material was solution annealed at 1060 ° C, producing from it Samples were also examined at 604 ° C. The bar chart of Fig. 1 clearly shows an increase in the strength values of the material depending on of the degree of deformation, where (not shown in the diagram) Strength increase to a high degree already with a degree of cold deformation of more than 6%, in particular greater than 12%.

2, the fatigue strength of the material according to the invention is at Temperature of 600 ° C, determined by a hardness test in the cold state of the Samples, in comparison with materials according to DIN material No. 1.2083 and material No. 1.4028.

The material according to the invention has a composition of in Wt% C = 0.08, Si = 1.7, Mn = 1.15, P = 0.01, S = 0.002, Cr = 24.8, Ni = 19.8, N = 0.02, Mo = 0.26, V = 0.09, W = 0.11, Cu = 0.12, Co = 0.4, Ti = 0.01, Al = 0.02, Nb = 0.001, O = 0.0029 melted, poured into a test block and closed Sample material thermoformed. A was carried out on the sample material Solution heat treatment at 1060 ° C with subsequent quenching in the Water, after which samples with the designation H 5 undeformed and samples with the Designation H 525 with a cold deformation of 35% in long-term annealing 600 ° C were subjected. The comparison materials No. 1.2083 and No. 1.4028 were hardened in oil from 1020 ° C, tempered at 630 ° C and also the Long-term annealing exposed. After 45, 90, 140 and 180 hours, that became Sample material taken out of the oven, allowed to cool and the material hardness checked, after which a reinsertion of the samples (with a Thermal shock). The comparative material H 5 showed a expected behavior of hardness, whereas that with 35% cold-formed Material H 525 according to the invention has an increased hardness of 315 HB and a high hardness Exhibited endurance behavior. At 600 ° C even with changing thermal No reduction in hardness and no creeping of the material determined become. In contrast, the martensitic standard steels were used significant drop in hardness was observed with the glow duration of the samples.

Claims (13)

Material with high inertia, in particular high oxidation resistance and increased hardness for components and tools that can be thermally loaded at a temperature of up to 750 ° C, consisting of an alloy with a composition essentially in% by weight of Carbon (C) 0.01 to 0.25 Silicon (Si) 0.35 to 2.5 Manganese (Mn) 0.4 to 4.3 Chrome (Cr) 16.0 to 28.0 Nickel (Ni) 15.0 to 36.0 Nitrogen (N) 0.01 to 0.29 with the proviso that the nickel content of the alloy is equal to or greater than the value formed from the chromium plus 1.5 silicon minus 0.12 manganese minus 18 nitrogen minus 30 carbon minus the numerical value 6 Ni ≥ Cr + 1.5 x Si - 0.12 x Mn -18 x N - 30 x C - 6 Remainder iron (Fe), as well as accompanying elements and impurities, which material has a hardness of at least 230 HB formed by cold forming. Material according to claim 1 with a hardness of greater than 250 HB, in particular 300 HB and higher. The material of claim 1 or 2, wherein the nickel content of the alloy is around is at most 4.8% by weight greater than the value formed according to the relationship of claim 1. Material according to one of claims 1 to 3, which for one or more alloy elements contents in wt .-% of C = 0.02 to 0.20, preferably 0.04 to 0.15 Si = 0.50 to 2.48, preferably 1.22 to 2.36 Mn = 0.62 to 4.05, preferably 1.00 to 3.95 Cr = 20.1 to 27.6, preferably 23.9 to 26.5 Ni = 16.1 to 27.3, preferably 17.9 to 25.45 N = 0.014 to 0.23, preferably 0.018 to 0.20 having. Material according to one of claims 1 to 4, which for one or more accompanying elements and / or impurity elements concentration values in wt .-% of Molybdenum (Mo) less than 1.0 Vanadium (V) to 0.5 Tungsten (W) to 0.5 Copper (Cu) to 0.5 Cobalt (Co) to 6.5 Titanium (Ti) to 0.5 Aluminum (Al) to 1.5 Niobium (Nb) to 0.5 Oxygen (O) max 0.05 Phosphorus (P) max 0.03 Sulfur (S) max 0.03 having. Process for producing a material for components and tools with high inertia, in particular high oxidation resistance and increased hardness under thermal loads with a temperature of up to 750 ° C, according to which essentially consists of an alloy with a composition in wt .-% of Carbon (C) 0.01 to 0.25 Silicon (Si) 0.35 to 2.5 Manganese (Mn) 0.4 to 4.3 Chrome (Cr) 16.0 to 28.0 Nickel (Ni) 15.0 to 36.0 Nitrogen (N) 0.01 to 0.29 with the proviso that the nickel content of the alloy is equal to or greater than the value formed from the chromium plus 1.5 silicon minus 0.12 manganese minus 18 nitrogen minus 30 carbon minus the numerical value 6 Ni ≥ Cr + 1.5 x Si - 0.12 x Mn - 18 x N - 30 x C - 6 Remainder iron (Fe), as well as accompanying elements and impurities form a preliminary product and this is subsequently processed by cold forming into a material with a hardness of greater than 230 HB. A method according to claim 6, wherein the intermediate product by means of hot forming formed, this is subjected to a solution treatment or from the Deformation temperature, optionally increased, cooled and cold worked. A method according to claim 6 or 7, wherein the cold deformation is complete is carried out radially perpendicular to the longitudinal axis of the intermediate product. Method according to one of claims 6 to 8, according to which the nickel content of the Alloy is set by a maximum of 4.8 wt .-% larger than the value according to the context of claim 6. Method according to one of claims 6 to 9, according to which the alloy with contents of one or more alloy elements in wt .-% C = 0.02 to 0.20, preferably 0.04 to 0.15 Si = 0.50 to 2.48, preferably 1.22 to 2.36 Mn = 0.62 to 4.05, preferably 1.00 to 3.95 Cr = 20.1 to 27.6, preferably 23.9 to 26.5 Ni = 16.1 to 27.3, preferably 17.9 to 25.45 N = 0.014 to 0.23, preferably 0.018 to 0.2 is formed. A method according to any one of claims 6 to 10, wherein by cold working Material with a hardness greater than 250 HB, in particular 300 HB and is formed higher. Use of an iron-based alloy with alloying elements in% by weight Carbon (C) up to 0.25 Silicon (Si) to 2.5 Manganese (Mn) to 4.3 Chrome (Cr) 16.0 to 28.0 Nickel (Ni) 15.0 to 36.0 Nitrogen (N) 0.01 to 0.29 with the proviso that the nickel content of the alloy is equal to or possibly greater by a maximum of 4.8% by weight than the value formed from the content of chromium plus 1.5 silicon minus 0.12 manganese minus 18 nitrogen minus 30 carbon minus the numerical value 6 Ni ≥ Cr + 1.5 x Si - 0.12 x Mn - 18 x N - 30 x C - 6 Remainder iron (Fe) as well as accompanying elements and impurities, which alloy is hardened by cold forming of the preliminary product formed from it to a material hardness of at least 230 HB, preferably greater than 250 HB, as a material for hot work tools with a working temperature of higher than 555 ° C, preferably higher than 602 ° C, especially up to 750 ° C. Use of an iron-based alloy according to claim 10 as Tool material in the glass industry, especially as a mold material for Maschinenpreßgläser.

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