EP1420077B1 - Inert material with high hardness for elements used at high temperature - Google Patents

Description

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

According to DIN 50900, a reaction of a metallic material with its surroundings, which causes a measurable change in the material, is defined as corrosion. Corrosion can be done with and without mechanical stress of the component, as well as after various types of chemical attack and at different temperatures.

Most commonly, surface attack of articles is caused by electrochemical corrosion in the presence of an ion conducting phase or by chemical corrosion and hot corrosion at elevated temperatures. Even in molten media at elevated temperature, for example in liquid glasses, corrosion can occur with a change in the surface of a metal part in contact therewith.

In modern technology, construction and tool parts are usually exposed to a plurality of different stresses at the same time, of which in particular the thermal and mechanical stresses can also be changing or swelling effective. Accordingly, there are often intensified corrosion conditions, which are possibly reinforced by a deformation of the near-surface zone of the part.

Corrosion-resistant and heat-resistant steels and alloys are also said to have a cubic face-centered atomic lattice structure or an austenitic microstructure due to their thermal stability at temperatures above 600 ° C. In terms of alloying technology, this means that such materials have higher nickel and / or cobalt contents or, in view of increased strength and hardness at high temperatures, are in the form of nickel-base or cobalt-base alloys, although from corrosion-chemical Due to a chromium content of at least greater than 13 wt .-% must be present.

Although a material with a high nickel concentration throughout increased mechanical strength and high material hardness, whereby the performance characteristics of construction and tool parts are improved at high temperature, there is a desire for economic reasons to reduce the nickel content below 36 wt .-% and Increasing the corrosion resistance to increase the chromium content of the alloy to more than 16 wt .-%.

JP2001011583A discloses an austenitic heat-resistant steel having particular high-temperature strength for steam boiler tubes, which steel has a limited chromium equivalent and thereby no tendency to embrittlement by precipitates of sigma phase in long-term use. However, this material has a low strength and a low 0.2% yield strength at 650 ° C.

Although an austenitic iron-base material with a nickel content of less than 36% by weight can certainly withstand a corrosion attack at high temperatures, for example at 600 ° C. and above, over a required minimum period of time owing to a high chromium concentration, if appropriate in combination with other corrosion-inhibiting elements However, the material has a low hardness and a similar strength and a limited creep behavior. Despite these disadvantages, for example, alloys according to DIN material no. 1.2780 and 1.2782 and 1.2786 are used for reasons of economy and for reasons of production as tools for glass processing.

Here, the invention seeks to remedy the situation and sets itself the goal of specifying a material of the type mentioned above with a hardness of greater than 230 HB, which also at temperatures above 600 ° C high creep resistance and improved creep behavior and a similar corrosion resistance having.

It is another object of the invention to provide a method for the economic production of a material for components and tools, which have improved performance characteristics with high hardness and increased corrosion resistance.

Finally, the invention aims at the use of an iron-based alloy as a material for hot working tools, which are used at working temperatures of about 550 ° C from.

wahlweise eines oder mehrere der Elemente in Konzentrationen in Gew.-% Molybdän (Mo) kleiner 1,0 Vanadium (V) bis 0,5 Wolfram (W) bis 0,5 Kupfer (Cu) bis 0,5 Cobalt (Co) bis 6,5 Titan (Ti) bis 0,5 Aluminium (Al) bis 1,5 Niob (Nb) bis 0,5 Rest Eisen (Fe), sowie Verunreinigungen, welcher Werkstoff eine durch Kaltumformung von mehr als 6% gebildete Härte von mehr als 230 HB aufweist.The aforementioned object is achieved in a material of the type mentioned, consisting of an alloy with a composition in wt .-% of Carbon (C) 0.04 to 0.15 Silicon (Si) 1.22 to 2.36 Manganese (Mn) 1.0 to 3.95 Chrome (Cr) 23.9 to 26.5 Nickel (Ni) 17.9 to 25.45 Nitrogen (N) 0.018 to 0.2 with the proviso that the nickel content of the alloy is equal to or greater than the value formed by the content of chromium plus 1.5 silicon minus 0.12 manganese minus 18 nitrogen minus 30 carbon minus the numerical value 6 $$\mathrm{Ni}\ge \mathrm{Cr}+1.5\times \mathrm{Si}-0.12\times \mathrm{Mn}-18\times \mathrm{N}-30\times \mathrm{C}-6$$

optionally one or more of the elements in concentrations in% by weight 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 Remainder iron (Fe), as well as impurities, which material has a hardness of more than 230 HB formed by cold working of more than 6%.

The advantages achieved by the invention are in particular the synergy of corrosion resistance of the selected alloy and the achievable in this chemical composition by means of cold forming properties of the material. In the case of cold forming or deformation below the recrystallization temperature of the cubic face centered austenite, solidification of the material takes place by blocking dislocations in the crystal lattice. An associated increase in hardness and an increase in the strength of the material according to the invention remains, surprising for the expert, even at use temperatures of over 600 ° C, the expected recoveries in the strained grid, such as a thermally activated cross sliding and recombining dislocations can in usual Periods are not observed. In other words: increased by a cold deformation heat resistance of the composite material according to the invention remains contrary to the opinion even at high temperatures of use of the component obtained because 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 utility glasses, occur on the work surface each strong temperature fluctuations and thus local volume changes of the material. It has been found that by means of an inventively increased material hardness and heat resistance, the local or near-surface deformation of the material, for example a glass mold, takes place in its elastic region and thereby fatigue cracking occurs, which also results in small plastic deformations and leads to failure of the mold can, is counteracted.

In order to ensure an improved property profile of the material, it is important that it remains in the stable austenitic region even with a cold deformation and has no zones with deformation martensite. According to the invention, this is achieved by the nickel and chromium concentration specified in limits and by the limited concentration range of nickel as a function of chromium, silicon, manganese, nitrogen and carbon. Higher nickel levels have been found to degrade creep behavior. On the other hand, at low nickel concentrations the austenite stability and the heat resistance of the material are abruptly reduced. Essentially the same applies to the elements carbon and nitrogen, in particular nitrogen increases the fatigue strength of the material.

Although the elements molybdenum, vanadium, tungsten, titanium and niobium increase the creep resistance of the material at high temperatures and copper, and aluminum, are classical hardening elements, these steel companions have a maximum allowable concentration in the material according to the invention because it has been found that Higher levels of the same, the corrosion resistance, especially in case of temporary contact with doughy glass, lower and worsen due to a formed surface roughness of the mold, the glass transparency. The reason for this is not yet sufficiently clarified, but the acceptor atoms Na ⁺ , K ⁺ , Ca ²⁺ , B ³⁺ , Al ³⁺ and Si ^{4+ are} among the hard Lewis acids, with a hot corrosion stress on the mold after each glass forming is.

Impurities can of course deteriorate the material properties, so that the alloy according to the invention for the impurity elements concentration values in wt .-% of Oxygen (O) max 0.05 Phosphorus (P) max 0.03 Sulfur (S) max 0.03 having.

wahlweise eines oder mehrere der Elemente in Konzentrationen in Gew.-% Molybdän (Mo) kleiner 1,0 Vanadium (V) bis 0,5 Wolfram (W) bis 0,5 Kupfer (Cu) bis 0,5 Cobalt (Co) bis 6,5 Titan (Ti) bis 0,5 Aluminium (Al) bis 1,5 Niob (Nb) bis 0,5 Rest Eisen (Fe), sowie Verunreinigungen ein Vorprodukt gebildet und dieses nachfolgend durch Kaltumformung von mehr als 6% zu einem Werkstoff mit einer Härte von größer als 230 HB weiterverarbeitetwird, gelöst.The object of the invention is a method for producing a material for components and tools with high inertia, in particular high oxidation resistance and increased hardness under thermal stress at a temperature of up to 750 ° C, after which from an alloy having a composition in wt. -% from Carbon (C) 0.04 to 0.15 Silicon (Si) 1.22 to 2.36 Manganese (Mn) 1.0 to 3.95 Chrome (Cr) 23.9 to 26.5 Nickel (Ni) 17.9 to 25.45 Nitrogen (N) 0.018 to 0.2 with the proviso that the nickel content of the alloy is equal to or greater than the value formed by the content of chromium plus 1.5 silicon minus 0.12 manganese minus 18 nitrogen minus 30 carbon minus the numerical value 6 $$\mathrm{Ni}\ge \mathrm{Cr}+1.5\times \mathrm{Si}-0.12\times \mathrm{Mn}-18\times \mathrm{N}-30\times \mathrm{C}-6$$

optionally one or more of the elements in concentrations in% by weight 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 Residual iron (Fe), as well as impurities formed a precursor and this is subsequently processed by cold forming of more than 6% to a material having a hardness greater than 230 HB further.

By means of a cold deformation of the alloy according to the invention, the elastic limit of the material can be raised to a voltage level which is not reached near the working surface of the component or tool in a volume change due to alternating thermal load. Accordingly, even in the area of the grain boundaries, no zones which are plastically deformed during the temperature change occur, whereby cracking due to material fatigue can be avoided. Thus, a grain boundary attack by chemical or hot corrosion is largely avoidable, so that, as for example in a glass mold, a high Arbeitsflächen- or surface quality is maintained even at high loads and large quantities of production over a long time. Conventional glass molds, however, often show after a short period of use at the grain boundaries of the structure material erosion, which have a distance in the range of a few microns. As a result, the shaped glass is imparted with unevennesses in the lightwave area, which may result in reflection interference and frosted glass effects.

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

When a precursor having a composition of the invention is formed by hot working, subjected to a solution annealing treatment, or thermoformed, cooled, and cold worked from the deformation temperature, a particularly pattern-homogenous material having improved corrosion resistance can be prepared.

In particular, for substantially axially symmetric shaped tools, such as bottle molds and the like, it may be advantageous if the cold deformation of the material is performed fully radially perpendicular to the longitudinal axis of the precursor.

wahlweise eines oder mehrere der Elemente in Konzentrationen in Gew.-% Molybdän (Mo) kleiner 1,0 Vanadium (V) bis 0,5 Wolfram (W) bis 0,5 Kupfer (Cu) bis 0,5 Cobalt (Co) bis 6,5 Titan (Ti) bis 0,5 Aluminium (Al) bis 1,5 Niob (Nb) bis 0,5 Rest Eisen (Fe), sowie Verunreinigungen, welche Legierung durch Kaltverformungvon mehr als 6% des daraus gebildeten Vorproduktes auf eine Materialhärte von größer als 230 HB, vorzugsweise von größer 250 HB, verfestigt ist, als Werkstoff für Warmarbeitswerkzeuge in der Glasindustrie, insbesondere als Formenwerkstoff für Maschinenpressgläser mit einer Arbeitstemperatur von höher als 555°C, vorzugsweise von höher als 602°C, insbesondere bis 750°C.Finally, the further object of the invention is achieved when using an iron-based alloy with alloying elements in wt .-% of Carbon (C) 0.04 to 0.15 Silicon (Si) 1.22 to 2.36 Manganese (Mn) 1.0 to 3.95 Chrome (Cr) 23.9 to 26.5 Nickel (Ni) 17.9 to 25.45 Nitrogen (N) 0.018 to 0.2 with the proviso that the nickel content of the alloy is equal to or greater than the value formed by the content of chromium plus 1.5 silicon minus 0.12 manganese minus 18 nitrogen minus 30 carbon minus the numerical value 6 $$\mathrm{Ni}\ge \mathrm{Cr}+1.5\times \mathrm{Si}-0.12\times \mathrm{Mn}-18\times \mathrm{N}-30\times \mathrm{C}-6$$

optionally one or more of the elements in concentrations in% by weight 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 Residual iron (Fe), as well as impurities, which alloy by cold deformation of more than 6% of the precursor formed therefrom to a material hardness of greater than 230 HB, preferably greater than 250 HB, solidified as a material for hot working tools in the glass industry, especially as a mold material for machine press glasses with a working temperature higher than 555 ° C, preferably higher than 602 ° C, especially up to 750 ° C.

On the basis of comparative test results, the material according to the invention should be described in more detail.
Show it
Fig. 1 strength as a function of 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 shown at a test temperature of 604 ° C, depending on the extent of cold working. The sample material was forged at a temperature of 1010 ° C and increasingly cooled from the forming heat and subjected to solution annealing treatment at 1060 ° C. Each part of the material was cold worked with a degree of deformation of 21%, 35%, 47% and 55%, after which tensile tests were made. The strength determinations, namely 0.2% proof strength and tensile strength, were made at a temperature of 604 ° C with the samples kept at that temperature for 20 minutes. For comparison For example, standard material was solution heat treated at 1060 ° C and samples made from it were also tested at 604 ° C. The bar graph of FIG. 1 clearly shows an increase in the strength values of the material as a function of the degree of deformation, wherein (not shown in the diagram) an increase in strength is given to a great extent already at a cold deformation degree of more than 6%, in particular greater than 12% ,

In Fig. 2, the fatigue strength of the material according to the invention at a 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 shown.

The material according to the invention was made with a composition 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 this thermoformed to sample material. The sample material was solution heat treated at 1060 ° C. followed by quenching in water, after which samples designated H 5 were undeformed and samples designated H 525 were subjected to long-term annealing at 600 ° C. with a cold working of 35%. The comparative materials No. 1.2083 and No. 1.4028 were hardened from 1020 ° C in oil, tempered at 630 ° C and also subjected to the long-term annealing. After 45, 90, 140, and 180 hours, the sample material was removed from the oven, allowed to cool, and the hardness of the material tested, followed by back-loading of the samples (with thermal cycling). The comparison material H 5 showed an expected behavior of the hardness, whereas the 35% cold-worked material H 525 according to the invention had an increased hardness of 315 HB and a high creep behavior. At 600 ° C no hardness reduction and no creep of the material could be determined even with changing thermal load. In contrast, the martensitic standard steels showed a marked decrease in hardness with the annealing time of the samples.

Claims (10)

1. Material of high inertness, particularly high oxidation stability, and high hardness for components and tools to be loaded with a temperature of up to 750°C, consisting of an alloy having a composition in % by weight of Carbon (C) 0.04 to 0.15 silicone (Si) 1.22 to 2.36 manganese (Mn) 1.0 to 3.95 chromium (Cr) 23.9 to 26.5 nickel (Ni) 17.9 to 25.45 nitrogen (N) 0.018 to 0.2 with the proviso that the nickel contents of the alloy is equal or higher that that value, which is formed from the contents of chromium plus 1.5 silicon minus 0.12 manganese minus 18 nitrogen minus 30 carbon minus the numerical value of 6 $$\mathrm{Ni}\ge \mathrm{Cr}+1.5\times \mathrm{Si}-0.12\times \mathrm{Mn}-18\times \mathrm{N}-30\times \mathrm{C}-6$$

   

   and optionally one or more of the elements present in concentrations in % by weight of molybdenum (Mo) smaller than 1.0 vanadium (V) up to 0.5 tungsten (W) up to 0.5 copper (Cu) up to 0.5 cobalt (Co) up to 6.5 titanium (Ti) up to 0.5 aluminium (Al) up to 1.5 niobium (Nb) up to 0.5 the remainder being iron (Fe) as well as impurities, wherein the material exhibits a hardness of more than 230 HB formed by cold deformation of more than 6%.
2. Material according to claim 1 having a hardness greater than 250 HB, particularly of 300 HB or more.
3. Material according to claim 1 or 2, wherein the contents of nickel of the alloy is greater by 4.8 % by weight in maximum, than that value which is formed in accordance with claim 1.
4. Material according to any of claims 1 to 3, which comprises concentration values for one or more impurity elements, in % by weight of oxygen (O) 0.05 in maximum phosphorous (P) 0.03 in maximum sulphur (S) 0.03 in maximum
5. Process for fabricating a material for components and tools, having a high reaction inertness, particularly being of a high oxidation resistance and having an elevated hardness at thermal loads with a temperature of up to 750°C, according to which from an alloy having a composition in % by weight of Carbon (C) 0.04 to 0.15 silicon (Si) 1.22 to 2.36 manganese (Mn) 1.0 to 3.95 chromium (Cr) 23.9 to 26.5 nickel (Ni) 17.9 to 25.45 nitrogen (N) 0.018 to 0.2 with the proviso that the nickel contents of the alloy is equal or higher that that value, which is formed from the contents of chromium plus 1.5 silicon minus 0.12 manganese minus 18 nitrogen minus 30 carbon minus the numerical value of 6 $$\mathrm{Ni}\ge \mathrm{Cr}+1.5\times \mathrm{Si}-0.12\times \mathrm{Mn}-18\times \mathrm{N}-30\times \mathrm{C}-6$$

   

   and optionally one or more of the elements present in concentrations in % by weight of molybdenum (Mo) smaller than 1.0 vanadium (V) up to 0.5 tungsten (W) up to 0.5 copper (Cu) up to 0.5 cobalt (Co) up to 6.5 titanium (Ti) up to 0.5 aluminium (Al) up to 1.5 niobium (Nb) up to 0.5 the remainder being iron (Fe) as well as impurities, a base product is formed, and this is subsequently further processed into a material of a hardness greater than 230 HB by cold deformation of more than 6%.
6. Process according to claim 5, wherein the base product is formed by hot-deforming, and is subjected to a solution treatment or is cooled down from the deformation temperature, optionally in a forced manner, and is cold-deformed.
7. Process according to claim 5 or 6, wherein cold deforming is effected completely in radial perpendicular direction to the longitudinal axis of the base product.
8. Process according to any of claims 5 to 7, according to which the contents of nickel of the alloy is adjusted to be greater by 4.8 % by weight in maximum, than corresponds to that value which is formed in accordance with claim 5.
9. Process according to any of claims 5 to 8, wherein a material having a hardness greater than 250 HB, particularly of 300 HB or more, is formed by cold-deforming.
10. The use of an alloy on an iron basis comprising alloy elements 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 chromium (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 contents of the alloy is equal, or optionally higher by 4.8% in maximum, than that value, which is formed from the contents of chromium plus 1.5 silicon minus 0.12 manganese minus 18 nitrogen minus 30 carbon minus the numerical value of 6 $$\mathrm{Ni}\ge \mathrm{Cr}+1.5\times \mathrm{Si}-0.12\times \mathrm{Mn}-18\times \mathrm{N}-30\times \mathrm{C}-6$$

    

    and optionally one or more of the elements present in concentrations in % by weight of molybdenum (Mo) smaller than 1.0 vanadium (V) up to 0.5 tungsten (W) up to 0.5 copper (Cu) up to 0.5 cobalt (Co) up to 6.5 titanium (Ti) up to 0.5 aluminium (AI) up to 1.5 niobium (Nb) up to 0.5 the remainder being iron (Fe) as well as impurities, which alloy is strengthened to a material hardness of more than 230 HN, preferably more than 250 HB, by cold deformation of more than 6% of the base product formed from it, as a material for hot-working tools in the glass industry, particularly as a die material for machine pressed glass with a working temperature of higher than 555°C, preferably higher than 602°C, particularly of up to 750°C.

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