DE1758295A1 - Iron-chromium alloy - Google Patents

Description

PatbktanvXlts Dirt-- Inc ί. Φβϊ & εμΧνΚ? "Dk. Ino. A. Vsickk ann DiPL-InG. 3HLVbICXUANN, DiFU-PhTS. DlU K. FlNCKE Dipl.-Ing. F. A ^ bickmann, Dipl.-Chem. B. Hubir

_ J

t MÖNCHEN Xf, DBN

MOHUTkASSB 12, EUFNUMMEK 413 * 21/22

Sch / Gl- ¹ ^ 3? Ile no. 28 605-Ϊ

AXR RBDUCIION ΟΟΜΡΑίίΥ, IliCOBPORA! EED _f Hew Toric, HT, / USA

Eiean-Ohiöm alloy

The invention relates very generally to iron-based alloys and relates in particular to Bite-Oiiroia alloys which have markedly improved physical properties. The invention also relates to a process for the production of such alloys

Containing chromium Eioen-Ohroro-Legierungon in an excess of about 4 i>, are generally referred to as stainless steels. As the name suggests, the stainless, SiKhIe are used in areas of application

which they are exposed to corrosive effects. The corrosion protection is given to the stainless steel mainly by the presence of chromium, whereby an increasing chromium content generally leads to an increased corrosion protection. Other alloy elements, primarily nickel, are also added to stainless steel in order to achieve certain desired properties, and the type and amount of alloy constituents must be carefully controlled to achieve the desired properties. The term "Elsen-chromium alloy" ^{1 used is} intended to mean those alloys which are generally referred to as stainless steels, with iron-chromium alloys also being added which are not usually regarded as stainless steels.

The crystal structure of iron-chromium alloys has a noticeable effect on the alloy properties. Three different crystalline structures can be found on cooling to room temperature depending on the amount of chromium, nickel or other Alloying agents are formed, namely an austenitic one Structure, a ferritic structure and a martensitic structure Structure or mixtures of these structures. Niokel, cobalt, manganese, copper, carbon and nitrogen are used as agents considered to be the formation of an austenitic structure, since the presence of this material ion in stainless steels results that has a tendency to maintain an austenitic quality

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_ 3 -

Crystal structure is reinforced. Chromium-silicon-molybdenum, tungsten, vanadium, tin, Mob, phosphorus, aluminum and Eitan are known as ferrite-forming elements, since these materials tend to stabilize a ferritic grain structure in the steels. Martensitic crystal structures are created by the presence of appropriate combinations of both ferritic and austenitic structure constituents in the stainless steel. By balancing the relative amounts of materials which alloy in you make an austenitic or ferritic structure, a given Eiaen-Ohrom-Iegierung can often be controlled by known methods, that it comprises an austenitic _f ferritic or martensitic structure or a combination of these structure types owns ₀

Even if stainless iron-chromium steel alloys have a desired corrosion resistance, the addition of the alloy components, which are necessary to achieve corrosion resistance, has the consequence that the stainless steel alloys are more difficult to process than normal steel or unalloyed steel «Austenitic, Ferritic and martensitic iron-ear alloy alloys all have a tendency to form surface giants in the form of edge cracks. In addition, streaks occur when the alloys are machined in such a way that a high degree of area reduction takes place, whereby

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slttslioh work hardening occurs. Some ferritic alloys are against a particular undesirable upper. susceptible to the formation of surface cracks, which is generally known as "Ober * Fl & ohen-Roping ¹¹ '" To eliminate these disadvantages, various glow and surface conditioning treatments have been provided when eljaeBramw * ee * erial is valued on iron sheet. In addition, alloys are notch sensitive, especially if they contain more than 20% "ear", so that they can be processed with the prevention of acuohformation. must be carefully over * weighed because of the activity. Austenitic Sisen-Chroa alloys have a higher strain hardening consistency than fenitic or nartensitic alloys and tend to change to Martens when they are old-fashioned! t.

Because of the widespread use of stainless steel alloys in fields of application, on the one hand a surface corrosion resistance and on the other hand decorative appearance of the surface is sought « Numerous research work was carried out to find out about these properties. and swar in general through the development of new combinations of alloy constituents · ». Less attention was ready for the improvement of heredity. Alloys without retention of the usual corrosion *

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durability given

E3 is generally known that stainless steels which have a low content of vacancies, ie _o the carbon and nitrogen content is low, have an improved corrosion resistance, and generally easier to process at given tensile strengths than similar stainless steels having a higher carbon - and have nitrogen content «, It is assumed that the improved workability, which is found with a low content of castings, is due to the fact that no carbides and nitrites are present at the grain boundaries _e

Other materials are also present as impurities in the iron-chromium alloys, generally in small amounts o for example below about 0.1 weight - ^ = One class of impurities present in all stainless steels on the market is the "volatile metallic" Impurities ¹¹ , which include lead, vismuth, cadmium, sodium, potassium, silver, calcium, magnesium, barium, zinc and antimony. The volatile metallic impurities can be divided into two classes, namely lead, vismuth, cadmium, Sodium, potassium, silver, calcium, magnesium and barium, these elements being essentially insoluble in iron, as well as in zinc and antimony, which are easily soluble in elsen.

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Common iron and ear alloys contain these impurities in varying quantities, depending on the raw material source, as well as the manufacturing process, GewöhnlLoh are in the im Commercially available chromium alloys containing insoluble volatile metallic impurities in quantities The volatile metallic impurities soluble in iron are found in amounts between about 100 and 200 ppm. Sa one so far βτνηηΐηη that the presence of these impurities in Iron-Ohrom alloys did not affect the corrosion resistance as well as the physical properties of these alloys, the presence of these impurities was not observed Importance is given, especially with regard to the workability of the alloys, such as a micro-sample analysis of Shows fractures of the stools containing the impurities by means of an electron beam, there are noticeable zinc concentrations at the fracture point, from which it can be seen that the presence of soluble volatile metallic impurities in the iron-o-ear alloys can help that the alloys suffer damage

The relative ease with which a metal can be processed can be determined simply by: the metal can be deformed with great ease, for example by rolling or drop forging. Sin another The ductility is an indication of the ease of processing

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as well as the toughness of the metal, tlftö method of determination the toughness of iron-chromium alloys ordered therein * the Ability of the alloy to "determine an impact load su resist. In addition, the impact strength, which is obviously related to the possibility of high stresses as well as to withstand low cyclic strains "in use of the alloys in such areas of application are of importance in those with shock loads or strong impacts must be reckoned "

The impact strengths of commercially available austenitic iron-ohrom alloys ^{do not change noticeably within wide temperature ranges, for example between -196 and 93 0} O (-320 and 20O ⁰ F), the impact strength being in the longitudinal direction of the commercially available austenitic alloys generally sufficient for most purposes. In contrast, the impact strength of commercially available austenitic alloys in the transverse direction is significantly lower than in the longitudinal direction. Similarly, the impact strength of commercially available austenitic and ferritic alloys is significantly lower in the transverse direction than in the longitudinal direction.

In addition, the ferrite alloys show more typical Wise a noticeable reduction in impact strength in the longitudinal as well as in the transverse direction at temperatures in the vicinity

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from room temperature or above (the impact transition temperature), at temperatures below « The ferritic alloys have half room temperature very low impact strengths and are also very brittle, Therefore, the ferritic alloys cannot be used for such Purposes are used in which they are subject to a floor exposure at temperatures below the transition temperature »i.e. significantly below room temperature. In this way, the ferritic Elsen-Ohrom alloys remain closed to many areas of application in which they are In spite of adequate corrosion resistance, they have to be replaced by the relatively more expensive austenitic alloys because of the possibility of sagging stress. this applies particularly to welded structures, as ferritic welds oppose crack formation as a result of the Bohleohten Duktil! Did at room temperature as well as the carbide secretion on the welded parts, which occurred during heating occurs, are susceptible

The aim of the present invention is the acquisition of Sl

Chromium alloys, which have improved mechanical and physical properties. Invention Iron-Ohrom alloys are provided with improved ductility but which can be calibrated in a simpler manner than that allow previously known alloys to be processed.

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create> which have a superior ductility and resistance to impact stress at room temperature · Furthermore, the iron-chromium alloys according to the invention have improved impact strengths, especially in the transverse direction. It is also within the scope of the present invention to provide an improved method of making iron-earring alloys ₉ which have improved physical and mechanical properties as well as improved workability.

The present invention is illustrated by the accompanying drawings explained in more detail.

Figure 1 is a graph showing the dependence of impact strength on temperature for two in the trade available austenitic stainless steels as well as for one shows an austenitic iron-chromium alloy according to an embodiment of the present invention.

Figure 2 is a graph showing the dependency according to the true compressive stress from the hammer energy for some austenitic alloys. Embodiments of the invention shows.

Figure 3 is a graph showing the bottom transition temperature range in the longitudinal direction for a

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- ίο -

the available cold-processed dead and annealed ferritisols stainless steel and the transition temperature in the longitudinal direction for both a non-processed and a cold-processed and annealed ferritic iron-chromium alloy shows according to an embodiment of the present invention.

Figure 4 is a graphical representation similar to Figure 3 showing the impact temperature range in the transverse direction of the commercial available ferritic alloy as well as the ferritic alloy Alloy according to Figure 3 shows.

The present invention is concerned generally with iron-chromium alloys, which "between about A and about 40 Ί" of chromium, between about 0 and about 14 liters, carbon and nitrogen in slopes such that the carbon and nitrogen at room temperature in solid solution, no more than about 6 ppm insoluble volatile metallic impurities, ie lead, bismuth, cadmium, sodium. Contains potassium, silver, oalolum, magnesium and barium, and no more than about 20 ppm of soluble volatile metallic components, ie zinc and antimony. The iron-chromium alloys have significantly improved physical and mechanical properties and, compared to known iron-chromium alloys, have improved impact strengths. Austenitic iron-chromium alloys

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have improved impact strengths at all temperatures, for example at room temperature down to the temperature of liquid nitrogen (-196 ⁰ O (-520 ⁰ P)). The transverse impact strength of the austenitic and martensxtic egg-chromium alloys according to the invention is more than twice the impact strength in the transverse direction of similar known alloys which contain volatile metallic impurities ⁰ F)) noticeably improved impact strengths both. in the transverse * as well as in the longitudinal direction, the transition temperature ranges also generally being below room temperature.

The present invention also relates to a process for the production of iron-ohrom alloys, which consists in that a molten bath of the alloy is heated under a reduced pressure by means of an electron beam, the heat supply by the electron beam and the speed of the molten metal Alloy can be controlled such that the molten alloy is heated by the electron beam during such a period and at such heating rates that the content of volatile metallic impurities is less than about 6 ppm insoluble

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Low volatile metallic impurities and less all approximately 60 ppm soluble volatile metallic impurities is reduced.

In addition, the carbon and nitrogen content of the iron-chromium alloy is reduced to relatively low values _P so that solids and nitrogen are in solid solution in the iron-chromium alloy at room temperature. In an expedient manner, the process is controlled in such a way "that the total amount of carbon plus nitrogen is below * half 150 ppm and generally between 70 and 100 ppm ο larger amounts of carbon plus nitrogen can be tolerated in the austenitic alloys" for example up to 600 ppm, because these elements are more soluble in austenitic alloys than in ferritic or martensitic alloys.

The noticeably improved impact strength, both in transverse as well as in elongation, are proof of that markedly improved manufacturability and processability of the alloys described in comparison to similar iron-ohrom alloys known to date. Without relying on one wanting to define a certain theory, one can assume that the improved physical and mechanical properties of the alloys described are the direct result of the fact that practically no volatile metallic

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Impurities are present, with the fact that the content of carbon plus nitrogen in the alloys is low. As already mentioned, there are two classes of volatile metallic impurities present in iron-chromium alloys. According to the invention, the alloys contain less than 6 ppm of these volatile metallic impurities, which are defined as "insoluble", and less than 20 ppm of such volatile metallic impurities impurities true "in the definition vralche" soluble ¹¹ »Preferably, the volatile metallic impurities in an amount of not more than about 2 ppm, while the soluble volatile impurities are no longer encountered ppm in an amount of as approximately 10x.

It should be noted that the terms used "Insoluble" and "Soluble" are relative and only serve that purpose intended to clarify the difference between the two classes of volatile metallic impurities «These volatile Metallic impurities tend to be concentrated at or near the grain boundaries of the alloy to become. It is believed that this concentration of these impurities at the grain boundaries or near them the reason for this is that the iron-chromium alloys decreased Having strengths «The insoluble fleeting ones metallic impurities, namely lead, vismuth, cadmium, ITodium, potassium, silver, calcium, magnesium, and barium, are

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essentially insoluble in bis-chromium alloys at all concentrations. There is a tendency for these impurities to settle in the iron-chromium alloys at the grain boundaries concentrate in the form of precipitation eu. Ss is therefore from of great importance because the alloys are essentially free of insoluble volatile metallic impurities, doho that they contain less than 6 ppm of these impurities.

Zinc and antimony, referred to as "soluble" volatile metallic impurities, are somewhat more soluble in the iron-ear compounds than the insoluble volatile metallic impurities and are not as deleterious Effect from like this the insoluble impurities -tan there they are not in the form of precipitation. However, the soluble volatile metallic impurities also tend to be concentration at the grain boundaries. It is believed that their presence at the grain boundaries or in the vicinity of the grain boundaries is responsible for the fact that the alloys have reduced strengths «. Consequently, the iron-chromium alloys should be essentially free of soluble volatile metallic impurities, i.e., they should contain less than about 20 ppm.

It should be noted that the measurement of extremely low levels of volatile metallic impurities in

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the iron-chromium alloys a very difficult analytical task Problem is bio limits given above for volatile metallic impurities are approximate and not absolute limits slightly differ from the alloys given above, but with improved impact strength and processability own «also fall within the scope of the present invention«,

As mentioned, Bisen-Ohrom alloys and in particular stainless steel alloys in general by their crystalline Configuration, namely an austenitic, ferritic, martensitic configuration or combinations these configurations. Many stainless steel alloys are mixtures of the different crystal configurations · The properties of the alloys depend largely on the extent to which the various crystal configurations exist in the alloy. Because of dte ^ er various properties as well as vague the fact that the end uses of the alloys heretofore commercially available depend on the crystal configurations of the alloy, each of the three types of crystal configuration is separated discussed «Eb, however, it should be noted that in In many cases, the alloys can also have other crystal configurations to a certain extent, so that the statement that an alloy is austenitic, ferritic or

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zaartensitisoh, only that serves to serve the predominant crystal configuration in an alloy.

Austenitic alloys

$ ± e austenitic iron-chromium alloys are alloys solohe, sufficient amounts of austenite stabilizing agents containing _r to result in, that the LE

w may have an austenitic crystal configuration at room temperature. The primary austenite stabilizer is niokel. Essentially all commercially available austenitic iron-chromium alloys contain nickel, usually in an amount between about 6 and about 12 weight percent, while the chromium content is generally between about 17 and about 22 percent _o Other austenite stabilizers such as carbon, nitrogen! Manganese, cobalt or copper can replace part of the nickel. In the AISI figuring system, the 300 series of stainless steels is generally austenitic. The presence of nickel in stainless steel-iron-chromium alloys is primarily intended to provide sufficient ductility that the stainless steel alloys can be processed into desired shapes and the alloys can be whitened.

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BAD ORIGtNAL

7 κ

The alloys produced according to the invention have, compared to conventional ones made of ten! Table alloys that are produced by customary manufacturing methods, "for example, by methods that are run using an oxygen-blowing furnace _9, a double-arc furnace or a vacuum induction furnace, markedly improved physical and mechanical properties. It was found that the austenitic alloys according to the invention are simple can be processed cold and hot and can be so-whitened with better results than usual.

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1 Cr Hi Weight- ^ <0.3 M. Table X 220 ] ■ Μ
N / A ppm
0 S. 180 fleeting me
metallic 2 17.2 10.2 N / A 1.54 0.14 650 N / A N / A 70 270 50/150 BgisOiel 3 18.3 9.1 0.1 HA 0.3 Si Ti V W divide σ 140 110 N / A 240 170 > 300 total 4th 18.6 9.7 0.003 HA 0.10 0.55 <0.001 <&, 1 <0 ₉ 1 170 50 9 80 170 <6/20 5 17.6 9.8 0.003 HA 0.12 0.4 HA NA HA 0.16190
Zr N / A 9 80 170 <6/20 6th 16.8 10.0 0.003 0.34 0.11 0.55 <0.001 <0.04 <0.1 200 98 N / A 60 180 <6/20 7th 18.5 9.9 0.003 <0.03 0.12 0.55 0 "082 <D, 04 <0.1 60 35 12th 70 180 <6/20 8th 20.5 10.3 0.003 HA 0.1 0.58 <0.001 <0.04 <0.1 100 N / A 12th 60 110 <6/20, N>
O
(O 9 16.4 13.4 HA HA 2.2 0.55 <b, 001 <0.04 <0.1 100 HA N / A 90 350 <6/20 cd CO 10 17.3 13.0 HA HA 2.0 0.06 <0.001 <0.04 <0 ₉ 1 100 N / A N / A 90 340 <6/20 ^§ ^ 16.3 9.1 0.003 0.1 0.08 HA NA HA N / A 60 <6/20 ο
to
ο HA HA HA HA a » 0.08 0.06 <0.04 <0.1

GD

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cn

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The table summarizes the compositions of some aueteniti ** ΰciier Sisen-Ghrom alloys. The examples ! and 2 represent commercially available auetenitisohe rosti'rsiö steels is that the iJSI-örad 304 correspond ο Example 1 shows a melt obtained by YakuumindvJrbion This Sohmelse wira according to the latest technical durohiUhrbaren Torfahren prepared _o Example 2 is a a Slektroofon obtained melt again. Examples 3-9 show nominal compositions that are comparable to commercially available stainless steels of the AISI 300 series, with; with the exception that according to Examples 3-9 each less than about 6 ppm of insoluble volatile metallic impurities and less than about 20 ppm of volatile metallic impurities are present. The alloys of Examples 3-9 also have such carbon and Nitrogen content means that the carbon and nitrogen are in solid solution at room temperature, ie that the total content of carbon plus nitrogen is below approximately 300 ppm. Therefore, the alloys described have slightly lower contents of carbon plus nitrogen than commercially available stainless steels with a corresponding nominal composition «

The noticeably improved properties of the objects of the invention Austenitic iron-chromium alloys go from the

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BATH

Pigur 1 "In FIG. 1, the Clrarpy-V-Xerb impact strength values (ASIM No., A 370-67) are plotted in both the transverse and longitudinal directions of the alloys of Examples 1, 2 and 3" How to As can be seen from the figure mentioned, the austenitic stainless steel described according to Example 3 has significantly higher impact strength values in transverse and longitudinal directions than one of the commercially available stainless steels according to Examples 1 and 2 ₀ 3, the impact strength in the longitudinal direction at room temperature * equivalent, being foot at -196 ⁰ C C-320 ° F) about 13? 0 mkg (100 pounds) exceeds. The excellent improvement in the impact strength according to Example 3 can also be seen from the fact that at -196 ⁰ O (-32O ⁰ F) * the impact strength of the commercial stainless steels according to Example 2 is greater in the transverse direction than in the longitudinal direction, which is the impact strength in the longitudinal direction according to Example 1 is the same.

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BAD ORlGiNAU table IX

CSharpy-V-NotchBchlag- pyg

Crowning with Sirner crowning "at -196 C area- ^ Αο,

temperature, mkg * (-320 ⁵ ^, a & g- mination ,, ^ ratio

Example ^r

in longitudinal direction in transverse direction in longer, in transverse " In Mngsr" in transverse "

O Ca> O CD

1 26.6 10.4 18 _S 2 7.8 10.0 7 * 4 0.74 2 19.3 - 14.0 - - «Ml 3 30.5 30.5 20.3 16.6 10 * 9 10.4 0.95 4th 29.9 27.9 17.4 13.9 10.7 10.1 0.96 VJl 27.4 9.7 11.1 3 ₉ 9 10.3 9.9 0.96 6th 30.5 27.9 20.5 16.9 10.6 9.9 0.93. _f 7th 29.9 29.9 18.2 13.0 11.2 10.8 0.97? 8th 27.9 14.3 22.1 8 _S 4 9.7 9.4 . 0.96 ^! 9 23 ₉ 4 15.6 16.9 5.2 9 * 7 9.5 0.97 10 20.8 13.0 11.7 5.2 1O _ft 5 10.4 0.99

Table II shows the impact strengths of the alloys according to Examples 1-9 in the longitudinal and transverse directions at room temperature and at -196 ⁰ O (-320 ⁰ F) ppm of insoluble volatile metallic impurities and less than about 20 ppm of soluble metallic impurities, have substantially improved longitudinal and transverse impact strengths than the conventional stainless steel alloys of Examples 1 and 2. The alloys of Examples 4-9 have nominal compositions which correspond to some stainless steels of the AISI series 300, further alloy components being included. The alloy according to Example 5 contains 0.16 zirconium. It can be seen that the transverse impact strength is reduced by the presence of zircon in the alloy. However, the impact strength values of the alloy according to Example 5 are superior to the values of conventional, zirconium-containing stainless steels with a similar nominal composition. The alloys of Examples 4 and 6 contain titanium and manganese alloy components, respectively. It can be seen that these alloy components do not affect the transverse impact strength of the alloy, hence it is possible to add manganese, which is usually added to stainless steels to reduce their sulfur content. Trots of this addition will still have significantly superior impact strengths in transverse and longitudinal rioh

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received.

In de ?: Table II also gives values for the area reduction (in. %) In. Longitudinal and transverse direction. In addition, the Ec A "/ J. Ratios of Examples 1-9 are listed" The R, A · Tβ " Ratio is the ratio of the surface area reduction in the transverse direction {in $) {ASiEM-Kr, A370-67) au. the area reduction (in fi) in the longitudinal direction? expressed as decimal Ksahlο The E.AoE ₀ ratio is an indication of the anisotropy «, Eohe E ₀ A ₀ T» ratios indicate sirae low anisotropy and therefore give an indication of the ductility. It can be seen that the R ₆ A _e To ratios of the austenitic alloys according to Examples 3-9 are all above 3.9 and mostly exceed 0.95 «Conventional austenitic stainless steels have much lower R _C AI ₀ ratios of 0.75 or below, ■ as from your E. * A. T, ratio of Example 1 is shown.

In addition to the significantly improved impact strengths and Ε, Α.ϊο ratios, the noticeably improved Properties of the austenitic alloys according to the invention also emerges from other reads and comparisons with common austenitic stainless steel alloys. For example a 16 cm (2 1/2 inch square) ingot is made from the stainless made by a vacuum induction process Steel according to example 1 (the mentioned manufacture

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s-feeilenaverfahren is the most modern steel production process, which is carried out on a technical scale, in an open drop forge to one. 25 mm (1 inch) ~ forged round bars. After about 40 £ lgen Fläohenverminderung the billet shears through completely at an angle of about 45 ⁰ C. His examination of the partially forged bar made of common stainless steel shows edge cracks and stresses inside the bar, as evidenced by a shift in the stress concentration lines on the surface,

2 which are visible to the naked eye emerges · A 16 cm {2 1/2 inch square) bars according to example 3. of the one im has essentially identical chromium and nickel content, but less than 6 ppm insoluble volatile metallic impurities and less than 20 ppm soluble metallic impurities Contains impurities, is forged in the same device under identical conditions into a 25 mm (1 inch) soundbar, with no signs of embrittlement being discernible.

In simulated hot rolling, pieces 76 mm (3 inohm) long, each cut from a 16om (2 1/2 inohm square) ingot of an alloy of Examples 3, 4 and 6, are hot to form a hot strip rolled to a thickness of 3 mm (0.12 inches). The hot processing sees a low finishing temperature (76O ⁰ C (1400 °?)) Compared to a normal finishing temperature of

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of 982 ⁰ O (16θβ ° ^?> before the low finishing temperature which normally promotes edge cracks, none of the austenitic alloys of Examples 3, 4 and 6 show any cracking.

In other Heise rolling tests, it turns out that _f require as is the case with conventional austenitic system stainless steels, the novel austenitic alloys smaller Walzenb. In addition, it is possible ₉ with the austenitic alloys according to the invention to carry out separate barefcgSage and to carry out the finishing at lower temperatures without problems with regard to the roller load or the winding, Sin hot rolling of the alloys of Examples 3? 4 and 6 at a finishing temperature of 899 ⁰ O (165O ⁰ F) itsct Walsen First Load, which are similar to those using AISI-304 steels which are finished at a temperature of 982 ⁰ C (), appear. This enables the production of thinner hot strips from the alloys according to the invention, with the fact that subsequent cold rolling and annealing are superfluous.

To carry out cold rolling tests, 25 mm wide Strips made of alloys of Examples 3, 4 and 6 made of 3 mm thick hedbevmr ^ others cold-rolled. In doing so, surface areas are

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reductions of more than 80 1 ° are achieved without any of the samples forming streaks or tearing.

Cold upsets using alloys of Examples 2, 3, 4 and 6 are performed by cutting cylindrical blanks from cold drawn and annealed bars and then forging the blanks together using a 54 leg {120 pound) hammer dropped from various heights The results of the cold upsetting test are summarized in FIG. 2, in which the true upsetting that is generated in the sample is plotted against the energy imparted by the hammer. The curves for Examples 3 and 6 are identical. Figure 2 also indicates the expansion in the Bruoh of each alloy by means of a horizontal arrow · In addition, the expansion in the Bruoh of a common austenitic stainless steel (AISI 305) is shown in Figure 2 by means of a cross, the 18 $> chromium and 13 tons Contains nickel.

In the cold condensation tests, the test blanks reach temperatures above 316 ⁰ O (600 °?) At high elongations.The energy required to generate the given elongations represents a qualitative factor in the relative strengths at temperatures of 316 ⁰ O (60O ⁰ P) or above.

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175c, :::

The stainless steel alloys Y / ie 3üäü sees give dsr Examples 3 »4 and 6 elongations ,, which that of a conventional stainless steel (AISI 305) _s of the higher-Hickelge Iialto having" ,, are äcmivalent. This shows that the auatenitic alloys described can be used instead of the usual alloys with a higher molten content to achieve the same cold diving properties are, conventional alloys (AISI 384) that are used for cold upsetting, for example for the production of screws and rivets, replace * As can be seen from FIG - replace alloys »

Are calculated using the alloys of Examples 2, 3, 4 and 6 t Kaltziehversuohe after Swift Napfziehversuch and by the Olsen ITapfziehversuch (ASIM Hr ₀ A344) performed Austenitic alloys of Examples 3 »4 and 6 are in this case by 15 & or more superior to the usual alloys of Example 2.

Sorrosion tests are also carried out, whereby it is established that the austenitic alloys according to the invention

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In general, better stress corrosion resistance, intergranular corrosion resistance and massive corrosion than is the case with equivalent customary stainless steels. Standard ASiPM-Huey-IEeste (no. A262-64), "in execution, the corrosion rate in boiling 65 $ nitric acid is measured» aeigen that the austenicisehen alloys of Examples 3 _e 4 and 6 as compared to the alloy of Example 2 have superior corrosion resistance in the sensitized form, comparing to their gate portion when compared to stabilized common stainless steels (AISI 321 and 347) when used for white vex driving

Ferritic alloys

As can be seen from the above paragraphs, the austenitic alloys according to the invention have significantly improved impact strengths in both the transverse and longitudinal directions. These impact strengths are improved over the entire temperature range from -196 ⁰ O (-320 ⁰ P) to room temperature and above. From FIG. 1 it can be seen that the impact strengths decrease with decreasing temperature, this decrease generally taking place linearly. Ferritic alloys, which contain relatively small amounts of nickel, generally less than 2 fi and often less than 1 #, have completely different impact strength curves

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175829

as this is "at austenitisohen alloys of the Pall conventional ferritic stainless steels" possess impact strengths which are generally the impact strengths of conventional austenitisoher stainless StMhIe at elevated temperatures, ie (? 200 ⁰ I) are similar at temperatures above 93 ⁰ O. However, in ferritic stainless steels, a noticeable reduction in bottom toughness occurs generally within a temperature range from about room temperature up to 66 ⁰ O (150 ⁰ F), with conventional ferritic stainless steels having a negligible impact strength at temperatures below room temperature.

I) the temperature or the temperature range at which or «within whose impact strength of ferritic steel is noticeably reduced, is referred to as transition temperature. At temperatures below the transition temperature are ferritic stainless steels brittle and prone to breakage, while at temperatures above the transition range the orritic stainless steels are regarded as tough become «The transition temperature range of a ferritic alloy is important for the usability of the alloy. For example, for welded components »such as For example, ship hulls or Bruckkessel, rapidly advancing fractures caused by protruding, which by a shock load at temperatures below dcx transition temperature, a complete decomposition

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disruption of the components. It is therefore important that the transition temperature of ferrite-insulating alloys Unterhall) is room temperature if this material type is used Manufacture of welded components should be used

It is known that it is difficult to specify a specific temperature as the transition temperature of ferritic alloys. When testing different samples from the same Block are generally determined different transition temperatures «It is believed that this is due to differences can be attributed to the processing of the samples, with the respective grain orientation at the break point as well as other mechanically induced defects which lead to a spread in the transition temperature values for similar ferritic alloys should be taken into account ferritic alloys according to the invention have because of the complete absence of volatile metallic impurities and because of the very low carbon and Nitrogen content much broader transition temperature range. Therefore, the specified invert toughness values, although they are representative for a large number of samples, should not be regarded as absolute. Higher. and lower values as well as slight shifts in the transition temperature range can also occur.

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1758

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• 3-series ferritic stainless steels are nevertheless of importance, whereby the values explain the improved processibility and integrity of these alloys in the same way as conventional ferritic alloys Operating conditions as well as being able to use the ferritinous alloys according to the invention in welded components under ambient conditions.

814/0308

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2098U / 0308

BATH ORIGINAL

lengthways in Transverse direction Tabel IY £ ELäohea- iiisrriehl ILAoiiL-Ver
WLtnXß 15.0 6.5 transitional
temperature
in Ii £? igBrich, ~ Transitional
temperature
in Querrich
tung ρ C In the meantime "" C 6.5 6.5 Gharpy ~ V ~ Impact
sehiskeit at 9T ¹ O 30.5 30.5 80/107 121 92 (200 ^σ Ρ)
Example mlcg 30.5
30.5 30.5
30.5 66/107 66/107 88 89
84 0.94 30.5 30.5 -18/10 -40 / -18 89
85 81 0, · ,; 11 30.5 30.5 -18/10
-40 / -18 * -4O / -7
-18/21 79 80 1.03, _? 12th 30.5
30.5 30.5
30.5 -40 / -18 * 84 75
13th 0.95; '· « 13th 38/66 24/60 61
54 6th 0.61 ^: 14th
to
ο 15
CD 4/38
80/107 66/99
93/121 60 0.09 107/163 135/163 C17 ** ο
O
«19 ** 20 **

* cold processed xmd annealed at 788 ⁰ O (HSO ⁰ P). «Hi impact strengths measured at 149 ° C (30O ⁰ F).

In Table III the compositions of a ferritic alloy leg are given, which are nominal compositions corresponding to typical stainless steels from the AISI 400 range "You own alloy of example 11 is a common one, melted in an electric furnace, while the alloy of Example 12 is a melt that is in a The alloys of Examples 13-20 are ferri-

Table alloys containing less than 6 ppm insoluble volatile metallic impurities and less than 20 ppm soluble volatile metallic impurities. In Table IV, the Charpy V-notch toughness values in the longitudinal and transverse directions of the alloys of Examples 11-16 are at 93 ^° O (SOO ⁰ F) and in Examples 17-20 at 149 ⁰ C (300 ⁰ P), the transition temperature ranges are also listed both in the longitudinal and in the transverse direction

) Transition temperature for a number of samples.

However, such a measurement can only be relatively reliable. Table IV is not intended to specify absolute transition temperature ranges, but a comparison of the impact strengths shows as well the transition temperature ranges of the ferritic alloys according to the invention with the corresponding values are more common rostfxelor steel alloys clearly show the noticeably improved physical and mechanical properties that the have alloys according to the invention.

2098U / 0308

175829η

Gaaäee example 11 has a stainless steel (AISI 430) ei? I <-

ohlagzähigkeit in the longitudinal direction of less than 13 mkg {100: tt _e lb _a) at 93 ⁰ C (200 ⁰ P) and an impact strength in transverse direction at 93 ⁰ O (200 ⁰ F) of Veniger than 6.5 mkg (50 ft. lb.). According to Example 12, another sample made of a conventional stainless steel (AISI 430) has impact strength values in the transverse direction in the longitudinal direction of approximately 6.5 mkg (50 ft.lbo) at 93 ⁰ O c 20 O ⁰ Jf). Examples 13-16 describe alloys which. OKiinelle compositions have "the ferritisohen LE" alloys of the AISI 400 series corresponding to "These alloys possess impact strengths in the longitudinal and transverse direction at 93 ⁰ C (200 ⁰ F) * which are appreciably larger than the impact strengths of the alloys of Examples 11 and 12,

Furthermore, "and this is even more important," the alloys of Examples 13-16 have markedly lower overtemperature ranges than is the case with conventional ferritic stainless steels of Examples 11 and 12. The alloy described in Example 11, namely a melt melted in an electric furnace, has a transition temperature range in the longitudinal direction between approximately 80 and 107 ⁰ O (175-225 ° 3?) And a transition temperature range in the transverse direction of over 121 ⁰ C (250 ⁰⁾ F), The vacuum induction melt described in Example 12 has transition temperature ranges in the longitudinal and transverse directions between approximately 66 ⁰ O and 107 ⁰ C (150 ⁰ P and

2098U / 0308

225 ° 2?) O The alloy according to example 14 has a transition temperature range in the longitudinal direction between approximately -18 and 10 ⁰ O (0 and 50 ⁰ P), as well as a transition temperature range in the transverse direction between approximately -40 and -7 ⁰ C (-40 and 2O ⁰ P) c The alloy according to Example 15 has a transition temperature range in the longitudinal direction of approximately -40 to -18 ⁰ O (-40 to O ⁰ P) and a transition temperature range in the transverse direction between approximately -18 and 21 ⁰ O (0 and 7O ⁰ P) o The downward shift of the transition temperature • fcurbereiohes of the alloy according to example 5 in comparison SU of the alloy according to example 14 takes place during cold processing up to at least about 50 ^ igen deformation ₉ whereupon a grain refinement annealing, for example at 788 ⁰ C (145 ⁰ P ) This shift is explained in FIG. 3, in which the dashed area A represents the transition temperature range in the longitudinal direction of the hot-rolled material according to Example 15 and the dashed area B corresponds to the transition temperature range in the longitudinal direction of the material according to Example 15 after cold processing and annealing at a temperature of 788 ⁰ O (145O ⁰ P) o The dashed area 0 corresponds to the transition temperature range in the longitudinal direction of the alloys of Examples 11 and 12,

FIG. 4 shows the transition temperature range in the transverse direction a hot-rolled and not annealed sample of the le-

2098 1A / 0308

BATH ORIGINAL

Alloy according to Example 15 in the dashed coat A and the transverse temperature range of the alloys of Examples 11 and 12 in the dashed rope Co If transition temperature *) eroxohe maintenance) -18 ⁰ O is therefore desired, this can be obtained by simple cold processing and annealing will <,

From Table IV and from Figures 3 and 4 it can be seen that the transition temperature ranges of the alloys according to the invention are significantly lower than those of conventional alloys which have similar nominal compositions if the alloys are to be welded "As mentioned above," having usual ferritic alloys transition temperature ranges at or lie above room temperature ,, wherein occur under the influence of shock loads Hisse in Sohweissungen. usual (iron-chromium-Legieriuigen containing 25 1 »contain chromium can not be welded without cracking Therefore, the usual ferritic alloys are often welded for manufacturing structures. In contrast, possess the novel ferritic alloys containing 10 to about $ 25> chromium, less than about 6. ppm insoluble volatile metallic impurities and less than about 20 ppm soluble volatile metallic impurities

2098U / 0308

and contain less than about 150 ppm carbon plus BuB, transition temperature ranges in both longitudinal directions in the transverse direction, which are generally below room temperature, with no crack formation in the welds under ambient conditions

The ferritic alloys according to the invention are capable of such areas of application »in which at room temperature | a weldability and / or impact strength is required, austenitic alloys for the production of Structures that are welded or the. Be exposed to impact loads. Since the corrosion resistance depends primarily on the chromium content of the alloy, the ferritic alloys according to the invention can be used instead of the more expensive ones containing nickel Austenitic alloys can be used, so that the manufacturing cost can be reduced without doing so neither the corrosion resistance nor the impact strength is lost «

Table II also contains values for the expansion reduction (in Jt) of the ferritic alloys from the table that Ro A, T, ratios of about 1.0 are easily obtained · This is a further indication of the excellent ductility of the ferritic alloys and shows the extremely low anisotropy these alloys.

2098U / 0308

175829;

The improved processability and audibility of the he-Ind-angßgeniässen alloys is also shown by the Heissvai «r ---- m. The ferritic alloys according to the invention can be rolled up to a surface reduction of 50 # box less than that required for 30 # 3 surface milling of equivalent customary ferritic alloys. As stated above in connection with the austenitic alloys, does the lightness? With which the hot rolling can be carried out, a "double" gate part, namely a reduction in the number of centuries by the rolling mill and a reduction in the load on the rollers _{, etc.}

In cold rolling of the inventive ferritic alloys, it has been found that these levels with higher Verfornrungs "without Kastenglühung (760 ⁰ G (1400 ⁰ P) over a period of 15 hours), which customary in cold rolling ferri" tisoher alloys to prevent intergranular Kor - j rosion is required during pickling and to increase deformability, can be deformed. Cold-rolled ferritic alloys according to the invention are, according to the orphan, using a non-annealed hot strip with a degree of deformation of 40 % softer than usual ferritic alloys that have been rolled from an annealed hot strip, consequently it is possible to omit the box annealing of the ferritic alloys according to the invention.

2098U / 0308

Samples Ohrom iron alloys containing from non-annealed heieeen ferritieohen bands of the 10 »16 or 26 f> chromium, can be of a Dioke of 25 mm (1 inch) to a thickness of 0.15 mm (0.006 inch) (Deformation degree 99.4 SO cold-roll without cracks in the edges. A sample of the alloy similar to Example 12 is deformed at a deformation degree of approximately 50 pounds.

The grain refinement of the ferric alloys according to the invention can also be carried out at lower temperatures. Cold rolling with a Verfornungegrad from 80 $> and a an3ohlleesendes annealing at a temperature of 760 ⁰ O (1400 °?) Lower for a period of 5 minutes (c £ ° 0 (75 ⁰ F) than that for ttbliohe AISI 43O- Alloys required temperature) produces a tape with an ASTM grain size number of 7-8, which is equivalent to that of conventional AISI-430 steel alloys.

HLn rolling of customary ferrule-rough alloys »in particular the AISI-430 alloys »can cause surface damage have »which are known as" roping ". Included ridges or corrugations form on the surface when the tape is partially stretched or pulled. This phenomenon is extremely disadvantageous and has the consequence that common AISI-430 ferritic stainless steels for certain Uses »belsplelsweiee for use in the Automotive industry, are unsuitable. Sin rollers as well as the

2098U / 0308

generation of the ferritic according to the invention. Alloys, including those alloys that make up AISI 430 steels are equivalent does not result in the formation of these surface defects, eo that the alloys according to the invention can be used in areas for which the usual AISI-430 alloys were not suitable.

In addition to the typical ferritic AISi-400 alloys, the invention is also directed to special ferritic alloys. Examples 25-28 of Tables III and IT are directed to ferritic alloys which contain aluminum. The alloys of Examples 25-28 loaded alloys with a low chromium content, the aluminum causing hardening and solidification of such alloys and increasing their resistance to oxidation. These alloys have excellent corrosion and oxidation resistance and can be used in many areas which are free from moderately high temperatures «. However, the presence of aluminum in the alloys poses problems in the manufacture of these alloys. Ia commercially available ferrltlsohe alloys i 1 "or more of aluminum included are, for example, limited to the production of automobile mufflers and furnace burners generally not decorative uses. The aluminum-containing ferritic alloys according to the invention can be produced in a simple manner and can be used without difficulty

2098U / 0308

In a tin mold for a use for decoration eswooke, if a pronounced corrosion resistance is required « be convicted.

It can be seen from Table IV that the effect of adding aluminum is to increase the transition temperature range of the alloy in both the longitudinal and transverse directions to values above room temperature. However, these transition temperatures are significantly below the usual transition temperatures of conventional aluminum-containing ferrite alloys. At a temperature of 149 ⁰ O (30 ⁰ T), the alloys of Examples 17 have 18 and 19, which contain 1.2% aluminum , Impact strengths in both the longitudinal and transverse directions that are above 30.5 mkg (235 ftolbo) With an aluminum content of 6 pounds, the busateliohe aluminum drives the transition temperature range up to a point where a temperature of 149 ⁰ O (300 °?) Within the transition temperature range, whereby the bottom viscosity cannot be easily determined at this temperature

The effect of cold processing and annealing of the aluminum-containing alloy according to the present invention can be seen from Examples 17 and 18, from which it appears that a glow has the effect of aar

2098U / 0308 ■

Transition temperature range in the longitudinal direction around about 15 ⁰ O; (5O ⁰ P) is lowered.

The bio-effect of an increased aluminum content on the alloys of Examples 17-20 is also due to the fact that the R ₈ A _e T. ratio is directly influenced ! has sur follow in the alloys of Examples 13-16, can be as SiOH, the alloys of Examples 17-20 ψ yet easily develop, either by Heise- or KaItwalEen, being compared to conventional aluminum alloys containing improved ductility and Have toughness

Marteonaitic alloys

The Martensltisohen Slsen-Ohrom alloys are generally hardenable by heat treatment, have high tensile strengths and good ductility and toughness and are used when high strength and good corrosion resistance are required. These materials however, have been used in the past for technical reasons Little attention is paid to it, especially because of the difficult processability, the relatively low base layer in comparison to austenitic lodgings as well as the low elasticity.

20981 4/0308

The marteneitischen Blsen-chromium alloys have a low chromium content, the swieohen generally »is about 10 and about 20 £ and gewöhnlioh swisohen about 10 and about 14 1, and containing such amount of a Aueteni ^ stabilization · littels that ausreioht DAAU, that there is a martensitic crystal configuration at room temperature. Depending on the relative amounts of chromium and auetenite stabilizers, the alloys without martensitis can be completely martensitic or consist of fartensitilus Jerrit, Karienait plus Auetenit plus ferrite or Martensit plus λusten! T In general, consider that the martensitic alloys are relatively low in carbon plus nitrogen and contain less than about 10 # ferrite crystals.

A number of commercially available martens-like alloys include those alloys which contain about 10 and about 14 pounds of chromium, and about 2 and about 7 pounds of nickel. Ser-like alloys have essentially a 100 l long martensitic Xrietall configuration. These alloys have tensile strengths in excess of 7090 kg / cm ² (100,000 pel). If the carbon content is reduced to a value below approximately 0.03 Ctewlohts-Jt, then the alloys have good weldability. Sin higher carbon content, and was up to about 0.06% by weight, can for

2098U / Q3Q8

White purposes are tolerated if 0.01 weight-56 Si tan are present «

Since the Martenaitic alloys are hardenable in the air: are measurements of ductility and toughness, such as impact strength and B.AoXo ratios, only then of importance when they are at the same level of severity be carried out · Therefore, a comparison of the invention according to martens! tischen! alloys with common alloys somewhat more difficult than comparing the austenitic and ferritic alloys with the conventional alloys. Nevertheless, it has been found that martensitic alloys containing less than about 6 ppm of insoluble volatile metallic impurities and containing less than about 20 ppm of soluble volatile metallic impurities, greatly improved physical properties and mechanical sigens in comparison to common martensitic alloys.

The impact strengths of the martensitic alloys are generally similar to those of austenitic alloys and ferritic alloys. The marteneltic alloys have somewhat lower impact strengths at room temperature than all the austenitic alloys, while the alloys without martensitics have a transition temperature range which is different from that of the xerritic alloys.

2098U / 0308

rangen and the austenitic alloys. However lies the transition temperature range of the Martensltl alloys well below room temperature. Conventional, 13 Jf chrome

■ ■ *

Marteneitlsohe alloys containing violcel and 4 pounds have longitudinal impact strengths between about 3.9 and 5.2 mkg (30 and 40 ft.lb.) at -70 ⁰ O (-95 ⁰ J) martensitic alloys are significantly improved and are above 13 bend (100 ft. Ib ₀ ) at room temperature.

Another example of a martensitic alloy is an alloy that contains about 16 J & Chromium and about 9 JfHiokel, less than 6 ppm insoluble volatile metallic impurities, and less than 20 ppm soluble volatile metallic impurities. This alloy is a mixture of · iustenit martensite and Jerrit crystals and containing less than about 10 + Perrit. These alloys have tensile strengths in excess of 7030 kg / cm ² (100,000 psi) while at room temperature the longitudinal bottom strengths are approximately 150 ft.lb. and the transverse bottom strengths are approximately 11.7-13.0 mkg (90-100 ft.lb.). At a temperature of -196 ⁰ O (-320 ⁰ I) the longitudinal impact strength is approximately 11.7 ng (90 ft.lb.) while the transverse sole strength is approximately 5.2 mkg (40 ft.lb ·) will. The RAfi-relation lake of the im-

2098U / 0308

so rubbed martens! tic alloys are above 0.90 and usually above 0.95 »from which the extremely low aniootropy and the excellent ductile! did the martensi-: table alloys that are free from volatile metallic impurities emerge.

With the ferritic alloys, the weldability of the martensitic alloys according to the invention is excellent if the total carbon content plus nitrogen content of the alloys is reduced to fairly low values, ie below approximately 150 ppm. To sohweissen the ability martensitieohen alloys without risk of bite formation of Sohweissungen and a Versprudung during Bineataes, makes the novel marteneitisohen alloys su attractive building materials, to be used at temperatures below -16 ⁰ C (O ^0?) And high tensile strength must own. Auseerdem enables excellent ductility of erfindungsgemUsBen mattensi- (tables alloys in a simple catfish an orphan and a processing of the alloys bu desired shapes ·

production method

From the foregoing it can be seen that iron-ear alloys that total less than about 6 ppm insoluble volatile metallic impurities and

20981 4/030 8

contain less than about 20 ppm of soluble volatile metallic impurities, have markedly improved physical and mechanical properties compared to conventional iron-chromium alloys. The removal of volatile met aiii impurities from iron-ohrom alloys in 'technically attractive amounts and in particular the production of these alloys from cheap raw material sources is advantageously carried out in that a molten iron-chromium alloy of the bee chi it solution with a Electron beam under a reduced pressure of below about 10 torr. The strength of the electron beam bombardment vxTö. so regulated, that the energy supply is above

about 222 kw / m ² (20 kw / equare foot) of the molten alloy surface, while the duration of irradiation of the molten iron-ear alloy with the electron beam is about 500-10 000 kg / hour / m of the molten alloy surface (100 to about 2000 pounds per hour per square foot) is regulated ₀

A heating of the iron-chroat alloys using An electron beam has been used to produce ice-chromium alloys which have less than 6 ppm of insoluble volatile metallic impurities and less than about 20 ppm of soluble volatile metallic impurities

2098U / 0308

Contain impurities, al3 proven to be beneficial, It is believed to be necessary _? to use a bombardment by means of an electron beam for heating; in order to be able to carry out the method according to the invention in an economical manner. Although the present invention should not be limited to © in such a procedure, it is believed that by the impact of the electron beam on the surface of the molten Bisen alloy local ä overheating axif the surface of the bath of the molten alloy is produced, which is of considerable It is important to achieve the desired finish and to remove volatile metallic impurities.

Due to the local overheating on the surface of the weld pool, thermal differences are created in the weld pool, and thermal convection currents occur thermal convection currents create turbulence and stir the molten bath so that it is continuous fresh molten metal from the lower parts of the bath leaked to the surface of the bath continuous supply of fresh molten metal to the surface of the Sohmel bath as well as the turbulent Agitation of the bath promotes evaporation of the volatile metallic impurities in a by-resolution apparatus heated with an electron beam to a greater extent than with other types of conventional heating

2098U / 0308

directions, for example vacuum induction steps, is the case.

Other replacement leg directions do not have those described Uneven heat distribution and thus the same way achieved convection streaks result. A heating by means of An electron beam also has the advantage that it can be carried out using a stove which can be cooled down to the extent that a solidified bear (skull) is formed from the m processing material. Sine Withholding the Sohmelsbath in the bear removes Ver-8chmutarangprobleme as a result of the dissolution of the BaSgefäsaeSo Furthermore, there is no contamination of the Sohmelzbbad through the source of the electron beam, as is the case with one Heating by means of an arc is the case.

According to a preferred embodiment of the invention, one or more electron beams «! on dl · surface of the Sohmelzbad. Made of an Eismi-Ohrom alloy that is long of a cooled stove is flowing »reddish · Dl · Aufprallfläohe The electron beam on the weld pool can be stationary The electron beam can also cross to the Jodooh Molten bath can be moved. Moving the electron beam in the transverse direction to the molten bath at a speed which is so slow that local overheating occurs, has the advantage that the area of the turbulent stirring of the molten bath is shifted so that

2098U / 030S

a more even stirring of the molten bath takes place, whereby a lower energy input compared to stationary jets is required for a given degree of cleaning is.

The process can be carried out successfully without the use of carbon materials, which are used for the production of iron-gliroia alloys, which contain between about 4 and about 40 <$> chromium, with the usual alloy components such as them contained in Eisea-Ohrom alloys present his Köm .en _c particular, can, produce, as already mentioned stainless steels "The process can for the production of iron Ohro?" -!. alloys directly from common iron and ferrochrome ~ < RobTnaterialien are used "It is also possible to couple the process with conventional manufacturing methods. For example, the modite produced in an oxygen top-blowing furnace, furnace heated by means of an electric arc or vacuum induction furnace can be bombarded with an electron beam under reduced pressure in the manner described.

The surface of the molten bath, which flieset along the cooled hearth, during the bombardment with the electron beam under a reduced pressure of not more than ungöfä & r 1 (T ¹ lorr and preferably below about 10 "" ² Eorr

2098U / 0308

SAD ORiGiNAL

held "pressures that are significantly below 10 ~ * Torr, Although they do not improve the process yields, prints as low as 10 "Torr be respected. In order to bring the amount of irradiated alloy at the evacuated point to a maximum value, the weld pool is preferably contained in a crucible or stove, who has a large area in relation to his run, whereby the evacuated point preferably extends over the entire irradiated bath surface «bath depths between approximately 12 and 76 mm (1/2 and 3 inches) are provided. Have baths deeper than about 3 inches insufficient drilling due to the overheated areas with the result that the molten material at the bottom of the bath is not brought to the surface « The process can be carried out batchwise, continuously, or semi-continuously, with a stream from a molten alloy is fed to the hearth and withdrawn from it.

The molten Elsen-Ohrom bath is heated to a temperature which is sufficient in order to keep the iron Ohrom alloy in a molten state and to evaporate volatile by dl · metallic impurities. However, the temperature must not be so high that small amounts of iron and chromium or other desired alloy elements are evaporated, otherwise the process will be destroyed

2098U / 0308

impresohaf tlich would be "This e.? requires an entopreefcende 3in ~ position of the reduced pressure, which is maintained above the Schaelaöades, as well as a corresponding level of the temperature of the Sohmelabadee »Typically lies the temperature of the broth is about 15 and about 60 ° 0 (50 and 200 °?) above the Soholz point of the alloy «You tempered the overheated localized fcaim «.vrlfcohen« ng ^ fttbr 15 and about 90 σ (50 and F) Above the Duroheohnittstecxperatur of the weld pool a of the Eieen-Oiironi alloy rune: lie * below an

from 15 ⁰ C (SO ⁰ F) »between the surohechtiitt temperature of the bath and the sestpexattü * of the lolcalieiorten overheated fl & c & en tdrlj Jc« i »auerel <Äeiidee stirring dee Sohmelsbades er-Rlflt, wiliix'3xid whether« rhialb of a difference ⁰ O (300 ⁰ I ¹ ) excessive menffeu aa Eietn tctd CJhro "rerdeucpftn. Temporary differences between 30 and 60 ⁰ O (100 and 200 °?) Provide good results"

The respective duration of the day with the light electron beam depends on the outward flow of the alloys, the temperature, the impact part of the StVahlec wa £ the building surface, the "Äruoic" at the evaJcuierfee-bath above the sea " away. With so many au b # rüo! CBa.ciitigendQÄ variables, ee Sewöbulloh YoratiftUhen, which are unrelated to empirical evidence. You should choose the procedure to be followed

j θ do oh be taken in such a way that it is ensured that there are insoluble volatile metallic impurities to a content below about 6 ppm and the annual volatile metallic impurities to a level below about 20 ppm, preferably below about 2 haw In addition, the carbon and nitrogen content of the Bisen-Ohrom alloy should be reduced so that all of the carbon and nitrogen W in the alloy is in solid solution at room temperature. As already mentioned, this critical value for the content of carbon plus nitrogen is below approximately 150 ppm for ferritic and martensitic alloys and below approximately 600 ppnu for austenitic alloys

Sufficient exposure to the electron beam results in the formation of an alloy which has improved physical and mechanical properties. With a continuously carried out process, good results can be obtained when a molten Bisen-Ohrom alloy is passed over a cooled stove installed in a device that is evacuated to less than 10 Torr Alloy is passed over the range in an amount as high as about 505 and about 10 066 kg / hour / m ^{2 of} stove (about 100 to about 2000 pounds per hour per square foot of stove). At lower pressures, larger yiieesgieohwin-

2098U / Q308

_o For a pressure of 10 "*! Dorr, the flow rate should be kept at the lower end of the specified range, for example at about 503 to 1509 kg / hour / m ² stove (about 100 to 300 pounds per hour per square foot hearth) to achieve the desired results. At even lower pressures, such as 10 ^ Torr, full viewing speeds up to 10 066 kg (2000 pounds) / hour / m ^{2 of} hearth can be maintained between about 1006 and about 5030 kg (about 200 to about 1000 pounds) / hour / m ^{2 of} stove.

As already mentioned, the energy supplied to the molten pool by the electron beam is set in such a way that if the molten alloy is sufficiently blown, the surface of the alloy is sufficiently overheated so that the molten pool is thermally stirred.The energy supplied to the molten pool by means of the electron beam exceeds in two-tier catfish about 222 kw / m (20 kw / square foot) stove and can be up to 1110 kw / m ² (100 kw / square foot) stove, although excessive evaporation losses can occur in the latter case. The maximum energy supplied by the electron beam is determined by coordinating the costs against the increased evaporation losses of iron and chromium

2098U / 0308

The method described can be carried out in a furnace heated by means of an electron beam in a single Druokeone or in a refining device consisting of many Druokaqnen, as for example in the VS patent draft 3,343,823. The use of a refining device consisting of many Druokssonen is particularly advantageous when the iron-chromium alloy is produced directly from ferrochrome raw materials.

Using the most common types of commercially available iron-ear alloys, such as stainless steels of the AISI-30O and -400 series, then Satisfactory results were obtained when the gaochmolpsne alloy was cooled over, through two successive stoves Vacuum bones or stages is performed, as in the U.S. Patent 3,343,828. The first stage can be evacuated to a pressure of about 10 torr and but removal of dissolved oasis as well as highly volatile Contaminants are used, and some volatile metallic contaminants can also be removed. the the second stage can be set to a pressure of about 10 * 'Torr or less evacuated, the volatile metallic Impurities and gaseous impurities in this zone are removed to the usual extent. Means of the electron beams introduced energies of approximately

2098U / 0308

335 to 888 kw / m ² stove (50 - 80 kw / square foot) can be used in both zones?

Each alloy of Examples 3-9 and 13-20 is according to the described method in a herd like _fl by means of an electron beam-heated furnace of U.S. Patent No. 3,343,828 gemäse prepared. The pressure in the first zone is kept at 10 ~ ² lorr, while the pressure in the second zone is regulated to 10 "** lorr. The speed of the molten alloy through the furnace varies from about 754 to about 2012 kg / hour / m ² hearth (about 150 to about 400 pounds / hour / square foot hearth) with the electron beam sae energy density varying from about 444 to about 888 kw / m ² hearth (about 40 to about 80 kw / square foot hearth).

From the above it can be seen that according to the invention Iron-chromium alloys with noticeably improved physical and mechanical properties Are made available, and a specific process for the production of such alloys is also created will. The superior toughness, ductility, isotropy, corrosion resistance and processability of the invention Alloys is such that they can be used for such purposes

2098 U / 0308

can be used for which common iron-chromium alloys were previously considered unsuitable.

The process described for the production of iron-chromium alloys is versatile and can be used to produce Iron-chromium alloys can be used directly from iron and ferro-tubular hollow materials. In addition, he can » _ foundungsgeiaäsee processes can be coupled with conventional processes carried out in oxygen inflation furnaces »electric furnaces or vacuum induction furnaces. With such a Coupling is the Sisen-Chrom-Ialierung in the means of dee Electron beam heated furnace in a balanced state introduced and in this oven in a «! inclined pressure zone or processed in two pressure zones · Of course, several Druokeons can also be used if necessary.

The invention has been described above using specific iron w chromium alloys and specific production methods. It should be noted, however, that other embodiments and equivalent methods also fall within the scope of the present invention.

2098U / 0308 -

Claims (2)

Claims Iron-chromium ~ alloy ₉ characterized by about 4 his about 40 Gewiohts ~? S chromium, 0 to about 14 Gewiohts ~ 5 £ nickel "carbon and nitrogen in such amounts _p that substantially all of the carbon and nitrogen at room temperature in the form of a solid Solution in the iron-chromium alloy is no more | than about 6 ppm total of the insoluble volatile metallic impurities lead, bismuth, cadmium, sodium, potassium, silver, calcium, magnesium and barium and no more than about 20 ppm total of the soluble volatile metallic impurities zinc and antimony. 2. Alloy according to Anopruch 1, characterized in that it has an H.A. "S. ratio above 0.90. I. 3. Alloy according to claim 1, characterized in that it has predominantly an au3tenitic crystal configuration at room temperature and between about 14 and about 20% by weight of chromium and between about Contains 8 and approximately 14% by weight * nickel. 2098U / 0308 The alloy according to claim 1, characterized in that it has a predominantly austenitic crystal structure at room temperature and contains between about 14 and about 20 weight- ^ chromium and between about 8 and about 12 weight- ^ handles, the alloy having a Chaxpy-V- Kerbeohlagzähigkeit in longitudinal and transverse direction at room temperature of more than 26 mkg (200 ftalb.) and at -196 ⁰ C (-320 ⁰ F) of more than 13 mkg (100 ftclbo) besitzte 5 » Alloy according to claim 4n, characterized in that it contains between about 16 and about 20 weight ^ chromium and between about 8 and about 10 weight ^ nickel. 6. Alloy according to claim 1, characterized in that it has a predominantly ferritic crystal configuration at room temperature and contains between about 10 and about 40 parts by weight of chromium and less than about 150 ppm carbon plus nitrogen. ?, Alloy according to claim 6, characterized in that it has a Charpy V-notch bottom toughness at 93 ⁰ C (200 ⁰ P) in the longitudinal and transverse directions of more than about 26 mkg (200 foot pounds) and a RAT ratio above 0 , 90 owned. 2098U / 0308 3. Alloy according to claim 7, characterized in that it has a transition temperature in the longitudinal and transverse directions after salt processing to at least 50% deformation and grain refinement annealing, which is below room temperature. 9α alloy according to claim 8 »characterized in that Bio has a predominantly ferritic crystal configuration ^ b © i room temperature "and contains between about 10 and about 28 weight * * ^ chromium * 10. Alloy according to claim 6, characterized in that they have a predominantly ferritic crystal configuration at room temperature and between about 10 and about 12 ßewiohts- # chromium, less than 150 ppm Carbon plus nitrogen and up to about 6 weight ~ # Contains aluminum. 11. Alloy according to claim 1, characterized daduroh, daee they have a predominantly martensitic crystal configuration at room temperature and between about 8 and about 16 weights- ^ ohroms, between about 2 and about 10% by weight nickel and less than about 150 ppm Contains carbon plus nitrogen 209814/0308 -ΑΙ 2. Method eur production of an iron-chromium alloy according to s claims 1-11, characterized in that the surface of a molten bath of the alloy by bombarding with venige least an electron current at a point at which a reduced DruoJc of no more is present than 10 Torr, is heated , the energy density of the electron beam θ β is kept at a value above 222 kw / m of the molten alloy surface dee Schmelzbadeθ (20 kw / square foot) and the molten alloy is exposed to the action of the electron beam for a period of time is, while a weloher! Sohmelzbadee throughput of the surface of about 503 -10066 kg / hour / m of Sohnelsbades (about 100 to about 2000 pounde / hour / equare foot) has occurred · 13 · The method according Anspruoh 12, daduroh gekennaeichnet that · an alloy .hergestellt in geeohmolaener Jorm, the geschmoleene alloy along a refrigerated oven is passed is "the SiOH within a Vakuuaeone kept under a pressure of not more than 10 Torr B the surface of the molten alloy is exposed to at least one electron beam by suction of a localized overheating of the molten alloy surface, the energy sensation by the metal electron beam to a value above 2Q98U / 03II about 222 kw / ro ² cooker (20 kw / sauero foot) is held ₉ regulated the Semperaturgefälle between the location of the localized overheating and the Surehschnittstemperatur of Schmelsbades to values between about 15 ⁰ O and about 90 ⁰ O (50 and 300 ⁰ P) and swish the molten alloy along the hearth in a quantity. about 503 and 10066 kg / hour / m hearth (about 100 to about 2000 pounds / hour / square foot hearth) is allowed to flow » 14. The method of claim 13 * characterized in that the melt pool has a depth of no more than about 75 mm (3 inches), ο method NaOH claim 14 'characterized in that _t the molten alloy along the oven in an amount between about 1006 and 5030 kg / m oven (about 200 to 1000 pounds / square foot cooker) flows. ( ! 6, Terfahren according to claim 15 »characterized ₉ that the! Energy supply by means of the electron beam to a. Value is kept above about 333 kw / m Berd (about 30 kw / square foot stove) 17 · The method according to claim 16, characterized in that the temperature gradient between the point of localization 2098U / Q308 the overheating on the molten metal surface and the Durohson average temperature of the geeohmolaen alloy bath is kept between about 30 and about 60 ⁰ O (about 100 and 200 °?) « 18. The method according to claim 13 »characterized in that the molten alloy traverses at least two pressure zones along a hearth, the first pressure zone under a pressure of no more than about 10 torr and the pressure zone under a pressure of no more —2 than about 10 torr. 19 · The method according to claim 18 »characterized in that the s * esolaolsone alloy duroh introduction of xlsen and Perroohrom raw materials in the first Dtuokaone is made available. 20. The method according to claim 14 »characterized in that the molten alloy can be placed in an oxygen inflation furnace, an electric furnace equipped with an oxygen lance, or a vacuum induction furnace performed procedure is made available. 2098U / 0308 , ^6ζ Blank page