US3837846A

US3837846A - Austenitic steel alloy adapted to be welded without cracking

Info

Publication number: US3837846A
Application number: US00237488A
Authority: US
Inventors: H Becker; G Kohlert
Original assignee: Ver Deutsche Metallwerke AG
Current assignee: Vereinigte Deutsche Metallwerke AG; Ver Deutsche Metallwerke AG
Priority date: 1971-04-08
Filing date: 1972-03-23
Publication date: 1974-09-24
Anticipated expiration: 1991-09-24
Also published as: ZA722219B; AT327261B; AU3918872A; IT953617B; DE2117233B2; ATA193972A; DE2117233A1; AU466713B2; FR2135963A5; HU162963B; NL7203419A

Abstract

An austenitic steel alloy capable of being welded without cracking by the argon arc-welding process, consists of substantially 16 to 35 percent by weight chromium, 15 to 45 percent by weight nickel, 0 to 5 percent by weight molybdenum, 0 to 3 percent by weight copper, 0.1 to 1.5 percent by weight aluminum, 0.01 to 0.10 percent by weight carbon, 0.30 to 0.60 percent by weight silicon, 0 to 0.008 percent by weight calcium, 0 to 0.05 percent by weight zirconium, and manganese, titanium, sulfur and phosphorus in weight-percent concentrations within the area to the left of curve I in the graph of FIG. 2 of the drawing, the balance being iron and the usual (inevitable) impurities.

Description

United States Patent Becker et al.

[4 1 Sept. 24, 1974 AUSTENITIC STEEL ALLOY ADAPTED TO BE WELDED WITHOUT CRACKING Inventors: Horst Becker; Gerhard Kohlert,

both of Altena, Germany Vereinigte Deutsche Metallwerke AG, Zeilweg, Germany Filed: Mar. 23, 1972 Appl. No.: 237,488

Assignee:

Foreign Application Priority Data Apr. 8, 1971 Germany 2117233 U.S. Cl. 75/124, 75/128 W, 75/128 E,

75/128 Z Int. Cl. C27c 37/10 Field of Search 75/128 W, 124

3,519,419 7/1970 Gibson 75/128 W 3,563,729 4/1968 Kovach 75/128 W 3,573,034 3/1971 Denhard 75/128 W 3,573,899 4/1971 Groethe 75/128 W 3,594,158 7/1971 Sadowski 75/124 Primary ExaminerHyland Bizot Attorney, Agent, or Firm-l(arl F. Ross; Herbert Dubno [57] ABSTRACT An austenitic steel alloy capable of being welded without cracking by the argon arc-welding process, consists of substantially 16 to 35 percent by weight chromium, 15 to 45 percent by weight nickel, 0 to 5 percent by weight molybdenum, 0 to 3 percent by weight copper, 0.1 to 1.5 percent by weight aluminum, 0.01 to 0.10 percent by weight carbon, 0.30 to 0.60 percent by weight silicon, 0 to 0.008 percent by weight calcium, 0 to 0.05 percent by weight zirconium, and manganese, titanium, sulfur and phosphorus in weightpercent concentrations within the area to the left of curve I in the graph of FIG. 2 of the drawing, the balance being iron and the usual (inevitable) impurities.

14 Claims, 2 Drawing Figures 2.0 II Z 1 1.6 hr

7 F I 7.0 I l 1.4 l

7.0 (x) CRACK SUSCEPT/B/LITY Pmmmsvzmn 3.8 37. 846

Fig. 7

PATENIEDsemzsm s'mzuz Fig.2

. CEACK- FEE'E WELD/IB/L/TV 0.612 1 0.514 7 110 70 la 5 P=fi 12001, 0.006- 0.055 abla AUSTENITIC STEEL ALLOY ADAPTED TO BE WELDED WITHOUT CRACKING FIELD OF THE INVENTION Our present invention relates to austenitic steel alloys and, more particularly, to rust-resistant or so-called stainless steels of the nickel-chromium type which are stabilized in the sense that the crystalline configuration or infrastructure is unaffected by welding operations, such as argon arc welding whereby hot cracking does not occur.

BACKGROUND OF THE INVENTION Austenitic steel alloys of various compositions, generally containing high concentrations of nickel and chromium, have been proposed for many purposes and can be welded by argon arc-welding techniques, i.e. filler-free welding under an argon blanket or atmosphere. The compositions of such alloys are adjusted to a deltaferrite concentration of 3 to percent by weight.

The presence of delta-ferrite in an austenitic matrix is associated with destressing of the crystal structure or infra structure in the hot-cracking range, especially when relatively small cross-sections are welded together without fillers. It has been assumed that the delta-ferrite acts by dissolving substance such as sulfur, phosphorus, arsenic, bismuth, selenium and tellurium which may concentrate during the welding process and give rise to hot cracking. The delta-ferrite, therefore, renders high concentrations of the crack-promoting constituents less detrimental.

OBJECTS OF THE INVENTION It is the principal object of the present invention to provide an improved austenitic steel alloy which is high in nickel concentration but free from the disadvantages of earlier austenitic steel alloys as described above.

Another object of the invention is to provide an austenitic-alloy steel having low susceptibility to hot cracking upon argon arc welding without the use of fillers and which is relatively inexpensive or can be produced in an inexpensive manner.

It is also an object of the invention to provide a stabilized austenitic alloy steel which is insusceptible to weld cracking and capable of economical production.

SUMMARY OF THE INVENTION These objects are attained, in accordance with our invention, with a system based upon our surprising discovery that it is possible to overcome the disadvantages of substantially irreducible high concentrations of sulfur and phosphorus, by providing manganese and titanium in a certain relationship with the phosphorus and sulfur content as to render an austentic steel alloy less susceptible or insusceptible to cracking when the steel' by weight zirconium, and manganese, titanium, sulfur and phosphorus in specific weight-percent concentrations, the balance being iron and the usual inevitable impurities.

DESCRIPTION OF THE DRAWING The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a graph of the phosphorus and sulfur concentrations plotted in percents by weight along the ordinate, against the nickel concentration plotted in percents by weight along the abscissa, showing the maximum permissible values of phosphorus and sulfur in an austenitic alloy steel which is to be free from cracking in the manner described;

FIG. 2 is a composition diagram illustrating the principles of the present invention.

SPECIFIC DESCRIPTION Prior to describing the principles of the present invention in somewhat greater detail, a consideration of FIG. 1 is in order. Known investigations of steels having different concentrations of chromium, nickel sulfur and phosphore have demonstrated that an increased nickel concentration requires a reduction in the phosphorus and sulfur concentrations if weld-cracking is to be avoided. To illustrate this point, we have shown in FIG. 1 the maximum permissible concentrations of sulfur and phosphorus plotted in percent by weight along the ordinate, in dependance upon the nickel concentration (plotted in percent by weight along the abscissa), at which weld cracking is excluded. Phosphoric and sulfur concentrations above these levels result in aus tenitic steel alloys susceptible to weld cracking, e.g. when subjected to argon arc welding without filler electrodes.

Reduction of the sulfur and phosphorus concentrations, however, to levels below those shown in FIG. 1 for most austenitic steel alloys is difiicult, especially with bodies of increased size. For example, as the mass of slab ingots increases, there is an increased risk of nonuniform distribution of the crackinducing elements (sulfur, phosphorus, etc.) as a result of increased concentrations of these elements in certain areas. Thus, to ensure that slab ingots having a weight of more than 5 metric tons consist of material which is insusceptible to weld cracking, it is found that the sulfur content must be adjusted to about 0.0015 percent and the phosphoric content to about 0.005 in the final produce to avoid such enrichment or segregation. These levels are well below those defined by the curves P and S of FIG. 1 and are necessary because phosphoric and sulfur concentrations at the concentrations represented by the curves give rise to detrimental enrichment at localized areas as indicated. The reduction of the phosphoric and sulfur levels to such low values is uneconomical or attainable only at considerable expense by prior-art methods.

As already noted, we are able to achieve the objects of the invention and eliminate the disadvantages of the prior art systems as a result of our discovery that instead of removing phosphorus and sulfur, manganese and/or titanium are added to the alloy in certain amounts which depend upon the sulfur and phosphoric content and may be given in the graph of FIG. 2.

Referring now to FIG. 2 of the drawing, it will be seen that we have plotted the percent by weight of manganese and titanium (together 04) along the ordinate while the sum (6) of the sulfur and phosphorus are plotted along the bscissa. The curves 1, I1 and III define certain zones which can be defined as a zone X corresponding to crack susceptibility underargon arc welding, a zone Y corresponding to a transition range in which crack susceptibility is reduced and a zone Z corresponding to crack-free weldability, Curve 1 represents the boundary to the left of which an improved austenitic steel composition is obtained to the left of the curve, with reduced tendency toward cracking. Curve II, or course, represents the boundary of the zone Z, to the left of this boundary being the region in which crack-free welding can be carried out as indicated. The curve 111 represents a linear or pseudolinear approximation of the latter boundary curve and has been provided to facilitate the definition of the manganese and titanium boundary. Thus we have found that the sum of the manganese and titanium weight percentages should be related to the sum of the phosphorus and sulfur weight percentages by the relationship (Mn% +Ti%) Z A +B P%) where (3% P%) is defined, for the present purposes, by the value [3 and (Mn% Ti%) is defined as 04. Where B ranges between 0.0065 to 0.0145 percent, A is preferably 0.05 percent and B 100. Where B lies above 0.0145 percent, A 9.48 percent and B 750.

These values have been found to be critical, as shown by the graph, for a system in which the steel contains 16 to 35 percent by weight chromium, to 45 percent by weight nickel, up to 5 percent by weight molybdenum, up to 3 percent by weight copper, 0.1 to 1.5 weight-percent aluminum, 0.01 to 0.1 percent by weight carbon and about 0.5 percent by weight silicon, the balance being iron and, of course, the usual or unavoidable impurities.

When reference is made herein to about 0.5 percent silicon, it should be noted that the silicon concentration may range between 0.3 and 0.6 percent but preferably is 0.5 percent i 0.005 percent.

Advantageously, the system contains 0.001 to 0.008 percent by weight calcium, preferably 0.004 to 0.006 percent by weight calcium and/or 0.01 to 0.05 percent by weight zirconium, perferably about 0.02 percent thereof. It has been found to be especially advantageous when the manganese concentration is approximately twice the silicon content.

SPECIFIC EXAMPLES The invention will be explained more fully by the following illustrative analyses (all percentages by weight) selected from a large number of investigations, in which the susceptibility to weld cracking has been tested by the so-called Focke-Wulf Test, the results of which agreed well with practical results.

' EXAMPLE 1 A body having the following analysis:

chromium nickel aluminum manganese silicon titanium Continued 0.015 carbon 0.004 sulfur 0.007 phosphorus 0.010 calcium could not be welded without cracking.

EXAMPLE 2 A body having the following composition:

20.9 chromium 3 i .7 nickel 0.23 aluminum 0.80 manganese 0. 39 silicon 0.44 titanium 0.01 3 carbon 0.00 sulfur 0.009 phosphorus 0.001 calcium 0.01 zirconium enabled the formation of satisfactory seam welds.

EXAMPLES 3 AND 4 Bodies having the following analyses also could be welded without difficulty.

3) chromium 21.0 4) 20.50 nickel 316 31.80 aluminum 0.14 0.32 manganese 0.78 0.88 silicon 0.46 0.30 titanium 0,22 0.45 carbon 0.012 0.027 sulfur 0.003 0.003 phosphorus 0.005 0.010 calcium 0.005 0.004

The charges were melted in accordance with known melting processes, for instance, in an electric arc furnacc or induction furnace. Improvement was obtained by a subsequent vacuum treatment but was not essen tial. The charge was preferably teemed under a protective atmosphere.

The alloys which can be welded satisfactorily thus lie in the field on the left of the limiting curve. The curve is adjoined on the right by a transitional range, in which welding cracks may be expected. Alloys in which the ratio of the sulfur and phosphorus contents to the manganese and titanium contents is on the right of this range cannot be welded without cracking.

FIG. 2 indicates that the formula defines a safe limit, and the alloys may be slightly beyond said limit without a risk of welding cracks. Specifically, no attempt has been made to find a more complicated formula for a better approximation to the limiting curve found in the tests. The linear function which has been selected bet ter defines the relationship between the contents of sulfur and phosphorus, on the one hand, and those of manganese and titanium, on the other hand. The linear substitute function can be used more easily in practice. This formula defining the limiting condition has been selected to facilitate the understanding, however, and is not intended to restrict the scope of the invention.

The analysis values of the above Examples 1 to 4 are also plotted in FIG. 2.

We claim:

about 0.50 percent by weight silicon, 0.001 to 0.008-

percent by weight calcium, 0 to 0.05 percent by weight zirconium, and an effective amount of manganese, titanium, sulfur and phosphorus limited to the weightpercent concentrations within the area to the left of curve I in the graph of FIG. 2 of the drawing, the balance being iron and the usual inevitable impurities.

2. The alloy defined in claim 1 wherein the manganese, titanium, sulfur and phosphorus weight-percent concentrations are substantially within the area to the left of the curve II in the graph of FIG. 2 of the drawing.

3. The alloy defined in claim 1 wherein the manganese, titanium, sulfur and phosphorus weight concentrations are defined by the relationship a a A (B X [3) where a is the sum of the weight percentages of manganese and titanium, B is the sum of weight percentages of sulphur and phosphorous, A is 0.05 percent and B is 100 for ,8 0.0065 to 0.0145 percent, and A is 9.48 percent and B is 750 for [3 0.0145 percent.

4. The alloy defined in claim 1 which contains at least 7. The alloy defined in claim 1 wherein the manganese content is approximately twice the silicon content.

8. An austenitic steel alloy adapted to be welded without cracking, consisting of essentially 16 to 35 percent by weight chromium, 15 to 45 percent by weight nickel, 0 to 5 percent by weight molybdenum, 0 to 3 percent by weight copper, 0.1 to 1.5 percent by weight aluminum, 0.01 to 0.1 percent by weight carbon, 0.30 to 0.60 percent by weight silicon, 0.004 to 0.006 percent by weight calcium, 0 to 0.05 percent by weight zirconium, and an effective amount of manganese, titanium, sulfur and phosphorous limited to the weightpercentage concentrations within the area to the left of the curve I in the graph of FIG. 2 of the drawing, the balance being iron and the usual inevitable impurities.

9. The alloy defined in claim 8 wherein the manganese, titanium, sulfur and phosphorous weightpercentage concentrations are substantially within the area to the left of the curve II in the graph of FIG. 2 of the drawing.

10. The alloy defined in claim 8 wherein the silicon content is about 0.50 percent by weight.

11. The alloy defined in claim 8 which contains at least 0.01 percent zirconium.

12. The alloy defined in claim 11 having a silicon content of about 0.02 percent by weight.

13. The alloy defined in claim 8 wherein the manganese content is approximately twice the silicon content.

14. An austenitic steel alloy adapted to be welded without cracking and consisting of essentially 16 to 35 percent by weight chromium, 15 to 45 percent by weight nickel, 0 to 5 percent by weight molybdenum, 0 to 3 percent by weight copper, 0.1 to 1.5 percent by weight aluminum, 0.01 to 0.1 percent by weight carbon, 0.3 to 0.6 percent by weight silicon, 0.001 to 0.008 percent by weight calcium, 0 to 0.05 percent by weight zirconium, and an effective amount of manganese, titanium, sulfur and phosphorous limited to the weight-percentage concentrations within the area to the left of curve I of the graph of FIG. 2 of the drawing, the balance being iron and theusual inevitable impurities.

Claims

2. The alloy defined in claim 1 wherein the manganese, titanium, sulfur and phosphorus weight-percent concentrations are substantially within the area to the left of the curve II in the graph of FIG. 2 of the drawing.
3. The alloy defined in claim 1 wherein the manganese, titanium, sulfur and phosphorus weight concentrations are defined by the relationship Alpha > or = A + (B X Beta ) where Alpha is the sum of the weight percentages of manganese and titanium, B is the sum of weight percentages of sulphur and phosphorous, A is -0.05 percent and B is 100 for Beta 0.0065 to 0.0145 percent, and A is -9.48 percent and B is 750 for Beta > 0.0145 percent.
4. The alloy defined in claim 1 which contains at least 0.01 percent zirconium.
5. The alloy defined in claim 4 having a zirconium content of about 0.02 percent by weight.
6. The alloy defined in claim 1 having a calcium content of substantially 0.004 to 0.006 percent by weight.
7. The alloy defined in claim 1 wherein the manganese content is approximately twice the silicon content.
8. An austenitic steel alloy adapted to be welded without cracking, consisting of essentially 16 to 35 percent by weight chromium, 15 to 45 percent by weight nickel, 0 to 5 percent by weight molybdenum, 0 to 3 percent by weight copper, 0.1 to 1.5 percent by weight aluminum, 0.01 to 0.1 percent by weight carbon, 0.30 to 0.60 percent by weight silicon, 0.004 to 0.006 percent by weight calcium, 0 to 0.05 percent by weight zirconium, and an effective amount of manganese, titanium, sulfur and phosphorous limited to the weight-percentage concentrations within the area to the left of the curve I in the graph of FIG. 2 of the drawing, the balance being iron and the usual inevitable impurities.
9. The alloy defined in claim 8 wherein the manganese, titanium, sulfur and phosphorous weight-percentage concentrations are substantially within the area to the left of the curve II in the graph of FIG. 2 of the drawing.
10. The alloy defined in claim 8 wherein the silicon content is about 0.50 percent by weight.
11. The alloy defined in claim 8 which contains at least 0.01 percent zirconium.
12. The alloy defined in claim 11 having a silicon content of about 0.02 percent by weight.
13. The alloy defined in claim 8 wherein the manganese content is approximately twice the silicon content.
14. An austenitic steel alloy adapted to be welded without cracking and consisting of essentially 16 to 35 percent by weight chromium, 15 to 45 percent by weight nickel, 0 to 5 percent by weight molybdenum, 0 to 3 percent by weight copper, 0.1 to 1.5 percent by weight aluminum, 0.01 to 0.1 percent by weight carbon, 0.3 to 0.6 percent by weight silicon, 0.001 to 0.008 percent by weight calcium, 0 to 0.05 percent by weight zirconium, and an effective amount of manganese, titanium, sulfur and phosphorous limited to the weight-percentage concentrations within the area to the left of curve I of the graph of FIG. 2 of the drawing, the balance being iron and the usual inevitable impurities.