DE1929116B1 - USING A MARTENSITIC STAINLESS DEFORMABILITY AND HIGH SPRING BENDING LIMIT - Google Patents

Description

impurities, ^

in the solution-annealed and cold-formed state as a material for objects with good ductility and high elastic limit.

2. Use of a steel according to claim 1, the 0.1 to 1% aluminum and 0.3 to 1.5% niobium contains, for the purpose of claim 1.

3. Use of a steel according to claim 1 or 2, wherein the martensite transformation by Cooling to temperatures below 0 ° C has been brought about for the purpose of claim 1.

4. Use of a steel according to claim 1 or 2, wherein the martensite transformation by a Cold deformation with a reduction in cross-section of 50 and more percent has been brought about is, for the purpose of claim 1.

5. Use of a steel according to claim 1, in which up to 4% of the chromium by up to 4% Molybdenum is replaced for the purpose according to claim 1.

35

The invention relates to the use of a martensitic, precipitation hardening, stainless Steel, which is an essentially austenitic structure or a significant amount of retained austenite and for transforming this Structure into an essentially martensitic structure by using cold deformation is suitable, as a material for objects with good deformability and high elastic limit.

The precipitation hardening stainless steel to be used is a recently developed stainless steel Steel with the addition of Al and Mo to the rustproof 17-Cr-7-Ni steel, which was previously used as a solid stainless steel with suitability for use directly after cold forming with precipitation hardenability as well as for Was known to produce properties suitable for a wide range of uses.

When one selects a certain composition of ingredients that are responsible for a conversion from austenite tends to martensite, then a precipitation phase occurs which is soluble in austenite, is insoluble in martensite after the conversion, on the other hand, in the martensite matrix. ·

It is known that there are two kinds of martensite type stainless steel, namely stainless steel (17-Cr-4-Ni stainless steel) in which transformation from austenite to martensite occurs immediately in a cooling step after the solution treatment and precipitation hardening can be carried out by heat treatment of the converted stainless steel, and stainless steel (17-Cr-7-Ni stainless steel) in which all or most of the structures are austenitic even after the steel is allowed to cool after the solution heat treatment remain, the austenite can only be converted into martensite by means of an intermediate heat treatment or cold deformation ™. ^dw f? ^rd f precipitation hardening can be brought about by heat treatment of the steel. ^{The Be} S ^ "spring deflection limit" in the invention is defined as the surface tension of a metal

_{ISTJ strip when the} R _est deformation stress is 0.05 or 0.025 mm is reached in the middle of the strip.

The spring deflection limit represents a degree of resistance to the so-called "relaxation" of the The 17-Cr-7-Ni steel with a nominal chemical composition:

Weight percent

r '<0 09

". <1Ό

_p "\,

"'<OYn

^. Z ™ u ·

J-?

_, 16 'to 18

.F η 7S V> *

^A1 · 'J ¹ J ³ J

p _e n ' _est

After precipitation hardening with 50% reduction in cross-section, it has a flexural limit of about 120 kg / mm ² . Next is a 17-Cr-7-Ni stainless steel of this nominal chemical composition to which very small amounts of Ti, Zr, V and the like are added to increase the weldability of the 17-Cr-7-Ni steel or a 17-Cr-7-Ni stainless steel in which 4% by weight or less of Cr is replaced with the same amount of Mo in order to improve the high-temperature strength is known.

The stainless steel to be used in the present invention should have both good formability at the same time as well as a high elastic limit.

The invention relates to the use of a martensitic stainless steel consisting of

η 1 ν ^1S i «ο /

^u ' ^x ° ^{1S 1} ^ ^ fSfS ^ K _t "
/ ⁰ carbon,

^{More than 1} J ^{5 / o} manganese,
^{Elsen and} impurities caused by the melting process,

in the solution-annealed and cold-deformed state as a material for objects with good ductility and high elastic limit.

It is also appropriate to replace part of the Cr with Mo.

Part of the composition range of the invention to be used steel, namely with

9 to 10% nickel, 12 to 15.5% chromium, 0.15 to 1% niobium, 0.5 to 1.5% aluminum, up to 0.03% carbon, 0 to 0.2% silicon, 0 to 0.2% manganese, remainder iron, is already from the German patent 1239 108 known, but is in terms of use there of a hardenable stainless steel with a Strength and toughness are mentioned, which for example make it a material for pressure vessels and aircraft parts or the like. Make suitable.

The invention is to be explained in more detail below with reference to the drawing and examples; in it shows

F i g. 1 is a block diagram of the precipitation hardening steps of the present stainless steel and

F i g. 2 shows a diagram of the characteristic curves of the hardness and the spring bending limit according to an exemplary embodiment the invention.

The stainless steel to be used in the present invention has an austenitic structure or a substantial amount of residual austenitic structure when the steel is subjected to a solution heat treatment and then directly cooled as it is and has an appropriately selected, certain mixing ratio of Cr and Ni so that a such a structure can be converted into an essentially martensitic structure by cold deformation with a certain degree of cross-section reduction.
As methods for precipitation hardening treatment of 17-Cr-7-Ni steel, three methods, ie TH method, RH (below 0 ° C) method and CH method are known, which differ depending on the type of transformation of the structure Differentiate between steel and martensite after solution heat treatment.

F i g. Fig. 1 shows a typical block diagram of the precipitation hardening treatment after this three procedures are undertaken. Of these, the CH method is the most excellent; the RH method and TH method follow from the viewpoint of obtaining a stainless steel with a high spring deflection limit from in that order.

Table 1 shows compositions and spring deflection limits after the final annealing treatment of the stainless steel to be used according to the invention (Examples 1 to 6) and the conventional 17-Cr-7-Ni steels (Reference Examples 1 to 3) of the standard compositions.

Table 1

Composition (weight percent)

Si

Mn

Cr

Ni

Al

Nb

Spring deflection limit

after
treatment

(kg / mm ² )

Reference example

PI

P-2

P-3

example
1

0.00
0.09
0.09

0.08
0.07
0.06
0.06
0.03
0.08

0.12
0.03
0.43

0.02
0.87
0.55
0.64
0.35
0.45

0.20
0.18
0.62

0.14
0.96
0.52
0.54
0.45
0.35

18.0
16.7
17.0

18.0

16.4

16.77

16.79

16.55

17.05

7.3
6.94

7.2

7.3

7.0

7.02

6.82

6.95

6.90

0.98
0.98
1.03

0.22
0.19
0.21
0.20
0.40
0.98

0 0 0

0.30
0.47
1.05
1.44
3.02
0.15

124
111
125

168
172
178
181
180
165

In the various examples and reference examples, cold working is carried out with 50% deformation after the solution heat treatment. The cold-rolled steels are heat treated for 60 minutes at 480 to 500 ⁰ C as Schlußglühbehandlung; in Examples 1 to 5, the amount of Al is slightly less than that in a standard composition of 17-Cr-7-Ni steel.

As can be seen from the table, the addition of about 0.15% Nb to the 17-Cr-7-Ni steel with a standard composition can ^{increase the spring deflection limit above 160 kg / mm 2} , and the spring deflection limit shows an improvement in accordance with the increase in the added amount of Nb.

Table 2 shows an example in which a 17-Cr-7-Ni steel with the standard composition 1.04% Nb is added, the amount of Al comparatively is increased, and an example in which only about 0.1% Nb is added along with the Spring deflection limits of these steels to which the same precipitation hardening treatment as after the examples in Table 1 was used.

Table 2

Spring deflection limit

after
treatment

(kg / mm ² )

Composition (weight percent)

Example 7
Example 8

By comparing the results thus obtained with the result according to Example 3, FIG Table 1 shows that when the amounts of Nb are equal, i.e. H. about 1.0% is a steel with a higher Spring deflection limit is available in the case when the amount of Al is slightly larger. It also becomes clear that a steel with a much higher spring deflection limit cannot be obtained in the case where the Amount of Nb very small, e.g. B. 0.1 weight percent.

If the ductility of the 17-7-PH steel in Needless to say, hardness becomes important in shaping. That means that the Deformability of a steel is better if the hardness before the final annealing treatment after CH procedure is lower.

F i g. Fig. 2 is a diagram for explaining the relationships among the amount of Al, Vickers hardness and the spring bending limit in the steel to be used according to the invention.

The composition of the stainless steel used in the examples is 17.0% Cr, 7.0% Ni, 1.0% Nb, 0.6% Si, 0.1% C, 0.4% Mn, 0.05 to 1.4% aluminum, remainder Fe. They were rustproof Steels used that are cold-rolled after solution heat treatment at a 50% degree of deformation and subjected to a final annealing treatment at 480 to 500 ° C for 60 minutes.

It is apparent from the results that the spring deflection limit of the stainless steel after the final annealing treatment within a range of 0.1 to 0.3% Al to increase in proportion to the amount of Al added tends and the increase in the spring deflection limit tends to saturate when the amount of Al Exceeds 0.3%.

It can also be said that the hardness before the final annealing treatment by a point above 1.0% Al addition has a tendency to increase sharply. So it should be noted that in order to make a stainless steel with a high flexural limit and good ductility to obtain a preferred amount of Al to be selected within a range of 0.3 to 1%. Table 3 shows a comparison of several examples according to the present invention with various reference examples.

Tabel

Composition (weight percent)

Si Mn Cr Ni Al

Nb

Spring bending limit (kg / mm ² )

before the
treatment

after the treatment

Hardness (kg / mm ² )

before treatment

after treatment

Examples

9

10

11th

12th

13th

14th

15th

16

17th

18th

Reference examples

4th

5

6th

7th

8th

9

0.06
0.07
0.06
0.05
0.06
0.08
0.08
0.05
0.03
0.05

0.07
0.05
0.09
0.08
0.07
0.05

0.53 0.52 0.55 0.62 0.64 1.08 0.02 0.07 0.35 0.07

0.53 -0.52 0.62 0.70 0.53 0.53

0.32 16.76 0.43 16.78 0.52 16.77 0.58 16.92 0.54 16.79 0.27 17.32 0.23 17.81 0.28 14.93 0.45 16.55 0.29 12.53 0.37 16.77 0.40 16.74 1.14 18.43 0.30 16.56 0.74 16.66 0.69 16.75

7.02 6.81 7.02 6.86 6.82 7.52 7.43 6.85 6.95 6.75

6.94 6.93 8.53 10.80 6.93 7.03 0.39
0.79
0.21
0.09
0.20
0.73
0.72
0.75
0.40
0.73

0.89

1.40

1.10

1.01

1.05

0.42

1.44

1.04

0.97

1.05 *)

3.02

0.95 **)

1.07

0.96

55
62
70
49
57
52
55
51
60

115
47
61
63
99
65

191 180 178 169 181 194 182 180 167 165

126 111 114 122 179 163

340 346 341 397 353 362 367 380 393 390

533 588 404 354 431 342

483 521 476 483 498 519 521 520 530 540

546 597 367 373 603 466

*) (Mo) 2.06. **) (Mo) 4.13.

The stainless steels which were used in the examples and reference examples according to Table 3 were cold-rolled sheet materials after the solution heat treatment with 50% reduction in cross-section after a subsequent final heat treatment. A heat treatment of 60 minutes at 600 ° C and in the other Examples and Reference Examples 45 minutes at 480 was applied to 500 ⁰ C in the Reference Example 6 as Schlußglühbehandlung.

Reference example 4 relates to a type of well-known stainless steel for spring use, which is disclosed in US Pat Solution heat treatment have an unstable austenite structure, but are not precipitation hardenable, although they develop a martensite structure through cold processing. The steel after this Reference example has a problem that the hardness after cold rolling is very large, and he does not have as high a spring deflection limit after the heat treatment as that of the invention using stainless steel.

The stainless steels of Reference Examples 6 and 7 have the conventional stable austenite structure. In doing so, the hardness of the cold-rolled steel can be reduced to a certain extent, but the spring bending limit after the precipitation hardening treatment, it cannot be increased excessively.

Reference example 8 shows a case where the amount of Al is relative to that of the present examples Invention is increased. It is the hardness of the steel before the precipitation hardening treatment considerably high.

Reference example 9 shows a case where no Al was added at all. Here is the Hardness of the steel before the final annealing treatment is not too great, but the spring bending limit can be not be made high.

According to the examples according to the invention in this table, a stainless steel with a Vickers hardness of 350 after 50% cold rolling and a spring deflection limit of 180 kg / mm ² after the final annealing treatment can easily be produced.

As shown in Examples 16 and 18, a stainless steel in which a part of Cr is replaced by Mo is replaced, also has a high spring deflection limit.

As explained above, as the examples show, a stainless steel was found to work with a low hardness before the final annealing treatment, a favorable deformability and a very high one After the final annealing treatment, the elastic limit can be achieved by adding certain amounts of Adds Nb and Al. These improved properties can have a very good effect, when the stainless steel to be used in the present invention is used for various spring materials. as For example, a spring material for the holder of a shadow mask in a color television set can be mentioned will. The spring is one of two depending on the method of holding the shadow mask Species. That is, a material of low thermal expansion is required in one case and in the other In this case, you need a material with a coefficient of thermal expansion close to that of the shadow mask constituting material (usually pure iron).

In the latter case, the stainless steel selected according to the invention can advantageously be used as the spring use for holding purposes. Here, a material with an austenite structure is unsuitable because it has a has an excessively high coefficient of thermal expansion. You need a material with a martensite structure, as it has the stainless steel to be used according to the invention.

To an occurrence of a shift in the shadow mask position due to a vibration or a To avoid shock, it is necessary to use a spring with a high resistance to the so-called To use "relaxation". In this regard, the stainless steel to be used in the present invention can provide an excellent service with its high spring deflection limit.

Further, in the mass production of springs, it is necessary that the shaping be easily can be done by means of a punch press and a compression loss is saved. In this regard it is the stainless steel to be used according to the invention is excellent because its hardness at the time of shaping, d. H. before the precipitation hardening treatment, is low.

1 sheet of drawings

copy

209 511/286

Claims (1)

Patent claims: 1. Using a martensitic stainless steel consisting of 5 h '10 ° / N'ck 1 io k, v loo / rn, L
12 to iy% chromium, 0 15 to W N 'b 0! L to 1.5% aluminum, ' no more than 0.1% carbon, no more than 1% silicon ^I0