JPH02118052A - austenitic stainless steel - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an austenitic stainless steel having excellent hot workability, particularly good blooming property.

Conventional technology Conventionally, stainless steel used as a base material for welding has a slight amount (approximately 10 to 2006) of delta steel applied to the base material for welding.
Ferrite remains and weldability is improved.

(For example, low carbon steel 5US309.5IIS347.
5us316, etc.) Problems to be Solved by the Invention Incidentally, the hot workability of stainless steel containing approximately 10 to 2006 delta ferrites in austenite is significantly deteriorated by the presence of S. Therefore, the above-mentioned conventional austenitic steel containing about 10 to 2006 delta ferrites has a problem in that the hot workability of the product is significantly inferior due to blooming. That is, the actual 1. In the process, there was a problem in that even if the ingot was heated at a low speed in a press, the ingot would be overflowing, and many of the ingots could not be used as products.

The present inventors have discovered that when austenitic steel containing delta ferrite is subjected to soaking treatment to linearize the net-like delta ferrite, to some extent,
It was discovered that the hot workability could be improved, but there was a limit to its improvement, and it was still unsatisfactory. Therefore, it has been desired to improve the hot workability of austenitic steels that have improved weldability due to the inclusion of delta ferrite.

The present invention was made under the circumstances F as described in =L. Therefore, it is an object of the present invention to improve weldability and to improve the weldability of austenitic steel that has been degraded due to hot workability.
We have so much to share.

Means for Solving the Problems The inventors have developed delta ferrite from approximately 10 to 2006
Further study on the austenitic steel content revealed that the austenitic steel contained 0.0005
They discovered that adding ~0.003% of S in steel fixes the S content and improves hot workability, leading to the completion of the present invention.

The first austenitic stainless steel of the present invention has a weight percentage of Coo. 005-0.08%; St: 0.2-2.
006; Mn: 0.1-3.006; Ni
: 8.0~i5.006; Cr: 17.0~
25.006;S: 0.002% or less-N20.0
05-0.1%; Ca: 0.0005-0.00
3%: The balance consists of Fe, Ca/S is 0.2 ~
3.75 and delta ferrite or 10-2
Be 006! t,'f signs.

The second austenitic stainless steel of the present invention has C: 0.005-0.08%; Si: 0.2-2 in weight%.
．． 006; Mn: O91-3.006; Ni:
8.0-15.006; Cr: 17.0-25.
006; S: 0.002% or more 7'; N: 0.00
5-0.1%; Ca: 0.0005-0.0
03%; Nb: 0.05-1.006, Mo
: 1.0~3.006 and 'j: 0.05~
Contains 1,006: balance [2 (=), and is characterized in that Ca/S is 0.25 to 3.75, and Tilter 7 Elite is 10 to 2006.

The reason for limiting the range of use of each element constituting the austenitic stainless steel of the present invention will be explained.

C: 0.005-0.08% Carbon is a heavy element that gives strength to steel, so in order to exhibit its effect, it should be added at least o, oos%.
Must be included. However, if it is contained in too large a quantity, carbides such as Cr 3 Cb will be produced, resulting in deterioration of corrosion resistance, so the upper limit is 0.08
Is it necessary to set it to %?

Si: 0.2 to 2.006, Si has a deoxidizing effect and is an element that increases fluidity during welding, so it must be included at least 0.2% in order to exhibit its effect. There is.

However, if it exceeds 2.006, ferrite starts to increase, so the 1st limit is set to 2,006.

Mn: 0.1 to 3.006 Mn is an element that has a deoxidizing effect like Si, so it needs to be contained at least 0.1% in order to exhibit its effect. However, it is desirable to set the upper limit to 3.006.

Nr: 8.0-15.006 Ni is an essential element for austenitic stainless steel and is a strong austenite-forming element. However, if Ni is less than 8,006, the amount of delta ferrite increases and exceeds 2,006, which is not preferable. Moreover, when it exceeds 15%, the amount of delta ferrite becomes less than 1006 depending on the balance with other elements, so the upper limit is 15.006.

(Similar to: r: 17.0-25.006Ni,
It is an essential element for austenitic stainless steel, and is an important element for improving heat resistance and corrosion resistance. In order to ensure corrosion resistance and the amount of delta ferrite to be at least 1006, the lower limit should be 17.006. Moreover, if it exceeds 25.006, σ embrittlement is likely to occur, and delta ferrite will be in a furnace with a value exceeding 2006, so it is necessary to set the upper limit to 25.006.

S: 0.002% or less S is an impurity element that exists alone or forms an intermetallic compound with Ni and inhibits the hot workability of steel at a low melting point. It is necessary that the content be at least 0.001%, preferably 0.001% or less.

N: 0.005 to 0.1% Like C, N is a strong austenite-forming element and greatly contributes to controlling delta ferrite, so it is contained in an amount of 0.005% or more to obtain this effect. However, if the amount exceeds 0.1%, bubbles will form during welding, making welding difficult, so the upper limit is 0.1%.
．． Must be set to 1%.

Nb: 0.05 to 1.006 Nb reacts with C, fixes C bonded to Cr, and exhibits the effect of improving corrosion resistance, so the presence of 1 of 8 or more of C is required. Or preferable. So, Nb is
1ilff! l! It is mainly added when obtaining steel whose properties are extremely important. Note that if the amount of Nb exceeds 1.006, no improvement in corrosion resistance can be expected. MO: 1.
0 to 3.006 MO is added to improve corrosion resistance (general corrosion, pitting corrosion, intergranular corrosion, etc.). Therefore, like Nb, it is mainly added when producing steel in which corrosion resistance is particularly important. In order to produce such an effect, it is preferable that the F content is 1.006 or more, more preferably 2.0 to 3.00 F.
The range is 6. When the MO rate reaches 3.0% or more,
Beyond that, no further improvement in the corrosion resistance of L can be expected, and the cost will also increase, leading to economic problems.
Since there is also the problem of reducing the increase in ferrite rats by (/1),
It is preferable to contain 3006 or less.

1' i: 0.05 to 1.006 ``I' Since I exhibits strong +iif corrosive properties, it is preferable to contain it in an amount of 0.05% or more in order to obtain such an effect.

However, if it exceeds 1.006, the fluidity of the weld metal during welding will deteriorate, so it is preferable to contain y of 1.006 or more.

Ca: 0.0005 to 0.003%Ca is a type of deoxidizing agent, and is added to fix harmful S that worsens hot workability. must be at least 0,0005%. Moreover, if it exceeds 0.003%, hot workability deteriorates and is rather harmful, so the upper limit needs to be 0.003%.

Further, in the ausbunite stainless steel of the present invention, it is necessary that the Ca/S ratio is in the range of 0.25 to 3.75, and the optimal case is Ca/S = 1. When the Ca/S ratio is lower than 0.25, hot workability deteriorates. On the other hand, if it is higher than 3.75, hot working cracks will occur instead.

When P, 0, etc. are included as one of the unavoidable impurity elements, it is desirable that the content thereof be as low as possible.

Example Next, the present invention will be explained with reference to examples.

50ktr-! ”+ ′!: Due to q aA induction furnace,
A steel ingot 2bkK having the composition shown in Table 1 below was melted by a conventional method.

In addition, the 112th middle A MY is 21Cr -11N i
Group B is 23Cr-13N austenitic steel.
I-series austenitic steel, p).

Next, material for a creeple specimen was collected from the surface layer of a 25 kg small lump having the composition shown in No. 1k, and both groups A and B were subjected to soaking treatment at +25 +1 °C for 8 hours. After mounting, a hot tensile test (creeple test) was conducted.

The connection is shown in Figures 1 and 2.
1] and the 21a 11.17 axis indicate the creeple aperture value, and the +(/11 axis indicates λJt+inspection quality.

this! 9. As is clear from FIGS. 1 and 2, A-2, A-4, A-5, and B-3 which are embodiments of the present invention
, [1-4, B-5 are comparative examples A-1, A-3,
[3-1 and [3-1] showed a higher creeple area of area than B-2, and therefore it can be seen that the addition of C made the hot working process more difficult.

In addition, 124 1.3L steel ingots with the same composition as sample 1B-3 were
After soaking for a long time at 0°C and blooming, (iil
A billet was obtained without any of the troubles described in '4.

Moreover, even when the steel strip was rolled, no edge warping or the like occurred.

For ratio IF12, when a Ca-free test;'l [1-1 and steel with the same composition +5ν was similarly bloomed, K/I separation occurred, and a slight bending of the steel strip occurred during rolling of the strip. A breakup occurred.

Effects of the Invention The austenitic stainless steel containing delta ferrite 10 to 2006 of the present invention has a Ca content of 0.0005 to 0.
．． 003% and Ca/S ratio 0.25-3.75
Since it was added at the same time, the harmful S due to Ca was added.
This results in significantly improved hot workability. Therefore, the austenitic stainless steel of the present invention can be suitably used for welding base materials and the like.

[Brief explanation of the drawing]

FIGS. 1 and 2 are graphs showing the relationship between the test temperature and the Grieple aperture value in the hot tensile test of Group A and Group B austenitic stainless steels in Examples, respectively. Patent applicant Daido Steel Co., Ltd. agent Patent attorney Liquid department Rigid test temperature ('C) Test temperature (''C)

Claims (2)

[Claims] (1) C: 0.005-0.08% by weight; Si: 0
．． 2-2.0%; Mn: 0.1-3.0%; Ni: 8.
0-15.006; Cr: 17.0-25.0%; S:
0.002% or less; N: 0.005-0.1%; Ca:
0.0005-0.003%; balance consists of Fe, Ca
An austenitic stainless steel with excellent hot workability, characterized in that /S is 0.25 to 3.75 and delta ferrite is 10 to 20%. (2) C: 0.005-0.08% by weight; Si: 0
．． 2-2.0%; Mn: 0.1-3.0%; Ni: 8.
0-15.0%: Cr: 17.0-25.0%; S: 0
．． 002% or less; N: 0.005-0.1%; Ca: 0
．． 0005 to 0.003%; and an element selected from the group consisting of Nb, Mo and Ti to Nb: 0.05 to 1.0%;
%, Mo: 1.0-3.0% and Ti: 0.05-1.
Contains 0%; remainder consists of Fe, Ca/S is 0.25~
3.75 and delta ferrite is 10-2
Austenitic stainless steel with excellent hot workability.