JPH03219044A - structural steel - Google Patents

Abstract

PURPOSE: To develop low alloy base age hardening property ferritic-pearlitic steel for structural purposes by adding specified alloying elements to medium carbon steel as steel for structural purposes.

CONSTITUTION: The steel for structural proposes is manufactured from the low alloy steel consisting of, by weight, 0.2-0.5% C, 0.4-1.0% Si, 0.8-1.8% Mn, 0.008-0.2% S, 0.04-0.04% N, 0.05-0.20% V or Nb, or further additively <0.7% Cr, <0.1% Al, <0.05% Ti and the balance Fe. The steel for structural purposes having high particulate resistibility till deformation working temp. of 1300°C or anneal temp., at least 800N/mm² tensile strength, at leasst 550N/mm² 0.2% bearing force, ≥15% elongation and ≥45% reduction of area at the room temp. and having age hardening property ferritic-pearitic structure in a particulate shape of at least 35 joule notched bar cross section absorption energy of a DVM sample at the room temp. and having excellent strength properties without executing heat treatment is manufactured.

COPYRIGHT: (C)1991,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to structural steel, and more particularly to age-hardenable (self-hardening) ferritic-pearlite structural steel, which age-hardenable structural steel is heated at 1300°C. It has high resistance to fine particles (high ability to maintain fine particles), and its composition is: Carbon...0.2-0.5% Silicon...0.4-1.0% Magnesium...・0.8-1.8% Sulfur...0.008-0.2% Iron and incidental impurities...The remainder, mixed sulfides are precipitated at grain boundaries, and high temperatures up to 560℃ Used for structural members that are subjected to forces underneath.

In the specified type of steel with a similar fine-grained ferrite-pearlite structure, the cross-sectional absorbed energy value of the notched bar at room temperature can be improved to at least 25 joules by simple controlled cooling from the heat during processing but without heat treatment. , in some cases was found to be higher.

Table 1 shows the chemical composition of the steel according to the invention.

Table 2 shows the properties of strength and toughness at room temperature, and also shows the properties of the comparative example steel. Compared to unalloyed or low alloyed heat-resistant steels, these are conventionally annealed, whereas the steels according to the invention are cooled (BY-s) without heat treatment.
It can be seen that higher strength characteristics were obtained even though the test was carried out under

Table 3 shows the strength properties at high temperatures as in Table 2. In this case, the steel according to the invention has higher values than the standard steel taken for comparison.

Tables 4a, 4b and 4c show the results of creep rupture tests on steels according to the invention. These results are compared to 450℃ constant temperature creep rupture in Figure 1 and 5 in Figure 2.
The isothermal creep rupture is shown at 00°C and the isothermal creep rupture is shown at 550°C in FIG.

Table 5 shows the creep rupture strength of the steel according to the present invention, 103.10' and 10
Characteristic values during a 5-hour load application period are shown. For comparison, Table 5 also shows the values of the comparative example steel, which corresponds to the standard. The steel according to the invention has higher values. In FIG. 4, the characteristic values of AFPm according to the present invention are plotted according to the test temperature.

Figure 5 combines the 0 and 2% yield strength and creep rupture strength depending on the test temperature, and from this figure, depending on the time, calculations above the intersection temperature are the high temperature yield point or 0.2%
Although it is not necessary to use yield strength, it is clear that characteristic values in creep rupture tests should be used.

Table 1 Chemical composition of steel according to the present invention (% by weight)
, 41 (1967), S, 65/692
) Norton, J. F.; SLrang
+ Eight, :J, Iron 5teelInst
, 207 (1959), S, 193/2033)
Prnka, T.; Foldyna, ν:
Arch, EisenhLIttenwesen
40 (1969) S, 49915044)
Florin, C.; Haa+merstein,
p, ; ImgrundIf, : Arch,
Eisenhi;ttenwesen 41 (1
970) 3.231/36 5) Baerlecken+ E,; Fab
ritius H.: Arch.

33 (196
2), S, 261/676) Florin
, C, ;) Iorstmann, D,; I
s+ground.

11,: Arch, Eisenhi;ttenw
esen 45 (1974) +5.457/63 7) 5tone, P, G,; Murr
ay, J, D, :J, IronSteel
In5t, 203 (1965), S.
1094/11078) lluchtemann,
B., Rademacher L.: TEW-
Techn, Ber, 2 (1976) H, 2,
S, 137/1449) DB-PS 37 19
569

[Brief explanation of drawings]

Figure 1 is a graph of the relationship between time and stress showing creep rupture at 450°C and constant temperature for the structural steel according to the present invention, and Figure 2 is a graph showing the relationship between stress and time at 500°C for the structural steel according to the present invention. FIG. 3 is a graph of the relationship between time and stress showing creep rupture at a constant temperature; FIG. , FIG. 4 is a graph of the creep rupture strength of steel as a function of test temperature for loading periods (1,000, 10,000 and 100,000 hours), and FIG.
Creep rupture strength of steel as a function of test temperature and 0.
It is a graph of 2% yield strength. Procedural amendment (method) % formula %2 Display of the case 1990 Patent Application No. 148836 Name of the invention Structural steel hli +E Relationship with the 11 projects Name of the patent applicant Thirasen Nyblstahl Herkeakchengesellschaft i. 6. Subject of amendment (1) "Applicant's representative" field in the application (2) Power of attorney (3) Drawings 7. Contents of amendment (as per Attachment 21 (3) Engraving of drawings (contents) 8. List of attached documents (11. Request for correction (2) Power of attorney and translation (3) 1 engraving drawing 1 each 4. Agent address: 8-10 Toranomon-chome, Minato-ku, Tokyo 105 Japan) Month

Claims (1)

[Claims] 1. Age hardenable ferritic-pearlitic structural steel with high grain resistance up to 300°C, comprising: 0.2-0.5% carbon; 0.4-1.0% silicon; 0.8 ~1.8% manganese; 0.008-0.2% sulfur; 0.004-0.04% nitrogen; 0.05-0.20% vanadium and/or niobium; balance iron and associated Structural steel for structural members that are subjected to forces at high temperatures up to 560°C. 2. Structural steel according to claim 1, characterized in that it additionally contains not more than 0.7% chromium, not more than 0.1% aluminum and not more than 0.05% titanium. 3, 0.20-0.35% carbon; 0.5-0.8% silicon; 1.0-1.7% manganese; 0.01-0.
09% sulfur; 0.2-0.5% chromium; 0.015
~0.06% aluminum; 0.015-0.030
% nitrogen; 0.05-0.15% vanadium and/or
or 0.02-0.10% niobium; 0.01-0.
Structural steel consisting of 0.4% titanium; balance iron with incidental impurities, with high fine-grain resistance up to deforming or annealing temperatures of 1300°C and a tensile strength of at least 800 N/mm^2 at room temperature. and at least 550
The notched bar has a 0.2% yield strength of N/mm^2, an elongation of at least 15%, a cross-sectional shrinkage of at least 45%, and a notched bar cross-sectional absorbed energy of at least 35 Joules in a DVM sample at room temperature. The structural steel according to claim 2. 4, 0.35-0.45% carbon; 0.5-0.8% silicon; 1.0-1.7% manganese; 0.01-0.
09% sulfur; 0.2-0.5% chromium; 0.015
~0.06% aluminum; 0.015-0.03%
of nitrogen; 0.05-0.15% vanadium and/or 0.02-0.10% niobium; 0.01-0.0
Structural steel consisting of 4% titanium; balance iron with incidental impurities, having high fine grain resistance up to deforming or annealing temperatures of 1300°C and at least 850°C.
Tensile strength of N/mm^2 and at least 600 N/mm
0.2% yield strength of ^2, elongation of at least 12%, cross-sectional shrinkage of at least 40%, and DV at room temperature.
3. Structural steel according to claim 2, wherein the notched bar cross-sectional absorbed energy reaches at least 25 Joules in the M sample. 5. Structural steel according to any one of claims 1 to 4, which is used for structural members used at high temperatures in the temperature range of 300 to 560°C.