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SM490A SM490B.C.YA.YB

SM490A SM490B.C.YA.YB

InJapan developed the SM490A SM490B.C. SM490YA. SM490YB steels as commercial materials. Specific property of this steel is that the grain size is about 3 µm, which is one-third smaller than conventional steels. Therefore, the tensile strength becomes 1.5 times stronger. Naturally, the hardness becomes high, and the wear resistance and fatigue life are also improved.

In the practical use of steel, processing like machining or grinding affects on the surface layer of steel. Therefore it is important to understand the residual stress state of new fine-grained materials. Some researcher investigated the surface residual stress state of grinded steels using X-ray stress measurement in past.
conventional steel, because the ratio of the X-ray penetration depth to the distance between grain walls in fine-grained steel is high compared with conventional steel. In present study, specimens of NFG steel and conventional JIS-SM490 steel were prepared. The chemical composition of two materials is the same. Then, two kinds of similar mechanical processing were given to both specimens. The residual stresses of specimens ground and polished were obtained by X-ray stress measurement through three kinds of analysis methods.

Fine-grained rolling steels that are named NFG600 by Henan BEBON international co.,ltd. and conventional Mn rich steels that are named SM490 in Japanese Industrial Standard were used in present study. SM490 is an initial material of NFG600 that is refined by severe plastic deformation and quick quenching. The chemical composition of two materials is the same.consisted of ferrite and pearlite, however, each average grain size was different. The average grain size of NFG600 and SM490 were 3 µm and 15 µm respectively. Accordingly, mechanical properties of NFG600 were different from SM490 as expected by Hall-Petch relation. Mechanical properties obtained by tensile test and micro Vickers hardness test are summarized in the follows.

JIS G3106-2008 Rolled Steels for Welded Structure

 

 
 
 
 
Grade
 
 
 
 
Thickness
(mm)
 
 
Chemical Compositions %
Mechanical Properties
 
Tensile Test
 
Impact Test
Yield Point N/mm²
 
Tensile Strength N/mm²
Elongation
 
Test
Temp
(℃)
Charpy
Absorbed Energy Average (Joule)
Test piece
 
C (max)
 
Si
(max)
 
Mn
 
P (max)
 
S (max)
Thickness (mm)
 
Thickness
(mm)
 
Test
Piece
 
% (min)
 
t≦16
16＜t
≦40
40＜t
≦75
75＜t
≦90
 
t≦50
0.20
 
0.55
1.65 max
 
 
 
0.035
 
 
 
0.035
 
 
 
325 min
 
 
 
315 min
 
 
 
295 min
 
 
 
295 min
 
 
 
490~610
 
 
6≦t≦16
16＜t≦50
40＜t
 
 
No.1A No.1A No.4
 
 
17
21
23
 
─
 
─
50＜t≦90
0.22
 
t≦50
0.18
 
0.55
 
1.65 max
 
0
 
27 min
50＜t≦65
0.20
t≦50
0.18
0.55
1.65
max
0
47 min
 
t≦50
 
0.20
 
0.55
 
1.65 max
 
0.035
 
0.035
 
365 min
 
355 min
 
335 min
 
325 min
 
490~610
6≦t≦16
16＜t≦50
40＜t
No.1A No.1A No.4
15
19
21
─
─
0
27 min
Remarks:1. Alloy elements other than those shown in the above table may be added necessary.

2. Impact test is applicable to thickness over 12.0mm of steel.
3. SM570 is produced by Thermo-Mechanical Controlled Process(TMC).
4. Carbon Equivalent＝C＋Mn/6＋Si/24＋Ni/40＋Cr/5＋Mo/4＋V/14.
5. Sensitivity of welding crack＝C＋Si/30＋Mn/20＋Cu/20＋Ni/60＋Cr/20＋Mo/15＋V/10＋5B.
6. Grade SM400A through Grade SM520C may be subjected to normalizing by agreement between purchaser and manufacturer.

 

Source:

Tags: sm490a, sm490b, sm490c, sm490ya, sm490yb, steel plate, JIS G3106-2008 Rolled Steels for Welded Structure

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