Seamless steel pipe for oxygen tank

Introduction of seamless steel pipe for oxygen tank.

(1)used for seamless gas cylinder billet of blooming mill production.

GB18248-2000 (cylinders with seamless steel pipe), mainly used in the production of various kinds of gas, hydraulic cylinders.It represents material for 37 Mn, 34 Mn2V, 35 CrMo, etc.

(2)  the dimensions are shown in table 1.

         Table 1 oxygen bottles billet section size (mm)

Side length	Radius R≈	allowed length  deviation	Diagonal length	Diagonal difference
200×200	30	士4.5	<265	≤6

Note: the usual length of steel billet for 4 ~ 6 m.

(3) grades and chemical composition are shown in table 2

Table 2 steel grades and chemical composition

Steel grade	chemical composition(mass fraction)(%)
	C	Si	Mn	P	S	V	Cr	M0
40Mn2	0.37～0.42	0.17～O.37	1.50～ 1.75	≤0.030	≤0.035
40Mn2	O.39～O.44	O.17～O.37	1.50～ 1.75	≤0.030	≤O.035
34Mn2V	0.30～0.37	O.17～O.37	1.50～1.75	≤O.03O	≤O.035	0.070～0.12
30CrM0	0.26～O.34	O.17～0.37	O.40～O.70	≤O.030	≤0.035		0.80～ 1.10	0.15～O.25

Note: the content of residual copper in steel should be no greater than 0.20%, chromium content should be not greater than 0.35%, nickel content should be not greater than 0.30%, acid soluble not less than 0.018%, if the steel mill can guarantee, can not be analyzed.The above content are all mass fraction.

(4) mechanical properties are shown in table 2.

 Table 3  mechanical properties of the blank sample after heat treatment

Steel grade	sample  status	yield point ós／MPa	Tensile strength  ób／MPa	Elongation δ5 (％)	Reduction of area Ψ(％)	Impact toughness  ak／(J／c㎡)
40Mn2	quenched	≥470	≥765	≥12	≥45	≥69
42Mn2	quenched	≥490	≥785	≥12	≥45	≥69
34MnV	quenched	≥530	≥745	≥16	≥45	≥69
40Mn2	quenched and tempered	≥765	≥900	≥12	≥45	≥59
40Mn2	quenched and tempered	≥765	≥900	≥12	≥45	≥59
30CrMo	quenched and tempered	≥785	≥930	≥12	≥50	≥79

(5) delivery state: billet should have been delivered with slow cooling after rolling.