Seamless cold-drawn / cold-rolled steel tubes Standard No： EN 10305-1:2002；GB/T 3639-2009
Seamless cold-drawn / cold-rolled steel tubes for precision is one of high precision steel pipe made of fine drawn or cold-rolled. Seamless cold-drawn / cold-rolled steel tubes for precision has following advantages: no oxidation layer on inside/outside wall, without leakage withstand high pressure, high precision, high degree of finish, no deformation, flaring while bending, flattening without cracks. So they are mainly used in the production of pneumatic or hydraulic components, such as cylinder or oil cylinder which can be seamless or welded tube. Chemical components of precision bright tube have carbon C, silicon Si, manganese Mn, sulfur S, phosphorus P, chromium Cr.
1 Process:
High quality carbon steel, finishing, no oxidation of the bright heat treatment (NBK), nondestructive testing, pipe wall with high pressure washing, brushing and anticorrosive processing, both cover for dustproof.
2 Main features:
The pipe have high precision with both pipe sides, high degree of finish, without oxidation layer after heat treatment, high cleanliness in the inner wall, bearing high pressure, no deformation, flaring while bending, flattening without cracks. Color of steel tube: white with bright, with higher metal luster.
3 Standard, material and delivery status
The main standards: GB/T3639, DIN2391-94/C, DIN2445, EN10305, DIN1630, DIN1629, ASTM A106, ASTM A179, JIS G3445
Main material: 10#, 20#, 35, 45, 40Cr, 25Mn.37Mn5, St35 (E235), St37.4, St45 (E255), St52 (E355)
The main condition of delivery: NBK (+N), GBK (+A), BK (+C), BKW (+LC), BKS (+SR
4 Main purposes of precision bright tube:
Automobile, machinery and other accessories for high requirements of mechanical properties with precision, smoothness need the pipe. Precision steel tube user is not just of the relatively high precision, smoothness requirements of users, because the precision bright tube of high precision, tolerance can be maintained at 2–8 silk, so a lot of machining users gradually select precision bright tube in order to save labor and material loss.
5 Precision bright tube mechanical properties
Precision bright tube mechanical properties of [1]
Grade
Delivery state
Cold processing / hard (Y)
Cold processing / soft (R)
Stress relief annealing (T)
6 Precision bright tube chemical composition
10# 0.07~0.13 0.17~0.37 0.35~0.65 ≤ 0.035 ≤ 0.035
20# 0.17~0.23 0.17~0.37 0.35~0.65 ≤ 0.035 ≤ 0.035
35# 0.32~0.39 0.17~0.37 0.35~0.65 ≤ 0.035 ≤ 0.035
45# 0.42~0.50 0.17~0.37 0.50~0.80 ≤ 0.035 ≤ 0.035
40Cr 0.37~0.44 0.17~0.37 0.50~0.80 ≤ 0.035 ≤ 0.035 0.08~1.10
25Mn 0.22~0.2 0.17~0.37 0.70~1.00 ≤ 0.035 ≤ 0.035 ≤ 0.25
37Mn5 0.30~0.39 0.15~0.30 1.20~1.50 ≤ 0.015 ≤ 0.020
7 pressure calculation formula
A: known seamless tube light outside diameter, wall thickness, specifications for the calculation methods of stress (different tensile strength of steel pipes with different materials)
Pressure = (wall thickness *2* steel material tensile strength) / (diameter * coefficient)
B: Known seamless steel pipe diameter and pressure calculation of wall thickness:
Wall thickness= (diameter * pressure * coefficient) / (2* steel material tensile strength)
C: seamless tube light pressure coefficient method:
Steel pipe pressure P<7Mpa coefficient S=8
7< steel pipe pressure <17.5 coefficient S=6
Steel pipe pressure P>17.5 coefficient of S=4
The specifications of commonly used precision bright tube:
18*2 23*3 30*6 38*2.5 50*2 58*3 68*3 78*8
10*2.5 23*4 32*2 38*3 50*2.5 58*4 68*4 80*2
16*2 24*2 32*2.5 38*3.5 50*3 58*6 68*6 80*3
16*2.5 24*3 32*3 38*4 50*4 59*2 70*2 80*4
16*3 24*4 32*3.5 38*6 50*6 59*3 70*3 80*6
17*2 25*2 32*4 40*2 51*2 59*4 70*4 80*8
17*2.5 25*3 32*5 40*3 51*3 59*6 70*6 80*12
17*3 25*4 32*6 40*4 51*4 60*2 72*2 81*2
18*2 27*2 34*2 40*5 52*2 60*3 72*3 81*4
18*2.5 27*3 34*2.5 40*6 52*3 60*4 72*4 81*6
18*3 27*4 34*3 42*2 52*4 60*6 72*6 81*8
19*2 28*2 34*4 42*3 52*6 62*2 75*2 81*12
19*2.5 28*2.5 34*5 42*4 53*2 62*3 75*3 82*4
19*3 28*3 34*6 42*6 53*3 62*4 75*4 82*6
19*3.5 28*3.5 35*2 45*2 53*4 62*6 75*6 82*8
8. Temper brittleness
Precision bright tube quenching are martensite, tempering at 450 ～ 600 ℃ or tempering at 650 ℃ slow cooling between 350 ～ 600 ℃; or at 650 ℃ tempering, heated for a long time between 350 ～ 650 ℃, all make the precision bright tube has the property of embrittlement. if brittled 20# precision steel pipe reheated to 650 ℃ and fast cooling, it can restore the toughness, therefore it also known as %26ldquo. High temperature temper brittleness fracture is more serious, the intergranular fracture proportion is higher for precision bright tube.
The measures of reducing high temperature temper brittleness of precision bright pipe are:
(1) After high temperature tempering use oil or water cooling to inhibit the impurity elements in grain boundary segregation.
(2) Use precision bright tube containing molybdenum. When the molybdenum content in the steel increases to 0.7% the high temperature tempering embrittlement tendency is greatly reduced. If more than this limit 20# precision tube will form carbide with rich molybdenum. Embrittlement tendency of precision bright tube will increase when molybdenum content in the matrix is reduced.
(3)Reduce the content of impurity elements in 20# precision steel tube.
(4) Working in high temperature temper embrittlement zone with long time only molybdenum added is also difficult to prevent brittle. The way to effectively prevent the high temperature temper brittleness is reducing the content of impurity elements of 20# precision steel tube to improve the precision bright tube cleanliness, at the same time supplementing the composite alloy aluminum and rare earth elements. It can reach good result.
