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1. SCOPE
 This Japanese Industrial Standard secifies the steel tubes, hereinafter referred to as the "tubes", used for the purpose of exchanging heat on the inside and outside of the tube at exceptionally low temperatures below freezing point, such as heat exchanger tubes, condenser tues, etc.

Remarks
1. The purchaser may designate n addition to the items specified in this text, by prior agreement with the manufacturer, part or all of the items in the spcial requirements Z1, Z3, Z4, specified in Appendix 1 and the items of the U-bend tube specified in Appendix 2.
            

Appendix 1 Z1 hardness

Appendix 1 Z3 Ultrasonic examination

Appendix 1 Z4 Eddy cureent examination

Appendix 2 U-bend tube  

         2. The austenitic steel tubes among the steel tubes specified in JIS G 3463 may be used.
In this case, the impact test need not be particularly performed.

3. The units and numerical values given in { } in this Standard are based on the International System of Units (SI) and are appended for informative reference.
Further, the traditional units accompnied by numerical values in this Standard shall be converted to the SI units and numerical values on Jan. 1, 1991.

2. Clases and Symbols
The tubes shall be classified into three classes and their symbols shall be as given in Table 1.

표 1

* World standard comparative table *

3. Heat Treatment

Table Heat Treatment

4. 3.  Chemical Composition
The tube shall be tested in accordance with 9.1 and the resulting ladle analysis values shall conform to Table 3

Table 3

Symbol of class	Chemical composition (%)
	C	Si	Mn	p	s	NiI
STBL 380 STBL 450 STBL 690	0.25 max 0.18 max 0.13 max	0.35 max 0.10~0.35 0.10~0.35	1.35 max 0.30~0.60 0.90 max	0.035 max 0.030 max 0.030 max	0.035 max 0.030 max 0.030 max	- 3.20~3.80 8.50~9.50

Remarks

1. When it is practically difficult to apply the impact test due to the dimensions of a tube, STBL 380 shall, by way of compensation, contain 0.010 % or more of acid soluble aluminium, or alternatively, 0.015 % or more of tatal aluminium.

2. When product analysis is required by the purchaser, the telerances for the values given in the above table shall be as specified in Table 2 in JIS G 0321 for the seamless steel tube of STBL 380 and likewise in Table 1 for the electric resistance welded steel tube.
The tube of STBL 450 an STBL 690 shall be in accordance with Table 3. 

5. Mechanical Properties
(Tensile Strength, Yield Point or Proof Stress and Elongation)

6.Dimensions, Mass and Dimensional Tolerances

7. Apperance 

  7.1 The tube shall be practically straight and its both ends shall be at right angles to the axis injurious to use.
7.2 The inside and outside surfaces of the tube shall be well-finished and free from defect injurious to use.

8. Test

9. Inspection

10. Reinspection
 
  10.1  The tube which fails to pass the tests specified in 9.2 to 9.4 may be retested in accordance with 4.4 in JIS G 0303 to determine whether it is acceptable or not.

 10.2  when the tube fails to pass the test specified in 9.5, but satisfies the following two conditions as well as the specified linit of the average value of the absorbed energy, a retest may be conducted to determine whether it is acceptable or not.
   
(a) In the case where the values for two out of the three are equal to or higher than the average value specified in Table 5 but each individual one fails to satisify the specified value.

(b) In the case where the values for two out of the three satisfy the value specified for two pieces given in Table 5 but fail to satisfy the average value specified in the relevant Table.

In this case, three additional test pieces shall be taken from the same lot for a retet, and each value of the three test pieces shall conforom to the average balue of one set (3 pieces) specified in Table 5

11. Marking
 Each tube having passed the inspection shall be marked with the following items.
However, in the case of either smaller tubes or a request fro the purchaser, the tubes may be bundled together and marked for each bundle by sutable means.
The order of arranging the items is not specified.

When approved by the purchaser, part of the items may be omitted:

(1) Letter symbol of grade
(2) Letter symbol indicationg the manufacturing process (³)

(3) Dimensions

(4) Manufacturer's name or its abbreviation

(5) Letter symbol Z denoting the supplementary quality requirement

Note (³)
The letter symbol indicating the manufacturing process shall be as follows, provided that thedash may be replaced by a blank.

Hot finished seamless steel tube-S-H

Cold finishedseamless steel tube-S-C

Electric resistance welded steel tube other than hot finished or cold finished ones-E-G

Hot finished electric resistance welded steel tube-E-H

Cold finished electric resistance welded steel tube-E-C

12. Report
The manufacturer shall, in genearl, submit to the purchaser a detailed statement carrying the test results, method of manufacture, ordered dimensions, quantity, work number indicating the history of manufacture, etc.