Following test methods are required for testing spring steel wire quality.
Tensile test
The tensile test shall be carried out according to EN 10002-1, on samples with the full cross-section of the wire. For the calculation of the tensile strength the actual cross-section based on the actual wire diameter is applied.
Coiling test
The coiling test shall be carried out in the following manner: A test piece - approximately 500 mm in length - shall be closely wound, under slight but reasonably uniform tension on a mandrel three to three and a half times the nominal diameter. The mandrel diameter shall however be at least 1,00 mm. The close coil shall be stretched so that after releasing the stress it sets to approximately three times its original length.
The surface condition of the wire and the regularity of the spring pitch and individual windings shall be inspected with the test piece in this condition.
Wrapping test
The wrapping test shall be carried out according to EN 10218-1; the wire shall be wrapped 8 turns around a mandrel with a diameter equal to the wire diameter.
Torsion test
For the torsion test, the test piece shall be clamped into the device in such manner that its longitudinal axis is aligned to the axis of the clamping heads and the test piece remains straight during the test. One clamping head shall be turned at as uniform a speed of rotation as possible (not exceeding one rotation per second) until the test piece fractures. The number of complete rotations of the turning clamping head is counted. The free length between grips shall be uniformly 100 x d (d = nominal diameter of the wire) with a maximum of 300 mm.
Bending test
For the bending test, a wire sample of sufficient length shall be bent in U form around a mandrel with a diameter equal to twice the wire diameter for sizes above 3,00 mm to 6,50 mm and equal to three times the wire diameter for sizes above 6,50 mm. For practical reasons the wire shall be deemed to have met the requirements of this standard if it withstands bending around a mandrel smaller than the one specified. In carrying out the test the wire shall be free to move longitudinally in the forming device.
Surface defects test
Testing for surface defects shall be carried out on test pieces from the ends of the wire units after deep etching or on microsections. It may be agreed for wire diameters below 2,00 mm at the time of order, that microscopic testing be carried out immediately after the last heat treatment.
The deep etch test shall be carried out according to EN 10218-1.
In cases where the sensitivity of eddy current testing is adequate, this method may be used by agreement.
In cases of dispute the result of measurement on the microsection applies.
Decarburization Inspection
Decarburization shall be inspected by microscope in accordance with EU 104 on a transverse metallographic test piece, suitably etched with a magnification of x 200. The depth of decarburization is considered as being the mean of 8 measurements at the ends of four diameters located at 45° to each other, starting from the zone of maximum decarburization and avoid starting from a defective zone. In the calculation of the above mean value, any measuring point of the seven remaining situated in a local surface defect, shall not be taken into account in the calculation.
It may be agreed for wire diameters less than 2,00 mm at the time of ordering that testing be carried out immediately after the last heat treatment.
Spring Wire Diameter Measuring Method
The diameter shall be measured using limit gauges, a micrometer or any other appropriate method. The out of roundness shall be determined as the difference between the maximum and minimum diameters at any one cross-section. Below 0,65 mm the relative value of individual measurement shall be taken into consideration because the measurements are situated at the limit of the technical capability for the instruments.
Zinc and zinc/aluminium coating test
The zinc or zinc/aluminium coating shall be measured according to EN 10244-2 by the volumetric method or the gravimetric method.
Adherence of coating for spring steel wire test
Adherence of zinc or zinc/aluminium coating shall be tested for wire diameters up to 5 mm in accordance with EN 10244-2 by a wrapping test on a mandrel of 3 x d.
Retests of spring steel wire
Retests shall be performed according to EN 10021.
Extent of testing and sampling for specific inspection and summary of the information on test procedure and requirements
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | |
| Test method | Applies to wire grades | a | Test unit | Number of products per test unit | Number of samples per product | Number of test pieces per sample | Sampling | Test procedure acc. to | Requirements See ….. | |
| 1 | Product analysis | all | 0 b |
Quantity supplied per heat | 1 | 1 | 1 | ISO 14284 | 7.4.1 | 6.1.2 b |
| 2 | Tensile test Rm Z | All >= 0,80 mm | m | Quantity supplied per production batch d | 10% c | 1 | 1 | Test pieces taken from the ends of the coils | 7.4.2 | 6.4 d |
| 3 | Coiling test | DM, SH, DH <= 0,70 mm | o | The scope of testing shall be agreed on ordering | 7.4.3 | 6.5.1 | ||||
| 3a | Wrapping test | All <= 3 mm | o | 10% c | 1 | 1 | 7.4.4 | 6.5.3 | ||
| 3b | Bending test | All <= 3 mm | o | 7.4.6 | 6.5.4 | |||||
| 4 | Torsion test e | All | m | 7.4.5 | 6.5.2 d | |||||
| 5 | Testing for Freedom from twists | All | m | 6.6.3 6.6.4 |
6.6.3 6.6.4 |
|||||
| 6 | Testing for Surface defects | DM, DH | m | 7.4.7 | 6.7 d | |||||
| 7 | Testing for decarburization | DM, DH | m | 7.4.8 | 6.7.2 d | |||||
| 8 | Check on dimensions | All | m | 100 % | 7.4.9 | 6.8 d | ||||
| 9 | Testing of coating mass | Z and ZA | o | To be agreed at the order | 7.4.10 | 6.7.3 | ||||
| 9a | Coating adherence | Z and ZA d <= 5 mm | m | 10% c | 7.4.11 | 6.7.3 | ||||
am (= mandatory): the test is to be carried out in each case / o (= optional): the test is carried out only if so agreed at the order. bThe results of the cast analysis for the elements listed in Table 1 for the grade concerned shall be notified to the customer in all cases. c10 % of the wire units in the production batch, at least 2 but no more than 10 coils/reels or spools. dA production batch is defined as a quantity of production originating from the same cast, which has been subjected to the same conditions of heat treatment, and drawn with the same reduction in cross-section and with the same surface finish. eOnly for diameters over 0,70 and up to 10 mm. |
||||||||||