TU 14-1-2687-79 extract

1.3. The tape is supplied trimmed, with normal manufacturing accuracy in width with maximum deviations in width according to GOST 2284-79. Rib curvature - according to GOST 2284-69.

1.3.1. Tape with a thickness of more than 1.5 mm, subject to calibration after cutting the strip to the width specified in the order, may have a width deviation of up to +0.5 mm.

2. TECHNICAL REQUIREMENTS

2.1. The chemical composition of grade 50PA steel must comply with the requirements specified in Table 2.

Table 2

Note to Table 2: Boron is introduced based on calculations without taking into account losses in an amount of no more than 0.0045%, while its residual content in steel must be no less than 0.001%.

2.1.1. An increase in the content of phosphorus or sulfur by 0.001% is permitted, with the total content of these elements not exceeding 0.026%.

2.1.2. In the finished tape, subject to compliance with all requirements of these technical conditions, the following deviations in chemical composition are allowed:

for carbon - plus, minus 0.01%,

for silicon, manganese, chromium - plus, minus 0.02% of each element;

for phosphorus and sulfur - plus 0.003% of each element, provided that their total content is no more than 0.023%.

Carrying out control of the carbon content in the tape is mandatory.

2.2. The tape is supplied in a light-annealed condition (low light annealing). The quality of the surface and edges of the tape must meet the requirements of GOST 2284-79, imposed on the tape after light annealing.

2.3. Delamination of the tape is not permitted.

2.4. The mechanical properties of the annealed strip must comply with the following standards:

ultimate strength, σ _in - no more than 590 MPa (60 kgf/mm ² ),

relative elongation, δ ₄ - not less than 20%

2.5. Annealed cold-rolled strip must withstand a bending test at 90° along the grain and at 180° across the grain in a cold state on a mandrel with a bluntness radius equal to the thickness of the strip. Specimens bent at 180° are subjected to final bending without a mandrel until the sides touch. After the test, there must be no cracks or delaminations at the bending points.

2.6. The tape must be tested for hardenability by hardness after quenching from a temperature of 850±10°C in oil. The hardness measured on the surface of the samples after removing the decarburized layer must be at least 54 HRC units.

2.7. The microstructure of the metal in the delivery condition must be:

- according to the nature of the structure of perlite, no more than 3 points on the scale

No. I rows "a" and "b" (Appendix I to these TU);

- for cavitation no more than 4 points on scale No. 2 (Appendix 2 to these TU).

2.8. Contamination of the tape with non-metallic inclusions shall be determined using scale No. 3 (Appendix 3 to these TU).

Points no more than 4 are considered valid.

2.9. In annealed strip, the total depth of one-sided decarburization should not exceed the standards for group I according to GOST 2284-79.

The depth of the decarburized layer is taken as the zone of complete decarburization (ferrite) + transition zone.

2.10. Surface roughness of the tape - according to GOST 2284-79.

3. ACCEPTANCE RULES AND TEST METHODS

3.1. The finished tape must be accepted by the quality control department of the manufacturing plant, which must guarantee that the quality of the tape meets the requirements of these technical conditions.

3.2. The tape is supplied in rolls in accordance with the requirements of GOST 2284-79. A roll must consist of one section. It is allowed to supply rolls consisting of two sections, in quantities not exceeding 10% of the batch. In this case, the length of a separate section must not be less than 10 meters. A roll consisting of two sections must be clearly marked.

3.3. The tape is presented for acceptance and delivered in batches.

The batch must consist of a strip of one melt, one size and one annealing batch.