TEST. Hardness Control of Welded Links in Round-Link Chains with Diameters of 16 and 28 mm

Customer. The "Krasny Press" Plant (Vologda region, Cherepovets district, Suda settlement), which is the largest Russian manufacturer of round-link chains for various equipment purposes.

Object of Control. Samples of round-link chains of the 3rd strength class made of welded links of different diameters:

• 16 mm, test load 50 kN (kilonewtons), breaking load - 100 kN (fig.1)
• 28 mm, test load 148 kN, breaking load - 296 kN (fig.2)

The test load is the tensile load to which the finished chain sample can be subjected without exceeding the specified elongation value.

The breaking load is the maximum load that the finished chain sample withstands during tensile testing until the moment of destruction (breaking).

Task. Selection of optimal equipment for hardness testing of round-link chains.

Hypothesis and Test Preparation. Considering the material (carbon steel) and the dimensions of the links, the specialists assumed that the task could be handled by the ultrasonic hardness tester TKM-459C with the standard "A" type sensor.

Experiment Features. Before starting work, the control zones were cleaned, as the surface of the links has high roughness.

The links have a round cross-section ("volumetric" shape) and insufficient mass, so the samples were clamped in heavy metal vices - p. 1.8 "Requirements for the controlled product" Operating Manual of the Ultrasonic Hardness Tester TKM-459C.

The device testing was conducted in the presence of the Customer's representative.

Results. Five Brinell hardness measurements were taken at each object.

Control Samples	Series Measurement Results, HB	Average Value, HB
Chain link d=16 mm	210, 221, 207, 214, 218	214
Chain link d=28mm	207, 210, 202, 206, 213	207

The obtained measurement results fully satisfied the Customer, who claims the quality of their products according to TU 314831-008-00257118-10, based on GOST 7070-75 "General Purpose Welded Round-Link Chains".

As a result, the Customer purchased the ultrasonic hardness tester TKM-459C and, following our specialists' recommendations, the U-459 positioning attachment. The attachment ensures a stable perpendicular position of the sensor on the round surface of the chain links.

A representative of the Plant also wrote a review, expressing gratitude to our employees for the equipment selection, professional consultation, and customer orientation!

Our Recommendations. For the control of similar products, it is necessary to:

• clean the control zone;
• use vices to fix the objects;
• ensure the sensor is positioned perpendicular to the measured surface (it is advisable to use the U-459 positioning attachment);
• observe the recommended distances between puncture marks.

Contact the specialists at NPP "Mashproject" to select equipment that meets your specific needs.