304 Type - Overview

#The 304 impact tester, although there have been multiple versions, is still based on the base of the old song, equipped with a cantilever that clamps the dropper tube in the groove with screws. In ISO and DIN versions, the screw is locked with a clamping handle, allowing the instrument to quickly adapt to samples of different thicknesses. The handle can be pulled out by spring force, allowing it to be released and freely rotated.

A base pier is installed on the bottom plate below the dropper according to the corresponding standards. The base pier is easy to replace, but it is also precisely installed to ensure that the centerline of the conduit and the pier seat coincide.

The bottom of the falling weight is equipped with a spherical punch based on the base pier used, and there is also a protruding needle on the falling weight that can move up and down along the narrow groove on the tube to lift the weight to the desired height. In ISO, DIN, and ECCA versions, the mass of the descending weight can be doubled by connecting an additional weight.

The scale is installed along the groove. For ISO, DIN, AFNOR, and SNV standards, instruments are calibrated in "cm". For SATM standards, instruments are calibrated in "inch lbs". In the ECCA version, there is a different "inches" scale on each side of the groove.

According to the standard# The 304-ISO tester is equipped with a clamping sleeve to keep the test panel in the correct position and pause at different thicknesses to limit the depth of the indentation of the descending weight.

In addition# The 304-ISO and # 304-DIN models also have a feature of a movable ring on the downcomer. The ring is installed in the groove and clamped by engraved screws to secure the protruding pin on the brake descending weight. This design provides precise potential energy presetting, which is particularly convenient when multiple tests need to be conducted from a fixed height.

Impact testing program

According to the standard preparation of samples (such as substrate surface treatment, coating application, hardening procedures, storage, coating thickness measurement, and perhaps cross scratch testing), two basic principles must be followed:

The ball (punch) falls directly onto the coating to obtain a concave deformation (sinking) or a convex deformation (protrusion) on the other side. The standard list provides users with a choice between the two; Users must choose or develop a method. The following situations are exceptions: ECCA standards (T5 and T6) are clearly known and must use convex deformation.

In terms of deformation energy, at the beginning of the descent, * may be the position value using a protocol. The impact test provides feasible/infeasible or qualified/unqualified answers in this situation. Analyze the resistance performance of coatings from the formation of cracks in rapid deformation. This method can only provide a qualitative result, but it can enable a batch of tested samples to be tested at a very fast speed.

If repeated impact testing is performed to create the smallest energy value for damaged materials, only quantitative results will be obtained. In this case, the distance of descent or impact capability continuously changes until cracks appear or the adhesion force disappears. The energy value that causes this type of damage must be confirmed through repeated testing using more sample plates. If different results are obtained, it is recommended to take an average.

A basic principle (which can also be used for feasible/infeasible testing) - it is necessary to ensure that the test point is at a sufficient distance from the edge (at least 35mm) and at a sufficient distance from previous test points on the same sample (minimum center distance of 70mm).

Evaluation and Analysis

The deformation, cracking, and peeling caused by the impact of the ball on the product (which may require the assistance of a magnifying glass) can be observed with the naked eye. To ensure that fewer ruptures can be identified, ASTM D 2794 standard recommends two more sensitive detection methods.

Applying copper sulfate solution to the sample causes the coating (such as phosphate) to rupture upon impact.

When applying insulation material onto a metal substrate, this area can also be tested using a porosity testing instrument. A simple conductivity tester uses a 9VDC power supply and a moist sponge. The instrument used for this type of testing is POROCHECK (ERICHSEN Model 524). It is an easy-to-use porosity tester that does not require the use of a mains power supply.

The impact energy is expressed in different categories according to different standards. In ISO, DIN \ \ NF, and SNV standards, the descending height (mm) plus the weight of the impact object is used for the relevant measurement scales. The remaining impact testing standards (as shown below) use independent energy units:

Kg m(ISO 6272,ASTM D 2794),Joule(ASTM D 3029,ECCA T5); inch ibs(astm d 2794 and ASTM D 3029)

The conversion relationship between these energy units is: 1 J (oule)=0.1 kg m=8.8 inches ibs

The conversion factor can be used to compare the energy values set on different versions of instruments. Due to the different sizes of the balls and base piers, it is not possible to convert the results obtained from different ball impact testing methods through any precise calculations.

The composite ECCA T6 test occupies a special position. In this case, the coating previously damaged by cross scratches is subjected to a convex deformation (back impact), which damages a special location. In this case, the coating that was previously damaged by cross scratches undergoes another convex deformation (back impact), and the extent of damage can be expressed as the percentage of peeling area on the substrate.