The quality of mold steel directly determines the service life of the mold and the quality of the workpiece. Many purchasers encounter the problem of poor mold steel quality (such as inclusions, uneven hardness, cracks) after purchase, which leads to production losses. Therefore, testing the quality of mold steel before purchase or use is crucial. This article provides a step-by-step guide to mold steel quality testing, including common testing methods, operation steps and key points, helping you easily identify high-quality mold steel and avoid purchasing inferior products.

Preparations Before Mold Steel Quality Testing

Before testing, it is necessary to make full preparations to ensure the accuracy of the test results. The preparations include:

• Prepare Testing Tools: According to the testing method, prepare the corresponding tools, such as magnifying glass, hardness tester, ultrasonic testing equipment, chemical composition analyzer, etc.
• Sample Preparation: Take a small sample from the mold steel (the sample should be representative, avoiding the edge and defective parts), and process the sample into a suitable shape (such as polishing the surface for visual inspection and hardness testing).
• Understand the Standard: Understand the quality standards of the corresponding mold steel grade (such as hardness range, chemical composition range) to judge whether the test results meet the requirements.

Step-by-Step Mold Steel Quality Testing Guide

We recommend 4 key testing steps to comprehensively detect mold steel quality, from surface to internal, from appearance to performance, ensuring no omissions. You can complete the basic test by yourself, and the professional test can be entrusted to a third-party institution or our technical team.

Step 1: Visual Inspection (Basic Test, Easy to Operate)

Visual inspection is the simplest and most direct testing method, mainly used to detect surface defects of mold steel. It can be completed with the naked eye or a magnifying glass (10-20 times magnification).

Operation Steps:

1. Polish the surface of the mold steel sample to remove oil stains, rust and dust, so that the surface is smooth and easy to observe.
2. Observe the surface with the naked eye first, check whether there are obvious defects such as cracks, rust, scratches, and inclusions.
3. Use a magnifying glass to observe carefully, check for tiny cracks (especially near the edge of the steel), tiny inclusions, and uneven surface texture.

Judgment Standard: High-quality mold steel should have a smooth surface, no obvious cracks, rust, scratches, or inclusions; the surface texture should be uniform, without obvious segregation or unevenness.

Step 2: Hardness Test (Core Performance Test)

Hardness is one of the core performance indicators of mold steel, directly affecting its wear resistance and service life. The Brinell hardness tester or Rockwell hardness tester is commonly used for testing (Rockwell hardness tester is more suitable for mold steel).

Operation Steps:

1. Place the polished mold steel sample on the test bench of the hardness tester, and ensure that the sample is flat and fixed firmly.
2. Select the appropriate test head and load according to the mold steel grade (for example, use HRC scale for pre-hardened steel such as P20, 718H).
3. Press the test button, let the test head press into the sample surface, and wait for the tester to display the hardness value.
4. Test 3-5 points on different positions of the sample, take the average value as the final hardness of the mold steel.

Judgment Standard: The hardness value should be within the standard range of the corresponding mold steel grade (for example, P20 is 28-32 HRC, S136 after heat treatment is 48-52 HRC). If the hardness is too high or too low, it indicates that the heat treatment process is improper or the steel quality is problematic.

Step 3: Chemical Composition Test (Fundamental Quality Test)

The chemical composition of mold steel determines its performance (such as corrosion resistance, high-temperature resistance). The chemical composition test can detect whether the content of elements such as C, Cr, Mo, Ni meets the standard.

Operation Steps:

1. Take a small sample (about 5-10g) from the mold steel, and grind it into powder (or cut into small pieces).
2. Put the sample into a chemical composition analyzer (such as a spectrophotometer), and start the analyzer for detection.
3. Wait for the analyzer to display the content of each element, and record the data.

Judgment Standard: The content of each element should be within the standard range of the corresponding mold steel grade (for example, S136 contains 12.00-14.00% Cr, 0.38-0.45% C). If the element content is unqualified, the performance of the mold steel will be affected (such as insufficient Cr content leading to poor corrosion resistance).

Step 4: Ultrasonic Testing (Internal Defect Test)

Ultrasonic testing is used to detect internal defects of mold steel (such as internal cracks, inclusions) that cannot be observed by visual inspection. This test requires professional equipment and operation, and is suitable for high-precision mold steel.

Operation Steps:

1. Apply coupling agent (such as glycerin) on the surface of the mold steel sample to ensure good contact between the ultrasonic probe and the sample.
2. Hold the ultrasonic probe, move it slowly on the sample surface, and observe the waveform displayed on the instrument.
3. If there is an internal defect (such as a crack), the waveform will change (such as a peak appearing at an abnormal position), and the position and size of the defect can be judged according to the waveform.

Judgment Standard: High-quality mold steel should have no internal cracks, inclusions or other defects; if there are defects, it is necessary to judge whether it affects the use according to the size and position of the defects.

Key Tips for Mold Steel Quality Testing

• Test Timing: It is best to test the mold steel after purchase and before use, so as to find quality problems in time and avoid losses caused by use.
• Sample Representative: The sample should be taken from the middle part of the mold steel, avoiding the edge, corner or defective parts, to ensure that the test results are representative.
• Professional Help: If you do not have professional testing equipment or technology, you can entrust our technical team to conduct quality testing for you, and we will provide a detailed test report.
• Check Material Certificate: Before testing, check the material certificate provided by the manufacturer, which records the chemical composition, heat treatment process, hardness and other information of the mold steel, which can be used as a reference for testing.

What to Do If Mold Steel Quality Is Unqualified?

If the mold steel fails the quality test (such as unqualified hardness, internal cracks, unqualified chemical composition), you should immediately contact the manufacturer to request replacement or return, and claim compensation for losses caused by unqualified products.

Our mold steel products are strictly inspected before leaving the factory, and each batch of products is accompanied by a complete material certificate and test report. We promise that all mold steel meets the national standard and industry standard, and we can provide free quality testing services for you. If you have any questions about mold steel quality testing, please contact us, and our professional team will provide you with free consultation and technical support!