Technical Exchange Report on Indentation Tester

Test Request: Evaluation of Residual Stress Relief Effectiveness During the Manufacturing Process(Including Heat Treatment and Cold Brittleness Treatment)

Materials and Processes:The cylinder body is made of 20CrMo, while the piston is made of 20Cr2Ni4Mo (26V). Both have undergone carburizing,quenching, and deep cryogenic treatment.

Date:12th, Dec 2024

1.Customer Products and Pain Points:

1.1Products:（1-3 years cost recovery！！）

Hydraulic breaker products, including pistons, cylinder sleeves, and hammer cores.

1.2Pain Points:

1.2.1Cracks and Fractures:

Pistons and cylinder sleeves frequently develop cracks and fractures, leading to customer

complaints and penalties. Each penalty incurs a cost of approximately 200,000 CNY.

 1.2.2High Operational Stress: In actual engineering applications, pistons perform tens of thousands of reciprocating

motions daily, subjecting them to significant wear and stress.

1.2.3Root Cause：The residual stress in the products cannot be quantified effectively before and after

manufacturing processes.

Lack of Data: No measurable data to monitor and adjust residual stress levels. Inadequate

data-driven insights to refine and optimize manufacturing parameters.

1.On-Site Testing Capabi

Base Material Zero-Point Finished Product after Processing

lities and Performance Evaluation of the

Indentation Instrument (Customer's Intuitive Perception of Testing

Features)

2. 3Cylinder Body Residual Stress Testing and Evaluation

2.1 Yield Strength Tests of Base Material vs. Processed Product : Material 20Cr2Ni4Mo

(26V)

      Piston Base Material Yield Strength: 865 MPa                                              Finished Product Yield Strength After Heat Treatment    and Cold Brittleness Treatment: 2014 MPa

2.2 Cylinder Body Yield Strength Testing: Material 20CrMo

                                                 Yield Strength Testing: 1886 MPa

2.3 Cylinder Body Residual Stress Testing and Evaluation

                   Base Material Zero-Point                                                                                     Finished Product after Processing

2.4.Residual Stress Test Results:

2.4.1 The test results, after integrating the data from the base material (0-point) and the

processed product (1-point), show a value of -474 MPa. (This represents residual compressive stress).

2.4.2 Client was very satisfied with the results. The negative value of the test results

indicates the presence of residual compressive stress, which aligns with his understanding.

2.4.3 The residual stress testing refers to the yield strength values for reference.

A. The indicator for unsatisfactory residual stress treatment effect is: Yield strength * 80%

(requires further treatment and optimization).

B. The indicator for satisfactory residual stress treatment effect is: Yield strength * 30% (ideal effect).

3. Customer Feedback and Invitation (Phase Two) March 2025, Evaluation

of Residual Stress Tester Results Before and After Process Treatment.

3.1 Through on-site testing, Clients gained a clear understanding of our instrument and was

satisfied with its testing functions and performance. (Positive feedback on the product)