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1、 Product Introduction: GC-JJ

The Intergranular corrosion testing machine is mainly used due to the differences in chemical composition between grain surfaces and interiors, as well as the presence of grain boundary impurities or internal stresses.

Intergranular corrosion destroys the bonding between grains, greatly reducing the mechanical strength of the metal. Moreover, after corrosion occurs, the surface of metals and alloys still maintains a certain metallic luster, with no signs of damage visible. However, the bonding force between grains is significantly weakened, and the mechanical properties deteriorate, making it unable to withstand impact, making it a very dangerous form of corrosion.

Usually found in brass, hard aluminum alloys, and some stainless steel and nickel based alloys. The intergranular corrosion of stainless steel welds is a major issue in the chemical industry.

The corrosion phenomenon that occurs between grains in stainless steel under the action of corrosive media is called intergranular corrosion.

Stainless steel that undergoes intergranular corrosion will fracture along grain boundaries and almost completely lose strength when subjected to stress, which is one of the most dangerous forms of stainless steel failure. Intergranular corrosion can occur in the heat affected zone (HAZ) of the welded joint, the weld seam, or the fusion line. The intergranular corrosion generated on the fusion line is also known as knife line corrosion (KLA). The necessary condition for intergranular corrosion resistant stainless steel to have corrosion resistance is that the mass fraction of chromium must be greater than 10-12%. When the temperature increases, the diffusion rate of carbon inside the stainless steel grains is greater than that of chromium.

Because the solubility of carbon in austenite is very low at room temperature, about 0.02% to 0.03%, and the carbon content in general austenitic stainless steels exceeds this value, excess carbon continuously diffuses towards the boundaries of austenite grains and combines with chromium to form chromium carbide compounds between grains, such as (CrFe) 23C6. The data shows that the activation ability of chromium diffusion along grain boundaries is 162-252 KJ/mol, while the activation energy of chromium diffusion within grains is about 540 KJ/mol. That is to say, the diffusion rate of chromium within grains is slower than that along grain boundaries, and the internal chromium does not have time to diffuse to the grain boundaries. Therefore, the chromium required for the formation of chromium carbide between grains mainly comes from near the grain boundaries, rather than from within the austenite grains. As a result, the chromium content near the grain boundaries is greatly reduced. When the mass fraction of chromium at the grain boundaries is less than 12%, a so-called "chromium poor zone" is formed. Under the action of corrosive media, the chromium poor zone will lose its corrosion resistance and produce intergranular corrosion.

2、 Related domestic and international standards:

There are several existing testing standards for intergranular corrosion both domestically and internationally, including the following methods:

GB/T 4334. (1-5) -2000 Standard Test Method for Susceptibility to intergranular Corrosion of Stainless Steel (Select the corresponding standard according to the sensitivity of different materials)

GB/T 15260-1994 "Standard Test Method for Susceptibility to intergranular Corrosion of Nickel Alloys"

GB/T 21433-2008 "Sensitivity Test for intergranular Corrosion of Stainless Steel Pressure Vessels"

CB/T 3949-2001 "Test Method for intergranular Corrosion of Stainless Steel Welded Joints in Ships"

ASTM G28-02 (2008) Standard Test Methods for Detecting Susceptibility to Interstitial Corrosion in Wear, Nickel Rich, Chromium Bearing Alloys

GB/T 7998-2005 "Determination of intergranular corrosion of aluminum alloys"

HG/T 3173-2002 "Test for intergranular corrosion tendency of urea grade ultra-low carbon chromium nickel key austenitic stainless steel"

3、 Main technical parameters:

1. Glass container size (mm): diameter 185x height 200; Maximum capacity 5L

2. Heating plate size (mm): diameter 190x height 30;

3. Size of water storage tank (mm): depth 400x width 300x30; Maximum capacity 4L

4. Temperature range of tempered glass container: RT+10~+110 ℃;

5. Temperature fluctuation: ≤ ±0.5℃;

6. Display accuracy: 0.1 ℃;

7. Power: Approximately 3.5KW

8. Power supply: 220V ± 22V 50HZ ± 1HZ

This device is suitable for intergranular corrosion testing of stainless steel using sulfuric acid copper sulfate copper chip method.,

4、 Equipment structure:

1. Equipment structure form

The testing machine adopts a split type combination structure, which consists of a heating system, a multi parameter precision control system, and a cooling cycle control system.

The heating system includes a glass container, a sealed lid, and a heater; The multi parameter precision control system consists of a temperature control system and a time control system; The cooling cycle control system consists of a glass condenser, bracket, and circulation control system.

This structure is convenient for equipment installation and maintenance, and the electrical control cabinet is placed on the right side of the testing machine for easy operation, observation, and maintenance.

2. Equipment materials and main parameters

Main material of equipment: high-quality 304 stainless steel

Heating system:

Glass container: tempered quartz glass material with a wall thickness of about 5mm;

Sealing cover: The substrate is made of acid resistant and corrosion-resistant materials, and a layer of silicone rubber sealing strip is coated on the outside of the substrate to ensure the sealing of the equipment.

Multi parameter precision control system:

Temperature control: The temperature sensor provides feedback on the temperature information of the solution, automatically adjusts the output power of the heater, and controls the heating speed of the solution. It also has an independent over temperature protection control system.

Time control: Meet the intergranular corrosion test of stainless steel sulfuric acid copper sulfate copper chip method, automatically timing after reaching temperature, and automatically stopping after 16 hours of corrosion.

The controller adopts the Korean ternary true color LCD display capacitive touch screen controller TEMI880

Controller, which controls the heating of the test bottle and the water temperature of the chiller separately.

LCD Touchscreen Controller TEMI880 Program Capacity and Control Function Available Program Quantity: Maximum of 120 groups, 1 program can be combined from 1 to 99 segments

Usable memory capacity: 1200 segments, can execute commands repeatedly: each command can be executed up to 999 times, program slope can be set by the timeline, programs can be linked and used, and program creation adopts conversational operation with simple operation

Equipped with functions such as editing, clearing, and inserting, with 4 sets of time signal output control (controllable control of the ON/OFF action of the test object)

It has 9 sets of PID parameter settings, with jump and hold functions during program execution, and can display curves and obtain data; Date and time adjustment function; Button and screen lock (LOCK) function, can be connected to a computer for use

5、 Security protection measures:

1. Overtemperature protection

2. Power leakage protection

3. Automatic shutdown protection for low water pressure of cooling water

4. Low water level alarm in cooling water storage tank

6、 Equipment usage conditions:

1. Power supply: 220V ± 22V 50HZ ± 1HZ

2. Environmental temperature: 5-30 ℃

3. Environmental humidity: ≤ 85% R.H, non condensing

7、 Quality assurance system:

Our company has officially obtained ISO9001 quality system certification;

Our company's quality assurance system strictly follows the requirements of ISO9001:2000 standard;