20MND5 is a low alloy high-strength steel of Mn-Ni-Mo, which is a specialized material for the main equipment of the pressurized nuclear island. Due to the role of Mn, Ni, Mo and other elements in the steel, this type of steel has good hardenability, high temperature performance, low temperature tempering brittleness and low non-ductile transformation temperature. Through the control of the manufacturing process and heat treatment, it is possible to obtain better low-temperature and high-temperature mechanical properties required by the project for the manufacture of oversized and ultra-thick components. This material is used for the shells and heads of steam generators in the nuclear islands of nuclear power plants. Due to the special characteristics of nuclear power plants, the requirements for safety are of primary importance, so the requirements for welding of these materials are also extremely strict.
Chemical composition of 20MnD5 nuclear power steel plate:
C: 0.23; Si: 0.15-0.30; Mn: 1.11-1.59; P: 0.008; S: 0.005; Mo: 0.43-0.62; Ni: 0.37-0.73; Cu: 0.20; Cr: 0.25; V: 0.03.
Mechanical properties of 20MnD5 nuclear power steel plate:
Tensile strength of 20MnD5 nuclear power steel plate: 450
Yield strength of 20MnD5 nuclear power steel plate: 620-790
20MnD5 nuclear power steel plate thickness reduction of area: 35%
20MnD5 Steel Plate Test Sampling
Tensile, impact, and bend test specimens may be taken from the same test blank. The test blank shall be taken from 1/4 of the width of the steel plate. When the length of the heat-treated steel plate does not exceed 15 m, the test blank is taken from one end of the plate; when the length exceeds 15 m, one test blank is taken from each end of the plate, with each test blank providing a set of specimens (1 tensile, 3 impact, and 1 bend). Shearing or flame cutting may be used to obtain the test blank, but the dimensions of the test blank must ensure that the specimens avoid the work-hardened or heat-affected zones caused by shearing or flame cutting.
The axes of the tensile, impact, and bend test specimens shall be perpendicular to the rolling direction of the steel plate; the notch axis of the Charpy (V-notch) impact specimens shall be perpendicular to the rolled surface of the steel plate.
The sampling locations for tensile and impact tests shall comply with the provisions of GB/T 2975. For steel plates with a thickness greater than 25 mm, the axis of the impact specimens shall be located at 1/4 of the thickness. For bend test specimens of all thicknesses, at least one rolled surface shall be retained, and the rolled surface shall be the outer surface of the bend test.
Surface Quality of 20MnD5 Steel Plate
The steel plate surface shall not contain defects such as cracks, bubbles, scars, folds, or inclusions. If such surface defects are present, they may be removed, provided the removal depth does not exceed half of the thickness tolerance of the steel plate, calculated from the actual dimension, and the minimum thickness of the steel plate is ensured. The area where defects are removed shall be smooth and free of sharp edges. The steel plate shall be free of delamination.
Other defects are permitted, provided their depth does not exceed half of the allowable thickness tolerance, calculated from the actual dimension, and the thickness at the defect location is not less than the allowable minimum thickness of the steel plate.
Production and Cutting Process Flow of 20MnD5 Steel Plate
Production process: Primary smelting → LF refining → VD treatment → Continuous casting (ingot casting) → Cleaning, heating → Rolling → Stacking → Surface inspection → Batching → Ultrasonic testing → Heat treatment → Cutting and sampling → Performance testing
Cutting process: After the performance indicators of the 20MnD5 steel plate meet the requirements in the factory inspection, cutting processing is carried out according to the cutting technology. It can be cut and processed according to drawings. Generally, when the steel plate thickness is ≤20 mm, CNC plasma cutting or CNC laser cutting is preferred. If the steel plate thickness is >30 mm, CNC flame cutting is typically selected to control cutting precision and time.
Conventional Dimensions of 20MnD5 Steel Plate(Thickness*Width*Length / Unit: mm)
8mm–50mm *1600mm–2000mm * 6000–10000mm
50mm–150mm* 1600mm–2500mm * 6000–12000mm
150mm–200mm * 2000mm–2500mm * 10000mm–12000mm
