ordinary B -class marine open plate and medium plate

Through the new process, the thickness specifications of the B -class marine open slab and the traditional B -class marine mid-plate are [10 , 12 ] mm , [14 , 16 ] mm , [18 , 20 [ mm , [22 , 24 ] mm 4 group distances The mechanical properties such as tensile strength, yield strength, tensile properties and residual stress were compared and analyzed, and a series of test results were obtained.

The test results show that: the longitudinal and transverse tensile strength and yield strength indicators of the B-grade open slab are better than those of the B-grade medium plate of the same specification ; the longitudinal elongation of the B -grade open slab is higher than the transverse elongation. The difference in longitudinal and transverse mechanical properties may be caused by the different degrees of longitudinal and transverse deformation.

Class B marine open flat plate is formed by hot rolling and flattening. Compared with the traditional B class marine medium plate , it has obvious cost advantages and good development prospects due to the lack of cold rolling process [ 1-5 ] . Ship plates have strict requirements on surface quality and welding performance. With different process parameters during Kaiping operation, the distribution of internal stress is also different, and the bearing capacity in different directions of vertical length will be different. Therefore, the use of B -class marine slabs is greatly restricted. For this reason , a factory optimizes the composition of B -grade steel through the control of CSP rolling process [ -9 ] and the introduction of advanced Kaiping shearing production equipment to improve its microstructure and properties. In this paper, by comparing the performance of B -grade marine open slabs and traditional B -grade marine mid-plates under the new process, in order to further grasp the differences in performance between marine open slabs and ship plates produced by traditional medium and heavy plate factories, and fully understand the quality of marine slabs characteristics lay the foundation.
1.Sample preparation and test method
The specific production process of Class B ship plate is : 120t converter — LF refiningf 220mm / 250mm thick slab continuous castingfcontinuous casting slab finishingfheating — 2250mm rolling mill rollingflaminar coolingfstraighteningffinishingfsampling , check f and identify f storage. Combined with the requirements , the test includes ordinary B -grade marine open slabs and B -grade marine mid-plates, thickness specifications: [ 10 , 12 ] mm , [ 14 , 16 ] mm , [ 18 , 20 ] mm , [ 22 , 24 ] mm 4 pieces Specification group spacing , covering all parts where the thickness specifications of marine open and medium plates intersect _ _ _ _ _ _ _ _ _ _ There are 4 kinds of specifications with the thickness of 10 ~ 12mm , 14 ~ 16mm , 18 ~ 20mm , 22 ~ 24mm ) .
The composition design idea of the marine open plate is different from that of the traditional medium plate. As shown in Table 1 , it is characterized in that it is very beneficial to the product’s low-temperature impact performance, welding performance, and especially the lamellar fracture control of ordinary ship plates. Table 2 is the actual measured composition of ordinary B -grade marine open slabs and B -grade marine mid-plates. It can be seen from the table that the content of C , P and S elements in ordinary B -grade marine open slabs is more strictly controlled , while the content of A1 is higher.
Table 1 Composition Design of Ordinary Class B Open Plate and Medium Plate
Table 1 Design of chemical compositions of B opened plate and
middle thickness plate

product type	Composition Design Ideas
open tablet	C + Mn (low) + Al
Middle plate	C + Mn

Test results and analysis
21 Comparison of transverse tensile properties
comparisons of transverse strength and elongation between B -grade open flat panels and B -grade mid-slabs of different specifications are shown in Figure 1 and Figure 2 , respectively. It can be seen from Figure 1 that the transverse tensile properties of the open plate and the middle plate all meet the requirements of the China Classification Society 's standard ship regulations . The transverse strength index of the graded flat plate is better than that of the medium plate of the same specification.

Table 2 Comparison of chemical composition between open plate and medium plate for ordinary Class B ships ( % , mass fraction)
Table 2 Component of B opened plate and middle thickness plate ( % , mass fraction )
Chemical composition/ %
Brand Product Type Composition Range

Min ~ Max
C：0. 1 2 ~ 0. 1 4
Si：0. 1 8 — 0. 2
Mn：0. 6 1 ~ 0. 7 1
P：0. 0 16 ~ 0. 032
S：0. 0 052 - 0. 0 12
Al ：0. 0 094 - 0.027

Note: The maximum Cep represents the carbon equivalent; the maximum Pcm represents the maximum deviation between the theoretical addition of phosphorus and the actual measurement.

2.2 Comparison of longitudinal tensile properties
Longitudinal properties of B -grade open slabs and B -grade mid-slabs of different specifications .
The longitudinal tensile strength of the open plate is better than that of the middle plate, and the longitudinal yield strength of the open plate of all thickness specifications is also better than that of the middle plate; the longitudinal elongation of the open plate (except [ 22 , 24 ] mm ) is higher than that of the middle plate The longitudinal elongation of the board.
23 Comparison of vertical and horizontal tensile properties
Comparison of vertical and horizontal properties of B -grade open slabs and B -grade medium slabs with different specifications . It can be seen that the longitudinal and transverse yield strengths and tensile strengths of Class B open flat plates have little difference;

Ordinary B -class ship plate adopts the composition design idea of C + Mn (low ) + Al microalloy. There are certain vertical and horizontal performance differences in the open plate, but it is not obvious. The product structure, low temperature impact toughness, and ductile-brittle transition temperature are all different. The larger improvement obtained can satisfy the ship

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