Production method of steel plate for narrow-interval yield strength end socket

Abstract

The invention discloses a production method of a steel plate for a narrow-interval yield strength end socket, and relates to the field of steel production. The steel plate comprises the following alloy components in percentage by mass: less than or equal to 0.12% of C, less than or equal to 0.30% of Si, 0.80-1.20% of Mn, less than or equal to 0.020% of P, less than or equal to 0.002% of S and the balance of Fe and inevitable impurities. The yield strength of the steel plate is 290-345 Mpa, and the tensile strength of the steel plate is 390-570 Mpa; comprising the following process steps that narrow interval control of a plate blank heating temperature interval is adopted, the heating temperature is controlled to be 1180-1220 DEG C, a two-stage rolling process is adopted, the initial rolling temperature in the rough rolling stage is 1050 + / -20 DEG C, and the finish rolling temperature in the finish rolling stage is 830-850 DEG C. The yield strength of the steel plate is 290-345 Mpa, and the tensile strength of the steel plate is 390-570 Mpa. The yield strength with good stability is obtained by controlling the plate blank heating temperature and the rolling finishing temperature.

Description

Technical Field

[0001] The invention relates to the technical field of steel production, and in particular to a method for producing a steel plate for a narrow range yield strength end cap. Background Art

[0002] With the rapid development of chemical, petrochemical and other industries, the use conditions of many head steels have become more demanding. In addition to meeting the strength requirements, the calculation of head thickness should also meet the stability requirements. It is necessary to consider the shape of the head and the distribution of its stress, as well as the difficulty of stamping, welding and assembly, and conduct a comprehensive technical and economic analysis.

[0003] In terms of geometry, the surface area of ​​a hemispherical head is the smallest for the same volume, and the elliptical head is basically the same as the dished head. In terms of mechanics, under the conditions of the same diameter, wall thickness, and working pressure, the hemispherical head has the smallest stress, the two-way film stress is equal, and it is evenly distributed along the meridian. For example, when connected to a cylinder with the same wall thickness, the maximum stress near the edge is not significantly different from the film stress. The stress of the elliptical head is not as uniform as that of the hemispherical head, but it is worse than that of the dished head. The stress at the vertex is the largest, and circumferential compressive stress appears at the equator. When Di / (2h)=2 is connected to a cylinder with the same wall thickness, the elliptical head can reach the same strength as the cylinder. The biggest disadvantage of the dished head in mechanics is that it has a small folding radius r. The existence of this folding area makes the meridian of the head discontinuous, resulting in large meridian bending stress and circumferential compressive stress. However, the smaller the r / R, the greater the stress in the folding area, so circumferential cracks may occur, and circumferential wrinkles may also occur. When r=0, the dished head becomes a spherical cover without folding edges, and the mechanical properties of the head are not good. Peak stress will appear in the local area of ​​the folding point, and the weld at the folding point will become a source of danger. The fillet weld between the head and the cylinder is a full-penetration structure. The purpose of using a conical head in a chemical container is that the conical shell is conducive to uniform distribution and discharge of fluids. In terms of mechanical characteristics, the top of the cone is very strong, and the opening at the top of the cone generally does not need to be reinforced.

[0004] Manufacturing and material consumption Various heads are generally manufactured by hammering, stamping, rolling or explosive forming. Hemispherical and elliptical heads are usually manufactured by stamping. Large hemispherical heads can also be stamped into spherical petals first, and then assembled and welded. Disc heads are usually hammered, stamped or explosively formed, and the folded edges can be rolled or hammered. From the perspective of manufacturing process, the deeper the head, the larger the diameter and wall thickness, the more difficult it is to manufacture, especially when high-strength steel is selected. The integrally stamped hemispherical head is not as easy to manufacture as the elliptical head. The elliptical head must have a geometrically correct elliptical surface mold and is manufactured by manual hammering. The elliptical head has great manufacturing flexibility, and the cone top part of the conical head is difficult to roll. When the cone top angle is small, in order to avoid manufacturing difficulties and reduce the cone height, a combined head can sometimes be used.

[0005] Narrow range yield strength means that the yield strength has upper and lower limit requirements, and the upper and lower limit range is controlled within 55Mpa. Summary of the invention

[0006] In view of the difficulties existing in the above-mentioned prior art, the present invention provides a method for producing a steel plate for head end with a narrow range yield strength, which meets the requirement of stable strength performance of steel for head end.

[0007] The alloy composition and mass percentage of the steel plate are C ≤0.12%, Si ≤0.30%, Mn0.80~1.20%, P≤0.020, S≤0.002, and the rest are Fe and inevitable impurities; the steel plate has a yield strength of 290~345Mpa, and a tensile strength of 390~570Mpa; the steel plate has a yield strength of 290~345Mpa, and a tensile strength of 390~570Mpa; and includes the following process steps: adopting a narrow range control of the slab heating temperature range, the heating temperature is controlled at 1180~1220℃, a two-stage rolling process, the starting rolling temperature of the rough rolling stage is 1050±20℃, and the finishing rolling temperature is 830~850℃.

[0008] The present invention studies the influence of the temperature-controlled rolling process parameters (deformation temperature, deformation amount, rolling temperature, etc.) of the test steel plate on the microstructure and properties of the test steel, and focuses on the influence of the slab heating temperature range control and the finishing rolling temperature range control on the strength and performance stability of the test steel. The beneficial effect of the above invention is that the present invention adopts the narrow range control of the slab heating temperature and the narrow range temperature control of the finishing rolling to ensure the narrow range yield strength of the steel plate, effectively control the upper and lower limit ranges within 55Mpa, and ensure the stability of the performance strength of the head steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 This is the microstructure morphology at 1 / 2 thickness of the 12 mm 325 MPa grade steel plate for head in Example 1. DETAILED DESCRIPTION

[0010] The present invention is further described in detail below with reference to specific embodiments. Example 1

[0011] The thicknesses of the 325MPa grade steel plates for head ends in this embodiment are 8mm and 10mm respectively, the chemical composition mass percentage is shown in Table 1, and the mechanical properties are shown in Table 2.

[0012] The production method of the 325MPa grade steel plate for end caps in this embodiment includes smelting, continuous casting, heating, and rolling processes. The specific parameters of the rolling process are as follows: (1) Rolling process: slab heating temperature is 1180℃, two-stage rolling, the starting rolling temperature of the rough rolling stage is 1030℃, and the final rolling temperature of the finishing rolling stage is 830℃.

[0013] Example 2 The thickness of the 325MPa grade steel plate for head end in this embodiment is 10mm-12mm, the chemical composition mass percentage is shown in Table 1, and the mechanical properties are shown in Table 3. The production method of the 325MPa grade steel plate for head end in this embodiment includes smelting, continuous casting, heating, and rolling processes, and the rolling process includes: the slab heating temperature is 1200°C, a two-stage rolling process, the starting rolling temperature in the rough rolling stage is 1050°C, and the finishing rolling temperature is 840°C.

[0014] Example 3 The thickness of the 325MPa grade steel plate for head end in this embodiment is 14 mm and 16 mm respectively, the chemical composition mass percentage is shown in Table 1, and the mechanical properties are shown in Table 4. The production process includes smelting, continuous casting, heating, and rolling processes, and the rolling process includes: the slab heating temperature is 1220°C, a two-stage rolling process, the starting rolling temperature in the rough rolling stage is 1070°C, and the finishing rolling temperature is 850°C.

[0015] Table 1 Chemical composition of the examples Mass percentage, % .

[0016] Table 2 Mechanical properties of the steel plate produced in Example 1 .

[0017] Table 3 Mechanical properties of the steel plate produced in Example 2 .

[0018] Table 4 Mechanical properties of the steel plate produced in Example 3 .

Claims

1. A method for producing a steel plate for a narrow range yield strength end cap, characterized in that: The alloy composition and mass percentage of the steel plate are C ≤ 0.12%, Si ≤ 0.30%, Mn 0.80-1.20%, P ≤ 0.020, S ≤ 0.002, and the rest are Fe and unavoidable impurities; The yield strength of the steel plate is 290~345Mpa, and the tensile strength is 390~570Mpa; The yield strength of the steel plate is 290~345Mpa, and the tensile strength is 390~570Mpa; The key process steps include: narrow range control of the slab heating temperature range, the heating temperature is controlled at 1180~1220℃, a two-stage rolling process, the starting rolling temperature of the rough rolling stage is 1050±20℃, and the finishing rolling temperature is 830~850℃.

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