Abstract
An integral manufacturing process with hot drawing and cold flow forming was proposed for large-diameter seamless steel gas cylinders. The main purpose of this study was to find out the effects of the manufacturing process on the microstructure and mechanical properties of gas cylinders made of 34CrMo4 steel. Two preformed cylinders were produced by hot drawing. One cylinder was then further manufactured by cold flow forming. The experiments were carried out using three types of material sample, namely, base material (BM), hot drawing cylinder (HD), and cold flow-formed cylinder (CF). Tensile and impact tests were performed to examine the mechanical properties of the cylinders in longitudinal and transverse directions. Microstructure evolution was analyzed by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) to reveal the relation between the mechanical properties and the microstructure of the material. It is found that the mechanical properties of the 34CrMo4 steel gas cylinders were significantly improved after hot drawing and flow forming plus a designed heat treatment, compared with the base material. The observations of microstructure features such as grain size, subgrain boundaries, and residual strain support the increase in mechanical properties due to the proposed manufacturing process.
Highlights
Gas cylinders are widely used to store and transport clean energy, such as compressed natural gas cylinders on vehicles and tube trailers for the transportation of hydrogen
This paper presents a systematic investigation of the effects of the manufacturing process proposed in [5] on the performance of gas cylinders, especially the effect of the cold flow forming on the product material properties
The mechanical properties of the product cylinder materials all satisfy the requirements of the material standard
Summary
Gas cylinders are widely used to store and transport clean energy, such as compressed natural gas cylinders on vehicles and tube trailers for the transportation of hydrogen. These cylinders containing corrosive compressive gases are always operated under a high pressure over 20 MPa, which presents fatality risk and challenges for the safety of the gas cylinders throughout their anticipated long service life. Materials 2019, 12, 1351 dedicated to raw materials and manufacturing processes. A brief patent review of steel alloys used in the manufacture of gas cylinders was made by Nourani et al [3]. One of the authorized steels for gas cylinders is 34CrMo4 (AISI 4130) steel which has superior corrosion resistance, mechanical properties, hardenability, and deformation characteristics
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