The presence of shielding gas acts like an invisible barrier, blocking the intrusion of oxygen and moisture from the air into the weld seam. If the barrier is stable, an oxide film will not easily form on the metal surface, the purity of the weld pool will be improved, and ultimately the strength and appearance of the weld seam will be more reliable. There are many factors involved, but the core lies in three key aspects: gas type, gas purity…

In structural steel procurement, S235JR is one of the most widely used non-alloy structural steels due to its stable performance and excellent processability. It is commonly applied in steel structures, mechanical components, infrastructure, and pipe systems. However, different projects have different requirements for strength, ductility, and safety factors. Therefore, customers' most frequent questions usually include: What is the S235JR tensile strength? Does the S235JR yield strength meet the project requirements? Do the S235JR mechanical properties vary with thickness? How does the…

Vacuum heat treatment refers to a heat-treating process in which the workpiece is heated to the required temperature in a vacuum atmosphere of 10⁻¹~10⁻² Pa, followed by cooling in different media using different methods. Vacuum heat treatment is recognized in the modern heat-treatment industry as an efficient, energy-saving, and pollution-free clean heat-treatment technology. Parts treated by vacuum heat treatment feature no oxidation, no decarburization, degassing, degreasing, excellent surface quality, minimal deformation, high comprehensive mechanical properties, and stable reliability. Therefore, vacuum…

In the fields of steel structures, pressure components, bridge engineering, and pipeline manufacturing, engineers often need to choose among S235JR, S275JR, S355JR, and Q235, four commonly used structural steels. However, different projects have different requirements for strength, weldability, impact toughness, and cost. So which grade is the most reliable choice? This article analyzes the topic from five dimensions: standards, chemical & mechanical properties, testing methods, application scenarios, and procurement risk control—helping you clearly determine which steel grade best fits your…

In the process of steel procurement and engineering material selection, questions such as “Which Werkstoff number corresponds to S235JR?” or “Why do some documents show 1.0037 while others show 1.0038?” are very common. Properly understanding the relationship between the S235JR steel number and the historical/modern numbering systems is essential for technical specification review, MTC (Mill Test Certificate) verification, and cross-standard comparison (DIN, EN, JIS, ASTM). This article analyzes the topic from five perspectives: numbering origin, standard evolution, technical differences, inspection…

Visual inspection is a commonly used welding quality inspection method. Its main purpose is to check the surface quality of welding joints, including weld shape, dimensions, undercut, depression, porosity, etc. Visual inspection can be carried out by the naked eye or with the help of magnifying glasses, as well as auxiliary tools such as laser rangefinders and optical measuring instruments. This method can effectively detect surface defects of welding joints but cannot identify internal defects. Overview of Core Standard Systems…

Among global structural steel standards, EN 10025 S235JR is one of the most widely used baseline grades in engineering, steel structure fabrication, and machinery manufacturing. Since different projects require different levels of toughness, weldability, and load-bearing capacity, choosing the correct delivery condition—such as +AR / s235jr ar or +N / s235jr+n—directly affects engineering safety, welding quality, and procurement risk control. Based on the EN standard framework, this article analyzes EN 10025-2 S235JR from five angles: delivery conditions, testing methods, service condition selection, quality…

The performance of welding defects on radioscopic films is a key basis for welding quality evaluation. Various common welding defects have distinct image characteristics and corresponding standard specifications on the films. There are 18 typical defects, including uneven welds, root incomplete fusion, insufficient reinforcement, root weld bead, external undercut, internal undercut, root depression, burn-through, isolated slag inclusion, linear slag inclusion, internal incomplete fusion, inner-side incomplete fusion, porosity, chain porosity, bead inclusion, transverse crack, centerline crack, and root crack. By systematically…

In engineering material selection and procurement, S235JR and S275JR are commonly used non-alloy structural steels defined in EN 10025-2. At first glance, they seem similar in application, but they differ clearly in strength grade, chemical composition limits, mechanical properties, and inspection requirements—differences that directly impact structural safety, weldability, and low-temperature performance, determining whether they can be considered “equivalent alternatives.” Key Performance Comparison at a Glance   Parameter S235JR S275JR Nominal minimum yield strength 235 MPa 275 MPa Tensile strength Rm (typical range) ~360–510…

In engineering procurement and structural design, one of the most frequently asked questions is:Can the European standard steel S235JR (EN 10025-2) be interchanged with the American standard ASTM A36? The short answer: They are similar in most general structural applications, but not strictly identical. There are key differences in mechanical properties, delivery conditions, and impact toughness requirements, which must be verified through testing and certification to minimize procurement risk. Differences in Standards and Definitions S235JR (EN 10025-2) Non-alloy structural steel with a…

With global investments in energy and infrastructure rebounding, astm a691 alloy steel pipes are experiencing a steady surge in demand due to their superior performance under high-temperature and high-pressure conditions. As a manufacturer with over 20 years of industry experience, LONGMA not only provides high-quality products such as astm a691 grade 2.1 4cr, but also ensures risk-free procurement through its advanced in-house testing laboratory and traceable quality control system. This article analyzes the market dynamics, industrial applications, inspection requirements, and procurement strategies of ASTM A691…

In refinery and natural gas transmission projects, material selection directly determines the system’s safety, operational reliability, and lifecycle cost. With over 20 years of manufacturing experience, LONGMA has successfully supplied astm a691 alloy steel pipes to numerous large-scale projects, proving their exceptional performance in high-temperature, high-pressure, and corrosive service environments. This article analyzes real-world applications, technical comparisons, inspection methods, and procurement control measures to help engineers and buyers make informed decisions — while reinforcing LONGMA’s credibility as a trusted supplier. Typical Engineering Case…

In the refining, petrochemical, and power generation industries, welding quality and post weld heat treatment (PWHT) are critical factors affecting the long-term safety and performance of astm a691 alloy steel pipes. With over 20 years of manufacturing and quality control experience, LONGMA provides a detailed explanation of ASTM A691 welding and PWHT requirements, offering practical guidance for engineers and procurement teams to ensure compliance and reduce project risks. Key Standards and Technical Basis ASTM A691– Specifies the manufacturing, heat treatment, and inspection requirements for…

In industries such as refining, petrochemical, and power generation, pipelines operate under extreme temperature and pressure conditions. Choosing the right pipe material is not just a matter of performance — it’s a matter of safety, reliability, and long-term cost efficiency. Among various alloy steels, ASTM A691 alloy steel pipes stand out for their exceptional strength, heat resistance, and durability, making them the first choice for critical applications. As a manufacturer with more than 20 years of industry experience, LONGMA provides a full…

As a steel pipe manufacturer and quality control expert with over 20 years of experience in the refining and petrochemical industries, LONGMA provides a comprehensive analysis of ASTM A691 (Electric-Fusion-Welded Alloy Steel Pipes) and the commonly used P-Grades (P1, P5, P9, P22) — covering industrial applications, inspection methods, and procurement risk management. This article uses comparative tables to help engineers, buyers, and project managers make accurate decisions quickly. Overview of P-Grades (Why Focus on P1, P5, P9, and P22) The “P-Grades” (commonly seen…