As industrial raw materials, metal materials of the same brand, different production methods, product performance is different.For example, strip has hot rolling and cold rolling, the product surface and mechanical properties are different;There are seamless pipe and welded pipe, production methods are widely different, the applicable[SCALE STEEL.] occasions are also different.Therefore, it is necessary to develop special procurement specifications to guide procurement.How to compile the purchase specification of metal material, what matters needing attention?
First of all, the factors of procurement must be considered when designing products.
The design department selects the appropriate brand according to the actual working conditions of the parts, including the working environment, the stress situation, and the special performance requirements.Relevant information should [SCALE STEEL.]be provided to the purchasing department in as much detail as possible. Accurate information transmission will help the purchasing personnel to make inquiries externally.
Specifically, the service temperature (high temperature, low temperature or alternating hot and cold), the type and concentration of corrosive media around, whether to withstand vibration, impact, wear, whether there is high speed or high load, mechanical performance requirements, can be magnetic, etc., must be considered factors.
In order to improve the reliability, in the candidate materials, we should choose the mature brand under the same working condition as far as possible, in order to reduce the safety risk and guarantee the service life, but also easy to purchase.
After the material brand is determined, the engineer [SCALE STEEL.]should fully consider the technological performance of the material from the perspective of improving the utilization rate of the metal, and select the appropriate technology from several molding methods such as casting, forging, welding and cutting, so as to reduce the material waste as far as possible and achieve the purpose of reducing cost and increasing efficiency.
Normally a Complete Procurement Specification Should Include The Following:
01 Material Grades and Standards
The standard includes national standard, American standard, European standard or pressure vessel standard, nuclear power standard, military industry standard and chemical industry standard.Providing standard numbers helps to accurately locate and improve the efficiency of communication with suppliers.
Usually, a material brand will be included in different standards. In most cases, the chemical composition of the same material brand is the same[SCALE STEEL.] in different standards. However, due to the evolution of standards and different product forms, the composition may be slightly different, and the performance data are not the same.
02 Smelting Method
Common smelting methods: ordinary smelting, induction smelting, electroslag remelting, vacuum arc remelting, etc.Different smelting methods have different manufacturing costs. For example, the cost of vacuum smelting is higher than[SCALE STEEL.] that of non-vacuum smelting.
03 Dimensions, Quantity and Weight
When ordering bar, sheet, pipe, etc., the length of the part should be stated as far as possible so as to reasonably determine the length of the product to be delivered, such as indefinite, definite, or double length.
When ordering forgings, part drawing should be provided as far as possible to ensure that the supplier has accurate final size and shape in order to develop a reasonable and economical forming process.
There are two methods of weight calculation, theoretical calculation and practical calculation.The adjustment involves density and tolerances.The density is related to the brand, and there are many kinds of metal materials (there are more than 350,000 metal brands in the world). Generally, the density of the material in the[SCALE STEEL.] same category is the same, but there are also differences according to the different alloy ratios.Tolerances are related to production capacity and manufacturing method. For example, forging tolerances are relatively large, resulting in that the actual delivered weight of forgings can sometimes differ by 10% or more from the theoretical weight.
The method of receiving goods should be agreed with the supplier.It is generally recommended that the forgings should be delivered in the light state after machining, and the piece-by-piece method of settlement is preferred.
04 The Delivery Status
According to the deformation mode: forging state, hot rolling state, cold rolling (drawing) state, etc.The grade of forgings used in pressure [SCALE STEEL.]equipment shall be indicated.
According to the heat treatment state: annealing state, solid solution state, solid solution + aging state, etc.Mechanical properties are required and numerical values should be marked.For example, the hardness range of pre-hardened steel should be specified.
According to the surface state: forging blank, pickling state, rough turning state, fine turning state, polishing state, polishing state, etc.
05 Performance and Testing Requirements
Conventional detection scope including: chemical composition, mechanical properties at room temperature (e.g., hardness test, tensile test, impact test, etc.), high temperature mechanical properties, metallographic analysis, such as non-metallic inclusions, grain size, etc.), corrosion test (such as intergranular corrosion test, etc.), inspection of tolerances for size, surface defect inspection, nondestructive testing (such as [SCALE STEEL.]ultrasonic testing, dye penetrant testing, etc.).
06 Identification and Packaging
General identification includes: brand number, batch number, name, dimension specification.If there is a special part identification number, it should be specified when ordering.
Common identification methods include: [SCALE STEEL.]paint pen, spray printing, label paper and steel logo.
Conventional packing: bundling, wooden cases, simple pallets, etc.