116 Qualitätsstahl Werkzeugstahl Technical delivery terms (Prst) – Dimensions in mm – Range of application These specifications apply for fine-machinedbars in the following ranges of application: - from 10 to 500 width for flat steel dimensions - from 1 to 100 mm thickness for flat steel dimensions - 500, 1000 and 1030 mm lengths for flat steel dimensions - from 4 to 150 mm side length for square steel dimensions. It does not apply to: - bright flat steel according to EN 10278 - bright squares according to EN 10278 - cold-rolled steel strip according to EN 10140 Concept Precision flat steel and square steel are sharp-edged bars with fine-machinedlongitudinal surfaces free of decarburisation. Designation The following are to be indicated in the designation in the sequence given below: - Name (precision flat steel, precision square steel bars), - Delivery conditions (DIN 59350, with machining over measure), - Abbreviation or material number - Nominal sizes (width, thickness, length of flat steel; thickness, length of square steel). Example: Flat steel - Prst – 1.2842 – 150 x 30 x 500 DIN 59359 – Vkt – 1.2436 – 20,4 x 500 Dimensions, permissible dimensional deviations and deviations of form The permissible deviations from the nominal sizes are as follows: For PRÄZI-flat steel according to DIN 59350 Thickness grounded / fine-machined Tol.: + 0,05 /-0 mm Width grounded / fine-machined Tol.: + 0,20 /- 0 mm Length, one fine-machined end face, one rough-machined end face Tol.: + 5 mm Square steel dimensions, thickness Tol.: + 0,05 / - 0 mm For PRÄZI-flat steel according to DIN 59350 with machining allowance Thickness grounded / fine-machined Tol.: + 0,2 / - 0 mm Width grounded / fine-machined Tol.: + 0,2 / - 0 mm Length, one fine-machined end face, one rough-machined end face Tol.: + 5 mm Square steel dimensions, thickness Tol.: +0,20 / - 0 mm Angular deviation for PRÄZI-flat steel according to DIN 59350 The permissible angular deviation between the side faces and between the end faces and these faces 0°15” For PRÄZI-flat steel with machining allowance Thickness grounded / fine-machined Tol.: + 0,25 / - 0 mm Width grounded / fine-machined Tol.: + 0,40 / - 0 mm Length fine-machined / sawn length 500 mm Tol.: + 20 mm Length fine-machined / sawn length 1030 mm Tol.: +/- 20 mm Square steel dimensions, thickness Tol.: + 0,25 / - 0 mm Angular deviation The permissible angular deviation between the side faces is 0°15” Parallelism The parallelism lies within the permissible dimensional tolerances. Deviations there from are to be agreed when ordering. Surface roughness The figures for the peak-to-valley height relate in the case of - precision flat steel to the wide longitudinal sides - precision square steel bars to all longitudinal sides It is for - bars without machining allowance Ra ≤ 2 µm - bars with machining allowance Ra ≤ 6 µm - bars with machining over measure Ra ≤ 6 µm Heat treatment condition The steels are normally delivered in a soft-annealed condition, other heat treatment conditions are to be agreed when ordering. Planeness and straightness The deviation from the planeness and straightness are indicated in the table below. They are measured on an individual piece along the longitudinal and short sides with a feeler gauge. The test specimen is to lie freely on a plane board.
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