SANS 10217-2008 The heat treatment of ground-engaging parts for farming implements《农用工具接触地面零件的热处理》.pdf

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1、 Collection of SANS standards in electronic format (PDF) 1. Copyright This standard is available to staff members of companies that have subscribed to the complete collection of SANS standards in accordance with a formal copyright agreement. This document may reside on a CENTRAL FILE SERVER or INTRA

2、NET SYSTEM only. Unless specific permission has been granted, this document MAY NOT be sent or given to staff members from other companies or organizations. Doing so would constitute a VIOLATION of SABS copyright rules. 2. Indemnity The South African Bureau of Standards accepts no liability for any

3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. ISBN 978-0-626-21317-6 SANS 10217:2008Edition 1.1Any reference to SABS 0217 is deemedto be a reference to this standard(Government Notice No. 1373 of 8 N

4、ovember 2002)SOUTH AFRICAN NATIONAL STANDARD The heat treatment of ground-engaging parts for farming implements Published by Standards South Africa 1 dr lategan road groenkloof private bag x191 pretoria 0001 tel: 012 428 7911 fax: 012 344 1568 international code + 27 12 www.stansa.co.za Standards So

5、uth Africa SANS 10217:2008 Edition 1.1 Table of changes Change No. Date Scope Amdt 1 2008 Amended to change the designation of SABS standards to SANS standards, with no technical changes. Foreword This South African standard was approved by National Committee StanSA TC 5120.77, Engineering materials

6、 Ferrous metals, in accordance with procedures of Standards South Africa, in compliance with annex 3 of the WTO/TBT agreement. This document was published in June 2008. This document supersedes SABS 0217:1988 (first edition). Preface The purpose of this code of practice is to provide technical infor

7、mation for use in conjunction with quality assurance actions in ensuring the correct heat treatment of ground-engaging parts for farming implements. This will enable parts manufacturers to supply a consistently good product to consumers. It is also intended as a code which can be referred to if part

8、s manufacturers have to comply with the provisions of SANS 9001. SANS 10217:2008 Edition 1.1 1 Contents Page Foreword Preface 1 Scope 3 2 Definitions . 3 3 Requirements for ground-engaging parts for farming implements . 3 4 Important aspects to be considered for obtaining a suitable hardness of grou

9、nd-engaging parts by means of heat treatment 3 5 Provisions 4 Appendix A Acceptable steel grades 6 Appendix B Hardness testing and hardness range . 6 SANS 10217:2008 Edition 1.1 2 This page is intentionally left blank SANS 10217:2008 Edition 1.1 3 The heat treatment of ground-engaging parts for farm

10、ing implements 1 Scope 1.1 This code of practice provides technical information on and lays down provisions for the heat treatment of through-hardening steels used in the manufacture of ground-engaging parts for farming implements, in order to achieve an optimum compromise between hardness and tough

11、ness. NOTE a) Acceptable steel grades are discussed in appendix A. b) A recommended method of hardness testing and a recommended hardness range for ground-engaging parts for farming implements are given in appendix B. 2 Definitions 2.1 For the purposes of this code the following definition shall app

12、ly: through-hardening steel a grade of steel which can be hardened throughout its thickness by means of heat treatment NOTE The depth and degree of hardening obtained is dependent on the section thickness and the chemical composition of the steel, as well as on the effectiveness of the heat treatmen

13、t. 3 Requirements for ground-engaging parts for farming implements 3.1 Ground-engaging parts for farming implements must be of a grade of steel that will withstand abrasion in service and will have adequate resistance to fracture. NOTE The abrasion resistance of a steel is to a large extent dependen

14、t on its hardness and this hardness is achieved mainly by proper heat treatment. The rapid wear of ground-engaging parts can therefore generally be attributed to the steel being too soft owing to shortcomings in the heat-treatment process. 4 Important aspects to be considered for obtaining a suitabl

15、e hardness of ground-engaging parts by means of heat treatment 4.1 General Steels supplied for the manufacture of ground-engaging parts are normally rolled to size while hot and then allowed to cool down at a slow rate. This leaves the steel in a comparatively soft condition and permits blanking, fo

16、rming and drilling operations to be carried out easily. Furthermore, most ground-engaging parts are manufactured by a hot-forming process and allowed to cool slowly, SANS 10217:2008 Edition 1.1 4 which also leaves them relatively soft. Before they will be suitable for use, they must be hardened and

17、toughened. 4.2 Available processes In order to harden these steels, it is necessary to heat treat the parts. Several processes can be used, the most common being a) water quenching; b) oil1)quenching; and c) austempering. In each case, it is necessary to reheat the steel to a temperature (called the

18、 hardening temperature) above a certain critical value. The steel is maintained at this temperature for a specified time (called the soaking time) before being cooled very rapidly by immersing it either in water or in oil or in molten salt, depending on the process used. In the case of water quenchi

19、ng, the part may be used in the as-quenched condition or it may be tempered after quenching. This process can be applied to steels, the carbon content of which does not exceed about 0,35 %. With steels of a higher carbon content, there is an increasing risk of cracking taking place when the steel is

20、 quenched in water. Steels for oil quenching usually have a high carbon content and are always tempered. Austempered products are simply immersed in the hot salt for a certain period of time until the steel has been transformed. They are then ready for use. NOTE Tempering involves heating the steel

21、to a certain temperature which will reduce the hardness to such levels as required for the particular application but will increase the toughness. Tempering should be carried out immediately after quenching. 4.3 Effect of chemical composition The hardness which can be obtained in a steel is closely

22、linked to its carbon content, whereas the hardenability, i.e. the through-hardening characteristics, is determined by the overall chemical composition of the steel, in particular by the carbon, manganese, chromium, molybdenum and boron contents. NOTE Owing to its high cost, nickel is not used for gr

23、ound-engaging parts. 4.4 Effect of temperature The temperature at which steel is hot-rolled and the temperature to which it is heated for hardening operations is of the order of 850-900 C. At these temperatures, the carbon at the surface of the steel will be removed by oxidization, and therefore the

24、 higher the temperature employed and the longer the steel is held at the elevated temperature, the greater will be the amount of carbon removed and the greater the depth to which carbon will be removed from the steel. Consequently, when heavily decarburized steel is heat treated to be hardened, the

25、surface will not harden sufficiently. 5 Provisions NOTE See also appendices A and B. 5.1 General provisions The composition of the steel must be such that when the steel is hardened by heat treatment in accordance with the recommendations of the steelmaker or the supplier of the steel, it will have

26、a 1) Oil is often replaced as a quenching medium by a solution of certain polymers in water. SANS 10217:2008 Edition 1.1 5 fully hardened structure, i.e. an acceptable hardness across the full section of the steel, and will, in addition, possess adequate toughness for the intended purpose. 5.2 Speci

27、fic provisions 5.2.1 In order to determine whether the steel has a fully hardened structure, samples must be taken from a consignment, sectioned and examined microscopically to confirm that the structure is almost entirely martensitic. 5.2.2 In order to check the uniformity of hardness and the degre

28、e of hardness of a consignment of steel, the hardness across a section of the steel must be determined. 5.2.3 In order to check whether decarburization of the steel has been excessive, the steel must be examined microscopically (see 5.2.1). 5.2.4 In order to ensure that the steel has maximum abrasio

29、n-resistant properties, the following procedures can be followed: a) confirm that the steel conforms to the required composition and that no excessive decarburization is present; b) heat treat the steel in accordance with the steelmakers or the suppliers recommendations, and paying particular attent

30、ion to the following aspects: 1) the steel must not be subject to any working or forming process between the reheating furnace and the quenching bath; 2) the temperature of reheating must be within the limits recommended by the steelmaker; 3) furnace temperatures must be controlled by pyrometers whi

31、ch are checked regularly for accuracy, at least every 3 months; 4) the parts must be uniformly heated throughout; 5) the time the steel is maintained at the reheating temperature (i.e. the soaking time) must be within the limits recommended; 6) oxidization at the elevated temperature must be kept to

32、 a minimum by not exceeding the recommended soaking time and by sealing the furnace or using an inert atmosphere, where practicable; 7) the steel must be transferred from the reheating furnace into the quenching medium with negligible loss of temperature, i.e. the temperature must not drop below the

33、 minimum laid down by the steelmaker; and 8) the quenching medium must be so circulated that the parts are cooled as rapidly as possible. 5.2.5 Regular hardness measurements must be taken of the heat-treated parts after quenching and after tempering. This must be coupled to a statistical evaluation.

34、 All readings must consistently be within predefined scatter bands. Periodic measurements must also be made at mid-thicknesses to check through thickness hardening. SANS 10217:2008 Edition 1.1 6 Appendix A Acceptable steel grades (This appendix does not form part of the provisions of the code) A.1 S

35、teel grades will in general be selected for different components by the respective parts manufacturers in consultation with the steelmakers or metallurgical consultants. Appendix B Hardness testing and hardness range (This appendix does not form part of the provisions of the code) B.1 It is consider

36、ed that satisfactory control of the quality of ground-engaging parts can be maintained by regular hardness testing of such components. The Rockwell C hardness test is commonly used for this purpose. B.2 It is recommended that, for practical reasons, the hardness of ground-engaging parts be in the ra

37、nge 32-45 HRC, and that the scatter of readings for any particular component does not exceed 5 HRC units. B.3 If surface hardnesses are low and decarburization of the steel is suspected, this can be checked by removing a layer of approximately 0,3 mm from the surface of the steel and performing hardness tests at this depth. If these hardnesses are still low, then decarburization is probably present. NOTE Care should be taken to keep the steel cool when removing the surface layer. Standards South Africa