AISI 4145H and 4145H MOD forgings

The chemical composition of AISI 4145H follows the H band limits of ASTM A29 and ASTM A304 together with SAE J1268. Because the H grade is sold against a Jominy end quench band, the element ranges sit a little wider than plain AISI 4145. AISI 4145H MOD narrows phosphorus and sulphur and shifts manganese and chromium, which improves cleanliness and impact toughness for downhole service.

Mechanical properties of AISI 4145H depend on section size and tempering temperature. The figures below are what Jiangyin Jiangnan Metal Co., Ltd. supplies for quenched and tempered AISI 4145H forgings in the 110 to 125 ksi class, tested one inch (25 mm) below the surface at room temperature.

AISI 4145H goes into service quenched and tempered in almost every load bearing application. Jiangyin Jiangnan Metal Co., Ltd. runs annealing, normalising, quenching and tempering in house on AISI 4145H forgings, with furnaces surveyed to AMS 2750 practice and chart recordings issued with the material certificate.

AISI 4145H has no exact one to one equivalent in the European, Chinese or Japanese systems, because the H grade is defined by a hardenability band and not by chemistry alone. The table lists the nearest grades used when AISI 4145H is cross referenced for procurement.

AISI 4145H, AISI 4140 and AISI 4130 are all chromium molybdenum steels and differ mainly in carbon. More carbon raises strength and hardenability and lowers weldability at the same time. Oil and gas designers therefore keep AISI 4130 for welded pressure containing bodies. AISI 4140 covers most general machinery. AISI 4145H is held back for heavy drill string parts that have to through harden.

Jiangyin Jiangnan Metal Co., Ltd. produces AISI 4145H as open die forgings and seamless rolled rings to customer drawing, rough machined or finish machined. AISI 4145H forgings are press forged with a minimum reduction ratio of 3 to 1, which breaks down the cast structure, refines grain and closes internal porosity. The works runs 1, 3, 5 and 9 tonne open die hammers alongside a 5000 tonne hydraulic press, covering 80 mm to 6000 mm diameter and 10 kg to 15000 kg per piece.

AISI 4145H is specified when a heavy section has to be hard and strong through its full thickness. Surface hardening will not do the job on a drill collar wall or a large shaft journal. That is how AISI 4145H became the standard drill string steel, and the same behaviour makes it useful for big rotating and pressure retaining parts in general heavy engineering.

Jiangyin Jiangnan Metal Co., Ltd. works to ISO 9001:2015 and employs about 460 people, among them 9 senior engineers and 32 intermediate engineers. Every AISI 4145H forging leaving the works is traceable from the steel heat number through forging, heat treatment and final inspection. The production route for AISI 4145H runs as follows.

• Melting. EAF plus LF plus VD, meaning electric arc furnace melting, ladle furnace refining and vacuum degassing. The result is fine grain aluminium killed steel with controlled hydrogen and low inclusion content.
• Forging. Open die press forging from ingot or continuous cast bloom, minimum 3 to 1 reduction ratio, upset and drawn as the part geometry requires.
• Heat treatment. Annealing, normalising, quenching and tempering with recorded furnace charts.
• Mechanical testing. Tensile, hardness and Charpy V-notch impact testing to ASTM A370, taken from integral or prolongation test blocks that represent the part.
• Ultrasonic testing. Volumetric UT to EN 10228-3, SEP 1921, ASTM A388 or the customer acceptance class.
• Surface and dimensional inspection. Magnetic particle inspection to ASTM E709 on request, plus a dimensional report against the approved drawing.
• Certification. EN 10204 3.1 material certificate as standard. EN 10204 3.2 is available, witnessed and countersigned by a third party inspectorate such as SGS, BV, TUV, DNV or Lloyd's Register.

Send a drawing or a dimensioned sketch to sales@steelforgepieces.com and Jiangyin Jiangnan Metal Co., Ltd. will come back with price and lead time. To quote AISI 4145H accurately we need:

• Grade and specification, whether AISI 4145H, AISI 4145H MOD, or the customer specification the part is bought to.
• Forged form and finished dimensions, or the drawing with machining allowance shown.
• Quantity and required delivery date.
• Delivery condition, whether as forged, normalised, or quenched and tempered to a stated hardness or strength class.
• Required mechanical properties and test temperature, including any Charpy impact requirement.
• NDT scope and acceptance class, meaning UT standard, MPI and any surface finish requirement.
• Certification level, EN 10204 3.1 or 3.2, and whether third party witness is required.
• Service conditions, in particular sour service to NACE MR0175 / ISO 15156 or low temperature service.