835M30

What 835M30 steel is

Grade character and typical use

835M30 is the most highly alloyed through-hardening grade in BS 970. Nominal contents of 4% nickel, 1.25% chromium and 0.3% molybdenum give it very high hardenability. A 150 mm ruling section hardens to the core, and sections up to roughly 65 mm will harden fully in still air.

This removes the need for a water or oil quench on parts of intricate shape, where distortion and quench cracking cause most of the scrap. Hardened and tempered at 200 to 280 °C the grade develops a tensile strength above 1550 MPa at 444 HB and above. Tempered higher it serves as a deeper-hardening substitute for 826M40 or AISI 4340.

Forgings are delivered annealed. In the as-forged or air-cooled condition the hardness is too high to machine economically.

The grade has two drawbacks. Its nickel content makes it expensive against 4140 or 4340. The same hardenability that makes it useful also makes it difficult to weld, and it is normally specified as a non-welded material.

How we forge it

We buy 835M30 melted by electric arc furnace with ladle refining and vacuum degassing, and electroslag remelted stock where the specification calls for tighter cleanliness and better through-thickness properties. Ingots or blooms are heated to forging temperature, upset and drawn on open dies, ring-rolled where the part is a ring, then slow-cooled and annealed before rough machining.

835M30 chemical composition

Limits to BS 970-1:1983, weight percent

Published P and S limits for this grade vary between editions of BS 970 and between mills, from 0.025% to 0.050% max. Where your specification calls for tighter residuals, state the limits on the enquiry and we will source ladle-refined or ESR material to suit. The values above are for design guidance. The mill certificate issued with the forging is the governing document for that order.

835M30 mechanical properties

Minimum values to BS 970-1:1983 unless noted

Mechanical properties are guaranteed only up to the limiting ruling section for the heat-treatment condition ordered. Above that section size only surface hardness is guaranteed and the tensile figures are for information. Test position and orientation should be agreed on the order for heavy forgings.

Physical properties

Typical room-temperature values for design calculation

Physical properties are typical for low-alloy Ni-Cr-Mo steels of this composition and are not specified in BS 970. Use them for preliminary calculation only.

835M30 heat treatment

Forging, annealing, hardening and tempering

Forging

Heat slowly and uniformly to 1150 to 1200 °C, soak until the section is at temperature throughout, and finish forging above 900 °C. Do not continue working below about 850 °C. Cool slowly after forging, in a furnace, in ash or under insulation. This steel will air-harden and crack if a heavy forging is dropped straight onto the floor.

Annealing

Heat to 650 to 680 °C and cool slowly in the furnace. A sub-critical anneal is used rather than a full anneal because the aim is to bring hardness down to a machinable 277 HB or less without coarsening the structure.

Normalising

Normalising is not a useful operation on 835M30. Because of its hardenability, cooling in still air from above the upper critical temperature produces martensite rather than a normalised structure. Anneal instead.

Hardening and tempering

Austenitise at 810 to 840 °C. Quench in oil for heavy sections, or cool in still air for sections up to roughly 65 mm, where the steel will still harden through. Temper immediately once the part has cooled to hand-warm. Tempering at 200 to 280 °C gives the full 1550 MPa condition Z properties. Higher tempering temperatures trade strength for toughness.

Embrittlement ranges to avoid

• Do not finish a temper in the 250 to 450 °C band. Tempered martensite embrittlement in this range drops impact toughness sharply even though hardness looks acceptable.
• For high-temperature tempers above 550 °C, cool quickly through 550 to 375 °C. Slow cooling through that band causes reversible temper embrittlement. The molybdenum in 835M30 reduces the susceptibility but does not remove it.
• Stress relieve rough-machined parts at 30 to 50 °C below the final tempering temperature to avoid losing hardness.

Welding

835M30 is not regarded as a weldable grade. Where a weld is unavoidable it must be made in the annealed condition, with a preheat and interpass temperature of 250 to 350 °C, low-hydrogen consumables, and a post-weld heat treatment started before the joint cools. Welding a hardened and tempered part will soften the heat-affected zone and risks hydrogen cracking. Discuss any welded design with us before the enquiry is priced.

835M30 equivalent grades

Nearest designations in other standards

Cross-references indicate the nearest known grade rather than interchangeability. Composition ranges, residual limits and property requirements differ between standards, and substitution should be approved by the design authority before ordering. If your drawing calls for one of these designations we can forge to that specification directly. Tell us which standard governs.

835M30 forged shapes and sizes

Product forms and size envelope

Everything is forged to the customer's drawing. We work from ingot or bloom, so there is no stock-shape restriction. If the part is within the size envelope below and the die work is feasible, we can forge it.

• Seamless rolled rings
• Forged rings and stepped rings
• Forged shafts and stepped shafts
• Eccentric shafts and crankshafts
• Forged round bar and flat bar
• Forged flanges
• Discs, disks and blanks
• Gear blanks and pinion blanks
• Sleeves, bushings and hollow bar
• Blocks, plates and mould blocks
• Spindles and rolls
• Valve bodies, stems and seat rings

Delivery condition can be as-forged, rough-machined with grinding allowance, proof-machined, or finish-machined to drawing. State the machining allowance you want on the enquiry, along with the heat-treatment condition and the test requirement.

Testing and certification

Inspection scope and documentation

Non-destructive testing

835M30 forgings are ultrasonically tested as standard. The acceptance standard is set by the customer's specification, commonly EN 10228-3 for ferritic steel forgings, SEP 1921 for the German quality classes, or ASTM A388 for the ASME route. Magnetic particle inspection to ASTM E709 or EN 10228-1 and dye penetrant inspection to ASTM E165 are available on machined surfaces.

Mechanical and chemical testing

• Ladle and product chemical analysis, reported element by element
• Tensile test: R_m, R_p0.2, elongation, reduction of area
• Charpy V-notch impact, at room temperature or at a specified sub-zero temperature
• Brinell hardness survey at the positions named on the drawing
• Austenitic grain size, and non-metallic inclusion rating to ASTM E45 or DIN 50602 where required
• Dimensional inspection report against the drawing

Certificates

Every 835M30 forging is supplied with an EN 10204 3.1 inspection certificate as standard. An EN 10204 3.2 certificate countersigned by a third-party inspection body such as BV, SGS, TUV or Lloyd's Register is available when requested at the order stage. Heat-treatment charts, NDT reports and material traceability to the heat number are issued with the certificate.

Where 835M30 is used

Typical parts and sectors

835M30 is specified where a part is large or intricate, carries a high stress, and cannot tolerate the distortion that a drastic quench would cause. Typical parts are:

Where a lower strength level is acceptable, 826M40, 817M40 or AISI 4340 will usually be cheaper. 835M30 is worth the extra cost when the section is too heavy for those grades to harden through, or when the geometry makes an oil quench too risky.

Buying 835M30 forgings from Jiangnan Metal

Enquiry requirements

Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory in Zhouzhuang Town, Jiangyin, Jiangsu Province, about 150 km from the port of Shanghai. We forge alloy steel, carbon steel, tool steel, stainless steel and nickel alloys to customer drawings, and we export to Europe, North America, the Middle East, Southeast Asia and Australia.

What to send with your enquiry

• A drawing or a sketch with dimensions, in PDF, DWG or STEP
• Quantity, and whether this is a one-off or a repeat order
• Delivery condition: as-forged, rough-machined, proof-machined or finish-machined
• Heat-treatment condition required, and the properties that must be met
• NDT standard and acceptance class
• Certificate type, EN 10204 3.1 or 3.2, and any third-party inspection

Send it to sales@steelforgepieces.com or message +86 189 2135 9659. If you do not have a drawing yet, tell us the shape, the rough dimensions and what the part does, and we will come back with a proposal.

Frequently asked questions about 835M30

Common questions from buyers and design engineers

Contact the forging works

Send a drawing and we will quote

Related alloy steel grades we forge

Grades commonly compared with 835M30

Standards referenced

1. BS 970-1:1983, Wrought steels for mechanical and allied engineering purposes. Part 1: General inspection and testing procedures and specific requirements for carbon, carbon manganese, alloy and stainless steels.
2. BS 970:1955, the withdrawn standard in which this grade was designated EN30B.
3. EN 10228-3, Non-destructive testing of steel forgings. Part 3: Ultrasonic testing of ferritic or martensitic steel forgings.
4. SEP 1921, Ultrasonic testing of steel forgings, quality classes.
5. ASTM A388 / A388M, Standard Practice for Ultrasonic Examination of Steel Forgings.
6. EN 10204, Metallic products. Types of inspection documents.
7. ASTM E45, Standard Test Methods for Determining the Inclusion Content of Steel.