write " ▁or ▁" draw " ▁a ▁picture ▁on ▁the ▁metal ▁surface ▁by ▁mel ting ▁a ▁thin ▁surface ▁layer . ▁ ▁Working ▁chamber ▁ ▁Since ▁the ▁appearance ▁of ▁the ▁first ▁electron - be am ▁w eld ing ▁machines ▁at ▁the ▁end ▁of ▁the ▁ 1 9 5 0 s , ▁the ▁application ▁of ▁electron - be am ▁w eld ing ▁spread ▁rapidly ▁into ▁industry ▁and ▁research ▁in ▁all ▁highly ▁developed ▁countries . ▁Up ▁to ▁now , ▁un count able ▁numbers ▁of ▁various ▁types ▁of ▁electron - be am ▁equipment ▁have ▁been ▁designed ▁and ▁realized . ▁In ▁most ▁of ▁them ▁the ▁w eld ing ▁takes ▁place ▁in ▁a ▁working ▁vac u um ▁chamber ▁in ▁a ▁high ▁or ▁low ▁vac u um ▁environment . ▁ ▁The ▁vac u um ▁working ▁chamber ▁may ▁have ▁any ▁desired ▁volume , ▁from ▁a ▁few ▁lit ers ▁up ▁to ▁hundreds ▁of ▁cub ic ▁meters . ▁They ▁can ▁be ▁provided ▁with ▁electron ▁guns ▁supp lying ▁an ▁electron ▁beam ▁with ▁any ▁required ▁power ▁up ▁to ▁ 1 0 0   k W , ▁or ▁even ▁more ▁if ▁needed . ▁In ▁micro - elect ron ▁beam ▁devices , ▁components ▁with ▁dimensions ▁in ▁t enth s ▁of ▁a ▁millimeter ▁can ▁be ▁precisely ▁w eld ed . ▁In ▁w eld ers ▁with ▁electron ▁be ams ▁of ▁high ▁enough ▁power , ▁w eld s ▁up ▁to ▁ 3 0 0   mm ▁deep ▁can ▁be ▁realized . ▁ ▁There ▁are ▁also ▁w eld ing ▁machines ▁in ▁which ▁the ▁electron ▁beam ▁is ▁brought ▁out ▁of ▁vac u